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Mirshahvalad SA, Farag A, Thiessen J, Wong R, Veit-Haibach P. Current Applications of PET/MR: Part I: Technical Basics and Preclinical/Clinical Applications. Can Assoc Radiol J 2024:8465371241255903. [PMID: 38813998 DOI: 10.1177/08465371241255903] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/31/2024] Open
Abstract
Positron emission tomography/magnetic resonance (PET/MR) imaging has gone through major hardware improvements in recent years, making it a reliable state-of-the-art hybrid modality in clinical practice. At the same time, image reconstruction, attenuation correction, and motion correction algorithms have significantly evolved to provide high-quality images. Part I of the current review discusses technical basics, pre-clinical applications, and clinical applications of PET/MR in radiation oncology and head and neck imaging. PET/MR offers a broad range of advantages in preclinical and clinical imaging. In the preclinic, small and large animal-dedicated devices were developed, making PET/MR capable of delivering new insight into animal models in diseases and facilitating the development of methods that inform clinical PET/MR. Regarding PET/MR's clinical applications in radiation medicine, PET and MR already play crucial roles in the radiotherapy process. Their combination is particularly significant as it can provide molecular and morphological characteristics that are not achievable with other modalities. In addition, the integration of PET/MR information for therapy planning with linear accelerators is expected to provide potentially unique biomarkers for treatment guidance. Furthermore, in clinical applications in the head and neck region, it has been shown that PET/MR can be an accurate modality in head and neck malignancies for staging and resectability assessment. Also, it can play a crucial role in diagnosing residual or recurrent diseases, reliably distinguishing from oedema and fibrosis. PET/MR can furthermore help with tumour characterization and patient prognostication. Lastly, in head and neck carcinoma of unknown origin, PET/MR, with its diagnostic potential, may obviate multiple imaging sessions in the near future.
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Affiliation(s)
- Seyed Ali Mirshahvalad
- University Medical Imaging Toronto, Toronto Joint Department Medical Imaging, University Health Network, Sinai Health System, Women's College Hospital, University of Toronto, Toronto, ON, Canada
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
| | - Adam Farag
- University Medical Imaging Toronto, Toronto Joint Department Medical Imaging, University Health Network, Sinai Health System, Women's College Hospital, University of Toronto, Toronto, ON, Canada
| | - Jonathan Thiessen
- Imaging Program, Lawson Health Research Institute, London, ON, Canada
- Medical Biophysics, Medical Imaging, Western University, London, ON, Canada
| | - Rebecca Wong
- Department of Radiation Oncology, Princess Margaret Cancer Centre, University Health Network, University of Toronto, Toronto, ON, Canada
| | - Patrick Veit-Haibach
- University Medical Imaging Toronto, Toronto Joint Department Medical Imaging, University Health Network, Sinai Health System, Women's College Hospital, University of Toronto, Toronto, ON, Canada
- Department of Medical Imaging, University of Toronto, Toronto, ON, Canada
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Yan Q, Yan X, Yang X, Li S, Song J. The use of PET/MRI in radiotherapy. Insights Imaging 2024; 15:63. [PMID: 38411742 PMCID: PMC10899128 DOI: 10.1186/s13244-024-01627-6] [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: 09/19/2023] [Accepted: 01/21/2024] [Indexed: 02/28/2024] Open
Abstract
Positron emission tomography/magnetic resonance imaging (PET/MRI) is a hybrid imaging technique that quantitatively combines the metabolic and functional data from positron emission tomography (PET) with anatomical and physiological information from MRI. As PET/MRI technology has advanced, its applications in cancer care have expanded. Recent studies have demonstrated that PET/MRI provides unique advantages in the field of radiotherapy and has become invaluable in guiding precision radiotherapy techniques. This review discusses the rationale and clinical evidence supporting the use of PET/MRI for radiation positioning, target delineation, efficacy evaluation, and patient surveillance.Critical relevance statement This article critically assesses the transformative role of PET/MRI in advancing precision radiotherapy, providing essential insights into improved radiation positioning, target delineation, efficacy evaluation, and patient surveillance in clinical radiology practice.Key points• The emergence of PET/MRI will be a key bridge for precise radiotherapy.• PET/MRI has unique advantages in the whole process of radiotherapy.• New tracers and nanoparticle probes will broaden the use of PET/MRI in radiation.• PET/MRI will be utilized more frequently for radiotherapy.
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Affiliation(s)
- Qi Yan
- Cancer Center, Third Hospital of Shanxi Medical University, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences Tongji Shanxi Hospital, Taiyuan, China
| | - Xia Yan
- Cancer Center, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University, Taiyuan, China
- Shanxi Provincial Key Laboratory for Translational Nuclear Medicine and Precision Protection, Taiyuan, China
| | - Xin Yang
- Cancer Center, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences, Tongji Shanxi Hospital, Third Hospital of Shanxi Medical University, Taiyuan, China
| | - Sijin Li
- Department of Nuclear Medicine, First Hospital of Shanxi Medical University, Shanxi Medical University, Taiyuan, China.
| | - Jianbo Song
- Cancer Center, Third Hospital of Shanxi Medical University, Shanxi Bethune Hospital, Shanxi Academy of Medical Sciences Tongji Shanxi Hospital, Taiyuan, China.
- Shanxi Provincial Key Laboratory for Translational Nuclear Medicine and Precision Protection, Taiyuan, China.
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Choi CH, Felder J, Lerche C, Shah NJ. MRI Coil Development Strategies for Hybrid MR-PET Systems: A Review. IEEE Rev Biomed Eng 2024; 17:342-350. [PMID: 37015609 DOI: 10.1109/rbme.2022.3227337] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Simultaneously operating MR-PET systems have the potential to provide synergetic multi-parametric information, and, as such, interest surrounding their use and development is increasing. However, despite the potential advantages offered by fully combined MR-PET systems, implementing this hybrid integration is technically laborious, and any factors degrading the quality of either modality must be circumvented to ensure optimal performance. In order to attain the best possible quality from both systems, most full MR-PET integrations tend to place the shielded PET system inside the MRI system, close to the target volume of the subject. The radiofrequency (RF) coil used in MRI systems is a key factor in determining the quality of the MR images, and, in simultaneous acquisition, it is generally positioned inside the PET system and PET imaging region, potentially resulting in attenuation and artefacts in the PET images. Therefore, when designing hybrid MR-PET systems, it is imperative that consideration be given to the RF coils inside the PET system. In this review, we present current state-of-the-art RF coil designs used for hybrid MR-PET experiments and discuss various design strategies for constructing PET transparent RF coils.
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Aizaz M, van der Pol JAJ, Wierts R, Zwart H, van der Werf AJ, Wildberger JE, Bucerius JA, Moonen RPM, Kooi ME. Evaluation of a Dedicated Radiofrequency Carotid PET/MRI Coil. J Clin Med 2022; 11:jcm11092569. [PMID: 35566694 PMCID: PMC9101928 DOI: 10.3390/jcm11092569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 04/27/2022] [Accepted: 05/02/2022] [Indexed: 01/25/2023] Open
Abstract
Carotid radiofrequency coils inside a PET/MRI system can result in PET quantification errors. We compared the performance of a dedicated PET/MRI carotid coil against a coil for MRI-only use. An 18F-fluorodeoxyglucose (18F-FDG) phantom was scanned without and with an MRI-only coil and with the PET/MRI coil. The decay-corrected normalized activity was compared for the different coil configurations. Eighteen patients were scanned with the three coil configurations. The maximal standardized uptake values (SUVmax) and signal-to-noise ratios (SNR) were calculated. Repeated measures ANOVA was performed to assess the differences in SUVmax and SNR between the coil configurations. In the phantom study, the PET/MRI coil demonstrated a slight decrease (<5%), while the MRI-only coil showed a substantial decrease (up to 10%) in normalized activity at the position of coil elements compared to no dedicated coil configuration. In the patient study, the SUVmax values for both no surface coil (3.59 ± 0.15) and PET/MRI coil (3.54 ± 0.15) were significantly higher (p = 0.03 and p = 0.04, respectively) as compared to the MRI-only coil (3.28 ± 0.16). No significant difference was observed between PET/MRI and no surface coil (p = 1.0). The SNR values for both PET/MRI (7.31 ± 0.44) and MRI-only (7.62 ± 0.42) configurations demonstrated significantly higher (p < 0.001) SNR values as compared to the no surface coil (3.78 ± 0.22), while no significant difference was observed in SNR between the PET/MRI and MRI-only coil (p = 1.0). This study demonstrated that the PET/MRI coil can be used for PET imaging without requiring attenuation correction while acquiring high-resolution MR images.
