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Shi Y, Li J, Li K, Zhang X, Chang P, Huang Z, Liu Y, Wang Y, Zhan Y, Cao X, Zhu S. Detector-trigger-based cardiac multiphase micro-CT imaging for small animals. JOURNAL OF X-RAY SCIENCE AND TECHNOLOGY 2023; 31:1047-1066. [PMID: 37483057 DOI: 10.3233/xst-230034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/25/2023]
Abstract
BACKGROUND Micro-computed tomography is important in cardiac imaging for preclinical small animal models, but motion artifacts may appear due to the rapid heart rates. To avoid influence of motion artifacts, the prospective ECG gating schemes based on an X-ray source trigger have been investigated. However, due to the lack of pulsed X-ray exposure modes, high-resolution micro-focus X-ray sources do not support source triggering in most cases. OBJECTIVE To develop a fast-cardiac multiphase acquisition strategy using prospective ECG gating for micro-focus X-ray tubes with a continuous emission mode. METHODS The proposed detector-trigger-based prospective ECG gating acquisition scheme (DTB-PG) triggers the X-ray detector at the R peak of ECG, and then collects multiple phase projections of the heart in one ECG cycle by sequence acquisition. Cardiac multiphase images are reconstructed after performing the same acquisition in all views. The feasibility of this strategy was verified in multiphase imaging experiments of a phantom with 150 ms motion period and a mouse heart on a micro-focus micro-CT system with continuous emission mode. RESULTS Using a high frame-rate CMOS detector, DTB-PG discriminates the positions of the motion phantom well in 10 different phases and enables to distinguish the changes in the cardiac volume of the mouse in different phases. The acquisition rate of DTB-PG is much faster than other prospective gating schemes as demonstrated by theoretical analysis. CONCLUSIONS DTB-PG combines the advantages of prospective ECG gating strategies and X-ray detector-trigger mode to suppress motion artifacts, achieve ultra-fast acquisition rates, and relax hardware limitations.
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Affiliation(s)
- Yu Shi
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Juntao Li
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Ke Li
- Xi'an Key Laboratory for Prevention and Treatment of Common Aging Diseases, Translational and Research Centre for Prevention and Therapy of Chronic Disease, Institute of Basic and Translational Medicine, Xi'an Medical University, Xi'an, China
| | - Xuexue Zhang
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Peng Chang
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
| | - Zujian Huang
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Yanyun Liu
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Yihan Wang
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Yonghua Zhan
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
| | - Xu Cao
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
| | - Shouping Zhu
- School of Life Science and Technology, Xidian University & Engineering Research Center of Molecular and Neuro Imaging, Ministry of Education, Xi'an, Shaanxi, China
- Xi'an Key Laboratory of Intelligent Sensing and Regulation of trans-Scale Life Information & International Joint Research Center for Advanced Medical Imaging and Intelligent Diagnosis and Treatment, School of Life Science and Technology, Xidian University, Xi'an, Shaanxi, China
- Innovation Center for Advanced Medical Imaging and Intelligent Medicine, Guangzhou Institute of Technology, Xidian University, Guangzhou, Guangdong, China
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Wehrse E, Klein L, Rotkopf LT, Stiller W, Finke M, Echner G, Glowa C, Heinze S, Ziener CH, Schlemmer HP, Kachelrieß M, Sawall S. Ultrahigh resolution whole body photon counting computed tomography as a novel versatile tool for translational research from mouse to man. Z Med Phys 2022:S0939-3889(22)00066-6. [PMID: 35868888 DOI: 10.1016/j.zemedi.2022.06.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2022] [Revised: 06/18/2022] [Accepted: 06/19/2022] [Indexed: 11/19/2022]
Abstract
X-ray computed tomography (CT) is a cardinal tool in clinical practice. It provides cross-sectional images within seconds. The recent introduction of clinical photon-counting CT allowed for an increase in spatial resolution by more than a factor of two resulting in a pixel size in the center of rotation of about 150 µm. This level of spatial resolution is in the order of dedicated preclinical micro-CT systems. However so far, the need for different dedicated clinical and preclinical systems often hinders the rapid translation of early research results to applications in men. This drawback might be overcome by ultra-high resolution (UHR) clinical photon-counting CT unifying preclinical and clinical research capabilities in a single machine. Herein, the prototype of a clinical UHR PCD CT (SOMATOM CounT, Siemens Healthineers, Forchheim, Germany) was used. The system comprises a conventional energy-integrating detector (EID) and a novel photon-counting detector (PCD). While the EID provides a pixel size of 0.6 mm in the centre of rotation, the PCD provides a pixel size of 0.25 mm. Additionally, it provides a quantification of photon energies by sorting them into up to four distinct energy bins. This acquisition of multi-energy data allows for a multitude of applications, e.g. pseudo-monochromatic imaging. In particular, we examine the relation between spatial resolution, image noise and administered radiation dose for a multitude of use-cases. These cases include ultra-high resolution and multi-energy acquisitions of mice administered with a prototype bismuth-based contrast agent (nanoPET Pharma, Berlin, Germany) as well as larger animals and actual patients. The clinical EID provides a spatial resolution of about 9 lp/cm (modulation transfer function at 10%, MTF10%) while UHR allows for the acquisition of images with up to 16 lp/cm allowing for the visualization of all relevant anatomical structures in preclinical and clinical specimen. The spectral capabilities of the system enable a variety of applications previously not available in preclinical research such as pseudo-monochromatic images. Clinical ultra-high resolution photon-counting CT has the potential to unify preclinical and clinical research on a single system enabling versatile imaging of specimens and individuals ranging from mice to man.
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Affiliation(s)
- E Wehrse
- Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Medical Faculty, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany
| | - L Klein
- Department of Physics and Astronomy, Heidelberg University, Heidelberg, Germany; Division of X-ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - L T Rotkopf
- Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - W Stiller
- Diagnostic and Interventional Radiology (DIR), Heidelberg University Hospital, Heidelberg, Germany
| | - M Finke
- Diagnostic and Interventional Radiology (DIR), Heidelberg University Hospital, Heidelberg, Germany
| | - G Echner
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - C Glowa
- Division of Medical Physics in Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany; Department of Radiation Oncology and Radiotherapy, University Hospital Heidelberg, Heidelberg, Germany; Heidelberg Institute for Radiation Oncology (HIRO), National Center for Radiation Research in Oncology (NCRO), Heidelberg, Germany
| | - S Heinze
- Institute of Forensic and Traffic Medicine, University Hospital Heidelberg, Heidelberg, Germany
| | - C H Ziener
- Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - H-P Schlemmer
- Division of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - M Kachelrieß
- Medical Faculty, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany; Division of X-ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany
| | - S Sawall
- Medical Faculty, Ruprecht-Karls-University Heidelberg, Heidelberg, Germany; Division of X-ray Imaging and CT, German Cancer Research Center (DKFZ), Heidelberg, Germany.
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Entezam A, Fielding A, Moi D, Bradley D, Ratnayake G, Sim L, Kralik C, Fontanarosa D. Investigation of scattered dose in a mouse phantom model for pre-clinical dosimetry studies. Radiat Phys Chem Oxf Engl 1993 2021. [DOI: 10.1016/j.radphyschem.2021.109691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Mendez C, Colpo N, Duzenli C, Atwal P, Gill B. Technical Note: Development of a phantom for dosimetric comparison of murine micro-CT protocols with optically stimulated luminescent dosimeters. Med Phys 2018; 45:3974-3979. [PMID: 29971794 DOI: 10.1002/mp.13079] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 06/04/2018] [Accepted: 06/27/2018] [Indexed: 11/08/2022] Open
Abstract
PURPOSE This work aims to evaluate the utility and accuracy of a mouse-like phantom and optically stimulated luminescent dosimeters (OSLDs) in measuring dose delivered to the body and lung of mice undergoing micro-CT imaging. METHODS A phantom with two cavities for NanoDot OSLDs (Landauer, Inc., Greenwood, IL) was designed and constructed using acrylic to model the mouse body and polyurethane foam to obtain an approximate lung tissue dose. The OSLD dose was compared to ion chamber measurements for the same imaging protocols delivered by a Siemens Inveon micro-CT (Siemens Medical Solutions USA, Inc., Hoffman Estates, IL, USA). A whole body scan, using 80 kV, 0.5 mA and 0.5 mm of aluminum filter, was used to compare results to previously published data. Additionally, dose was measured for the whole body scan without the aluminum filter and two chest protocols (full and half rotation). RESULTS OSLD dose results agree with chamber measurements within 3%. Average OSLD measurements for the whole body scan without filter were 10.7 ± 0.7 cGy in the abdomen and 11.2 ± 0.7 cGy in the lung. For the full rotation chest protocol, the average dose measured in the lung was 65.8 ± 4.3 cGy and 60.2 ± 3.9 cGy in the abdomen. Average doses were 41.1 ± 2.7 cGy in the lung and 38.2 ± 2.5 cGy in the abdomen for the half rotation chest protocol. The OSLD measurements showed a coefficient of variation under 1.4%. A maximum rotational geometry under-response of 0.86% with respect to exposure at normal incidence to the OSLD was measured. CONCLUSIONS The doses measured were found to be comparable to other studies for the scanner configuration and protocols chosen. The phantom built for this study was found to give reproducible dose measurements with 4% uncertainty. In this way, a robust and convenient method is established for future dose assessment of micro-CT protocols and interinstitutional comparisons.
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Affiliation(s)
- Claudia Mendez
- Department of Medical Physics, British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia, V5Z 4E6, Canada
| | - Nadine Colpo
- Molecular Oncology, British Columbia Cancer Research Centre, 675 West 10th Avenue, Vancouver, British Columbia, V5Z 1L3, Canada
| | - Cheryl Duzenli
- Department of Medical Physics, British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia, V5Z 4E6, Canada
- Department of Physics and Astronomy, University of British Columbia, 2329 West Mall, Vancouver, British Columbia, V6T 1Z4, Canada
| | - Parmveer Atwal
- Department of Medical Physics, British Columbia Cancer Agency, 32900 Marshall Road, Abbotsford, British Columbia, V2S 0C2, Canada
| | - Brad Gill
- Department of Medical Physics, British Columbia Cancer Agency, 600 West 10th Avenue, Vancouver, British Columbia, V5Z 4E6, Canada
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Meganck JA, Liu B. Dosimetry in Micro-computed Tomography: a Review of the Measurement Methods, Impacts, and Characterization of the Quantum GX Imaging System. Mol Imaging Biol 2018; 19:499-511. [PMID: 27957647 PMCID: PMC5498628 DOI: 10.1007/s11307-016-1026-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Purpose X-ray micro-computed tomography (μCT) is a widely used imaging modality in preclinical research with applications in many areas including orthopedics, pulmonology, oncology, cardiology, and infectious disease. X-rays are a form of ionizing radiation and, therefore, can potentially induce damage and cause detrimental effects. Previous reviews have touched on these effects but have not comprehensively covered the possible implications on study results. Furthermore, interpreting data across these studies is difficult because there is no widely accepted dose characterization methodology for preclinical μCT. The purpose of this paper is to ensure in vivo μCT studies can be properly designed and the data can be appropriately interpreted. Procedures Studies from the scientific literature that investigate the biological effects of radiation doses relevant to μCT were reviewed. The different dose measurement methodologies used in the peer-reviewed literature were also reviewed. The CT dose index 100 (CTDI100) was then measured on the Quantum GX μCT instrument. A low contrast phantom, a hydroxyapatite phantom, and a mouse were also imaged to provide examples of how the dose can affect image quality. Results Data in the scientific literature indicate that scenarios exist where radiation doses used in μCT imaging are high enough to potentially bias experimental results. The significance of this effect may relate to the study outcome and tissue being imaged. CTDI100 is a reasonable metric to use for dose characterization in μCT. Dose rates in the Quantum GX vary based on the amount of material in the beam path and are a function of X-ray tube voltage. The CTDI100 in air for a Quantum GX can be as low as 5.1 mGy for a 50 kVp scan and 9.9 mGy for a 90 kVp scan. This dose is low enough to visualize bone both in a mouse image and in a hydroxyapatite phantom, but applications requiring higher resolution in a mouse or less noise in a low-contrast phantom benefit from longer scan times with increased dose. Conclusions Dose management should be considered when designing μCT studies. Dose rates in the Quantum GX are compatible with longitudinal μCT imaging.
