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Calatayud-Jordán J, Carrasco-Vela N, Chimeno-Hernández J, Carles-Fariña M, Olivas-Arroyo C, Bello-Arqués P, Pérez-Enguix D, Martí-Bonmatí L, Torres-Espallardo I. Y-90 PET/MR imaging optimization with a Bayesian penalized likelihood reconstruction algorithm. Phys Eng Sci Med 2024:10.1007/s13246-024-01452-7. [PMID: 38884672 DOI: 10.1007/s13246-024-01452-7] [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: 02/17/2024] [Accepted: 05/23/2024] [Indexed: 06/18/2024]
Abstract
Positron Emission Tomography (PET) imaging after90 Y liver radioembolization is used for both lesion identification and dosimetry. Bayesian penalized likelihood (BPL) reconstruction algorithms are an alternative to ordered subset expectation maximization (OSEM) with improved image quality and lesion detectability. The investigation of optimal parameters for90 Y image reconstruction of Q.Clear, a commercial BPL algorithm developed by General Electric (GE), in PET/MR is a field of interest and the subject of this study. The NEMA phantom was filled at an 8:1 sphere-to-background ratio. Acquisitions were performed on a PET/MR scanner for clinically relevant activities between 0.7 and 3.3 MBq/ml. Reconstructions with Q.Clear were performed varying the β penalty parameter between 20 and 6000, the acquisition time between 5 and 20 min and pixel size between 1.56 and 4.69 mm. OSEM reconstructions of 28 subsets with 2 and 4 iterations with and without Time-of-Flight (TOF) were compared to Q.Clear with β = 4000. Recovery coefficients (RC), their coefficient of variation (COV), background variability (BV), contrast-to-noise ratio (CNR) and residual activity in the cold insert were evaluated. Increasing β parameter lowered RC, COV and BV, while CNR was maximized at β = 4000; further increase resulted in oversmoothing. For quantification purposes, β = 1000-2000 could be more appropriate. Longer acquisition times resulted in larger CNR due to reduced image noise. Q.Clear reconstructions led to higher CNR than OSEM. A β of 4000 was obtained for optimal image quality, although lower values could be considered for quantification purposes. An optimal acquisition time of 15 min was proposed considering its clinical use.
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Affiliation(s)
- José Calatayud-Jordán
- Department of Nuclear Medicine, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain.
| | - Nuria Carrasco-Vela
- Radiophysics and Radiological Protection Service, Clinical University Hospital of Valencia, Av. Blasco Ibáñez 17, 46010, Valencia, Spain
| | - José Chimeno-Hernández
- Department of Nuclear Medicine, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - Montserrat Carles-Fariña
- Biomedical Imaging Research Group (GIBI230) at Health Research Institute Hospital La Fe (IIS La Fe), La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - Consuelo Olivas-Arroyo
- Department of Nuclear Medicine, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - Pilar Bello-Arqués
- Department of Nuclear Medicine, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - Daniel Pérez-Enguix
- Department of Radiology, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - Luis Martí-Bonmatí
- Biomedical Imaging Research Group (GIBI230) at Health Research Institute Hospital La Fe (IIS La Fe), La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
- Department of Radiology, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
| | - Irene Torres-Espallardo
- Department of Nuclear Medicine, La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
- Biomedical Imaging Research Group (GIBI230) at Health Research Institute Hospital La Fe (IIS La Fe), La Fe University and Polytechnical Hospital, Av. Fernando Abril Martorell 106, 46026, Valencia, Spain
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2
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Sharma NK, Kappadath SC, Chuong M, Folkert M, Gibbs P, Jabbour SK, Jeyarajah DR, Kennedy A, Liu D, Meyer JE, Mikell J, Patel RS, Yang G, Mourtada F. The American Brachytherapy Society consensus statement for permanent implant brachytherapy using Yttrium-90 microsphere radioembolization for liver tumors. Brachytherapy 2022; 21:569-591. [PMID: 35599080 PMCID: PMC10868645 DOI: 10.1016/j.brachy.2022.04.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/25/2022] [Accepted: 04/14/2022] [Indexed: 11/02/2022]
Abstract