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Affiliation(s)
- Mueez Aizaz
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
- CARIM School for Cardiovascular Diseases, 6229 ER Maastricht, The Netherlands
| | - Jochem A. J. van der Pol
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
| | - Roel Wierts
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
| | - Hans Zwart
- Machnet B.V, 9301 LK Roden, The Netherlands; (H.Z.); (A.J.v.d.W.)
| | | | - Joachim E. Wildberger
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
- CARIM School for Cardiovascular Diseases, 6229 ER Maastricht, The Netherlands
| | - Jan A. Bucerius
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
- CARIM School for Cardiovascular Diseases, 6229 ER Maastricht, The Netherlands
- Department of Nuclear Medicine, University Medicine Goettingen, Georg-August-University Goettingen, 37073 Goettingen, Germany
| | - Rik P. M. Moonen
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
- CARIM School for Cardiovascular Diseases, 6229 ER Maastricht, The Netherlands
| | - Marianne Eline Kooi
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center+, 6202 AZ Maastricht, The Netherlands; (M.A.); (J.A.J.v.d.P.); (R.W.); (J.E.W.); (J.A.B.); (R.P.M.M.)
- CARIM School for Cardiovascular Diseases, 6229 ER Maastricht, The Netherlands
- Correspondence: ; Tel.: +31-43-387-4910
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Choi CH, Hong SM, Felder J, Tellmann L, Scheins J, Kops ER, Lerche C, Shah NJ. A Novel J-Shape Antenna Array for Simultaneous MR-PET or MR-SPECT Imaging. IEEE TRANSACTIONS ON MEDICAL IMAGING 2022; 41:1104-1113. [PMID: 34860648 DOI: 10.1109/tmi.2021.3132576] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Simultaneous MR-PET/-SPECT is an emerging technology that capitalises on the invaluable advantages of both modalities, allowing access to numerous sensitive tracers and superior soft-tissue contrast alongside versatile functional imaging capabilities. However, to optimise these capabilities, concurrent acquisitions require the MRI antenna located inside the PET/SPECT field-of-view to be operated without compromising any aspects of system performance or image quality compared to the stand-alone instrumentation. Here, we report a novel gamma-radiation-transparent antenna concept. The end-fed J-shape antenna is particularly adept for hybrid ultra-high field MR-PET/-SPECT applications as it enables all highly attenuating materials to be placed outside the imaging field-of-view. Furthermore, this unique configuration also provides advantages in stand-alone MR applications by reducing the amount of coupling between the cables and the antenna elements, and by lowering the potential specific absorption rate burden. The use of this new design was experimentally verified according to the important features for both ultra-high field MRI and the 511 keV transmission scan. The reconstructed attenuation maps evidently showed much lower attenuation ( ∼ 15 %) for the proposed array when compared to the conventional dipole antenna array since there were no high-density components. In MR, it was observed that the signal-to-noise ratio from the whole volume obtained using the proposed array was comparable to that acquired by the conventional array which was also in agreement with the simulation results. The unique feature, J-shape array, would enable simultaneous MR-PET/-SPECT experiments to be conducted without unduly compromising any aspects of system performance and image quality compared to the stand-alone instrumentation.
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6
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Jena A, Taneja S, Rana P, Goyal N, Vaish A, Botchu R, Vaishya R. Emerging role of integrated PET-MRI in osteoarthritis. Skeletal Radiol 2021; 50:2349-2363. [PMID: 34185124 DOI: 10.1007/s00256-021-03847-z] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 06/16/2021] [Accepted: 06/16/2021] [Indexed: 02/02/2023]
Abstract
Osteoarthritis (OA) is a common degenerative disorder of the articular cartilage, which is associated with hypertrophic changes in the bone, synovial inflammation, subchondral sclerosis, and joint space narrowing (JSN). Radiography remains the first line of imaging till now. Due to the lack of soft-tissue depiction in radiography, researchers are exploring various imaging techniques to detect OA at an early stage and understand its pathophysiology to restrict its progression and discover disease-modifying agents in OA. As the OA relates to the degradation of articular cartilage and remodeling of the underlying bone, an optimal imaging tool must be sensitive to the bone and soft tissue health. In that line, many non-invasive imaging and minimally invasive techniques have been explored. Out of these, the non-invasive compositional magnetic resonance imaging (MRI) for evaluation of the integrity of articular cartilage and positron emission tomography (PET) scan with fluorodeoxyglucose (FDG) and more specific bone-seeking tracer like sodium fluoride (18F-NaF) for bone cartilage interface are some of the leading areas of ongoing work. Integrated PET-MRI system, a new hybrid modality that combines the virtues of the above two individual modalities, allows detailed imaging of the entire joint, including soft tissue cartilage and bone, and holds great potential to research complex disease processes of OA. This narrative review attempts to signify individual characteristics of MRI, PET, the fusion of these characteristics in PET-MRI, and the ongoing research on PET-MRI as a potential tool to understand the pathophysiology of OA.
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Affiliation(s)
- Amarnath Jena
- PET SUITE (Indraprastha Apollo Hospitals and House of Diagnostics), Department of Molecular Imaging and Nuclear Medicine, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India
| | - Sangeeta Taneja
- PET SUITE (Indraprastha Apollo Hospitals and House of Diagnostics), Department of Molecular Imaging and Nuclear Medicine, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India
| | - Prerana Rana
- PET SUITE (Indraprastha Apollo Hospitals and House of Diagnostics), Department of Molecular Imaging and Nuclear Medicine, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India.,Apollo Hospitals Education & Research Foundation, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India
| | - Nidhi Goyal
- Department of Radiodiagnosis and Imaging, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India
| | - Abhishek Vaish
- Department of Orthopaedics and Joint Replacement Surgery, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India
| | - Rajesh Botchu
- Department of Musculoskeletal Radiology, Royal Orthopedic Hospital, Birmingham, UK.
| | - Raju Vaishya
- Department of Orthopaedics and Joint Replacement Surgery, Indraprastha Apollo Hospitals, Sarita Vihar, Delhi-Mathura Road, New Delhi, 110076, India
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7
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Husseini JS, Balza R, Evangelista L, Cañamaque LG, Catalano OA. PET/MR for evaluation of musculoskeletal malignancies. Clin Transl Imaging 2021. [DOI: 10.1007/s40336-021-00470-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Sander CY, Bovo S, Torrado-Carvajal A, Albrecht D, Deng H, Napadow V, Price JC, Hooker JM, Loggia ML. [ 11C]PBR28 radiotracer kinetics are not driven by alterations in cerebral blood flow. J Cereb Blood Flow Metab 2021; 41:3069-3084. [PMID: 34159823 PMCID: PMC8756484 DOI: 10.1177/0271678x211023387] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The positron emission tomography (PET) radiotracer [11C]PBR28 has been increasingly used to image the translocator protein (TSPO) as a marker of neuroinflammation in a variety of brain disorders. Interrelatedly, similar clinical populations can also exhibit altered brain perfusion, as has been shown using arterial spin labelling in magnetic resonance imaging (MRI) studies. Hence, an unsolved debate has revolved around whether changes in perfusion could alter delivery, uptake, or washout of the radiotracer [11C]PBR28, and thereby influence outcome measures that affect interpretation of TSPO upregulation. In this simultaneous PET/MRI study, we demonstrate that [11C]PBR28 signal elevations in chronic low back pain patients are not accompanied, in the same regions, by increases in cerebral blood flow (CBF) compared to healthy controls, and that areas of marginal hypoperfusion are not accompanied by decreases in [11C]PBR28 signal. In non-human primates, we show that hypercapnia-induced increases in CBF during radiotracer delivery or washout do not alter [11C]PBR28 outcome measures. The combined results from two methodologically distinct experiments provide support from human data and direct experimental evidence from non-human primates that changes in CBF do not influence outcome measures reported by [11C]PBR28 PET imaging studies and corresponding interpretations of the biological meaning of TSPO upregulation.