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Affiliation(s)
- Jeffrey A Meganck
- Research and Development, Life Sciences Technology, PerkinElmer, 68 Elm Street, Hopkinton, MA, 01748, USA.
| | - Bob Liu
- Department of Radiology, Massachusetts General Hospital, Boston, MA, USA
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Slimani FAA, Hamdi M, Bentourkia M. G4DARI: Geant4/GATE based Monte Carlo simulation interface for dosimetry calculation in radiotherapy. Comput Med Imaging Graph 2018; 67:30-39. [PMID: 29738914 DOI: 10.1016/j.compmedimag.2018.04.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 03/15/2018] [Accepted: 04/24/2018] [Indexed: 11/17/2022]
Abstract
Monte Carlo (MC) simulation is widely recognized as an important technique to study the physics of particle interactions in nuclear medicine and radiation therapy. There are different codes dedicated to dosimetry applications and widely used today in research or in clinical application, such as MCNP, EGSnrc and Geant4. However, such codes made the physics easier but the programming remains a tedious task even for physicists familiar with computer programming. In this paper we report the development of a new interface GEANT4 Dose And Radiation Interactions (G4DARI) based on GEANT4 for absorbed dose calculation and for particle tracking in humans, small animals and complex phantoms. The calculation of the absorbed dose is performed based on 3D CT human or animal images in DICOM format, from images of phantoms or from solid volumes which can be made from any pure or composite material to be specified by its molecular formula. G4DARI offers menus to the user and tabs to be filled with values or chemical formulas. The interface is described and as application, we show results obtained in a lung tumor in a digital mouse irradiated with seven energy beams, and in a patient with glioblastoma irradiated with five photon beams. In conclusion, G4DARI can be easily used by any researcher without the need to be familiar with computer programming, and it will be freely available as an application package.
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Affiliation(s)
- Faiçal A A Slimani
- Faculty of Medicine and Health Sciences, Université de Sherbrooke, Canada
| | - Mahdjoub Hamdi
- Département de Génie Électrique, Université de Mostaganem, Algeria
| | - M'hamed Bentourkia
- Faculty of Medicine and Health Sciences, Université de Sherbrooke, Canada.
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Zeller-Plumhoff B, Roose T, Clough GF, Schneider P. Image-based modelling of skeletal muscle oxygenation. J R Soc Interface 2017; 14:rsif.2016.0992. [PMID: 28202595 DOI: 10.1098/rsif.2016.0992] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2016] [Accepted: 01/25/2017] [Indexed: 12/12/2022] Open
Abstract
The supply of oxygen in sufficient quantity is vital for the correct functioning of all organs in the human body, in particular for skeletal muscle during exercise. Disease is often associated with both an inhibition of the microvascular supply capability and is thought to relate to changes in the structure of blood vessel networks. Different methods exist to investigate the influence of the microvascular structure on tissue oxygenation, varying over a range of application areas, i.e. biological in vivo and in vitro experiments, imaging and mathematical modelling. Ideally, all of these methods should be combined within the same framework in order to fully understand the processes involved. This review discusses the mathematical models of skeletal muscle oxygenation currently available that are based upon images taken of the muscle microvasculature in vivo and ex vivo Imaging systems suitable for capturing the blood vessel networks are discussed and respective contrasting methods presented. The review further informs the association between anatomical characteristics in health and disease. With this review we give the reader a tool to understand and establish the workflow of developing an image-based model of skeletal muscle oxygenation. Finally, we give an outlook for improvements needed for measurements and imaging techniques to adequately investigate the microvascular capability for oxygen exchange.
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Affiliation(s)
- B Zeller-Plumhoff
- Helmholtz-Zentrum für Material- und Küstenforschung, Geesthacht, Germany .,Bioengineering Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
| | - T Roose
- Bioengineering Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
| | - G F Clough
- Faculty of Medicine, University of Southampton, Southampton, UK
| | - P Schneider
- Bioengineering Research Group, Faculty of Engineering and the Environment, University of Southampton, Southampton, UK
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Hamdi M, Mimi M, Bentourkia M. Impact of X-ray energy on absorbed dose assessed with Monte Carlo simulations in a mouse tumor and in nearest organs irradiated with kilovoltage X-ray beams. Cancer Radiother 2017; 21:190-198. [DOI: 10.1016/j.canrad.2017.01.008] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2016] [Revised: 12/24/2016] [Accepted: 01/09/2017] [Indexed: 02/07/2023]
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Welch D, Turner L, Speiser M, Randers-Pehrson G, Brenner DJ. Scattered Dose Calculations and Measurements in a Life-Like Mouse Phantom. Radiat Res 2017; 187:433-442. [PMID: 28140787 DOI: 10.1667/rr004cc.1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Anatomically accurate phantoms are useful tools for radiation dosimetry studies. In this work, we demonstrate the construction of a new generation of life-like mouse phantoms in which the methods have been generalized to be applicable to the fabrication of any small animal. The mouse phantoms, with built-in density inhomogeneity, exhibit different scattering behavior dependent on where the radiation is delivered. Computer models of the mouse phantoms and a small animal irradiation platform were devised in Monte Carlo N-Particle code (MCNP). A baseline test replicating the irradiation system in a computational model shows minimal differences from experimental results from 50 Gy down to 0.1 Gy. We observe excellent agreement between scattered dose measurements and simulation results from X-ray irradiations focused at either the lung or the abdomen within our phantoms. This study demonstrates the utility of our mouse phantoms as measurement tools with the goal of using our phantoms to verify complex computational models.
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Affiliation(s)
- David Welch
- a Center for Radiological Research, Columbia University, New York, New York
| | - Leah Turner
- a Center for Radiological Research, Columbia University, New York, New York
| | - Michael Speiser
- b Englewood Hospital and Medical Center, Englewood, New Jersey
| | | | - David J Brenner
- a Center for Radiological Research, Columbia University, New York, New York
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Micro-CT vs. Whole Body Multirow Detector CT for Analysing Bone Regeneration in an Animal Model. PLoS One 2016; 11:e0166540. [PMID: 27880788 PMCID: PMC5120815 DOI: 10.1371/journal.pone.0166540] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 10/31/2016] [Indexed: 11/20/2022] Open
Abstract
OBJECTIVES Compared with multirow detector CT (MDCT), specimen (ex vivo) micro-CT (μCT) has a significantly higher (~ 30 x) spatial resolution and is considered the gold standard for assessing bone above the cellular level. However, it is expensive and time-consuming, and when applied in vivo, the radiation dose accumulates considerably. The aim of this study was to examine whether the lower resolution of the widely used MDCT is sufficient to qualitatively and quantitatively evaluate bone regeneration in rats. METHODS Forty critical-size defects (5mm) were placed in the mandibular angle of rats and covered with coated bioactive titanium implants to promote bone healing. Five time points were selected (7, 14, 28, 56 and 112 days). μCT and MDCT were used to evaluate the defect region to determine the bone volume (BV), tissue mineral density (TMD) and bone mineral content (BMC). RESULTS MDCT constantly achieved higher BV values than μCT (10.73±7.84 mm3 vs. 6.62±4.96 mm3, p<0.0001) and consistently lower TMD values (547.68±163.83 mm3 vs. 876.18±121.21 mm3, p<0.0001). No relevant difference was obtained for BMC (6.48±5.71 mm3 vs. 6.15±5.21 mm3, p = 0.40). BV and BMC showed very strong correlations between both methods, whereas TMD was only moderately correlated (r = 0.87, r = 0.90, r = 0.68, p < 0.0001). CONCLUSIONS Due to partial volume effects, MDCT overestimated BV and underestimated TMD but accurately determined BMC, even in small volumes, compared with μCT. Therefore, if bone quantity is a sufficient end point, a considerable number of animals and costs can be saved, and compared with in vivo μCT, the required dose of radiation can be reduced.
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Broeckhoven C, Plessis A, Roux SG, Mouton PLFN, Hui C. Beauty is more than skin deep: a non‐invasive protocol for
in vivo
anatomical study using micro‐CT. Methods Ecol Evol 2016. [DOI: 10.1111/2041-210x.12661] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Affiliation(s)
- Chris Broeckhoven
- Department of Botany & Zoology Stellenbosch University Private Bag X1 Matieland 7602 Stellenbosch South Africa
- Theoretical Ecology Group Department of Mathematical Sciences Stellenbosch University Private Bag X1 Matieland 7602 Stellenbosch South Africa
| | - Anton Plessis
- CT Scanner Facility Central Analytical Facilities Stellenbosch University Matieland 7602 Stellenbosch South Africa
| | - Stephan Gerhard Roux
- CT Scanner Facility Central Analytical Facilities Stellenbosch University Matieland 7602 Stellenbosch South Africa
| | | | - Cang Hui
- Theoretical Ecology Group Department of Mathematical Sciences Stellenbosch University Private Bag X1 Matieland 7602 Stellenbosch South Africa
- Theoretical and Physical Biosciences African Institute for Mathematical Sciences Cape Town 7945 South Africa
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Xie T, Zaidi H. Development of computational small animal models and their applications in preclinical imaging and therapy research. Med Phys 2016; 43:111. [PMID: 26745904 DOI: 10.1118/1.4937598] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The development of multimodality preclinical imaging techniques and the rapid growth of realistic computer simulation tools have promoted the construction and application of computational laboratory animal models in preclinical research. Since the early 1990s, over 120 realistic computational animal models have been reported in the literature and used as surrogates to characterize the anatomy of actual animals for the simulation of preclinical studies involving the use of bioluminescence tomography, fluorescence molecular tomography, positron emission tomography, single-photon emission computed tomography, microcomputed tomography, magnetic resonance imaging, and optical imaging. Other applications include electromagnetic field simulation, ionizing and nonionizing radiation dosimetry, and the development and evaluation of new methodologies for multimodality image coregistration, segmentation, and reconstruction of small animal images. This paper provides a comprehensive review of the history and fundamental technologies used for the development of computational small animal models with a particular focus on their application in preclinical imaging as well as nonionizing and ionizing radiation dosimetry calculations. An overview of the overall process involved in the design of these models, including the fundamental elements used for the construction of different types of computational models, the identification of original anatomical data, the simulation tools used for solving various computational problems, and the applications of computational animal models in preclinical research. The authors also analyze the characteristics of categories of computational models (stylized, voxel-based, and boundary representation) and discuss the technical challenges faced at the present time as well as research needs in the future.