PURPOSE To develop a multidisciplinary consensus for high quality multidisciplinary implementation of brachytherapy using Yttrium-90 (90Y) microspheres transarterial radioembolization (90Y TARE) for primary and metastatic cancers in the liver. METHODS AND MATERIALS Members of the American Brachytherapy Society (ABS) and colleagues with multidisciplinary expertise in liver tumor therapy formulated guidelines for 90Y TARE for unresectable primary liver malignancies and unresectable metastatic cancer to the liver. The consensus is provided on the most recent literature and clinical experience. RESULTS The ABS strongly recommends the use of 90Y microsphere brachytherapy for the definitive/palliative treatment of unresectable liver cancer when recommended by the multidisciplinary team. A quality management program must be implemented at the start of 90Y TARE program development and follow-up data should be tracked for efficacy and toxicity. Patient-specific dosimetry optimized for treatment intent is recommended when conducting 90Y TARE. Implementation in patients on systemic therapy should account for factors that may enhance treatment related toxicity without delaying treatment inappropriately. Further management and salvage therapy options including retreatment with 90Y TARE should be carefully considered. CONCLUSIONS ABS consensus for implementing a safe 90Y TARE program for liver cancer in the multidisciplinary setting is presented. It builds on previous guidelines to include recommendations for appropriate implementation based on current literature and practices in experienced centers. Practitioners and cooperative groups are encouraged to use this document as a guide to formulate their clinical practices and to adopt the most recent dose reporting policies that are critical for a unified outcome analysis of future effectiveness studies.
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Affiliation(s)
- Navesh K Sharma
- Department of Radiation Oncology, Penn State Hershey School of Medicine, Hershey, PA
| | - S Cheenu Kappadath
- Department of Imaging Physics, UT MD Anderson Cancer Center, Houston, TX
| | - Michael Chuong
- Department of Radiation Oncology, Miami Cancer Institute, Miami, FL
| | - Michael Folkert
- Northwell Health Cancer Institute, Radiation Medicine at the Center for Advanced Medicine, New Hyde Park, NY
| | - Peter Gibbs
- Personalised Oncology Division, Walter and Eliza Hall Institute, Melbourne, Victoria, Australia
| | - Salma K Jabbour
- Rutgers Cancer Institute of New Jersey, Rutgers University, New Brunswick, NJ
| | | | | | - David Liu
- Vancouver General Hospital, Vancouver, British Columbia, Canada
| | | | | | - Rahul S Patel
- Icahn School of Medicine at Mount Sinai, New York, NY
| | - Gary Yang
- Loma Linda University, Loma Linda, CA
| | - Firas Mourtada
- Helen F. Graham Cancer Center & Research Institute, Christiana Care Health System, Newark, DE; Department of Radiation Oncology, Sidney Kimmel Cancer Center at Thomas Jefferson University, Philadelphia, PA.
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3
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Rice M, Krosin M, Haste P. Post Yttrium-90 Imaging. Semin Intervent Radiol 2021; 38:460-465. [PMID: 34629714 DOI: 10.1055/s-0041-1735569] [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: 10/20/2022]
Abstract
Transarterial radioembolization with yttrium-90 ( 90 Y) is a mainstay for the treatment of liver cancer. Imaging the distribution following delivery is a concept that dates back to the 1960s. As β particles are created during 90 Y decay, bremsstrahlung radiation is created as the particles interact with tissues, allowing for imaging with a gamma camera. Inherent qualities of bremsstrahlung radiation make its imaging difficult. SPECT and SPECT/CT can be used but suffer from limitations related to low signal-to-noise bremsstrahlung radiation. However, with optimized imaging protocols, clinically adequate images can still be obtained. A finite but detectable number of positrons are also emitted during 90 Y decay, and many studies have demonstrated the ability of commercial PET/CT and PET/MR scanners to image these positrons to understand 90 Y distribution and help quantify dose. PET imaging has been proven to be superior to SPECT for quantitative imaging, and therefore will play an important role going forward as we try and better understand dose/response and dose/toxicity relationships to optimize personalized dosimetry. The availability of PET imaging will likely remain the biggest barrier to its use in routine post- 90 Y imaging; thus, SPECT/CT imaging with optimized protocols should be sufficient for most posttherapy subjective imaging.
