1
|
Biglin ER, Aitkenhead AH, Price GJ, Chadwick AL, Santina E, Williams KJ, Kirkby KJ. A preclinical radiotherapy dosimetry audit using a realistic 3D printed murine phantom. Sci Rep 2022; 12:6826. [PMID: 35474242 PMCID: PMC9042835 DOI: 10.1038/s41598-022-10895-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Accepted: 04/05/2022] [Indexed: 11/08/2022] Open
Abstract
Preclinical radiation research lacks standardized dosimetry procedures that provide traceability to a primary standard. Consequently, ensuring accuracy and reproducibility between studies is challenging. Using 3D printed murine phantoms we undertook a dosimetry audit of Xstrahl Small Animal Radiation Research Platforms (SARRPs) installed at 7 UK centres. The geometrically realistic phantom accommodated alanine pellets and Gafchromic EBT3 film for simultaneous measurement of the dose delivered and the dose distribution within a 2D plane, respectively. Two irradiation scenarios were developed: (1) a 10 × 10 mm2 static field targeting the pelvis, and (2) a 5 × 5 mm2 90° arc targeting the brain. For static fields, the absolute difference between the planned dose and alanine measurement across all centres was 4.1 ± 4.3% (mean ± standard deviation), with an overall range of - 2.3 to 10.5%. For arc fields, the difference was - 1.2% ± 6.1%, with a range of - 13.1 to 7.7%. EBT3 dose measurements were greater than alanine by 2.0 ± 2.5% and 3.5 ± 6.0% (mean ± standard deviation) for the static and arc fields, respectively. 2D dose distributions showed discrepancies to the planned dose at the field edges. The audit demonstrates that further work on preclinical radiotherapy quality assurance processes is merited.
Collapse
Affiliation(s)
- Emma R Biglin
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3rd floor Proton Beam Therapy Centre, Oak Road, Manchester, M20 4BX, UK.
| | - Adam H Aitkenhead
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3rd floor Proton Beam Therapy Centre, Oak Road, Manchester, M20 4BX, UK
- Christie Medical Physics and Engineering, The Christie NHS Foundation Trust, Manchester, UK
| | - Gareth J Price
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3rd floor Proton Beam Therapy Centre, Oak Road, Manchester, M20 4BX, UK
- The Christie NHS Foundation Trust, Manchester, UK
| | - Amy L Chadwick
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3rd floor Proton Beam Therapy Centre, Oak Road, Manchester, M20 4BX, UK
- The Christie NHS Foundation Trust, Manchester, UK
| | - Elham Santina
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3rd floor Proton Beam Therapy Centre, Oak Road, Manchester, M20 4BX, UK
- The Christie NHS Foundation Trust, Manchester, UK
| | - Kaye J Williams
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Karen J Kirkby
- Division of Cancer Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, 3rd floor Proton Beam Therapy Centre, Oak Road, Manchester, M20 4BX, UK
- The Christie NHS Foundation Trust, Manchester, UK
| |
Collapse
|
2
|
Sun H, Lu Z, Fan R, Xiong W, Xie K, Ni X, Yang J. Research on obtaining pseudo CT images based on stacked generative adversarial network. Quant Imaging Med Surg 2021; 11:1983-2000. [PMID: 33936980 DOI: 10.21037/qims-20-1019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background To investigate the feasibility of using a stacked generative adversarial network (sGAN) to synthesize pseudo computed tomography (CT) images based on ultrasound (US) images. Methods The pre-radiotherapy US and CT images of 75 patients with cervical cancer were selected for the training set of pseudo-image synthesis. In the first stage, labeled US images were used as the first conditional GAN input to obtain low-resolution pseudo CT images, and in the second stage, a super-resolution reconstruction GAN was used. The pseudo CT image obtained in the first stage was used as an input, following which a high-resolution pseudo CT image with clear texture and accurate grayscale information was obtained. Five cross validation tests were performed to verify our model. The mean absolute error (MAE) was used to compare each pseudo CT with the same patient's real CT image. Also, another 10 cases of patients with cervical cancer, before radiotherapy, were selected for testing, and the pseudo CT image obtained using the neural style transfer (NSF) and CycleGAN methods were compared with that obtained using the sGAN method proposed in this study. Finally, the dosimetric