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Affiliation(s)
- Tianwu Xie
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211, Switzerland
| | - Habib Zaidi
- Division of Nuclear Medicine and Molecular Imaging, Geneva University Hospital, Geneva 4 CH-1211, Switzerland; Geneva Neuroscience Center, Geneva University, Geneva CH-1205, Switzerland; and Department of Nuclear Medicine and Molecular Imaging, University of Groningen, University Medical Center Groningen, Groningen 9700 RB, The Netherlands
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Miyahara N, Kokubo T, Hara Y, Yamada A, Koike T, Arai Y. Evaluation of X-ray doses and their corresponding biological effects on experimental animals in cone-beam micro-CT scans (R-mCT2). Radiol Phys Technol 2016; 9:60-8. [PMID: 26441335 PMCID: PMC4722077 DOI: 10.1007/s12194-015-0334-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Revised: 09/03/2015] [Accepted: 09/07/2015] [Indexed: 11/13/2022]
Abstract
Studies show that the radiation dose received during a micro-CT examination may have adverse effects on living subjects. However, the correlations between the biological effects and the radiation doses have never been thoroughly evaluated in the majority of cases. In this study, we evaluated the biological radiation effects of measured radiation doses in ICR mice using cone-beam micro-CT scans. Long-term in vivo whole-body micro-CT scans of ICR mice were performed for a duration of 4 weeks. Although a scanning frequency of three scans per week is higher than that necessary for conventional studies, this study represents particular cases where the subjects may undergo an extreme number of examinations. The average X-ray dose of a CT scan measures 16.19 mGy at the center of a phantom and 16.24 mGy at an offset position of 7.5 mm from the center of the phantom. The total average dose at the center of the phantom during the 4-week scanning period was 194.3 mGy. No significant radiation effects were observed in the weight gain curves, organ weights, blood analyses, litter sizes, reared offspring sizes, and the histopathologic results. Therefore, it is unlikely that the measured doses for the CT scans caused any radiation damage in the mice.
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Affiliation(s)
- Nobuyuki Miyahara
- National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan.
| | - Toshiaki Kokubo
- National Institute of Radiological Sciences, 4-9-1 Anagawa, Inage-ku, Chiba, 263-8555, Japan
| | - Yukihiro Hara
- Rigaku Co., 3-9-12 Matubara-cho, Akisima-Shi, Tokyo, 196-8666, Japan
| | - Ayuta Yamada
- Rigaku Co., 3-9-12 Matubara-cho, Akisima-Shi, Tokyo, 196-8666, Japan
| | - Takafumi Koike
- Rigaku Co., 3-9-12 Matubara-cho, Akisima-Shi, Tokyo, 196-8666, Japan
| | - Yoshinori Arai
- Nihon University School of Dentistry, 1-8-13 Surugadai Kanda, Chiyoda-ku, Tokyo, 101-8310, Japan
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Bretin F, Bahri MA, Luxen A, Phillips C, Plenevaux A, Seret A. Monte Carlo simulations of the dose from imaging with GE eXplore 120 micro-CT using gate. Med Phys 2015; 42:5711-9. [DOI: 10.1118/1.4930056] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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15
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Starosolski Z, Villamizar CA, Rendon D, Paldino MJ, Milewicz DM, Ghaghada KB, Annapragada AV. Ultra High-Resolution In vivo Computed Tomography Imaging of Mouse Cerebrovasculature Using a Long Circulating Blood Pool Contrast Agent. Sci Rep 2015; 5:10178. [PMID: 25985192 PMCID: PMC4650815 DOI: 10.1038/srep10178] [Citation(s) in RCA: 56] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Accepted: 04/01/2015] [Indexed: 12/21/2022] Open
Abstract
Abnormalities in the cerebrovascular system play a central role in many neurologic diseases. The on-going expansion of rodent models of human cerebrovascular diseases and the need to use these models to understand disease progression and treatment has amplified the need for reproducible non-invasive imaging methods for high-resolution visualization of the complete cerebral vasculature. In this study, we present methods for in vivo high-resolution (19 μm isotropic) computed tomography imaging of complete mouse brain vasculature. This technique enabled 3D visualization of large cerebrovascular networks, including the Circle of Willis. Blood vessels as small as 40 μm were clearly delineated. ACTA2 mutations in humans cause cerebrovascular defects, including abnormally straightened arteries and a moyamoya-like arteriopathy characterized by bilateral narrowing of the internal carotid artery and stenosis of many large arteries. In vivo imaging studies performed in a mouse model of Acta2 mutations demonstrated the utility of this method for studying vascular morphometric changes that are practically impossible to identify using current histological methods. Specifically, the technique demonstrated changes in the width of the Circle of Willis, straightening of cerebral arteries and arterial stenoses. We believe the use of imaging methods described here will contribute substantially to the study of rodent cerebrovasculature.
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Affiliation(s)
- Zbigniew Starosolski
- 1] Edward B. Singleton Department of Pediatric Radiology, Texas Children's Hospital, Houston TX [2] Department of Radiology, Baylor College of Medicine, Houston, TX
| | - Carlos A Villamizar
- Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, TX
| | - David Rendon
- Department of Pediatrics, Baylor College of Medicine, Houston, TX
| | - Michael J Paldino
- 1] Edward B. Singleton Department of Pediatric Radiology, Texas Children's Hospital, Houston TX [2] Department of Radiology, Baylor College of Medicine, Houston, TX
| | - Dianna M Milewicz
- Department of Internal Medicine, University of Texas Health Science Center at Houston, Houston, TX
| | - Ketan B Ghaghada
- 1] Edward B. Singleton Department of Pediatric Radiology, Texas Children's Hospital, Houston TX [2] Department of Radiology, Baylor College of Medicine, Houston, TX
| | - Ananth V Annapragada
- 1] Edward B. Singleton Department of Pediatric Radiology, Texas Children's Hospital, Houston TX [2] Department of Radiology, Baylor College of Medicine, Houston, TX
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Imaging technologies and basic considerations for welfare of laboratory rodents. Lab Anim (NY) 2015; 44:97-105. [DOI: 10.1038/laban.665] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2014] [Accepted: 08/11/2014] [Indexed: 02/06/2023]
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Martinez NE, Johnson TE, Capello K, Pinder JE. Development and comparison of computational models for estimation of absorbed organ radiation dose in rainbow trout (Oncorhynchus mykiss) from uptake of iodine-131. JOURNAL OF ENVIRONMENTAL RADIOACTIVITY 2014; 138:50-59. [PMID: 25151639 DOI: 10.1016/j.jenvrad.2014.08.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2014] [Revised: 07/30/2014] [Accepted: 08/03/2014] [Indexed: 06/03/2023]
Abstract
This study develops and compares different, increasingly detailed anatomical phantoms for rainbow trout (Oncorhynchus mykiss) for the purpose of estimating organ absorbed radiation dose and dose rates from (131)I uptake in multiple organs. The models considered are: a simplistic geometry considering a single organ, a more specific geometry employing additional organs with anatomically relevant size and location, and voxel reconstruction of internal anatomy obtained from CT imaging (referred to as CSUTROUT). Dose Conversion Factors (DCFs) for whole body as well as selected organs of O. mykiss were computed using Monte Carlo modeling, and combined with estimated activity concentrations, to approximate dose rates and ultimately determine cumulative radiation dose (μGy) to selected organs after several half-lives of (131)I. The different computational models provided similar results, especially for source organs (less than 30% difference between estimated doses), and whole body DCFs for each model (∼3 × 10(-3) μGy d(-1) per Bq kg(-1)) were comparable to DCFs listed in ICRP 108 for (131)I. The main benefit provided by the computational models developed here is the ability to accurately determine organ dose. A conservative mass-ratio approach may provide reasonable results for sufficiently large organs, but is only applicable to individual source organs. Although CSUTROUT is the more anatomically realistic phantom, it required much more resource dedication to develop and is less flexible than the stylized phantom for similar results. There may be instances where a detailed phantom such as CSUTROUT is appropriate, but generally the stylized phantom appears to be the best choice for an ideal balance between accuracy and resource requirements.
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Affiliation(s)
- N E Martinez
- Department of Environmental Engineering and Earth Sciences, Clemson University, 342 Computer Ct, Anderson, SC 29625, USA.
| | - T E Johnson
- Department of Environmental and Radiological Health Sciences, Colorado State University, 1681 Campus Delivery, Fort Collins, CO 80523, USA
| | - K Capello
- Human Monitoring Laboratory, National Internal Radiation Assessment Section, Radiation Protection Bureau, 775 Brookfield Road, Ottawa, Ontario K1A 1C1, Canada
| | - J E Pinder
- Department of Environmental and Radiological Health Sciences, Colorado State University, 1681 Campus Delivery, Fort Collins, CO 80523, USA
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Abstract
PURPOSE The objective of this study was to compare a new generation of four-dimensional micro-single photon emission computed tomography (microSPECT) with microCT for the quantitative in vivo assessment of murine cardiac function. PROCEDURES Four-dimensional isotropic cardiac images were acquired from anesthetized normal C57BL/6 mice with either microSPECT (n = 6) or microCT (n = 6). One additional mouse with myocardial infarction (MI) was scanned with both modalities. Prior to imaging, mice were injected with either technetium tetrofosmin for microSPECT or a liposomal blood pool contrast agent for microCT. Segmentation of the left ventricle (LV) was performed using Vitrea (Vital Images) software, to derive global and regional function. RESULTS Measures of global LV function between microSPECT and microCT groups were comparable (e.g., ejection fraction = 71 ± 6 % microSPECT and 68 ± 4 % microCT). Regional functional indices (wall motion, wall thickening, regional ejection fraction) were also similar for the two modalities. In the mouse with MI, microSPECT identified a large perfusion defect that was not evident with microCT. CONCLUSIONS Despite lower spatial resolution, microSPECT was comparable to microCT in the quantitative evaluation of cardiac function. MicroSPECT offers an advantage over microCT in the ability to evaluate simultaneously myocardial radiotracer distribution and function, simultaneously. MicroSPECT should be considered as an alternative to microCT and magnetic resonance for preclinical cardiac imaging in the mouse.
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Ashton JR, Befera N, Clark D, Qi Y, Mao L, Rockman HA, Johnson GA, Badea CT. Anatomical and functional imaging of myocardial infarction in mice using micro-CT and eXIA 160 contrast agent. CONTRAST MEDIA & MOLECULAR IMAGING 2014; 9:161-8. [PMID: 24523061 DOI: 10.1002/cmmi.1557] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 05/10/2013] [Accepted: 06/17/2013] [Indexed: 11/09/2022]
Abstract
Noninvasive small animal imaging techniques are essential for evaluation of cardiac disease and potential therapeutics. A novel preclinical iodinated contrast agent called eXIA 160 has recently been developed, which has been evaluated for micro-CT cardiac imaging. eXIA 160 creates strong contrast between blood and tissue immediately after its injection and is subsequently taken up by the myocardium and other metabolically active tissues over time. We focus on these properties of eXIA and show its use in imaging myocardial infarction in mice. Five C57BL/6 mice were imaged ~2 weeks after left anterior descending coronary artery ligation. Six C57BL/6 mice were used as controls. Immediately after injection of eXIA 160, an enhancement difference between blood and myocardium of ~340 HU enabled cardiac function estimation via 4D micro-CT scanning with retrospective gating. Four hours post-injection, the healthy perfused myocardium had a contrast difference of ~140 HU relative to blood while the infarcted myocardium showed no enhancement. These differences allowed quantification of infarct size via dual-energy micro-CT. In vivo micro-SPECT imaging and ex vivo triphenyl tetrazolium chloride (TTC) staining provided validation for the micro-CT findings. Root mean squared error of infarct measurements was 2.7% between micro-CT and SPECT, and 4.7% between micro-CT and TTC. Thus, micro-CT with eXIA 160 can be used to provide both morphological and functional data for preclinical studies evaluating myocardial infarction and potential therapies. Further studies are warranted to study the potential use of eXIA 160 as a CT molecular imaging tool for other metabolically active tissues in the mouse.