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Affiliation(s)
- Mitchell Rice
- Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Matthew Krosin
- Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana
| | - Paul Haste
- Department of Radiology, Indiana University School of Medicine, Indianapolis, Indiana
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4
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Knešaurek K. An estimate of 90Y dosimetry for bremsstrahlung SPECT/CT imaging in liver therapy with 90Y microspheres. Eur J Radiol 2021; 139:109698. [PMID: 33848778 DOI: 10.1016/j.ejrad.2021.109698] [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: 09/15/2020] [Revised: 03/02/2021] [Accepted: 04/02/2021] [Indexed: 10/21/2022]
Abstract
OBJECTIVE Bremsstrahlung SPECT/CT (bSPECT/CT) is one of the most common methods for post-therapy imaging in 90Y microspheres selective internal radiation therapy (SIRT) of liver cancers. Here, we are proposing a simple approach using bSPECT/CT to estimate mean absorbed dose to the liver in patients undergoing treatment with 90Y microspheres. MATERIALS AND METHODS In our previous study comparing 90Y dosimetry obtained using bSPECT/CT vs PET/CT, we found that there was a large difference between the mean absorbed dose values to the whole-liver. However, there was a high linear correlation between the doses, which presented an opportunity for quantitative assessment using bSPECT/CT 90Y imaging. In this study, after treatment with 90Y microspheres, 43 patients were immediately imaged on a dual-head Infinia SPECT/CT gamma camera and on a mCT PET/CT system. Images from 25 of the patients, randomly selected, were used to calculate the correlation of mean liver doses obtained from bSPECT/CT vs. PET/CT. For the remaining 18 patients, the calculated correlation was used to estimate doses obtained from bSPECT/CT, and these estimations were then compared to the doses obtained from PET/CT, considered the gold standard for quantitative analysis. RESULTS From the 25 selected patients, the calculated linear correlation between bSPECT/CT and PET/CT 90Y mean absorbed doses in whole liver was high (r^2 = 0.97), with a slope of 2.80 and an intercept of -0.63. This linear fit was used to calculate the bSPECT/CT doses for the remaining 18 patients. For these patients, the mean whole-liver dose obtained from bSPECT/CT fitted data vs that obtained from PET/CT were 50.59 Gy and 50.81 Gy, respectively. The average dose difference was 0.2 ± 5.4 Gy (range -18.2%-13.0%). The repeatability coefficient was 10.5 (20.8 % of the mean). CONCLUSION Although quantitative bremsstrahlung imaging is difficult, it is possible to calculate adequate estimates of whole-liver dosimetry from bSPECT/CT imaging that is calibrated using its correlation with post-therapy PET/CT 90Y images.
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Affiliation(s)
- Karin Knešaurek
- Division of Nuclear Medicine, Department of Radiology, Icahn School of Medicine at Mount Sinai, Box 1141, One Gustave L. Levy Place, New York, NY, 10029, USA.