accuracy of pseudo CT images was verified by phantom experiments. Results The MAE metric values between the pseudo CT obtained based on sGAN, and the real CT in five-fold cross validation are 66.82±1.59 HU, 66.36±1.85 HU, 67.26±2.37 HU, 66.34±1.75 HU, and 67.22±1.30 HU, respectively. The results of the metrics, namely, normalized mutual information (NMI), structural similarity index (SSIM), and peak signal-to-noise ratio (PSNR), between the pseudo CT images obtained using the sGAN method and the ground truth CT (CTgt) images were compared with those of the other two methods via the paired t-test, and the differences were statistically significant. The dice similarity coefficient (DSC) measurement results showed that the pseudo CT images obtained using the sGAN method were more similar to the CTgt images of organs at risk. The dosimetric phantom experiments also showed that the dose distribution between the pseudo CT images synthesized by the new method was similar to that of the CTgt images. Conclusions Compared with NSF and CycleGAN methods, the sGAN method can obtain more accurate pseudo CT images, thereby providing a new method for image guidance in radiotherapy for cervical cancer.
Collapse
Affiliation(s)
- Hongfei Sun
- School of Automation, Northwestern Polytechnical University, Xi'an, China
| | - Zhengda Lu
- Department of Radiotherapy, Second People's Hospital of Changzhou, Nanjing Medical University, Changzhou, China.,The Center of Medical Physics, Nanjing Medical University, Changzhou, China.,The Key Laboratory of Medical Physics, Changzhou, China
| | - Rongbo Fan
- School of Automation, Northwestern Polytechnical University, Xi'an, China
| | - Wenjun Xiong
- School of Automation, Northwestern Polytechnical University, Xi'an, China
| | - Kai Xie
- Department of Radiotherapy, Second People's Hospital of Changzhou, Nanjing Medical University, Changzhou, China.,The Center of Medical Physics, Nanjing Medical University, Changzhou, China.,The Key Laboratory of Medical Physics, Changzhou, China
| | - Xinye Ni
- Department of Radiotherapy, Second People's Hospital of Changzhou, Nanjing Medical University, Changzhou, China.,The Center of Medical Physics, Nanjing Medical University, Changzhou, China.,The Key Laboratory of Medical Physics, Changzhou, China
| | - Jianhua Yang
- School of Automation, Northwestern Polytechnical University, Xi'an, China
| |
Collapse
|
3
|
Olaciregui-Ruiz I, Beddar S, Greer P, Jornet N, McCurdy B, Paiva-Fonseca G, Mijnheer B, Verhaegen F. In vivo dosimetry in external beam photon radiotherapy: Requirements and future directions for research, development, and clinical practice. Phys Imaging Radiat Oncol 2020; 15:108-116. [PMID: 33458335 PMCID: PMC7807612 DOI: 10.1016/j.phro.2020.08.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 08/17/2020] [Accepted: 08/18/2020] [Indexed: 11/18/2022] Open
Abstract
External beam radiotherapy with photon beams is a highly accurate treatment modality, but requires extensive quality assurance programs to confirm that radiation therapy will be or was administered appropriately. In vivo dosimetry (IVD) is an essential element of modern radiation therapy because it provides the ability to catch treatment delivery errors, assist in treatment adaptation, and record the actual dose delivered to the patient. However, for various reasons, its clinical implementation has been slow and limited. The purpose of this report is to stimulate the wider use of IVD for external beam radiotherapy, and in particular of systems using electronic portal imaging devices (EPIDs). After documenting the current IVD methods, this report provides detailed software, hardware and system requirements for in vivo EPID dosimetry systems in order to help in bridging the current vendor-user gap. The report also outlines directions for further development and research. In vivo EPID dosimetry vendors, in collaboration with users across multiple institutions, are requested to improve the understanding and reduce the uncertainties of the system and to help in the determination of optimal action limits for error detection. Finally, the report recommends that automation of all aspects of IVD is needed to help facilitate clinical adoption, including automation of image acquisition, analysis, result interpretation, and reporting/documentation. With the guidance of this report, it is hoped that widespread clinical use of IVD will be significantly accelerated.
