Xinchi Hou1, Julia Brosch2, Carlos Uribe3,4, Alessandro Desy5,6, Guido Böning2, Jean-Mathieu Beauregard5,6, Anna Celler3, Arman Rahmim1,4,7. 1. Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada; arman.rahmim@ubc.ca. 2. Department of Nuclear Medicine, University Hospital, Ludwig-Maximilians-Universität, Munich, Germany. 3. Department of Radiology, University of British Columbia, Vancouver, British Columbia, Canada. 4. Functional Imaging, BC Cancer, Vancouver, British Columbia, Canada. 5. Cancer Research Centre and Department of Radiology and Nuclear Medicine, Université Laval, Quebec City, Quebec, Canada. 6. Department of Medical Imaging and Oncology, Université Laval Research Centre, CHU de Québec-Université Laval, Quebec City, Quebec, Canada; and. 7. Department of Integrative Oncology, BC Cancer Research Institute, Vancouver, British Columbia, Canada.
Abstract
Because of challenges in performing routine personalized dosimetry in radiopharmaceutical therapies, interest in single-time-point (STP) dosimetry, particularly using only a single SPECT scan, is on the rise. Meanwhile, there are questions about the reliability of STP dosimetry, with limited independent validations. In the present work, we analyzed 2 STP dosimetry methods and evaluated dose errors for several radiopharmaceuticals based on effective half-life distributions. Methods: We first challenged the common assumption that radiopharmaceutical effective half-lives across the population are gaussian-distributed (i.e., follow a normal distribution). Then, dose accuracy was estimated using 2 STP dosimetry methods for a wide range of potential post injection (p.i.) scan time points for different radiopharmaceuticals applied to neuroendocrine tumors and prostate cancer. The accuracy and limitations of each of the STP methods were discussed. Results: A lognormal distribution was more appropriate for capturing effective half-life distributions. The STP framework was promising for dosimetry of 177Lu-DOTATATE and for kidney dosimetry of different radiopharmaceuticals (errors < 30%). Meanwhile, for some radiopharmaceuticals, STP accuracy was compromised (e.g., in bone marrow and tumors for 177-labeled prostate-specific membrane antigen [PSMA])). The optimal SPECT scanning time for 177Lu-DOTATATE was approximately 72 h p.i., whereas 48 h p.i. was better for 177Lu-PSMA. Conclusion: Simplified STP dosimetry methods may compromise the accuracy of dose estimates, with some exceptions, such as for 177Lu-DOTATATE and for kidney dosimetry in different radiopharmaceuticals. Simplified personalized dosimetry in the clinic continues to be challenging. On the basis of our results, we make suggestions and recommendations for improved personalized dosimetry using simplified imaging schemes.
Because of challenges in performing routine personalized dosimetry in radiopharmaceutical therapies, interest in single-time-point (STP) dosimetry, particularly using only a single SPECT scan, is on the rise. Meanwhile, there are questions about the reliability of STP dosimetry, with limited independent validations. In the present work, we analyzed 2 STP dosimetry methods and evaluated dose errors for several radiopharmaceuticals based on effective half-life distributions. Methods: We first challenged the common assumption that radiopharmaceutical effective half-lives across the population are gaussian-distributed (i.e., follow a normal distribution). Then, dose accuracy was estimated using 2 STP dosimetry methods for a wide range of potential post injection (p.i.) scan time points for different radiopharmaceuticals applied to neuroendocrine tumors and prostate cancer. The accuracy and limitations of each of the STP methods were discussed. Results: A lognormal distribution was more appropriate for capturing effective half-life distributions. The STP framework was promising for dosimetry of 177Lu-DOTATATE and for kidney dosimetry of different radiopharmaceuticals (errors < 30%). Meanwhile, for some radiopharmaceuticals, STP accuracy was compromised (e.g., in bone marrow and tumors for 177-labeled prostate-specific membrane antigen [PSMA])). The optimal SPECT scanning time for 177Lu-DOTATATE was approximately 72 h p.i., whereas 48 h p.i. was better for 177Lu-PSMA. Conclusion: Simplified STP dosimetry methods may compromise the accuracy of dose estimates, with some exceptions, such as for 177Lu-DOTATATE and for kidney dosimetry in different radiopharmaceuticals. Simplified personalized dosimetry in the clinic continues to be challenging. On the basis of our results, we make suggestions and recommendations for improved personalized dosimetry using simplified imaging schemes.
Authors: Heribert Hänscheid; Constantin Lapa; Andreas K Buck; Michael Lassmann; Rudolf A Werner Journal: J Nucl Med Date: 2017-06-06 Impact factor: 10.057