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Affiliation(s)
- Jeffrey R Ashton
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Durham, NC, 27710, USA
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Clark DP, Badea CT. Micro-CT of rodents: state-of-the-art and future perspectives. Phys Med 2014; 30:619-34. [PMID: 24974176 PMCID: PMC4138257 DOI: 10.1016/j.ejmp.2014.05.011] [Citation(s) in RCA: 134] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 05/15/2014] [Accepted: 05/28/2014] [Indexed: 02/06/2023] Open
Abstract
Micron-scale computed tomography (micro-CT) is an essential tool for phenotyping and for elucidating diseases and their therapies. This work is focused on preclinical micro-CT imaging, reviewing relevant principles, technologies, and applications. Commonly, micro-CT provides high-resolution anatomic information, either on its own or in conjunction with lower-resolution functional imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT). More recently, however, advanced applications of micro-CT produce functional information by translating clinical applications to model systems (e.g., measuring cardiac functional metrics) and by pioneering new ones (e.g. measuring tumor vascular permeability with nanoparticle contrast agents). The primary limitations of micro-CT imaging are the associated radiation dose and relatively poor soft tissue contrast. We review several image reconstruction strategies based on iterative, statistical, and gradient sparsity regularization, demonstrating that high image quality is achievable with low radiation dose given ever more powerful computational resources. We also review two contrast mechanisms under intense development. The first is spectral contrast for quantitative material discrimination in combination with passive or actively targeted nanoparticle contrast agents. The second is phase contrast which measures refraction in biological tissues for improved contrast and potentially reduced radiation dose relative to standard absorption imaging. These technological advancements promise to develop micro-CT into a commonplace, functional and even molecular imaging modality.
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Affiliation(s)
- D P Clark
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Box 3302, Durham, NC 27710, USA
| | - C T Badea
- Center for In Vivo Microscopy, Department of Radiology, Duke University Medical Center, Box 3302, Durham, NC 27710, USA.
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Gammon ST, Foje N, Brewer EM, Owers E, Downs CA, Budde MD, Leevy WM, Helms MN. Preclinical anatomical, molecular, and functional imaging of the lung with multiple modalities. Am J Physiol Lung Cell Mol Physiol 2014; 306:L897-914. [DOI: 10.1152/ajplung.00007.2014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In vivo imaging is an important tool for preclinical studies of lung function and disease. The widespread availability of multimodal animal imaging systems and the rapid rate of diagnostic contrast agent development have empowered researchers to noninvasively study lung function and pulmonary disorders. Investigators can identify, track, and quantify biological processes over time. In this review, we highlight the fundamental principles of bioluminescence, fluorescence, planar X-ray, X-ray computed tomography, magnetic resonance imaging, and nuclear imaging modalities (such as positron emission tomography and single photon emission computed tomography) that have been successfully employed for the study of lung function and pulmonary disorders in a preclinical setting. The major principles, benefits, and applications of each imaging modality and technology are reviewed. Limitations and the future prospective of multimodal imaging in pulmonary physiology are also discussed. In vivo imaging bridges molecular biological studies, drug design and discovery, and the imaging field with modern medical practice, and, as such, will continue to be a mainstay in biomedical research.
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Affiliation(s)
- Seth T. Gammon
- Department of Cancer Systems Imaging, The University of Texas MD Anderson Cancer Center, Houston, Texas
| | - Nathan Foje
- Department of Biological Sciences, Notre Dame Integrated Imaging Facility, Notre Dame, Indiana
| | - Elizabeth M. Brewer
- Department of Pediatrics Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, Georgia
| | - Elizabeth Owers
- Department of Biological Sciences, Notre Dame Integrated Imaging Facility, Notre Dame, Indiana
| | - Charles A. Downs
- Nell Hodgson Woodruff School of Nursing, Emory University, Atlanta, Georgia; and
| | - Matthew D. Budde
- Department of Neurosurgery, Medical College of Wisconsin, Milwaukee, Wisconsin
| | - W. Matthew Leevy
- Department of Biological Sciences, Notre Dame Integrated Imaging Facility, Notre Dame, Indiana
| | - My N. Helms
- Department of Pediatrics Center for Cystic Fibrosis and Airways Disease Research, Emory University, Atlanta, Georgia
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22
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Effects of freeze–thaw and micro-computed tomography irradiation on structure–property relations of porcine trabecular bone. J Biomech 2014; 47:1495-8. [DOI: 10.1016/j.jbiomech.2014.02.022] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/15/2014] [Accepted: 02/17/2014] [Indexed: 11/19/2022]
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Belley MD, Wang C, Nguyen G, Gunasingha R, Chao NJ, Chen BJ, Dewhirst MW, Yoshizumi TT. Toward an organ based dose prescription method for the improved accuracy of murine dose in orthovoltage x-ray irradiators. Med Phys 2014; 41:034101. [PMID: 24593746 PMCID: PMC3987731 DOI: 10.1118/1.4864237] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2013] [Revised: 12/16/2013] [Accepted: 01/16/2014] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Accurate dosimetry is essential when irradiating mice to ensure that functional and molecular endpoints are well understood for the radiation dose delivered. Conventional methods of prescribing dose in mice involve the use of a single dose rate measurement and assume a uniform average dose throughout all organs of the entire mouse. Here, the authors report the individual average organ dose values for the irradiation of a 12, 23, and 33 g mouse on a 320 kVp x-ray irradiator and calculate the resulting error from using conventional dose prescription methods. METHODS Organ doses were simulated in the Geant4 application for tomographic emission toolkit using the MOBY mouse whole-body phantom. Dosimetry was performed for three beams utilizing filters A (1.65 mm Al), B (2.0 mm Al), and C (0.1 mm Cu + 2.5 mm Al), respectively. In addition, simulated x-ray spectra were validated with physical half-value layer measurements. RESULTS Average doses in soft-tissue organs were found to vary by as much as 23%-32% depending on the filter. Compared to filters A and B, filter C provided the hardest beam and had the lowest variation in soft-tissue average organ doses across all mouse sizes, with a difference of 23% for the median mouse size of 23 g. CONCLUSIONS This work suggests a new dose prescription method in small animal dosimetry: it presents a departure from the conventional approach of assigninga single dose value for irradiation of mice to a more comprehensive approach of characterizing individual organ doses to minimize the error and uncertainty. In human radiation therapy, clinical treatment planning establishes the target dose as well as the dose distribution, however, this has generally not been done in small animal research. These results suggest that organ dose errors will be minimized by calibrating the dose rates for all filters, and using different dose rates for different organs.
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Affiliation(s)
- Matthew D Belley
- Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705
| | - Chu Wang
- Medical Physics Graduate Program, Duke University Medical Center, Durham, North Carolina 27705
| | - Giao Nguyen
- Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710
| | - Rathnayaka Gunasingha
- Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710
| | - Nelson J Chao
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710 and Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710
| | - Benny J Chen
- Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710
| | - Mark W Dewhirst
- Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710
| | - Terry T Yoshizumi
- Duke Radiation Dosimetry Laboratory, Duke University Medical Center, Durham, North Carolina 27710; Department of Radiology, Duke University Medical Center, Durham, North Carolina 27710; and Department of Radiation Oncology, Duke University Medical Center, Durham, North Carolina 27710
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Vrigneaud JM, Courteau A, Ranouil J, Morgand L, Raguin O, Walker P, Oudot A, Collin B, Brunotte F. Application of the optically stimulated luminescence (OSL) technique for mouse dosimetry in micro-CT imaging. Med Phys 2013; 40:122102. [PMID: 24320529 DOI: 10.1118/1.4829499] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
PURPOSE Micro-CT is considered to be a powerful tool to investigate various models of disease on anesthetized animals. In longitudinal studies, the radiation dose delivered by the micro-CT to the same animal is a major concern as it could potentially induce spurious effects in experimental results. Optically stimulated luminescence dosimeters (OSLDs) are a relatively new kind of detector used in radiation dosimetry for medical applications. The aim of this work was to assess the dose delivered by the CT component of a micro-SPECT (single-photon emission computed tomography)∕CT camera during a typical whole-body mouse study, using commercially available OSLDs based on Al2O3:C crystals. METHODS CTDI (computed tomography dose index) was measured in micro-CT with a properly calibrated pencil ionization chamber using a rat-like phantom (60 mm in diameter) and a mouse-like phantom (30 mm in diameter). OSLDs were checked for reproducibility and linearity in the range of doses delivered by the micro-CT. Dose measurements obtained with OSLDs were compared to those of the ionization chamber to correct for the radiation quality dependence of OSLDs in the low-kV range. Doses to tissue were then investigated in phantoms and cadavers. A 30 mm diameter phantom, specifically designed to insert OSLDs, was used to assess radiation dose over a typical whole-body mouse imaging study. Eighteen healthy female BALB∕c mice weighing 27.1 ± 0.8 g (1 SD) were euthanized for small animal measurements. OLSDs were placed externally or implanted internally in nine different locations by an experienced animal technician. Five commonly used micro-CT protocols were investigated. RESULTS CTDI measurements were between 78.0 ± 2.1 and 110.7 ± 3.0 mGy for the rat-like phantom and between 169.3 ± 4.6 and 203.6 ± 5.5 mGy for the mouse-like phantom. On average, the displayed CTDI at the operator console was underestimated by 1.19 for the rat-like phantom and 2.36 for the mouse-like phantom. OSLDs exhibited a reproducibility of 2.4% and good linearity was found between 60 and 450 mGy. The energy scaling factor was calculated to be between 1.80 ± 0.16 and 1.86 ± 0.16, depending on protocol used. In phantoms, mean doses to tissue over a whole-body CT examination were ranging from 186.4 ± 7.6 to 234.9 ± 7.1 mGy. In mice, mean doses to tissue in the mouse trunk (thorax, abdomen, pelvis, and flanks) were between 213.0 ± 17.0 and 251.2 ± 13.4 mGy. Skin doses (3 OSLDs) were much higher with average doses between 350.6 ± 25.3 and 432.5 ± 34.1 mGy. The dose delivered during a topogram was found to be below 10 mGy. Use of the multimouse bed of the system gave a significantly 20%-40% lower dose per animal (p < 0.05). CONCLUSIONS Absorbed doses in micro-CT were found to be relatively high. In micro-SPECT∕CT imaging, the micro-CT unit is mainly used to produce a localization frame. As a result, users should pay attention to adjustable CT parameters so as to minimize the radiation dose and avoid any adverse radiation effects which may interfere with biological parameters studied.