Collapse
Affiliation(s)
- Igor Olaciregui-Ruiz
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Sam Beddar
- Division of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Peter Greer
- Calvary Mater Newcastle Hospital and University of Newcastle, Newcastle, New South Wales, Australia
| | - Nuria Jornet
- Servei de Radiofísica i Radioprotecció, Hospital de la Santa Creu i Sant Pau, Barcelona, Spain
| | - Boyd McCurdy
- Medical Physics Department, CancerCare Manitoba, Winnipeg, Manitoba, Canada
| | - Gabriel Paiva-Fonseca
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, the Netherlands
| | - Ben Mijnheer
- Department of Radiation Oncology, Netherlands Cancer Institute, Amsterdam, the Netherlands
| | - Frank Verhaegen
- Department of Radiation Oncology (Maastro), GROW School for Oncology, Maastricht University Medical Centre+, Maastricht, the Netherlands
| |
Collapse
|
4
|
Spinelli AE, D'Agostino E, Broggi S, Claudio F, Boschi F. Small animal irradiator dose distribution verification using radioluminescence imaging. JOURNAL OF BIOPHOTONICS 2020; 13:e201960217. [PMID: 32163229 DOI: 10.1002/jbio.201960217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 02/05/2020] [Accepted: 03/08/2020] [Indexed: 06/10/2023]
Abstract
The main objective of this work was the development of a novel 2D dosimetry approach for small animal external radiotherapy using radioluminescence imaging (RLI) with a commercial complementary metal oxide semiconductor detector. Measurements of RLI were performed on the small animal image-guided platform SmART, RLI data were corrected for perspective distortion using Matlab. Four irradiation fields were tested and the planar 2D dose distributions and dose profiles were compared against dose calculations performed with a Monte Carlo based treatment planning system and gafchromic film. System linearity and RLI image noise against dose were also measured. The maximum difference between beam size measured with RLI and nominal beam size was less than 8% for all the tested beams. The image correction procedure was able to reduce perspective distortion. A novel RLI approach for quality assurance of a small animal irradiator was presented and tested. Results are in agreement with MC dose calculations and gafchromic film measurements.
Collapse
Affiliation(s)
| | | | - Sara Broggi
- Medical Physics Department, San Raffaele Scientific Institute, Italy
| | - Fiorino Claudio
- Medical Physics Department, San Raffaele Scientific Institute, Italy
| | | |
Collapse
|
5
|
Mahmood J, Pandita R, Zhang A, Kamlapurkar S, Saeed A, Chen M, Staats PN, Shukla HD, Anvari A, Sawant A, Vujaskovic Z. RhoA/ROCK pathway inhibitor ameliorates erectile dysfunction induced by radiation therapy in rats. Radiother Oncol 2020; 150:174-180. [PMID: 32565390 DOI: 10.1016/j.radonc.2020.06.021] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Revised: 06/11/2020] [Accepted: 06/12/2020] [Indexed: 10/24/2022]
Abstract
OBJECTIVES Prostate cancer (PCa) treatment with radiation therapy (RT) has an excellent cure rate. However, Radiation-induced Erectile Dysfunction (RiED) is a common and irreversible toxicity impacting quality of life, and there is no FDA approved specific drug for RiED. We previously showed that prostate RT increased RhoA/ROCK signaling in the cavernous nerve (CN) and penile tissues, which may lead to RiED in rats. In this study, we investigated whether RhoA/ROCK pathway inhibition by a specific inhibitor called Hydroxyfasudil (HF) can improve RiED in our well-established rat model. MATERIALS/METHODS Male Sprague-Dawley rats were randomized to the following groups: sham-RT, HF-only, RT-only, and RT + HF. Rats were either exposed to a single dose of 25 Gy prostate-confined RT or a sham procedure. 10 mg/kg HF or normal saline was injected intraperitoneally. Erectile function was evaluated by intracavernosal pressure (ICP) and mean arterial pressure (MAP) measurements at week 14 post-RT. Cavernous nerve (CN) injury was evaluated by transmission electron microscopy (TEM), and penile tissue fibrosis by Masson trichrome staining (MT). RESULTS We have found that the HF treatment prior to RT showed significant (p < 0.001) improvement in ICP/MAP ratio, area under the curve, and maximum ICP value, compared to RT-alone rats. Furthermore, RT + HF treated rats exhibited increased CN myelination and decreased axonal atrophy, comparted to RT-only. HF treatment showed significantly decreased penile tissue fibrosis (p < 0.05) compared to RT-alone treated rats. CONCLUSION Our results provide the first preclinical evidence that targeting RhoA/ROCK pathway by HF may provide a novel therapeutic option for the treatment of RiED.