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Affiliation(s)
- Christin Y Sander
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Stefano Bovo
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Department of Information Engineering, University of Padova, Padova, Italy
| | - Angel Torrado-Carvajal
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Medical Image Analysis and Biometry Laboratory, Universidad Rey Juan Carlos, Madrid, Spain
| | - Daniel Albrecht
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA
| | - Hongping Deng
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA
| | - Vitaly Napadow
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Julie C Price
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Jacob M Hooker
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Harvard Medical School, Boston, MA, USA
| | - Marco L Loggia
- Department of Radiology, Athinoula A. Martinos Center, Massachusetts General Hospital, Charlestown, MA, USA.,Harvard Medical School, Boston, MA, USA
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Lindemann ME, Oehmigen M, Lanz T, Grafe H, Bruckmann NM, Umutlu L, Quick HH. CAD-based hardware attenuation correction in PET/MRI: First methodical investigations and clinical application of a 16-channel RF breast coil. Med Phys 2021; 48:6696-6709. [PMID: 34655079 DOI: 10.1002/mp.15284] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 10/01/2021] [Accepted: 10/02/2021] [Indexed: 12/11/2022] Open
Abstract
PURPOSE Aim of this study was to evaluate the use of computer-aided design (CAD) models for attenuation correction (AC) of hardware components in positron emission tomography/magnetic resonance (PET/MR) imaging. METHODS The technical feasibility and quantitative impact of CAD-AC compared to computer tomography (CT)-based AC (reference) was investigated on a modular phantom consisting of 19 different material samples (plastics and metals arranged around a cylindrical emission phantom) typically used in phantoms, patient tables, and radiofrequency (RF) coils in PET/MR. The clinical applicability of the CAD-AC method was then evaluated on a 16-channel RF breast coil in a PET/MR patient study. The RF breast coil in this study was specifically designed PET compatible. Using this RF breast coil, the impact on clinical PET/MR breast imaging was systematically evaluated in breast phantom measurements and, furthermore, in n = 10 PET/MR patients with breast cancer. PET data were reconstructed three times: (1) no AC (NAC), (2) established CT-AC, and (3) CAD-AC. For both phantom measurements, a scan without attenuating hardware components (material probes or RF breast coil) was acquired serving as reference. Relative differences in PET data were calculated for all experiments. RESULTS In all phantom and patient measurements, significant gains in PET signal compared to NAC data were measurable with CT and CAD-AC. In initial phantom experiments, mean relative differences of -0.2% for CT-AC and 0.2% for CAD-AC were calculated compared to reference measurements without the material probes. The application to a RF breast coil depicts that CAD-AC results in significant gains compared to NAC data (10%) and a slight underestimation in PET signal of -1.3% in comparison to the no-coil reference measurement. In the patient study, a total of 15 congruent lesions in all 10 patients with a mean relative difference of 14% (CT and CAD-AC) in standardized uptake value compared to NAC data could be detected. CONCLUSIONS To ensure best possible PET image quality and accurate PET quantification in PET/MR imaging, the AC of hardware components such as phantoms and RF coils is important. In initial phantom experiments and in clinical application to an RF breast coil, it was found that CAD-based AC results in significant gains in PET signal compared to NAC data and provides comparably good results to the established method of CT-based AC.
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Affiliation(s)
- Maike E Lindemann
- High-Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Mark Oehmigen
- High-Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | | | - Hong Grafe
- Department of Nuclear Medicine, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Nils Martin Bruckmann
- Department of Diagnostic and Interventional Radiology, University Hospital Duesseldorf, University of Duesseldorf, Duesseldorf, Germany
| | - Lale Umutlu
- Department of Diagnostic and Interventional Radiology and Neuroradiology, University Hospital Essen, University of Duisburg-Essen, Essen, Germany
| | - Harald H Quick
- High-Field and Hybrid MR Imaging, University Hospital Essen, University of Duisburg-Essen, Essen, Germany.,Erwin L. Hahn Institute for Magnetic Resonance Imaging, University of Duisburg-Essen, Essen, Germany
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10
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Zijlema SE, Branderhorst W, Bastiaannet R, Tijssen RHN, Lagendijk JJW, van den Berg CAT. Minimizing the need for coil attenuation correction in integrated PET/MRI at 1.5 T using low-density MR-linac receive arrays. Phys Med Biol 2021; 66. [PMID: 34571496 DOI: 10.1088/1361-6560/ac2a8a] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Accepted: 09/27/2021] [Indexed: 11/12/2022]
Abstract
The simultaneous use of positron emission tomography (PET) and magnetic resonance imaging (MRI) requires attenuation correction (AC) of photon-attenuating objects, such as MRI receive arrays. However, AC of flexible, on-body arrays is complex and therefore often omitted. This can lead to significant, spatially varying PET signal losses when conventional MRI receive arrays are used. Only few dedicated, photon transparent PET/MRI arrays exist, none of which are compatible with our new, wide-bore 1.5 T PET/MRI system dedicated to radiotherapy planning. In this work, we investigated the use of 1.5 T MR-linac (MRL) receive arrays for PET/MRI, as these were designed to have a low photon attenuation for accurate dose delivery and can be connected to the new 1.5 T PET/MRI scanner. Three arrays were assessed: an 8-channel clinically-used MRL array, a 32-channel prototype MRL array, and a conventional MRI receive array. We experimentally determined, simulated, and compared the impact of these arrays on the PET sensitivity and image reconstructions. Furthermore, MRI performance was compared. Overall coil-induced PET sensitivity losses were reduced from 8.5% (conventional) to 1.7% (clinical MRL) and 0.7% (prototype MRL). Phantom measurements showed local signal errors of up to 32.7% (conventional) versus 3.6% (clinical MRL) and 3.5% (prototype MRL). Simulations with data of eight cancer patients showed average signal losses were reduced from 14.3% (conventional) to 1.2% (clinical MRL) and 1.0% (prototype MRL). MRI data showed that the signal-to-noise ratio of the MRL arrays was slightly lower at depth (110 versus 135). The parallel imaging performance of the conventional and prototype MRL arrays was similar, while the clinical MRL array's performance was lower. In conclusion, MRL arrays reducein-vivoPET signal losses >10×, which decreases, or eliminates, the need for coil AC on a new 1.5 T PET/MRI system. The prototype MRL array allows flexible coil positioning without compromising PET or MRI performance. One limitation of MRL arrays is their limited radiolucent PET window (field of view) in the craniocaudal direction.
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Affiliation(s)
- Stefan E Zijlema
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, The Netherlands
| | - Woutjan Branderhorst
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, The Netherlands
| | - Remco Bastiaannet
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, The Netherlands.,Department of Radiology, The Johns Hopkins University, School of Medicine, Baltimore, Maryland, United States of America
| | - Rob H N Tijssen
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands.,Department of Radiation Oncology, Catharina Hospital, Eindhoven, The Netherlands
| | - Jan J W Lagendijk
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands.,Computational Imaging Group for MR Diagnostics & Therapy, Center for Image Sciences, University Medical Center Utrecht, The Netherlands
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Celik AA, Choi CH, Tellmann L, Rick C, Shah NJ, Felder J. Design and Construction of a PET-Compatible Double-Tuned 1H/ 31P MR Head Coil. IEEE TRANSACTIONS ON MEDICAL IMAGING 2021; 40:2015-2022. [PMID: 33798075 DOI: 10.1109/tmi.2021.3070626] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Simultaneous MR-PET is an increasingly popular multimodal imaging technique that is able to combine metabolic information obtained from PET with anatomical/functional information from MRI. One of the key technological challenges of the technique is the integration of a PET-transparent MR coil system, a solution to which is demonstrated here for a double-tuned 1H/31P head coil at 3 T. Two single-resonant birdcage coils tuned to the 1H and 31P resonances were arranged in an interleaved fashion and electrically decoupled with the use of trap circuits. All high 511 keV quanta absorbing components were arranged outside the PET field-of-view in order to minimize count rate reduction. The materials inside the PET field-of-view were carefully evaluated and chosen for minimum impact on the PET image quality. As far as possible, the coil case was geometrically optimized to avoid sharp transitions in attenuation, which may potentially result in streaking artefacts during PET image reconstruction. The coil caused a count rate loss of just above 5% when inserted into the PET detector ring. Except for the anterior region, which was designed to maintain free openings for increased patient comfort, an almost uniform distribution of 511 keV attenuation was maintained around the circumference of the coil. MR-related performance for both nuclei was similar or slightly better than that of a commercial double-tuned coil, despite the MR-PET coil having a close-fitting RF screen to shield the PET and MR electronics from possible electromagnetic interferences.