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Affiliation(s)
- Jean-Marc Vrigneaud
- Department of Nuclear Medicine, Centre Georges-François Leclerc, 1 rue Professeur Marion, Dijon 21079 Cedex, France
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Thibaudeau C, Leroux JD, Fontaine R, Lecomte R. Fully 3D iterative CT reconstruction using polar coordinates. Med Phys 2013; 40:111904. [DOI: 10.1118/1.4822514] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
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Lee S, Gregor J, Osborne D. Development and Validation of a Complete GATE Model of the Siemens Inveon Trimodal Imaging Platform. Mol Imaging 2013. [DOI: 10.2310/7290.2013.00058] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Sanghyeb Lee
- From the Department of Electrical Engineering and Computer Science and Graduate School of Medicine, University of Tennessee, Knoxville, TN
| | - Jens Gregor
- From the Department of Electrical Engineering and Computer Science and Graduate School of Medicine, University of Tennessee, Knoxville, TN
| | - Dustin Osborne
- From the Department of Electrical Engineering and Computer Science and Graduate School of Medicine, University of Tennessee, Knoxville, TN
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Wathen CA, Foje N, van Avermaete T, Miramontes B, Chapaman SE, Sasser TA, Kannan R, Gerstler S, Leevy WM. In vivo X-ray computed tomographic imaging of soft tissue with native, intravenous, or oral contrast. SENSORS (BASEL, SWITZERLAND) 2013; 13:6957-80. [PMID: 23711461 PMCID: PMC3715264 DOI: 10.3390/s130606957] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/27/2013] [Revised: 05/16/2013] [Accepted: 05/23/2013] [Indexed: 02/07/2023]
Abstract
X-ray Computed Tomography (CT) is one of the most commonly utilized anatomical imaging modalities for both research and clinical purposes. CT combines high-resolution, three-dimensional data with relatively fast acquisition to provide a solid platform for non-invasive human or specimen imaging. The primary limitation of CT is its inability to distinguish many soft tissues based on native contrast. While bone has high contrast within a CT image due to its material density from calcium phosphate, soft tissue is less dense and many are homogenous in density. This presents a challenge in distinguishing one type of soft tissue from another. A couple exceptions include the lungs as well as fat, both of which have unique densities owing to the presence of air or bulk hydrocarbons, respectively. In order to facilitate X-ray CT imaging of other structures, a range of contrast agents have been developed to selectively identify and visualize the anatomical properties of individual tissues. Most agents incorporate atoms like iodine, gold, or barium because of their ability to absorb X-rays, and thus impart contrast to a given organ system. Here we review the strategies available to visualize lung, fat, brain, kidney, liver, spleen, vasculature, gastrointestinal tract, and liver tissues of living mice using either innate contrast, or commercial injectable or ingestible agents with selective perfusion. Further, we demonstrate how each of these approaches will facilitate the non-invasive, longitudinal, in vivo imaging of pre-clinical disease models at each anatomical site.
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Affiliation(s)
- Connor A. Wathen
- Department of Biological Sciences, 100 Galvin Life Sciences Center, University of Notre Dame, Notre Dame, IN 46556, USA; E-Mail:
| | - Nathan Foje
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA; E-Mails: (N.F.); (T.V.A.); (B.M.); (T.A.S.)
| | - Tony van Avermaete
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA; E-Mails: (N.F.); (T.V.A.); (B.M.); (T.A.S.)
- Penn High School, 55900 Bittersweet Road, Mishawaka, IN 46545, USA
| | - Bernadette Miramontes
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA; E-Mails: (N.F.); (T.V.A.); (B.M.); (T.A.S.)
- Penn High School, 55900 Bittersweet Road, Mishawaka, IN 46545, USA
| | - Sarah E. Chapaman
- Notre Dame Integrated Imaging Facility, Notre Dame, IN 46556, USA; E-Mail:
| | - Todd A. Sasser
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre Dame, Notre Dame, IN 46556, USA; E-Mails: (N.F.); (T.V.A.); (B.M.); (T.A.S.)
- Bruker-Biospin Corporation, 4 Research Drive, Woodbridge, CT 06525, USA
| | - Raghuraman Kannan
- Department of Radiology, University of Missouri, Columbia, MO 65212, USA; E-Mail:
| | - Steven Gerstler
- Saint Joseph Regional Medical Center, Mishawaka, IN 46545, USA; E-Mail:
| | - W. Matthew Leevy
- Department of Biological Sciences, 100 Galvin Life Sciences Center, University of Notre Dame, Notre Dame, IN 46556, USA; E-Mail:
- Notre Dame Integrated Imaging Facility, Notre Dame, IN 46556, USA; E-Mail:
- Harper Cancer Research Institute, A200 Harper Hall, Notre Dame, IN 46530, USA
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Detombe SA, Dunmore-Buyze J, Petrov IE, Drangova M. X-ray dose delivered during a longitudinal micro-CT study has no adverse effect on cardiac and pulmonary tissue in C57BL/6 mice. Acta Radiol 2013; 54:435-41. [PMID: 23436828 DOI: 10.1177/0284185113475608] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND Micro-computed tomography (micro-CT) offers numerous advantages for small animal imaging, including the ability to monitor the same animals throughout a longitudinal study. However, concerns are often raised regarding the effects of X-ray dose accumulated over the course of the experiment. PURPOSE To scan C57BL/6 mice multiple times per week for 6 weeks, in order to determine the effect of the cumulative dose on pulmonary and cardiac tissue at the end of the study. MATERIAL AND METHODS C57BL/6 male mice were split into two groups (irradiated group = 10, control group = 10). The irradiated group was scanned (80 kVp/50 mA) three times weekly for 6 weeks, resulting in a weekly dose of 0.84 Gy, and a total study dose of 5.04 Gy. The control group was scanned on the final week. Scans from week 6 were reconstructed and the lungs and heart were analyzed. RESULTS Overall, there was no significant difference in lung volume or lung density or in left ventricular volume or ejection fraction between the control group and the irradiated group. Histological samples taken from excised lung and myocardial tissue also showed no evidence of inflammation or fibrosis in the irradiated group. CONCLUSION This study demonstrated that a 5 Gy X-ray dose accumulated over 6 weeks during a longitudinal micro-CT study had no significant effects on the pulmonary and myocardial tissue of C57BL/6 mice. As a result, the many advantages of micro-CT imaging, including rapid acquisition of high-resolution, isotropic images in free-breathing mice, can be taken advantage of in longitudinal studies without concern for negative dose-related effects.
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Affiliation(s)
- Sarah A Detombe
- Imaging Research Laboratories, Robarts Research Institute, Western University, London, ON
- Department of Medical Biophysics, Western University, London, ON, Canada
| | - Joy Dunmore-Buyze
- Imaging Research Laboratories, Robarts Research Institute, Western University, London, ON
| | - Ivailo E Petrov
- Imaging Research Laboratories, Robarts Research Institute, Western University, London, ON
| | - Maria Drangova
- Imaging Research Laboratories, Robarts Research Institute, Western University, London, ON
- Department of Medical Biophysics, Western University, London, ON, Canada
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Herrmann K, Dahlbom M, Nathanson D, Wei L, Radu C, Chatziioannou A, Czernin J. Evaluation of the Genisys4, a bench-top preclinical PET scanner. J Nucl Med 2013; 54:1162-7. [PMID: 23628700 DOI: 10.2967/jnumed.112.114926] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Abstract
UNLABELLED The Genisys4 is a small bench-top preclinical PET scanner designed to enable imaging in biology, biochemistry, and pharmacology laboratories and imaging centers. Here, we compare its performance with that of a well-established preclinical PET scanner. METHODS Subcutaneous and lung tumor xenografts were used to compare lesion detectability and treatment responses to chemotherapy (gemcitabine) using (18)F-FDG PET. The size of subcutaneous xenografts (L1210 and L1210-10K leukemia cells) and lung metastases (B-16 melanoma cells) was measured on small-animal CT images. Tumor (18)F-FDG uptake was expressed as percentage injected dose per gram. Using list-mode data, serial images of the left ventricular blood pool were used to generate time-activity curves. RESULTS Subcutaneous xenografts (range, 4-12 mm; mean ± SD, 6.1 ± 1.7 mm) and lung metastases (range, 1-5 mm; mean, 2.1 ± 1.2 mm) were detected equally well with both scanners. Tumor (18)F-FDG uptake measured with both scanners was highly correlated for subcutaneous xenografts (r(2) = 0.93) and lung metastases (r(2) = 0.83). The new Genisys4 scanner and the established scanner provided comparable treatment response information (r(2) = 0.93). Dynamic imaging sequences permitted the generation of left ventricular blood-pool time-activity curves with both scanners. CONCLUSION Using subcutaneous and lung xenografts, a novel and an established preclinical PET scanner provided equivalent information with regard to lesion detection, tumor (18)F-FDG uptake, tumor response to treatment, and generation of time-activity curves. Thus, the Genisys4 provides a small, efficient bench-top preclinical PET alternative for quantitatively studying murine tumor models in biology, biochemistry, and pharmacology laboratories and preclinical imaging centers.
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Affiliation(s)
- Ken Herrmann
- Ahmanson Translational Imaging Division, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, UCLA, Los Angeles, California 90095-1782, USA
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Benhalouche S, Visvikis D, Le Maitre A, Pradier O, Boussion N. Evaluation of clinical IMRT treatment planning using the GATE Monte Carlo simulation platform for absolute and relative dose calculations. Med Phys 2013; 40:021711. [DOI: 10.1118/1.4774358] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
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Chapman SE, Diener JM, Sasser TA, Correcher C, González AJ, Avermaete TV, Leevy WM. Dual tracer imaging of SPECT and PET probes in living mice using a sequential protocol. AMERICAN JOURNAL OF NUCLEAR MEDICINE AND MOLECULAR IMAGING 2012; 2:405-414. [PMID: 23145357 PMCID: PMC3484419] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/08/2012] [Accepted: 08/28/2012] [Indexed: 06/01/2023]
Abstract
Over the past 20 years, multimodal imaging strategies have motivated the fusion of Positron Emission Tomography (PET) or Single Photon Emission Computed Tomography (SPECT) scans with an X-ray computed tomography (CT) image to provide anatomical information, as well as a framework with which molecular and functional images may be co-registered. Recently, pre-clinical nuclear imaging technology has evolved to capture multiple SPECT or multiple PET tracers to further enhance the information content gathered within an imaging experiment. However, the use of SPECT and PET probes together, in the same animal, has remained a challenge. Here we describe a straightforward method using an integrated trimodal imaging system and a sequential dosing/acquisition protocol to achieve dual tracer imaging with (99m)Tc and (18)F isotopes, along with anatomical CT, on an individual specimen. Dosing and imaging is completed so that minimal animal manipulations are required, full trimodal fusion is conserved, and tracer crosstalk including down-scatter of the PET tracer in SPECT mode is avoided. This technique will enhance the ability of preclinical researchers to detect multiple disease targets and perform functional, molecular, and anatomical imaging on individual specimens to increase the information content gathered within longitudinal in vivo studies.