Collapse
Affiliation(s)
- Javed Mahmood
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA.
| | - Ravina Pandita
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Angel Zhang
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Shriya Kamlapurkar
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Ali Saeed
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Minjie Chen
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Paul N Staats
- Department of Pathology, University of Maryland School of Medicine, Baltimore, USA
| | - Hem D Shukla
- Department of Neurology and Neurosurgery, Johns Hopkins University, School of Medicine, Baltimore, USA
| | - Akbar Anvari
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Amit Sawant
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| | - Zeljko Vujaskovic
- Division of Translational Radiation Sciences (DTRS), Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, USA
| |
Collapse
|
6
|
Anvari A, Modiri A, Pandita R, Mahmood J, Sawant A. Online dose delivery verification in small animal image‐guided radiotherapy. Med Phys 2020; 47:1871-1879. [DOI: 10.1002/mp.14070] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2019] [Revised: 01/27/2020] [Accepted: 01/28/2020] [Indexed: 11/11/2022] Open
Affiliation(s)
- Akbar Anvari
- Department of Radiation Oncology University of Maryland School of Medicine Baltimore MD 21201USA
- Department of Radiation Oncology Perelman Center for Advanced Medicine University of Pennsylvania Philadelphia PA 19104USA
| | - Arezoo Modiri
- Department of Radiation Oncology University of Maryland School of Medicine Baltimore MD 21201USA
| | - Ravina Pandita
- Department of Radiation Oncology University of Maryland School of Medicine Baltimore MD 21201USA
| | - Javed Mahmood
- Department of Radiation Oncology University of Maryland School of Medicine Baltimore MD 21201USA
| | - Amit Sawant
- Department of Radiation Oncology University of Maryland School of Medicine Baltimore MD 21201USA
| |
Collapse
|
7
|
Poirier Y, Johnstone CD, Anvari A, Brodin NP, Santos MD, Bazalova-Carter M, Sawant A. A failure modes and effects analysis quality management framework for image-guided small animal irradiators: A change in paradigm for radiation biology. Med Phys 2020; 47:2013-2022. [PMID: 31986221 DOI: 10.1002/mp.14049] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2019] [Revised: 12/17/2019] [Accepted: 01/10/2020] [Indexed: 12/28/2022] Open
Abstract
PURPOSE Image-guided small animal irradiators (IGSAI) are increasingly being adopted in radiation biology research. These animal irradiators, designed to deliver radiation with submillimeter accuracy, exhibit complexity similar to that of clinical radiation delivery systems, including image guidance, robotic stage motion, and treatment planning systems. However, physics expertise and resources are scarcer in radiation biology, which makes implementation of conventional prescriptive QA infeasible. In this study, we apply the failure modes and effect analysis (FMEA) popularized by the AAPM task group 100 (TG-100) report to IGSAI and radiation biological research. METHODS Radiation biological research requires a change in paradigm where small errors to large populations of animals are more severe than grievous errors that only affect individuals. To this end, we created a new adverse effects severity table adapted to radiation biology research based on the original AAPM TG-100 severity table. We also produced a process tree which outlines the main components of radiation biology studies performed on an IGSAI, adapted from the original clinical IMRT process tree from TG-100. Using this process tree, we created and distributed a preliminary survey to eight expert IGSAI operators in four institutions. Operators rated proposed failure modes for occurrence, severity, and lack of detectability, and were invited to share their own experienced failure modes. Risk probability numbers (RPN) were calculated and used to identify the failure modes which most urgently require intervention. RESULTS Surveyed operators indicated a number of high (RPN >125) failure modes specific to small animal irradiators. Errors due to equipment breakdown, such as loss