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Mok GSP, Dewaraja YK. Recent advances in voxel-based targeted radionuclide therapy dosimetry. Quant Imaging Med Surg 2021; 11:483-489. [PMID: 33532249 PMCID: PMC7779928 DOI: 10.21037/qims-20-1006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 09/27/2020] [Indexed: 02/04/2023]
Affiliation(s)
- Greta S. P. Mok
- Biomedical Imaging Laboratory (BIG), Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau, China
- Center for Cognitive and Brain Sciences, Institute of Collaborative Innovation, University of Macau, Macau, China
| | - Yuni K. Dewaraja
- Department of Radiology, University of Michigan Medical School, Ann Arbor, MI, USA
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Garrow AA, Andrews JPM, Gonzalez ZN, Corral CA, Portal C, Morgan TEF, Walton T, Wilson I, Newby DE, Lucatelli C, Tavares AAS. Preclinical dosimetry models and the prediction of clinical doses of novel positron emission tomography radiotracers. Sci Rep 2020; 10:15985. [PMID: 32994530 PMCID: PMC7525662 DOI: 10.1038/s41598-020-72830-w] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Accepted: 09/07/2020] [Indexed: 11/09/2022] Open
Abstract
Dosimetry models using preclinical positron emission tomography (PET) data are commonly employed to predict the clinical radiological safety of novel radiotracers. However, unbiased clinical safety profiling remains difficult during the translational exercise from preclinical research to first-in-human studies for novel PET radiotracers. In this study, we assessed PET dosimetry data of six 18F-labelled radiotracers using preclinical dosimetry models, different reconstruction methods and quantified the biases of these predictions relative to measured clinical doses to ease translation of new PET radiotracers to first-in-human studies. Whole-body PET images were taken from rats over 240 min after intravenous radiotracer bolus injection. Four existing and two novel PET radiotracers were investigated: [18F]FDG, [18F]AlF-NOTA-RGDfK, [18F]AlF-NOTA-octreotide ([18F]AlF-NOTA-OC), [18F]AlF-NOTA-NOC, [18F]ENC2015 and [18F]ENC2018. Filtered-back projection (FBP) and iterative methods were used for reconstruction of PET data. Predicted and true clinical absorbed doses for [18F]FDG and [18F]AlF-NOTA-OC were then used to quantify bias of preclinical model predictions versus clinical measurements. Our results show that most dosimetry models were biased in their predicted clinical dosimetry compared to empirical values. Therefore, normalization of rat:human organ sizes and correction for reconstruction method biases are required to achieve higher precision of dosimetry estimates.
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Affiliation(s)
- Adam A Garrow
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Jack P M Andrews
- University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK
| | - Zaniah N Gonzalez
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.,University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK
| | - Carlos A Corral
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.,University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK
| | - Christophe Portal
- Edinburgh Molecular Imaging (EMI), Nine Edinburgh Bioquarter, Edinburgh, EH16 4UX, UK
| | - Timaeus E F Morgan
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.,University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK
| | - Tashfeen Walton
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.,University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK
| | - Ian Wilson
- Edinburgh Molecular Imaging (EMI), Nine Edinburgh Bioquarter, Edinburgh, EH16 4UX, UK
| | - David E Newby
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK.,University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK
| | - Christophe Lucatelli
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK
| | - Adriana A S Tavares
- Preclinical PET-CT Facility, Edinburgh Imaging, Queen's Medical Research Institute, The University of Edinburgh, 47 Little France Crescent, Edinburgh, EH16 4TJ, UK. .,University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, Edinburgh, EH16 4TJ, UK.
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7
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Knešaurek K. Comparison of posttherapy 90Y positron emission tomography/computed tomography dosimetry methods in liver therapy with 90Y microspheres. World J Nucl Med 2020; 19:359-365. [PMID: 33623505 PMCID: PMC7875028 DOI: 10.4103/wjnm.wjnm_23_20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Revised: 05/13/2020] [Accepted: 05/17/2020] [Indexed: 12/04/2022] Open
Abstract
The aim of our study was to compare dosimetry methods for yttrium-90 (90Y) positron emission tomography/computed tomography (PET/CT). Twenty-five patients were taken to a PET/CT suite following therapy with 90Y microspheres. The low mA, nondiagnostic CT images were used for attenuation correction and localization of the 90Y microspheres. The acquisition time was 15 min, the reconstruction matrix size was 200 mm × 200 mm × 75 mm, and voxel size was 4.07 mm × 4.07 mm × 3.00 mm. Two software packages, MIM 6.8 and Planet Dose, were utilized to calculate 90Y dosimetry. Three methods were used for voxel-based dosimetry calculations: the local deposition method (LDM), LDM with scaling (LDMwS) for known injected activity, and a dose point kernel (DPK) method using the MIRD kernel. Only the DPK approach was applied to the Planet Dose software. LDM and LDMwS were only applied to the MIM software. The average total liver dosimetry values (mean ± standard deviation) were 60.93 ± 28.62 Gy, 53.59 ± 23.47 Gy, 55.33 ± 24.80 Gy, and 54.25 ± 23.70 Gy for LDMwS, LDM, DPK with MIM, and DPK with Planet Dose (DOSI), respectively. In most cases, the LDMwS method produced slightly higher dosimetry values than the other methods. The MIM and Planet Dose DPK dosimetry values (i.e., DPK vs. DOSI) were highly comparable. Bland–Altman analysis calculated a mean difference of 1.1 ± 2.2 Gy. The repeatability coefficient was 4.4 (7.9% of the mean). The MIM and Planet Dose DPK dosimetry values were practically interchangeable. 90Y dosimetry values obtained by all methods were similar, but LDMwS tended to produce slightly higher values.