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Affiliation(s)
- Sarah E Chapman
- Freimann Life Science Center, University of Notre Dame, 400 Galvin Life ScienceNotre Dame, IN 46556, USA
| | - Justin M Diener
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre DameNotre Dame, IN 46556, USA
| | - Todd A Sasser
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre DameNotre Dame, IN 46556, USA
- Carestream Molecular Imaging, 4 Research DriveWoodbridge, CT 06525, USA
| | - Carlos Correcher
- Oncovision, Ciudad Politécnica de la InnovaciónCamino de Vera s/n, E-46022 Valencia, Spain
| | - Antonio J González
- Oncovision, Ciudad Politécnica de la InnovaciónCamino de Vera s/n, E-46022 Valencia, Spain
| | | | - W Matthew Leevy
- Department of Chemistry and Biochemistry, 236 Nieuwland Science Hall, University of Notre DameNotre Dame, IN 46556, USA
- Notre Dame Integrated Imaging FacilityNotre Dame, IN 46556, USA
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Hupfer M, Nowak T, Brauweiler R, Eisa F, Kalender WA. Spectral optimization for micro-CT. Med Phys 2012; 39:3229-39. [PMID: 22755706 DOI: 10.1118/1.4718575] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
PURPOSE To optimize micro-CT protocols with respect to x-ray spectra and thereby reduce radiation dose at unimpaired image quality. METHODS Simulations were performed to assess image contrast, noise, and radiation dose for different imaging tasks. The figure of merit used to determine the optimal spectrum was the dose-weighted contrast-to-noise ratio (CNRD). Both optimal photon energy and tube voltage were considered. Three different types of filtration were investigated for polychromatic x-ray spectra: 0.5 mm Al, 3.0 mm Al, and 0.2 mm Cu. Phantoms consisted of water cylinders of 20, 32, and 50 mm in diameter with a central insert of 9 mm which was filled with different contrast materials: an iodine-based contrast medium (CM) to mimic contrast-enhanced (CE) imaging, hydroxyapatite to mimic bone structures, and water with reduced density to mimic soft tissue contrast. Validation measurements were conducted on a commercially available micro-CT scanner using phantoms consisting of water-equivalent plastics. Measurements on a mouse cadaver were performed to assess potential artifacts like beam hardening and to further validate simulation results. RESULTS The optimal photon energy for CE imaging was found at 34 keV. For bone imaging, optimal energies were 17, 20, and 23 keV for the 20, 32, and 50 mm phantom, respectively. For density differences, optimal energies varied between 18 and 50 keV for the 20 and 50 mm phantom, respectively. For the 32 mm phantom and density differences, CNRD was found to be constant within 2.5% for the energy range of 21-60 keV. For polychromatic spectra and CMs, optimal settings were 50 kV with 0.2 mm Cu filtration, allowing for a dose reduction of 58% compared to the optimal setting for 0.5 mm Al filtration. For bone imaging, optimal tube voltages were below 35 kV. For soft tissue imaging, optimal tube settings strongly depended on phantom size. For 20 mm, low voltages were preferred. For 32 mm, CNRD was found to be almost independent of tube voltage. For 50 mm, voltages larger than 50 kV were preferred. For all three phantom sizes stronger filtration led to notable dose reduction for soft tissue imaging. Validation measurements were found to match simulations well, with deviations being less than 10%. Mouse measurements confirmed simulation results. CONCLUSIONS Optimal photon energies and tube settings strongly depend on both phantom size and imaging task at hand. For in vivo CE imaging and density differences, strong filtration and voltages of 50-65 kV showed good overall results. For soft tissue imaging of animals the size of a rat or larger, voltages higher than 65 kV allow to greatly reduce scan times while maintaining dose efficiency. For imaging of bone structures, usage of only minimum filtration and low tube voltages of 40 kV and below allow exploiting the high contrast of bone at very low energies. Therefore, a combination of two filtrations could prove beneficial for micro-CT: a soft filtration allowing for bone imaging at low voltages, and a variable stronger filtration (e.g., 0.2 mm Cu) for soft tissue and contrast-enhanced imaging.
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Affiliation(s)
- Martin Hupfer
- Institute of Medical Physics, University of Erlangen-Nürnberg, Henkestrasse 91, 91052 Erlangen, Germany.
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Tremoleda JL, Kerton A, Gsell W. Anaesthesia and physiological monitoring during in vivo imaging of laboratory rodents: considerations on experimental outcomes and animal welfare. EJNMMI Res 2012; 2:44. [PMID: 22877315 PMCID: PMC3467189 DOI: 10.1186/2191-219x-2-44] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 07/16/2012] [Indexed: 12/15/2022] Open
Abstract
The implementation of imaging technologies has dramatically increased the efficiency of preclinical studies, enabling a powerful, non-invasive and clinically translatable way for monitoring disease progression in real time and testing new therapies. The ability to image live animals is one of the most important advantages of these technologies. However, this also represents an important challenge as, in contrast to human studies, imaging of animals generally requires anaesthesia to restrain the animals and their gross motion. Anaesthetic agents have a profound effect on the physiology of the animal and may thereby confound the image data acquired. It is therefore necessary to select the appropriate anaesthetic regime and to implement suitable systems for monitoring anaesthetised animals during image acquisition. In addition, repeated anaesthesia required for longitudinal studies, the exposure of ionising radiations and the use of contrast agents and/or imaging biomarkers may also have consequences on the physiology of the animal and its response to anaesthesia, which need to be considered while monitoring the animals during imaging studies. We will review the anaesthesia protocols and monitoring systems commonly used during imaging of laboratory rodents. A variety of imaging modalities are used for imaging rodents, including magnetic resonance imaging, computed tomography, positron emission tomography, single photon emission computed tomography, high frequency ultrasound and optical imaging techniques such as bioluminescence and fluorescence imaging. While all these modalities are implemented for non-invasive in vivo imaging, there are certain differences in terms of animal handling and preparation, how the monitoring systems are implemented and, importantly, how the imaging procedures themselves can affect mammalian physiology. The most important and critical adverse effects of anaesthetic agents are depression of respiration, cardiovascular system disruption and thermoregulation. When anaesthetising rodents, one must carefully consider if these adverse effects occur at the therapeutic dose required for anaesthesia, if they are likely to affect the image acquisitions and, importantly, if they compromise the well-being of the animals. We will review how these challenges can be successfully addressed through an appropriate understanding of anaesthetic protocols and the implementation of adequate physiological monitoring systems.
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Affiliation(s)
- Jordi L Tremoleda
- Biological Imaging Centre (BIC), Medical Research Council (MRC) Clinical Science Centre, Imperial College London, Hammersmith Campus, Cyclotron Building, Du Cane Road, London, W12 0NN, UK.
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Johnston SM, Johnson GA, Badea CT. Temporal and spectral imaging with micro-CT. Med Phys 2012; 39:4943-58. [PMID: 22894420 PMCID: PMC3416878 DOI: 10.1118/1.4736809] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2011] [Revised: 06/20/2012] [Accepted: 06/27/2012] [Indexed: 12/18/2022] Open
Abstract
PURPOSE Micro-CT is widely used for small animal imaging in preclinical studies of cardiopulmonary disease, but further development is needed to improve spatial resolution, temporal resolution, and material contrast. We present a technique for visualizing the changing distribution of iodine in the cardiac cycle with dual source micro-CT. METHODS The approach entails a retrospectively gated dual energy scan with optimized filters and voltages, and a series of computational operations to reconstruct the data. Projection interpolation and five-dimensional bilateral filtration (three spatial dimensions + time + energy) are used to reduce noise and artifacts associated with retrospective gating. We reconstruct separate volumes corresponding to different cardiac phases and apply a linear transformation to decompose these volumes into components representing concentrations of water and iodine. Since the resulting material images are still compromised by noise, we improve their quality in an iterative process that minimizes the discrepancy between the original acquired projections and the projections predicted by the reconstructed volumes. The values in the voxels of each of the reconstructed volumes represent the coefficients of linear combinations of basis functions over time and energy. We have implemented the reconstruction algorithm on a graphics processing unit (GPU) with CUDA. We tested the utility of the technique in simulations and applied the technique in an in vivo scan of a C57BL∕6 mouse injected with blood pool contrast agent at a dose of 0.01 ml∕g body weight. Postreconstruction, at each cardiac phase in the iodine images, we segmented the left ventricle and computed its volume. Using the maximum and minimum volumes in the left ventricle, we calculated the stroke volume, the ejection fraction, and the cardiac output. RESULTS Our proposed method produces five-dimensional volumetric images that distinguish different materials at different points in time, and can be used to segment regions containing iodinated blood and compute measures of cardiac function. CONCLUSIONS We believe this combined spectral and temporal imaging technique will be useful for future studies of cardiopulmonary disease in small animals.
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Affiliation(s)
- Samuel M Johnston
- Center for In Vivo Microscopy, Duke University Medical Center, Durham, North Carolina 27710, USA
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Automated analysis of small animal PET studies through deformable registration to an atlas. Eur J Nucl Med Mol Imaging 2012; 39:1807-20. [PMID: 22820650 PMCID: PMC3464388 DOI: 10.1007/s00259-012-2188-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2012] [Accepted: 06/28/2012] [Indexed: 11/06/2022]
Abstract
Purpose This work aims to develop a methodology for automated atlas-guided analysis of small animal positron emission tomography (PET) data through deformable registration to an anatomical mouse model. Methods A non-rigid registration technique is used to put into correspondence relevant anatomical regions of rodent CT images from combined PET/CT studies to corresponding CT images of the Digimouse anatomical mouse model. The latter provides a pre-segmented atlas consisting of 21 anatomical regions suitable for automated quantitative analysis. Image registration is performed using a package based on the Insight Toolkit allowing the implementation of various image registration algorithms. The optimal parameters obtained for deformable registration were applied to simulated and experimental mouse PET/CT studies. The accuracy of the image registration procedure was assessed by segmenting mouse CT images into seven regions: brain, lungs, heart, kidneys, bladder, skeleton and the rest of the body. This was accomplished prior to image registration using a semi-automated algorithm. Each mouse segmentation was transformed using the parameters obtained during CT to CT image registration. The resulting segmentation was compared with the original Digimouse atlas to quantify image registration accuracy using established metrics such as the Dice coefficient and Hausdorff distance. PET images were then transformed using the same technique and automated quantitative analysis of tracer uptake performed. Results The Dice coefficient and Hausdorff distance show fair to excellent agreement and a mean registration mismatch distance of about 6 mm. The results demonstrate good quantification accuracy in most of the regions, especially the brain, but not in the bladder, as expected. Normalized mean activity estimates were preserved between the reference and automated quantification techniques with relative errors below 10 % in most of the organs considered. Conclusion The proposed automated quantification technique is reliable, robust and suitable for fast quantification of preclinical PET data in large serial studies.
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Keereman V, Fierens Y, Vanhove C, Lahoutte T, Vandenberghe S. Magnetic Resonace–Based Attenuation Correction for Micro–Single-Photon Emission Computed Tomography. Mol Imaging 2012. [DOI: 10.2310/7290.2011.00036] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Attenuation correction is necessary for quantification in micro–single-photon emission computed tomography (micro-SPECT). In general, this is done based on micro–computed tomographic (micro-CT) images. Derivation of the attenuation map from magnetic resonance (MR) images is difficult because bone and lung are invisible in conventional MR images and hence indistinguishable from air. An ultrashort echo time (UTE) sequence yields signal in bone and lungs. Micro-SPECT, micro-CT, and MR images of 18 rats were acquired. Different tracers were used: hexamethylpropyleneamine oxime (brain), dimercaptosuccinic acid (kidney), colloids (liver and spleen), and macroaggregated albumin (lung). The micro-SPECT images were reconstructed without attenuation correction, with micro-CT-based attenuation maps, and with three MR-based attenuation maps: uniform, non-UTE-MR based (air, soft tissue), and UTE-MR based (air, lung, soft tissue, bone). The average difference with the micro-CT-based reconstruction was calculated. The UTE-MR-based attenuation correction performed best, with average errors ≤ 8% in the brain scans and ≤ 3% in the body scans. It yields nonsignificant differences for the body scans. The uniform map yields errors of ≤ 6% in the body scans. No attenuation correction yields errors ≥ 15% in the brain scans and ≥ 25% in the body scans. Attenuation correction should always be performed for quantification. The feasibility of MR-based attenuation correction was shown. When accurate quantification is necessary, a UTE-MR-based attenuation correction should be used.