of anesthesia or thermal control, received relatively low RPN (12-48) while errors related to the delivery of radiation dose received relatively high RPN (72-360). Errors identified could either be improved by manufacturer intervention (e.g., electronic interlocks for filter/collimator) or physics oversight (errors related to tube calibration or treatment planning system commissioning). Operators identified a number of failure modes including collision between the collimator and the stage, misalignment between imaging and treatment isocenter, inaccurate robotic stage homing/translation, and incorrect SSD applied to hand calculations. These were all relatively highly rated (90-192), indicating a possible bias in operators towards reporting high RPN failure modes. CONCLUSIONS The first FMEA specific to radiation biology research was applied to image-guided small animal irradiators following the TG-100 methodology. A new adverse effects severity table and a process tree recognizing the need for a new paradigm were produced, which will be of great use to future investigators wishing to pursue FMEA in radiation biology research. Future work will focus on expanding scope of user surveys to users of all commercial IGSAI and collaborating with manufacturers to increase the breadth of surveyed expert operators.
Collapse
Affiliation(s)
- Yannick Poirier
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Christopher Daniel Johnstone
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA.,Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
| | - Akbar Anvari
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA
| | - N Patrik Brodin
- Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine, Bronx, NY, USA
| | - Morgane Dos Santos
- Service de Recherche en Radiobiologie et en Médecine régénérative, Laboratoire de Radiobiologie des expositions Accidentelles, Institut de Radioprotection et de Sûreté Nucléaire (IRSN), Fontenay-aux-Roses, France
| | | | - Amit Sawant
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, USA
| |
Collapse
|
8
|
Soultanidis G, Subiel A, Renard I, Reinhart AM, Green VL, Oelfke U, Archibald SJ, Greenman J, Tulk A, Walker A, Schettino G, Cawthorne CJ. Development of an anatomically correct mouse phantom for dosimetry measurement in small animal radiotherapy research. Phys Med Biol 2019; 64:12NT02. [PMID: 31082807 DOI: 10.1088/1361-6560/ab215b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Significant improvements in radiotherapy are likely to come from biological rather than technical optimization, for example increasing tumour radiosensitivity via combination with targeted therapies. Such paradigms must first be evaluated in preclinical models for efficacy, and recent advances in small animal radiotherapy research platforms allow advanced irradiation protocols, similar to those used clinically, to be carried out in orthotopic models. Dose assessment in such systems is complex however, and a lack of established tools and methodologies for traceable and accurate dosimetry is currently limiting the capabilities of such platforms and slowing the clinical uptake of new approaches. Here we report the creation of an anatomically correct phantom, fabricated from materials with tissue-equivalent electron density, into which dosimetry detectors can be incorporated for measurement as part of quality control (QC). The phantom also allows training in preclinical radiotherapy planning and cross-institution validation of dose delivery protocols for small animal radiotherapy platforms without the need to sacrifice animals, with high reproducibility. Mouse CT data was acquired and segmented into soft tissue, bone and lung. The skeleton was fabricated using 3D printing, whilst lung was created using computer numerical control (CNC) milling. Skeleton and lung were then set into a surface-rendered mould and soft tissue material added to create a whole-body phantom. Materials for fabrication were characterized for atomic composition and attenuation for x-ray energies typically found in small animal irradiators. Finally cores were CNC milled to allow intracranial incorporation of bespoke detectors (alanine pellets) for dosimetry measurement.