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12
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Lee JS. A Review of Deep-Learning-Based Approaches for Attenuation Correction in Positron Emission Tomography. IEEE TRANSACTIONS ON RADIATION AND PLASMA MEDICAL SCIENCES 2021. [DOI: 10.1109/trpms.2020.3009269] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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13
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Abstract
Attenuation correction has been one of the main methodological challenges in the integrated positron emission tomography and magnetic resonance imaging (PET/MRI) field. As standard transmission or computed tomography approaches are not available in integrated PET/MRI scanners, MR-based attenuation correction approaches had to be developed. Aspects that have to be considered for implementing accurate methods include the need to account for attenuation in bone tissue, normal and pathological lung and the MR hardware present in the PET field-of-view, to reduce the impact of subject motion, to minimize truncation and susceptibility artifacts, and to address issues related to the data acquisition and processing both on the PET and MRI sides. The standard MR-based attenuation correction techniques implemented by the PET/MRI equipment manufacturers and their impact on clinical and research PET data interpretation and quantification are first discussed. Next, the more advanced methods, including the latest generation deep learning-based approaches that have been proposed for further minimizing the attenuation correction related bias are described. Finally, a future perspective focused on the needed developments in the field is given.
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Affiliation(s)
- Ciprian Catana
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, United States of America
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14
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Gerstner ER, Emblem KE, Yen YF, Dietrich J, Jordan JT, Catana C, Wenchin KL, Hooker JM, Duda DG, Rosen BR, Kalpathy-Cramer J, Jain RK, Batchelor TT. Vascular dysfunction promotes regional hypoxia after bevacizumab therapy in recurrent glioblastoma patients. Neurooncol Adv 2020; 2:vdaa157. [PMID: 33392506 PMCID: PMC7764510 DOI: 10.1093/noajnl/vdaa157] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Background Hypoxia is a driver of treatment resistance in glioblastoma. Antiangiogenic agents may transiently normalize blood vessels and decrease hypoxia before excessive pruning of vessels increases hypoxia. The time window of normalization is dose and time dependent. We sought to determine how VEGF blockade with bevacizumab modulates tumor vasculature and the impact that those vascular changes have on hypoxia in recurrent glioblastoma patients. Methods We measured tumor volume, vascular permeability (Ktrans), perfusion parameters (cerebral blood flow/volume, vessel caliber, and mean transit time), and regions of hypoxia in patients with recurrent glioblastoma before and after treatment with bevacizumab alone or with lomustine using [18F]FMISO PET-MRI. We also examined serial changes in plasma biomarkers of angiogenesis and inflammation. Results Eleven patients were studied. The magnitude of global tumor hypoxia was variable across these 11 patients prior to treatment and it did not significantly change after bevacizumab. The hypoxic regions had an inefficient vasculature characterized by elevated cerebral blood flow/volume and increased vessel caliber. In a subset of patients, there were tumor subregions with decreased mean transit times and a decrease in hypoxia, suggesting heterogeneous improvement in vascular efficiency. Bevacizumab significantly changed known pharmacodynamic biomarkers such as plasma VEGF and PlGF. Conclusions The vascular signature in hypoxic tumor regions indicates a disorganized vasculature which, in most tumors, does not significantly change after bevacizumab treatment. While some tumor regions showed improved vascular efficiency following treatment, bevacizumab did not globally alter hypoxia or normalize tumor vasculature in glioblastoma.
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Affiliation(s)
- Elizabeth R Gerstner
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Kyrre E Emblem
- Department of Diagnostic Physics, Oslo University, Oslo, Norway
| | - Yi-Fen Yen
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Jorg Dietrich
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Justin T Jordan
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Ciprian Catana
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Kevin Lou Wenchin
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA
| | - Jacob M Hooker
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Dan G Duda
- Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Bruce R Rosen
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Jayashree Kalpathy-Cramer
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Rakesh K Jain
- Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
| | - Tracy T Batchelor
- Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts, USA.,Harvard Medical School, Boston, Massachusetts, USA
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15
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Barta R, Volotovskyy V, Wachowicz K, Fallone BG, De Zanche N. How thin can you go? Performance of thin copper and aluminum RF coil conductors. Magn Reson Med 2020; 85:2327-2333. [PMID: 33058317 DOI: 10.1002/mrm.28540] [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: 06/03/2020] [Revised: 09/10/2020] [Accepted: 09/11/2020] [Indexed: 11/09/2022]
Abstract
PURPOSE To evaluate the impact of emerging conductor technology on RF coils. Performance and resulting image quality of thin or alternate conductors (eg, aluminum instead of copper) and thicknesses (9-600 μm) are compared in terms of SNR. METHODS Eight prototype RF coils (15 cm × 15 cm square loops) were constructed and bench-tested to measure quality factor. The coils used 6-mm-wide conducting strips of either copper or aluminum of a few different thicknesses (copper: 17, 32, 35, 127, 600 μm; aluminum: 9, 13, 20, 127 μm) on acetate projector sheets for backing. Corresponding image SNR was measured at 0.48 tesla (20.56 MHz). RESULTS The coils spanned a range of unloaded quality factors from 89 to 390 and a fivefold range of losses. The image SNRs were consistent with the coils' bench-measured efficiencies (0.33-0.73). Thin aluminum conductors (9 μm) led to the highest reduction in SNR (65% that of 127 μm copper). Thin copper (<32 μm) conductors lead to a much smaller decrease in SNR (approximately 10%) compared to 127 μm copper. No performance difference was observed between 127 μm thick copper and aluminum. The much thicker 600 μm copper bars only yield a 5% improvement in SNR. CONCLUSION Even at 0.48 tesla, copper RF coil conductors much thinner than those in conventional construction can be used while maintaining SNR greater than 50% that of thick copper. These emerging coil conductor technologies enable RF coil functionality that cannot be achieved otherwise.
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Affiliation(s)
- Radim Barta
- Department of Oncology, Division of Medical Physics, University of Alberta, Edmonton, Alberta, Canada
| | | | - Keith Wachowicz
- Department of Oncology, Division of Medical Physics, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - B Gino Fallone
- Department of Oncology, Division of Medical Physics, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.,Department of Physics, University of Alberta, Edmonton, Alberta, Canada
| | - Nicola De Zanche
- Department of Oncology, Division of Medical Physics, University of Alberta, Edmonton, Alberta, Canada.,Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
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16
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Choi CH, Hong SM, Felder J, Shah NJ. The state-of-the-art and emerging design approaches of double-tuned RF coils for X-nuclei, brain MR imaging and spectroscopy: A review. Magn Reson Imaging 2020; 72:103-116. [DOI: 10.1016/j.mri.2020.07.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2020] [Revised: 06/16/2020] [Accepted: 07/01/2020] [Indexed: 12/18/2022]
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17
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Aizaz M, Moonen RPM, van der Pol JAJ, Prieto C, Botnar RM, Kooi ME. PET/MRI of atherosclerosis. Cardiovasc Diagn Ther 2020; 10:1120-1139. [PMID: 32968664 DOI: 10.21037/cdt.2020.02.09] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Myocardial infarction and stroke are the most prevalent global causes of death. Each year 15 million people worldwide die due to myocardial infarction or stroke. Rupture of a vulnerable atherosclerotic plaque is the main underlying cause of stroke and myocardial infarction. Key features of a vulnerable plaque are inflammation, a large lipid-rich necrotic core (LRNC) with a thin or ruptured overlying fibrous cap, and intraplaque hemorrhage (IPH). Noninvasive imaging of these features could have a role in risk stratification of myocardial infarction and stroke and can potentially be utilized for treatment guidance and monitoring. The recent development of hybrid PET/MRI combining the superior soft tissue contrast of MRI with the opportunity to visualize specific plaque features using various radioactive tracers, paves the way for comprehensive plaque imaging. In this review, the use of hybrid PET/MRI for atherosclerotic plaque imaging in carotid and coronary arteries is discussed. The pros and cons of different hybrid PET/MRI systems are reviewed. The challenges in the development of PET/MRI and potential solutions are described. An overview of PET and MRI acquisition techniques for imaging of atherosclerosis including motion correction is provided, followed by a summary of vessel wall imaging PET/MRI studies in patients with carotid and coronary artery disease. Finally, the future of imaging of atherosclerosis with PET/MRI is discussed.