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Affiliation(s)
- Karin Knešaurek
- Department of Radiology, Icahn School of Medicine at Mount Sinai, New York, USA
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St James S, Bednarz B, Benedict S, Buchsbaum JC, Dewaraja Y, Frey E, Hobbs R, Grudzinski J, Roncali E, Sgouros G, Capala J, Xiao Y. Current Status of Radiopharmaceutical Therapy. Int J Radiat Oncol Biol Phys 2020; 109:891-901. [PMID: 32805300 DOI: 10.1016/j.ijrobp.2020.08.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2020] [Accepted: 08/06/2020] [Indexed: 02/02/2023]
Abstract
In radiopharmaceutical therapy (RPT), a radionuclide is systemically or locally delivered with the goal of targeting and delivering radiation to cancer cells while minimizing radiation exposure to untargeted cells. Examples of current RPTs include thyroid ablation with the administration of 131I, treatment of liver cancer with 90Y microspheres, the treatment of bony metastases with 223Ra, and the treatment of neuroendocrine tumors with 177Lu-DOTATATE. New RPTs are being developed where radionuclides are incorporated into systemic targeted therapies. To assure that RPT is appropriately implemented, advances in targeting need to be matched with advances in quantitative imaging and dosimetry methods. Currently, radiopharmaceutical therapy is administered by intravenous or locoregional injection, and the treatment planning has typically been implemented like chemotherapy, where the activity administered is either fixed or based on a patient's body weight or body surface area. RPT pharmacokinetics are measurable by quantitative imaging and are known to vary across patients, both in tumors and normal tissues. Therefore, fixed or weight-based activity prescriptions are not currently optimized to deliver a cytotoxic dose to targets while remaining within the tolerance dose of organs at risk. Methods that provide dose estimates to individual patients rather than to reference geometries are needed to assess and adjust the injected RPT dose. Accurate doses to targets and organs at risk will benefit the individual patients and decrease uncertainties in clinical trials. Imaging can be used to measure activity distribution in vivo, and this information can be used to determine patient-specific treatment plans where the dose to the targets and organs at risk can be calculated. The development and adoption of imaging-based dosimetry methods is particularly beneficial in early clinical trials. In this work we discuss dosimetric accuracy needs in modern radiation oncology, uncertainties in the dosimetry in RPT, and best approaches for imaging and dosimetry of internal radionuclide therapy.
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Affiliation(s)
- Sara St James
- Department of Radiation Oncology, University of California San Francisco, San Francisco, California.
| | - Bryan Bednarz
- Department of Medical Physics and Human Oncology, University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin
| | - Stanley Benedict
- Department of Radiation Oncology, University of California Davis, Sacramento, California
| | - Jeffrey C Buchsbaum
- Radiation Research Program, Division of Cancer Treatment and Diagnosis, NCI, NIH, Bethesda, Maryland
| | - Yuni Dewaraja
- Department of Radiology, University of Michigan, Ann Arbor, Michigan
| | - Eric Frey
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Robert Hobbs
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | | | - Emilie Roncali
- Department of Radiation Oncology, University of California Davis, Sacramento, California
| | - George Sgouros
- Department of Radiology, Johns Hopkins University, Baltimore, Maryland
| | - Jacek Capala
- Radiation Research Program, Division of Cancer Treatment and Diagnosis, NCI, NIH, Bethesda, Maryland
| | - Ying Xiao
- Hospital of the University of Pennsylvania
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