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Affiliation(s)
- Vincent Keereman
- From MEDISIP, Department of Electronics and Information Systems, Ghent University-IBBT-IBiTech, Ghent, Belgium, and Radiology/BEFY, In-Vivo Cellular and Molecular Imaging Center, and Department of Nuclear Medicine, UZ Brussel, Brussels, Belgium
| | - Yves Fierens
- From MEDISIP, Department of Electronics and Information Systems, Ghent University-IBBT-IBiTech, Ghent, Belgium, and Radiology/BEFY, In-Vivo Cellular and Molecular Imaging Center, and Department of Nuclear Medicine, UZ Brussel, Brussels, Belgium
| | - Christian Vanhove
- From MEDISIP, Department of Electronics and Information Systems, Ghent University-IBBT-IBiTech, Ghent, Belgium, and Radiology/BEFY, In-Vivo Cellular and Molecular Imaging Center, and Department of Nuclear Medicine, UZ Brussel, Brussels, Belgium
| | - Tony Lahoutte
- From MEDISIP, Department of Electronics and Information Systems, Ghent University-IBBT-IBiTech, Ghent, Belgium, and Radiology/BEFY, In-Vivo Cellular and Molecular Imaging Center, and Department of Nuclear Medicine, UZ Brussel, Brussels, Belgium
| | - Stefaan Vandenberghe
- From MEDISIP, Department of Electronics and Information Systems, Ghent University-IBBT-IBiTech, Ghent, Belgium, and Radiology/BEFY, In-Vivo Cellular and Molecular Imaging Center, and Department of Nuclear Medicine, UZ Brussel, Brussels, Belgium
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Hupfer M, Kolditz D, Nowak T, Eisa F, Brauweiler R, Kalender WA. Dosimetry concepts for scanner quality assurance and tissue dose assessment in micro-CT. Med Phys 2012; 39:658-70. [DOI: 10.1118/1.3675400] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Willekens I, Buls N, Lahoutte T, Baeyens L, Vanhove C, Caveliers V, Deklerck R, Bossuyt A, de Mey J. Evaluation of the radiation dose in micro-CT with optimization of the scan protocol. CONTRAST MEDIA & MOLECULAR IMAGING 2011; 5:201-7. [PMID: 20665903 DOI: 10.1002/cmmi.394] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
INTRODUCTION Micro-CT provides non-invasive anatomic evaluation of small animals. Serial micro-CT measurements are, however, hampered by the severity of ionizing radiation doses cumulating over the total period of follow-up. The dose levels may be sufficient to influence experimental outcomes such as animal survival or tumor growth. AIM This study was designed to evaluate the radiation dose of micro-CT and to optimize the scanning protocol for longitudinal micro-CT scans. METHODS AND MATERIALS Normal C57Bl/6 mice were euthanized. Radiation exposure was measured using individually calibrated lithium fluoride thermoluminescent dosimeters (TLDs). Thirteen TLDs were placed in the mice at the thyroid, lungs, liver, stomach, colon, bladder and near the spleen. Micro-CT (SkyScan 1178) was performed using two digital X-ray cameras which scanned over 180 degrees at a resolution of 83 microm, a rotation step of 1.08 degrees , 50 kV, 615 microA and 121 s image acquisition time. The TLDs were removed after each scan. CTDI(100) was measured with a 100 mm ionization chamber, centrally positioned in a 2.7 cm diameter water phantom, and rotation steps were increased to reduce both scan time and radiation dose. RESULTS Internal TLD analysis demonstrated median organ dose of 5.5 +/- 0.6 mGy per mA s, confirmed by CTDI(100) with result of 6.6 mGy per mA s. A rotation step of 2.16 resulted in qualitatively accurate images. At a resolution of 83 microm the scan time is reduced to 63 s with an estimated dose of 2.9 mGy per mA s. At 166 microm resolution, the scan time is limited to 27 s, with a concordant dose of 1.2 mGy per mA s. CONCLUSIONS The radiation dose of a standard micro-CT scan is relatively high and could influence the experimental outcome. We believe that the presented adaptation of the scan protocol allows for accurate imaging without the risk of interfering with the experimental outcome of the study.
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Affiliation(s)
- Inneke Willekens
- In Vivo Cellular and Molecular Imaging, ICMI, Vrije Universiteit Brussels, Brussels, Belgium.
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Rodt T, Luepke M, Boehm C, von Falck C, Stamm G, Borlak J, Seifert H, Galanski M. Phantom and cadaver measurements of dose and dose distribution in micro-CT of the chest in mice. Acta Radiol 2011; 52:75-80. [PMID: 21498330 DOI: 10.1258/ar.2010.100059] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
BACKGROUND Micro-computed tomography (CT) allows high-resolution imaging of the chest in mice for small animal research with a significant radiation dose applied. PURPOSE To report on measurement of the applied radiation dose using different scan protocols in micro-CT of the chest in mice. MATERIAL AND METHODS Repetitive dose measurements were performed for four different micro-CT protocols (with/without respiratory gating) and for micro-CT fluoroscopy used for chest imaging. Measurements were carried out using thermoluminescence dosimeters (TLD) in mouse cadavers and in a PMMA phantom allowing measurement of the radiation dose in the direct path of rays and assessment of scattered radiation. RESULTS The dose measured inside and outside the chests of the cadavers varied between 190 und 210 mGy, respectively. The expected mean doses in mice in the direct path of rays for the four examined micro-CT protocols varied between 170 and 280 mGy. The mean values for 1 and 5 minutes of fluoroscopy were 17 mGy and 105 mGy, respectively. CONCLUSION The measured dose values are similar to the dose values for micro-CT of the chest reported so far. A relevant dose can be delivered by micro-CT of the chest, which could possibly interact with small animal studies. Therefore, the applied dose for a specific protocol should be known and adverse radiation effects be considered.
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Affiliation(s)
- Thomas Rodt
- Department of Radiology, Hannover Medical School
- Department of Molecular Medicine and Medical Biotechnology, Fraunhofer Institute for Experimental Medicine
| | - Matthias Luepke
- Institute for General Radiology and Medical Physics; University of Veterinary Medicine Hannover, Hannover, Germany
| | - Claudia Boehm
- Institute for General Radiology and Medical Physics; University of Veterinary Medicine Hannover, Hannover, Germany
| | - Christian von Falck
- Department of Radiology, Hannover Medical School
- Department of Molecular Medicine and Medical Biotechnology, Fraunhofer Institute for Experimental Medicine
| | - Georg Stamm
- Department of Radiology, Hannover Medical School
| | - Jürgen Borlak
- Department of Molecular Medicine and Medical Biotechnology, Fraunhofer Institute for Experimental Medicine
| | - Hermann Seifert
- Institute for General Radiology and Medical Physics; University of Veterinary Medicine Hannover, Hannover, Germany
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Foster WK, Ford NL. Investigating the effect of longitudinal micro-CT imaging on tumour growth in mice. Phys Med Biol 2010; 56:315-26. [PMID: 21160110 DOI: 10.1088/0031-9155/56/2/002] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aim of this study is to determine the impact of longitudinal micro-CT imaging on the growth of B16F1 tumours in C57BL/6 mice. Sixty mice received 2 × 10(5) B16F1 cells subcutaneously in the hind flank and were divided into control (no scan), 'low-dose' (80 kVp, 70 mA, 8 s, 0.07 Gy), 'medium-dose' (80 kVp, 50 mA, 30 s, 0.18 Gy) and 'high-dose' (80 kVp, 50 mA, 50 s, 0.30 Gy) groups. All imaging was performed on a fast volumetric micro-CT scanner (GE Locus Ultra, London, Canada). Each mouse was imaged on days 4, 8, 12 and 16. After the final imaging session, each tumour was excised, weighed on an electronic balance, imaged to obtain the final tumour volume and processed for histology. Final tumour volume was used to evaluate the impact of longitudinal micro-CT imaging on the tumour growth. An ANOVA indicated no statistically significant difference in tumour volume (p = 0.331, α = β = 0.1) when discriminating against a treatment-sized effect. Histological samples revealed no observable differences in apoptosis or cell proliferation. We conclude that four imaging sessions, using standard protocols, over the course of 16 days did not cause significant changes in final tumour volume for B16F1 tumours in female C57BL/6 mice (ANOVA, α = β = 0.1, p = 0.331).
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Affiliation(s)
- W Kyle Foster
- Department of Physics, Ryerson University, Toronto, Ontario M5B 2K3, Canada
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Taschereau R, Silverman RW, Chatziioannou AF. Dual-energy attenuation coefficient decomposition with differential filtration and application to a microCT scanner. Phys Med Biol 2010; 55:1141-55. [PMID: 20107245 DOI: 10.1088/0031-9155/55/4/016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Dual-energy x-ray computed tomography (DECT) has the capability to decompose attenuation coefficients using two basis functions and has proved its potential in reducing beam-hardening artifacts from reconstructed images. The method typically involves two successive scans with different x-ray tube voltage settings. This work proposes an approach to dual-energy imaging through x-ray beam filtration that requires only one scan and a single tube voltage setting. It has been implemented in a preclinical microCT tomograph with minor modifications. Retrofitting of the microCT scanner involved the addition of an automated filter wheel and modifications to the acquisition and reconstruction software. Results show that beam-hardening artifacts are reduced to noise level. Acquisition of a mu-Compton image is well suited for attenuation-correction of PET images while dynamic energy selection (4D viewing) offers flexibility in image viewing by adjusting contrast and noise levels to suit the task at hand. All dual-energy and single energy reference scans were acquired at the same soft tissue dose level of 50 mGy.
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Affiliation(s)
- R Taschereau
- Crump Institute for Molecular Imaging, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA.
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Lederlin M, Ozier A, Montaudon M, Begueret H, Ousova O, Marthan R, Berger P, Laurent F. Airway remodeling in a mouse asthma model assessed by in-vivo respiratory-gated micro-computed tomography. Eur Radiol 2009; 20:128-37. [PMID: 19685058 DOI: 10.1007/s00330-009-1541-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2009] [Revised: 05/27/2009] [Accepted: 07/01/2009] [Indexed: 12/13/2022]
Abstract
The aim of our study was to evaluate the feasibility of non-invasive respiratory-gated micro-computed tomography (micro-CT) for assessment of airway remodelling in a mouse asthma model. Six female BALB/c mice were challenged intranasally with ovalbumin. A control group of six mice received saline inhalation. All mice underwent plethysmographic study and micro-CT. For each mouse, peribronchial attenuation values of 12 bronchi were measured, from which a peribronchial density index (PBDI) was computed. Mice were then sacrificed and lungs examined histologically. Final analysis involved 10 out of 12 mice. Agreement of measurements across observers and over time was very good (intraclass correlation coefficients: 0.94-0.98). There was a significant difference in PBDI between asthmatic and control mice (-210 vs. -338.9 HU, P = 0.008). PBDI values were correlated to bronchial muscle area (r = 0.72, P = 0.018). This study shows that respiratory-gated micro-CT may allow non-invasive monitoring of bronchial remodelling in asthmatic mice and evaluation of innovative treatment effects.