Collapse
Affiliation(s)
- George Soultanidis
- Department of Biomedical Sciences, University of Hull, Hull, United Kingdom. Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, New York, NY, United States of America
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Anvari A, Poirier Y, Sawant A. A comprehensive geometric quality assurance framework for preclinical microirradiators. Med Phys 2019; 46:1840-1851. [PMID: 30656713 DOI: 10.1002/mp.13387] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2018] [Revised: 12/21/2018] [Accepted: 01/07/2019] [Indexed: 11/12/2022] Open
Abstract
PURPOSE The mechanical and geometric accuracy of small animal image-guided radiotherapy (SA-IGRT) systems is critical and is affected by a number of system-related factors. Because of the small dimensions involved in preclinical radiotherapy research, such factors can individually and/or cumulatively contribute to significant errors in the small animal radiation research. In this study, we developed and implemented a comprehensive quality assurance (QA) framework for characterizing the mechanical and geometric constancy and accuracy of the small animal radiation research platform (SARRP) system. METHODS We quantified the accuracy of gantry and stage rotation isocentricity and positional stage translations. We determined the accuracy and symmetry of field sizes formed by collimators. We evaluated collimator assembly system performance by characterization of collimator axis alignment along the beam axis during gantry rotation. Furthermore, we quantified the end-to-end precision and accuracy of image-guided delivery by examining the congruence of intended (e.g., imaging) and actual delivery (measured during experiment) isocenters. RESULTS The fine and broad beams showed different central axes. The center of the beam was offset toward the cathode (0.22 ± 0.05 mm) when switching the beam from a fine to a broad focus. Larger (custom-made) collimators were more symmetrically centered than smaller (standard) collimators. The field formed by a 1-mm circular collimator was found to deviate from the circular shape, measuring 1.55 mm and 1.25 mm in the X and Y directions, respectively. The 40-mm collimator showed a field that was 1.65 (4.13%) and 1.3 (3.25%) mm smaller than nominal values in the X and Y directions, respectively, and the 30-mm collimator field was smaller by 0.75 mm (2.5%) in the X direction. Results showed that fields formed by other collimators were accurate in both directions and had ≤2% error. The size of the gantry rotation isocenter was 1.45 ± 0.15 mm. While the gantry rotated, lateral and longitudinal isocenter displacements ranged from 0 to -0.34 and -0.44 to 0.33 mm, respectively. Maximum lateral and longitudinal displacements were found at obliques gantry angles of -135° and 45°, respectively. The stage translational accuracies were 0.015, 0.010, and 0 mm in the X, Y, and Z directions, respectively. The size of the stage rotation runout was 2.73 ± 0.3 mm. Maximum displacements of the stage rotational axis were -0.38 (X direction) and -0.26 (Y direction) mm at stage angles of -45° and -135°, respectively. We found that displacements of intended and actual delivery isocenters were 0.24 ± 0.10, 0.12 ± 0.62, and 0.12 ± 0.42 mm in the X, Y, and Z directions, respectively. CONCLUSION We used the SARRP built-in electronic portal imaging device (EPID) to perform most of the geometric QA tests, demonstrating the utility of the EPID for characterizing the geometric accuracy and precision of the SA-IGRT system. However, in principle, the methodology and tests developed here are applicable to any digital imaging detector available in SA-IGRT systems or film. The flexibility of film allows these tests to be adapted for QA of non-IGRT, cabinet irradiators, which make up many of preclinical small animal irradiators.
Collapse
Affiliation(s)
- Akbar Anvari
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Yannick Poirier
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| | - Amit Sawant
- Department of Radiation Oncology, University of Maryland School of Medicine, Baltimore, MD, 21201, USA
| |
Collapse
|