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Affiliation(s)
- Mueez Aizaz
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.,CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
| | - Rik P M Moonen
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.,CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
| | - Jochem A J van der Pol
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands
| | - Claudia Prieto
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.,Escuela de Ingenieria, Pontificia Universidad Catolica de Chile, Santiago, Chile
| | - René M Botnar
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, UK.,Escuela de Ingenieria, Pontificia Universidad Catolica de Chile, Santiago, Chile
| | - M Eline Kooi
- Department of Radiology and Nuclear Medicine, Maastricht University Medical Center, Maastricht, The Netherlands.,CARIM School for Cardiovascular Diseases, Maastricht University, Maastricht, The Netherlands
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18
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Choi CH, Felder T, Felder J, Tellmann L, Hong SM, Wegener HP, Shah NJ, Ziemons K. Design, evaluation and comparison of endorectal coils for hybrid MR-PET imaging of the prostate. Phys Med Biol 2020; 65:115005. [PMID: 32268314 DOI: 10.1088/1361-6560/ab87f8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Prostate cancer is one of the most common cancers among men and its early detection is critical for its successful treatment. The use of multimodal imaging, such as MR-PET, is most advantageous as it is able to provide detailed information about the prostate. However, as the human prostate is flexible and can move into different positions under external conditions, it is important to localise the focused region-of-interest using both MRI and PET under identical circumstances. In this work, we designed five commonly used linear and quadrature radiofrequency surface coils suitable for hybrid MR-PET use in endorectal applications. Due to the endorectal design and the shielded PET insert, the outer face of the coils investigated was curved and the region to be imaged was outside the volume of the coil. The tilting angles of the coils were varied with respect to the main magnetic field direction. This was done to approximate the various positions from which the prostate could be imaged. The transmit efficiencies and safety excitation efficiencies from simulations, together with the signal-to-noise ratios from the MR images were calculated and analysed. Overall, it was found that the overlapped loops driven in quadrature were superior to the other types of coils we tested. In order to determine the effect of the different coil designs on PET, transmission scans were carried out, and it was observed that the differences between attenuation maps with and without the coils were negligible. The findings of this work can provide useful guidance for the integration of such coil designs into MR-PET hybrid systems in the future.
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Affiliation(s)
- Chang-Hoon Choi
- Institute of Neuroscience and Medicine - 4, Forschungszentrum Jülich, Jülich, Germany
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19
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Gerstner ER, Emblem KE, Chang K, Vakulenko-Lagun B, Yen YF, Beers AL, Dietrich J, Plotkin SR, Catana C, Hooker JM, Duda DG, Rosen B, Kalpathy-Cramer J, Jain RK, Batchelor T. Bevacizumab Reduces Permeability and Concurrent Temozolomide Delivery in a Subset of Patients with Recurrent Glioblastoma. Clin Cancer Res 2020; 26:206-212. [PMID: 31558474 PMCID: PMC7139851 DOI: 10.1158/1078-0432.ccr-19-1739] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2019] [Revised: 08/08/2019] [Accepted: 09/19/2019] [Indexed: 02/06/2023]
Abstract
PURPOSE Targeting tumor blood vessels is an attractive therapy in glioblastoma (GBM), but the mechanism of action of these agents and how they modulate delivery of concomitant chemotherapy are not clear in humans. We sought to elucidate how bevacizumab modulates tumor vasculature and the impact those vascular changes have on drug delivery in patients with recurrent GBM. EXPERIMENTAL DESIGN Temozolomide was labeled with [11C], and serial PET-MRI scans were performed in patients with recurrent GBM treated with bevacizumab and daily temozolomide. PET-MRI scans were performed prior to the first bevacizumab dose, 1 day after the first dose, and prior to the third dose of bevacizumab. We calculated tumor volume, vascular permeability (K trans), perfusion (cerebral blood flow), and the standardized uptake values (SUV) of [11C] temozolomide within the tumor. RESULTS Twelve patients were enrolled, resulting in 23 evaluable scans. Within the entire contrast-enhancing tumor volume, both temozolomide uptake and vascular permeability decreased after initiation of bevacizumab in most patients, whereas change in perfusion was more variable. In subregions of the tumor where permeability was low and the blood-brain barrier not compromised, increased perfusion correlated with increased temozolomide uptake. CONCLUSIONS Bevacizumab led to a decrease in permeability and concomitant delivery of temozolomide. However, in subregions of the tumor where permeability was low, increased perfusion improved delivery of temozolomide, suggesting that perfusion may modulate the delivery of chemotherapy in certain settings. These results support exploring whether lower doses of bevacizumab improve perfusion and concomitant drug delivery.
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Affiliation(s)
- Elizabeth R Gerstner
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts.
- Harvard Medical School, Boston, Massachusetts
| | - Kyrre E Emblem
- Department of Diagnostic Physics, Oslo University, Oslo, Norway
| | - Ken Chang
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Bella Vakulenko-Lagun
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts
| | - Yi-Fen Yen
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Andrew L Beers
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Jorg Dietrich
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Scott R Plotkin
- Stephen E. and Catherine Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts
- Harvard Medical School, Boston, Massachusetts
| | - Ciprian Catana
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Jacob M Hooker
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Dan G Duda
- Harvard Medical School, Boston, Massachusetts
- Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Bruce Rosen
- Harvard Medical School, Boston, Massachusetts
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Jayashree Kalpathy-Cramer
- Harvard Medical School, Boston, Massachusetts
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, Massachusetts
| | - Rakesh K Jain
- Harvard Medical School, Boston, Massachusetts
- Edwin L. Steele Laboratories, Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts
| | - Tracy Batchelor
- Harvard Medical School, Boston, Massachusetts
- Department of Neurology, Brigham and Women's Hospital, Boston, Massachusetts
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20
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Abstract
Purpose: We proposed and developed a new microstrip transmission line radiofrequency (RF) coil for a positron emission tomography (PET) insert for MRI, which has low electrical interactions with PET shield boxes. We performed imaging experiments using a single-channel and a four-channel proposed RF coils for proof-of-concept. Methods: A conventional microstrip coil consists of a microstrip conductor, a ground conductor, and a dielectric between the two conductors. We proposed a microstrip coil for the PET insert that replaced the conventional single-layer ground conductor with the RF shield of the PET insert. A dielectric material, which could otherwise attenuate gamma photons radiated from the PET imaging tracer, was not used. As proof-of-concept, we compared conventional and the proposed single-channel coils. To study multichannel performance, we further developed a four-channel proposed RF coil. Since the MRI system had a single-channel transmission port, an interfacing four-way RF power division circuit was designed. The coils were implemented as both RF transmitters and receivers in a cylindrical frame of diameter 150 mm. Coil bench performances were tested with a network analyzer (Rohde & Schwarz, Germany), and a homogeneous phantom study was conducted for gradient echo imaging and RF field (B1) mapping in a 3T clinical MRI system (Verio, Siemens, Erlangen, Germany). Results: For all coils, the power reflection coefficient was below −30 dB, and the transmission coefficients in the four-channel configuration were near or below −20 dB. The comparative single-channel coil study showed good similarity between the conventional and proposed coils. The gradient echo image of the four-channel coil showed expected flashing image intensity near the coils and no phase distortion was visible. Transmit B1 field map resembled the image performance. Conclusion: The proposed PET-microstrip coil performed similarly to the conventional microstrip transmission line coil and is promising for the development of a compact coil-PET system capable of simultaneous PET/MRI analysis with an existing MRI system.
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Affiliation(s)
- Md Shahadat Hossain Akram
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| | - Takayuki Obata
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
| | - Taiga Yamaya
- National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology
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21
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Kogan F, Broski SM, Yoon D, Gold GE. Applications of PET-MRI in musculoskeletal disease. J Magn Reson Imaging 2019; 48:27-47. [PMID: 29969193 DOI: 10.1002/jmri.26183] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Accepted: 04/19/2018] [Indexed: 12/26/2022] Open
Abstract
New integrated PET-MRI systems potentially provide a complete imaging modality for diagnosis and evaluation of musculoskeletal disease. MRI is able to provide excellent high-resolution morphologic information with multiple contrast mechanisms that has made it the imaging modality of choice in evaluation of many musculoskeletal disorders. PET offers incomparable abilities to provide quantitative information about molecular and physiologic changes that often precede structural and biochemical changes. In combination, hybrid PET-MRI can enhance imaging of musculoskeletal disorders through early detection of disease as well as improved diagnostic sensitivity and specificity. The purpose of this article is to review emerging applications of PET-MRI in musculoskeletal disease. Both clinical applications of malignant musculoskeletal disease as well as new opportunities to incorporate the molecular capabilities of nuclear imaging into studies of nononcologic musculoskeletal disease are discussed. Lastly, we discuss some of the technical considerations and challenges of PET-MRI as they specifically relate to musculoskeletal disease. LEVEL OF EVIDENCE 5 TECHNICAL EFFICACY: Stage 3 J. Magn. Reson. Imaging 2018;48:27-47.