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Affiliation(s)
- Mathieu Lederlin
- Laboratoire de Physiologie Cellulaire Respiratoire, Université Bordeaux 2, Bordeaux, France
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Abstract
Multimodality small-animal molecular imaging has become increasingly important as transgenic and knockout mice are produced to model human diseases. With the ever-increasing number and importance of human disease models, particularly in rodents (mice and rats), the ability of high-resolution multimodality molecular imaging instrumentation to contribute unique information is becoming more common and necessary. Multimodality imaging with high spatial resolution and good sensitivity, which combines modalities and records sequentially or simultaneously complementary information, offers many advantages in certain research experiments. This article discusses the current trends and new horizons in preclinical multimodality imaging in-vivo and its role in biomedical research.
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Affiliation(s)
- David B Stout
- Crump Institute for Molecular Imaging, Department of Molecular and Medical Pharmacology, The David Geffen School of Medicine at UCLA, 570 Westwood Plaza, CNSI Building, Room 2151, Los Angeles, CA 90095, USA
| | - Habib Zaidi
- Division of Nuclear Medicine, Geneva University Hospital, CH-1211 Geneva, Switzerland.
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Schreiber EC, Chang SX. Monte carlo simulation of an X-ray pixel beam microirradiation system. Radiat Res 2009; 171:332-41. [PMID: 19267560 DOI: 10.1667/rr1453.1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Monte Carlo simulations are used in the development of a nanotechnology-based multi-pixel beam array small animal microirradiation system. The microirradiation system uses carbon nanotube field emission technology to generate arrays of individually controllable X-ray pixel beams that electronically form irregular irradiation fields having intensity and temporal modulation without any mechanical motion. The microirradiation system, once developed, will be incorporated with the micro-CT system already developed that is based on the same nanotechnology to form an integrated image-guided and intensity-modulated microirradiation system for high-temporal-resolution small animal research. Prospective microirradiation designs were evaluated based on dosimetry calculated using EGSnrc-based Monte Carlo simulations. Design aspects studied included X-ray anode design, collimator design, and dosimetric considerations such as beam energy, dose rate, inhomogeneity correction, and the microirradiation treatment planning strategies. The dosimetric properties of beam energies between 80-400 kVp with varying filtration were studied, producing a pixel beam dose rate per current of 0.35-13 Gy per min per mA at the microirradiation isocenter. Using opposing multi-pixel-beam array pairs reduces the dose inhomogeneity between adjacent pixel beams to negligible levels near the isocenter and 20% near the mouse surface.
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Affiliation(s)
- E C Schreiber
- Department of Radiation Oncology, University of North Carolina, Chapel Hill, North Carolina 27599, USA.
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Sehmisch S, Dullin C, Zaroban A, Tezval M, Rack T, Schmelz U, Seidlova-Wuttke D, Dunkelberg H, Wuttke W, Marten K, Stuermer KM, Stuermer EK. The use of flat panel volumetric computed tomography (fpVCT) in osteoporosis research. Acad Radiol 2009; 16:394-400. [PMID: 19268850 DOI: 10.1016/j.acra.2008.09.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2008] [Revised: 09/23/2008] [Accepted: 09/24/2008] [Indexed: 11/18/2022]
Abstract
RATIONALE AND OBJECTIVES Improvements in imaging technology have led to the increased use of computed tomography (CT). For example, micro-CT and quantitative CT (QCT) are now often used in osteoporosis research, in which micro-CT is able to analyze small bones or bone samples with high spatial resolution. In contrast, QCT is able to investigate large samples with low spatial resolution. The aim of this study was to test the usefulness of flat-panel volumetric CT (fpVCT) in a rat model of osteopenia. MATERIAL AND METHODS Twenty-two 3-month-old rats underwent ovariectomy and were either left untreated or supplemented with estradiol for 15 weeks. After sacrificing, the rats' second lumbar vertebral body bone mineral density (BMD) was analyzed using fpVCT and ashing. The results were compared to those of a microstructural analysis of the first lumbar vertebrae and a biomechanical evaluation of the fourth lumbar vertebrae. RESULTS BMD measurements using both fpVCT (0.39 vs 0.35 mg/cm(3)) and ashing (0.52 vs 0.48 mg/cm(3)) demonstrated a significant improvement after estradiol supplementation. The correlation coefficient of the two methods was 0.858. After estradiol supplementation, the bone microstructural and bone biomechanical parameters were improved, compared to no treatment. The correlations of both the microstructural and the biomechanical evaluations were closer for BMD measured using fpVCT (r = 0.482-0.769) than on the basis of ashing (r = 0.345-0.573). FpVCT was not able to display the trabecular microstructure of the rat lumbar vertebrae. CONCLUSION The use of fpVCT demonstrated a close relationship between morphologic and biomechanical evaluations in a rat model of osteopenia. Because of its different proportions, fpVCT might be able to bridge the gap between micro-CT and QCT in analyzing larger animals.
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Affiliation(s)
- Stephan Sehmisch
- University of Goettingen, Robert-Koch-Strasse 40, 37075 Goettingen, Germany.
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Figueroa SD, Winkelmann CT, Miller HW, Volkert WA, Hoffman TJ. TLD assessment of mouse dosimetry during microCT imaging. Med Phys 2008; 35:3866-74. [PMID: 18841837 DOI: 10.1118/1.2959847] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Advances in laboratory animal imaging have provided new resources for noninvasive biomedical research. Among these technologies is microcomputed tomography (microCT) which is widely used to obtain high resolution anatomic images of small animals. Because microCT utilizes ionizing radiation for image formation, radiation exposure during imaging is a concern. The objective of this study was to quantify the radiation dose delivered during a standard microCT scan. Radiation dose was measured using thermoluminescent dosimeters (TLDs), which were irradiated employing an 80 kVp x-ray source, with 0.5 mm A1 filtration and a total of 54 mA s for a full 360 deg rotation of the unit. The TLD data were validated using a 3.2 cm3 CT ion chamber probe. TLD results showed a single microCT scan air kerma of 78.0 +/- 5.0 mGy when using a poly(methylmethacrylate) (PMMA) anesthesia support module and an air kerma of 92.0 +/- 6.0 mGy without the use of the anesthesia module. The validation CT ion chamber study provided a measured radiation air kerma of 81.0 +/- 4.0 mGy and 97.0 +/- 5.0 mGy with and without the PMMA anesthesia module, respectively. Internal TLD analysis demonstrated an average mouse organ radiation absorbed dose of 76.0 +/- 5.0 mGy. The author's results have defined x-ray exposure for a routine microCT study which must be taken into consideration when performing serial molecular imaging studies involving the microCT imaging modality.
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Kim HW, Cai QY, Jun HY, Chon KS, Park SH, Byun SJ, Lee MS, Oh JM, Kim HS, Yoon KH. Micro-CT imaging with a hepatocyte-selective contrast agent for detecting liver metastasis in living mice. Acad Radiol 2008; 15:1282-90. [PMID: 18790400 DOI: 10.1016/j.acra.2008.03.021] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2008] [Revised: 03/17/2008] [Accepted: 03/19/2008] [Indexed: 11/25/2022]
Abstract
RATIONALE AND OBJECTIVES Micro-computed tomography (CT) is a important tool for longitudinal imaging of tumor development. The detection and monitoring of tumors in the liver in live animals using micro-CT is challenging. We evaluated the feasibility of high-resolution micro-CT enhanced with a hepatocyte-selective contrast agent for detecting liver metastases in a live murine model. MATERIALS AND METHODS Hepatic metastases were induced in 10 BALB/C mice. Two mice each were randomly selected on days 3, 5, 7, 10, and 13 after CT26 colon adenocarcinoma cells were injected into the portal vein; micro-CT imaging was performed at 10 minutes and 4 hours after intravenous administration of a hepatocyte-selective contrast agent at a dose of 0.4 mL/mouse. The attenuation values of the normal liver and the tumors were obtained. The number of metastases was counted and their sizes were measured on the micro-CT images. Gross or histopathologic evaluation was performed for correlating the liver tumors with the micro-CT images. RESULTS A total of 74 separate tumor sites larger than 300 microm in diameter were detected on pathologic examination of the mice that were sacrificed 7 days after cell injection. On micro-CT, 66 of 74 tumors were detected (83.8%). The smallest tumor detected on micro-CT was 300 microm. There were eight false-negative readings on micro-CT. The sizes of the individual liver metastases measured by micro-CT and on the excised specimen were highly correlated (P < .001). The correlation between the CT scan measurement and the actual measurement was r = 0.8354 (P < .0001). CONCLUSIONS High-resolution micro-CT enhanced with a hepatocyte-selective contrast agent can be a promising tool for detecting liver metastases in a live murine model.
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Morphologic changes of mammary carcinomas in mice over time as monitored by flat-panel detector volume computed tomography. Neoplasia 2008; 10:663-73. [PMID: 18592006 DOI: 10.1593/neo.08270] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2008] [Revised: 04/10/2008] [Accepted: 04/11/2008] [Indexed: 11/18/2022] Open
Abstract
Noninvasive methods are strongly needed to detect and quantify not only tumor growth in murine tumor models but also the development of vascularization and necrosis within tumors. This study investigates the use of a new imaging technique, flat-panel detector volume computed tomography (fpVCT), to monitor in vivo tumor progression and structural changes within tumors of two murine carcinoma models. After tumor cell inoculation, single fpVCT scans of the entire mice were performed at different time points. The acquired isotropic, high-resolution volume data sets enable an accurate real-time assessment and precise measurements of tumor volumes. Spreading of contrast agent-containing blood vessels around and within the tumors was clearly visible over time. Furthermore, fpVCT permits the identification of differences in the uptake of contrast media within tumors, thus delineating necrosis, tumor tissues, and blood vessels. Classification of tumor tissues based on the decomposition of the underlying mixture distribution of tissue-related Hounsfield units allowed the quantitative acquisition of necrotic tissues at each time point. Morphologic alterations of the tumor depicted by fpVCT were confirmed by histopathologic examination. Concluding, our data show that fpVCT may be highly suitable for the noninvasive evaluation of tumor responses to anticancer therapies during the course of the disease.
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Abstract
PURPOSE We report here on a technique to implement high-resolution objects with voxels having variable dimensions (compressed) for the reduction of memory and central processing unit (CPU) requirements in Monte Carlo simulations. The technique, which was implemented in GATE, the GEANT4 application for positron emission tomography/single photon emission computed tomography (PET/SPECT) imaging simulations, was developed in response to our need for realistic high-resolution phantoms for dosimetry calculations. PROCEDURES A compression algorithm similar to run-length encoding for one-dimensional data streams, was used to fuse together adjacent voxels with identical physical properties. The algorithm was verified by conducting dosimetric calculations and imaging experiments on compressed and uncompressed phantoms. RESULTS Depending on the initial phantom size and composition, compression ratios of up to 99.9% were achieved allowing memory and CPU reductions of up to 85% and 70%, respectively. The output of the simulations was consistent with respect to the goals for each type of simulation performed (dosimetry and imaging). CONCLUSIONS The implementation of compressed voxels in GATE allows for significant memory and CPU reduction and is suitable for dosimetry as well as for imaging experiments.
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Affiliation(s)
- Richard Taschereau
- Department of Molecular and Medical Pharmacology, Crump Institute for Molecular Imaging, The David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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