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Affiliation(s)
- Feliks Kogan
- Department of Radiology, Stanford University, Stanford, California, USA
| | | | - Daehyun Yoon
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Garry E Gold
- Department of Radiology, Stanford University, Stanford, California, USA.,Department of Bioengineering, Stanford University, Stanford, California, USA.,Department of Orthopaedic Surgery, Stanford University, Stanford, California, USA
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22
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Farag A, Thompson RT, Thiessen JD, Butler J, Prato FS, Théberge J. Assessment of a novel 32-channel phased array for cardiovascular hybrid PET/MRI imaging: MRI performance. Eur J Hybrid Imaging 2019; 3:13. [PMID: 33283144 PMCID: PMC7717874 DOI: 10.1186/s41824-019-0061-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2019] [Accepted: 07/01/2019] [Indexed: 01/09/2023] Open
Abstract
BACKGROUND Cardiovascular imaging using hybrid positron emission tomography (PET) and magnetic resonance imaging (MRI) requires a radio frequency phased array resonator capable of high acceleration factors in order to achieve the shortest breath-holds while maintaining optimal MRI signal-to-noise ratio (SNR) and minimum PET photon attenuation. To our knowledge, the only two arrays used today for hybrid PET/MRI cardiovascular imaging are either incapable of achieving high acceleration or affect the PET photon count greatly. PURPOSE This study is focused on the evaluation of the MRI performance of a novel third-party prototype 32-channel phased array designed for simultaneous PET/MRI cardiovascular imaging. The study compares the quality parameters of MRI parallel imaging, such as g-factor, noise correlation coefficients, and SNR, to the conventional arrays (mMR 12-channel and MRI-only 32-channel) currently used with hybrid PET/MRI systems. The quality parameters of parallel imaging were estimated for multiple acceleration factors on a phantom and three healthy volunteers. Using a Germanium-68 (Ge-68) phantom, preliminary measurements of PET photon attenuation caused by the novel array were briefly compared to the photon counts produced from no-array measurements. RESULTS The global mean of the g-factor and SNRg produced by the novel 32-channel PET/MRI array were better than those produced by the MRI-only 32-channel array by 5% or more. The novel array has resulted in MRI SNR improvements of > 30% at all acceleration factors, in comparison to the mMR12-channel array. Preliminary evaluation of PET transparency showed less than 5% photon attenuation caused by both anterior and posterior parts of the novel array. CONCLUSIONS The MRI performance of the novel PET/MRI 32-channel array qualifies it to be a viable alternative to the conventional arrays for cardiovascular hybrid PET/MRI. A detailed evaluation of the novel array's PET performance remains to be conducted, but cursory assessment promises significantly reduced attenuation.
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Affiliation(s)
- Adam Farag
- Lawson Health Research Institute, Imaging Division, 268 Grosvenor St., Rm E5-118, PO Box 5777, STN B, London, ON N6A 4V2 Canada
- Department of Medical Biophysics, Western University, London, ON Canada
| | - R. Terry Thompson
- Lawson Health Research Institute, Imaging Division, 268 Grosvenor St., Rm E5-118, PO Box 5777, STN B, London, ON N6A 4V2 Canada
- Department of Medical Biophysics, Western University, London, ON Canada
| | - Jonathan D. Thiessen
- Lawson Health Research Institute, Imaging Division, 268 Grosvenor St., Rm E5-118, PO Box 5777, STN B, London, ON N6A 4V2 Canada
- Department of Medical Biophysics, Western University, London, ON Canada
- Department of Medical Imaging, Western University, London, ON Canada
| | - John Butler
- Lawson Health Research Institute, Imaging Division, 268 Grosvenor St., Rm E5-118, PO Box 5777, STN B, London, ON N6A 4V2 Canada
| | - Frank S. Prato
- Lawson Health Research Institute, Imaging Division, 268 Grosvenor St., Rm E5-118, PO Box 5777, STN B, London, ON N6A 4V2 Canada
- Department of Medical Biophysics, Western University, London, ON Canada
- Department of Medical Imaging, Western University, London, ON Canada
- St. Joseph’s Health Care, Diagnostic Imaging, London, ON Canada
| | - Jean Théberge
- Lawson Health Research Institute, Imaging Division, 268 Grosvenor St., Rm E5-118, PO Box 5777, STN B, London, ON N6A 4V2 Canada
- Department of Medical Biophysics, Western University, London, ON Canada
- Department of Medical Imaging, Western University, London, ON Canada
- St. Joseph’s Health Care, Diagnostic Imaging, London, ON Canada
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23
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Navarro de Lara LI, Frass-Kriegl R, Renner A, Sieg J, Pichler M, Bogner T, Moser E, Beyer T, Birkfellner W, Figl M, Laistler E. Design, Implementation, and Evaluation of a Head and Neck MRI RF Array Integrated with a 511 keV Transmission Source for Attenuation Correction in PET/MR. SENSORS 2019; 19:s19153297. [PMID: 31357545 PMCID: PMC6696210 DOI: 10.3390/s19153297] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Revised: 07/23/2019] [Accepted: 07/25/2019] [Indexed: 01/13/2023]
Abstract
The goal of this work is to further improve positron emission tomography (PET) attenuation correction and magnetic resonance (MR) sensitivity for head and neck applications of PET/MR. A dedicated 24-channel receive-only array, fully-integrated with a hydraulic system to move a transmission source helically around the patient and radiofrequency (RF) coil array, is designed, implemented, and evaluated. The device enables the calculation of attenuation coefficients from PET measurements at 511 keV including the RF coil and the particular patient. The RF coil design is PET-optimized by minimizing photon attenuation from coil components and housing. The functionality of the presented device is successfully demonstrated by calculating the attenuation map of a water bottle based on PET transmission measurements; results are in excellent agreement with reference values. It is shown that the device itself has marginal influence on the static magnetic field B0 and the radiofrequency transmit field B1 of the 3T PET/MR system. Furthermore, the developed RF array is shown to outperform a standard commercial 16-channel head and neck coil in terms of signal-to-noise ratio (SNR) and parallel imaging performance. In conclusion, the presented hardware enables accurate calculation of attenuation maps for PET/MR systems while improving the SNR of corresponding MR images in a single device without degrading the B0 and B1 homogeneity of the scanner.
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Affiliation(s)
- Lucia Isabel Navarro de Lara
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Roberta Frass-Kriegl
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Andreas Renner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
- Institute of Applied Physics, Vienna University of Technology, Wiedner Hauptstrasse 8-10/134, 1040 Vienna, Austria
| | - Jürgen Sieg
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Michael Pichler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Thomas Bogner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Ewald Moser
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Thomas Beyer
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Wolfgang Birkfellner
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Michael Figl
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria
| | - Elmar Laistler
- Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Waehringer Guertel 18-20, 1090 Vienna, Austria.
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Sander CY, Mandeville JB, Wey HY, Catana C, Hooker JM, Rosen BR. Effects of flow changes on radiotracer binding: Simultaneous measurement of neuroreceptor binding and cerebral blood flow modulation. J Cereb Blood Flow Metab 2019; 39:131-146. [PMID: 28816571 PMCID: PMC6311667 DOI: 10.1177/0271678x17725418] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The potential effects of changes in blood flow on the delivery and washout of radiotracers has been an ongoing question in PET bolus injection studies. This study provides practical insight into this topic by experimentally measuring cerebral blood flow (CBF) and neuroreceptor binding using simultaneous PET/MRI. Hypercapnic challenges (7% CO2) were administered to non-human primates in order to induce controlled increases in CBF, measured with pseudo-continuous arterial spin labeling. Simultaneously, dopamine D2/D3 receptor binding of [11C]raclopride or [18F]fallypride was monitored with dynamic PET. Experiments showed that neither time activity curves nor quantification of binding through binding potentials ( BPND) were measurably affected by CBF increases, which were larger than two-fold. Simulations of experimental procedures showed that even large changes in CBF should have little effect on the time activity curves of radiotracers, given a set of realistic assumptions. The proposed method can be applied to experimentally assess the flow sensitivity of other radiotracers. Results demonstrate that CBF changes, which often occur due to behavioral tasks or pharmacological challenges, do not affect PET [11C]raclopride or [18F]fallypride binding studies and their quantification. The results from this study suggest flow effects may have limited impact on many PET neuroreceptor tracers with similar properties.
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Affiliation(s)
- Christin Y Sander
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Joseph B Mandeville
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Hsiao-Ying Wey
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Ciprian Catana
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Jacob M Hooker
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA
| | - Bruce R Rosen
- 1 Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Charlestown, MA, USA.,2 Harvard Medical School, Boston, MA, USA.,3 Health Sciences and Technology, Harvard-MIT, Cambridge, MA, USA
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25
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Lee BJ, Watkins RD, Lee KS, Chang CM, Levin CS. Performance evaluation of RF coils integrated with an RF-penetrable PET insert for simultaneous PET/MRI. Magn Reson Med 2018; 81:1434-1446. [PMID: 30260501 DOI: 10.1002/mrm.27444] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2017] [Revised: 05/01/2018] [Accepted: 06/11/2018] [Indexed: 01/19/2023]
Abstract
PURPOSE An "RF-penetrable" PET insert that allows the MR body coil to be used for RF transmission was developed to make it easier for an existing MR center to achieve simultaneous PET/MRI. This study focuses on experiments and analyses to study PET/RF coil configurations for simultaneous PET/MR studies. METHODS To investigate the appropriate RF coil design, a transmit/receive (TX/RX) birdcage coil and an RX-only phased-array coil (TX from body coil), both fitting inside the PET ring were built and characterized. For MR performance evaluation, B1 field uniformity and MR image SNR were calculated. PET photon attenuation due to each coil was studied by means of CT-based attenuation maps and reconstructed PET images. RESULTS When using the RX-only phased-array coil (TX from body coil), compared with the TX/RX birdcage coil, the B1 field uniformity and the MR image (gradient echo and fast spin echo) SNR increased by 2.4±4.8%, 386.1±62.3%, and 205.0±56.5%, respectively. Although some components of the coil were distributed within the PET FOV, no significant PET photon attenuation was shown in the CT-based attenuation map and reconstructed PET images. CONCLUSION RF coil configurations for an RF-penetrable PET insert for simultaneous PET/MRI were studied. The RX-only phased-array coil (TX from body coil) outperformed the TX/RX birdcage coil with improved MR performance as well as negligible PET photon attenuation.
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Affiliation(s)
- Brian J Lee
- Department of Radiology, Stanford University, Stanford, California
- Department of Mechanical Engineering, Stanford University, Stanford, California
| | - Ronald D Watkins
- Department of Radiology, Stanford University, Stanford, California
| | - Keum Sil Lee
- Department of Radiology, Stanford University, Stanford, California
| | - Chen-Ming Chang
- Department of Radiology, Stanford University, Stanford, California
- Department of Applied Physics, Stanford University, Stanford, California
| | - Craig S Levin
- Department of Radiology, Stanford University, Stanford, California
- Department of Bioengineering, Stanford University, Stanford, California
- Department of Electrical Engineering, Stanford University, Stanford, California
- Department of Physics, Stanford University, Stanford, California
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26
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Lee BJ, Grant AM, Chang CM, Watkins RD, Glover GH, Levin CS. MR Performance in the Presence of a Radio Frequency-Penetrable Positron Emission Tomography (PET) Insert for Simultaneous PET/MRI. IEEE TRANSACTIONS ON MEDICAL IMAGING 2018; 37:2060-2069. [PMID: 29993864 PMCID: PMC6195123 DOI: 10.1109/tmi.2018.2815620] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
Despite the great promise of integrated positron emission tomography (PET)/magnetic resonance (MR) imaging to add molecular information to anatomical and functional MR, its potential impact in medicine is diminished by a very high cost, limiting its dissemination. An RF-penetrable PET ring that can be inserted into any existing MR system has been developed to address this issue. Employing optical signal transmission along with battery power enables the PET ring insert to electrically float with respect to the MR system. Then, inter-modular gaps of the PET ring allow the RF transmit field from the standard built-in body coil to penetrate into the PET fields-of-view (FOV) with some attenuation that can be compensated for. MR performance, including RF noise, magnetic susceptibility, RF penetrability through and $B_{1}$ uniformity within the PET insert, and MR image quality, were analyzed with and without the PET ring present. The simulated and experimentally measured RF field attenuation factors with the PET ring present were -2.7 and -3.2 dB, respectively. The magnetic susceptibility effect (0.063 ppm) and noise emitted from the PET ring in the MR receive channel were insignificant. $B_{1}$ homogeneity of a spherical agar phantom within the PET ring FOV dropped by 8.4% and MR image SNR was reduced by 3.5 and 4.3 dB with the PET present for gradient-recalled echo and fast-spin echo, respectively. This paper demonstrates, for the first time, an RF-penetrable PET insert comprising a full ring of operating detectors that achieves simultaneous PET/MR using the standard built-in body coil as the RF transmitter.
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27
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Chen Z, Jamadar SD, Li S, Sforazzini F, Baran J, Ferris N, Shah NJ, Egan GF. From simultaneous to synergistic MR-PET brain imaging: A review of hybrid MR-PET imaging methodologies. Hum Brain Mapp 2018; 39:5126-5144. [PMID: 30076750 DOI: 10.1002/hbm.24314] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2018] [Revised: 06/25/2018] [Accepted: 07/02/2018] [Indexed: 12/17/2022] Open
Abstract
Simultaneous Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) scanning is a recent major development in biomedical imaging. The full integration of the PET detector ring and electronics within the MR system has been a technologically challenging design to develop but provides capacity for simultaneous imaging and the potential for new diagnostic and research capability. This article reviews state-of-the-art MR-PET hardware and software, and discusses future developments focusing on neuroimaging methodologies for MR-PET scanning. We particularly focus on the methodologies that lead to an improved synergy between MRI and PET, including optimal data acquisition, PET attenuation and motion correction, and joint image reconstruction and processing methods based on the underlying complementary and mutual information. We further review the current and potential future applications of simultaneous MR-PET in both systems neuroscience and clinical neuroimaging research. We demonstrate a simultaneous data acquisition protocol to highlight new applications of MR-PET neuroimaging research studies.
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Affiliation(s)
- Zhaolin Chen
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Victoria, Australia
| | - Sharna D Jamadar
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Monash Institute of Cognitive and Clinical Neuroscience, Monash University, Clayton, Victoria, Australia.,Australian Research Council Centre of Excellence for Integrative Brain Function, Monash University, Clayton, Victoria, Australia
| | - Shenpeng Li
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Department of Electrical and Computer Systems Engineering, Monash University, Clayton, Victoria, Australia
| | | | - Jakub Baran
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Department of Biophysics, Faculty of Mathematics and Natural Sciences, University of Rzeszów, Rzeszów, Poland
| | - Nicholas Ferris
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Monash Imaging, Monash Health, Clayton, Victoria, Australia
| | - Nadim Jon Shah
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Institute of Neuroscience and Medicine 4, INM-4, Forschungszentrum, Jülich, Germany
| | - Gary F Egan
- Monash Biomedical Imaging, Monash University, Clayton, Victoria, Australia.,Monash Institute of Cognitive and Clinical Neuroscience, Monash University, Clayton, Victoria, Australia.,Australian Research Council Centre of Excellence for Integrative Brain Function, Monash University, Clayton, Victoria, Australia
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28
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Magnetic Resonance Imaging technology-bridging the gap between noninvasive human imaging and optical microscopy. Curr Opin Neurobiol 2018; 50:250-260. [PMID: 29753942 DOI: 10.1016/j.conb.2018.04.026] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2017] [Revised: 04/20/2018] [Accepted: 04/24/2018] [Indexed: 12/23/2022]
Abstract
Technological advances in Magnetic Resonance Imaging (MRI) have provided substantial gains in the sensitivity and specificity of functional neuroimaging. Mounting evidence demonstrates that the hemodynamic changes utilized in functional MRI can be far more spatially and thus neuronally specific than previously believed. This has motivated a push toward novel, high-resolution MR imaging strategies that can match this biological resolution limit while recording from the entire human brain. Although sensitivity increases are a necessary component, new MR encoding technologies are required to convert improved sensitivity into higher resolution. These new sampling strategies improve image acquisition efficiency and enable increased image encoding in the time-frame needed to follow hemodynamic changes associated with brain activation.
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Mannheim JG, Schmid AM, Schwenck J, Katiyar P, Herfert K, Pichler BJ, Disselhorst JA. PET/MRI Hybrid Systems. Semin Nucl Med 2018; 48:332-347. [PMID: 29852943 DOI: 10.1053/j.semnuclmed.2018.02.011] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Over the last decade, the combination of PET and MRI in one system has proven to be highly successful in basic preclinical research, as well as in clinical research. Nowadays, PET/MRI systems are well established in preclinical imaging and are progressing into clinical applications to provide further insights into specific diseases, therapeutic assessments, and biological pathways. Certain challenges in terms of hardware had to be resolved concurrently with the development of new techniques to be able to reach the full potential of both combined techniques. This review provides an overview of these challenges and describes the opportunities that simultaneous PET/MRI systems can exploit in comparison with stand-alone or other combined hybrid systems. New approaches were developed for simultaneous PET/MRI systems to correct for attenuation of 511 keV photons because MRI does not provide direct information on gamma photon attenuation properties. Furthermore, new algorithms to correct for motion were developed, because MRI can accurately detect motion with high temporal resolution. The additional information gained by the MRI can be employed to correct for partial volume effects as well. The development of new detector designs in combination with fast-decaying scintillator crystal materials enabled time-of-flight detection and incorporation in the reconstruction algorithms. Furthermore, this review lists the currently commercially available systems both for preclinical and clinical imaging and provides an overview of applications in both fields. In this regard, special emphasis has been placed on data analysis and the potential for both modalities to evolve with advanced image analysis tools, such as cluster analysis and machine learning.
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Affiliation(s)
- Julia G Mannheim
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Andreas M Schmid
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Johannes Schwenck
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany; Department of Nuclear Medicine and Clinical Molecular Imaging, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Prateek Katiyar
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Kristina Herfert
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany
| | - Bernd J Pichler
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany.
| | - Jonathan A Disselhorst
- Department of Preclinical Imaging and Radiopharmacy, Werner Siemens Imaging Center, Eberhard Karls University Tuebingen, Tuebingen, Germany
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30
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Schoenberger M, Schroeder FA, Placzek MS, Carter RL, Rosen BR, Hooker JM, Sander CY. In Vivo [ 18F]GE-179 Brain Signal Does Not Show NMDA-Specific Modulation with Drug Challenges in Rodents and Nonhuman Primates. ACS Chem Neurosci 2018; 9:298-305. [PMID: 29050469 PMCID: PMC5894869 DOI: 10.1021/acschemneuro.7b00327] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
As one of the major excitatory ion channels in the brain, NMDA receptors have been a leading research target for neuroscientists, physicians, medicinal chemists, and pharmaceutical companies for decades. Molecular imaging of NMDA receptors by means of positron emission tomography (PET) with [18F]GE-179 quickly progressed to clinical PET studies, but a thorough understanding of its binding specificity has been missing and has thus limited signal interpretation. Here a preclinical study with [18F]GE-179 in rodents and nonhuman primates (NHPs) is presented in an attempt to characterize [18F]GE-179 signal specificity. Rodent PET/CT was used to study drug occupancy and functional manipulation in rats by pretreating animals with NMDA targeted blocking/modulating drug doses followed by a single bolus of [18F]GE-179. Binding competition with GE-179, MK801, PCP, and ketamine, allosteric inhibition by ifenprodil, and brain activation with methamphetamine did not alter the [18F]GE-179 brain signal in rats. In addition, multimodal imaging with PET/MRI in NHPs was used to evaluate changes in radiotracer binding as a function of pharmacological challenges. Drug-induced hemodynamic changes were monitored simultaneously using functional MRI (fMRI). Comparisons of baseline and signal after drug challenge in NHPs demonstrated that the [18F]GE-179 signal cannot be manipulated in a predictable fashion in vivo. fMRI data acquired simultaneously with PET data supported this finding and provided evidence that radiotracer delivery is not altered by blood flow changes. In conclusion, the [18F]GE-179 brain signal is not readily interpretable in the context of NMDA receptor binding on the basis of the results shown in this study.
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Affiliation(s)
- Matthias Schoenberger
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown, Massachusetts 02129, United States
- Chemical Biology and Imaging, Department of Pharmaceutical and Pharmacological Sciences, KU Leuven , BE-3000 Leuven, Belgium
| | - Frederick A Schroeder
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown, Massachusetts 02129, United States
| | - Michael S Placzek
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown, Massachusetts 02129, United States
- Department of Psychiatry, McLean Imaging Center, McLean Hospital , Belmont, Massachusetts 02478, United States
- Harvard Medical School , Boston, Massachusetts 02115, United States
| | | | - Bruce R Rosen
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown, Massachusetts 02129, United States
- Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States
| | - Jacob M Hooker
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown, Massachusetts 02129, United States
- Harvard Medical School , Boston, Massachusetts 02115, United States
| | - Christin Y Sander
- Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital , Charlestown, Massachusetts 02129, United States
- Harvard Medical School , Boston, Massachusetts 02115, United States
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31
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Lerche CW, Kaltsas T, Caldeira L, Scheins J, Rota Kops E, Tellmann L, Pietrzyk U, Herzog H, Shah NJ. PET attenuation correction for rigid MR Tx/Rx coils from 176Lu background activity. Phys Med Biol 2018; 63:035039. [PMID: 29328049 DOI: 10.1088/1361-6560/aaa72a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
One challenge for PET-MR hybrid imaging is the correction for attenuation of the 511 keV annihilation radiation by the required RF transmit and/or RF receive coils. Although there are strategies for building PET transparent Tx/Rx coils, such optimised coils still cause significant attenuation of the annihilation radiation leading to artefacts and biases in the reconstructed activity concentrations. We present a straightforward method to measure the attenuation of Tx/Rx coils in simultaneous MR-PET imaging based on the natural 176Lu background contained in the scintillator of the PET detector without the requirement of an external CT scanner or PET scanner with transmission source. The method was evaluated on a prototype 3T MR-BrainPET produced by Siemens Healthcare GmbH, both with phantom studies and with true emission images from patient/volunteer examinations. Furthermore, the count rate stability of the PET scanner and the x-ray properties of the Tx/Rx head coil were investigated. Even without energy extrapolation from the two dominant γ energies of 176Lu to 511 keV, the presented method for attenuation correction, based on the measurement of 176Lu background attenuation, shows slightly better performance than the coil attenuation correction currently used. The coil attenuation correction currently used is based on an external transmission scan with rotating 68Ge sources acquired on a Siemens ECAT HR + PET scanner. However, the main advantage of the presented approach is its straightforwardness and ready availability without the need for additional accessories.
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Affiliation(s)
- Christoph W Lerche
- Medical Imaging Physics Department, Institute for Neuroscience and Medicine (INM-4), Forschungszentrum Jülich GmbH, Jülich, Germany
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32
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Eldib M, Bini J, Faul DD, Oesingmann N, Tsoumpas C, Fayad ZA. Attenuation Correction for Magnetic Resonance Coils in Combined PET/MR Imaging: A Review. PET Clin 2016; 11:151-60. [PMID: 26952728 PMCID: PMC4785842 DOI: 10.1016/j.cpet.2015.10.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
With the introduction of clinical PET/magnetic resonance (MR) systems, novel attenuation correction methods are needed, as there are no direct MR methods to measure the attenuation of the objects in the field of view (FOV). A unique challenge for PET/MR attenuation correction is that coils for MR data acquisition are located in the FOV of the PET camera and could induce significant quantitative errors. In this review, current methods and techniques to correct for the attenuation of a variety of coils are summarized and evaluated.
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Affiliation(s)
- Mootaz Eldib
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; Department of Biomedical Engineering, The City College of New York, 160 Convent Avenue, New York, NY 10031, USA
| | - Jason Bini
- Department of Diagnostic Radiology, PET Center, Yale School of Medicine, Yale University, 801 Howard Avenue, New Haven, CT 06520, USA
| | - David D Faul
- Siemens Healthcare, 527 Madison Avenue, New York, NY 10022, USA
| | | | - Charalampos Tsoumpas
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; Division of Biomedical Imaging, Faculty of Medicine and Health, University of Leeds, 8.001a Worsley Building, Clarendon Way, Leeds LS2 9JT, UK
| | - Zahi A Fayad
- Translational and Molecular Imaging Institute, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; Department of Radiology, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA; Department of Cardiology, Zena and Michael A. Weiner Cardiovascular Institute, Marie-Josée and Henry R. Kravis Cardiovascular Health Center, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, New York, NY 10029, USA.
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