Evaluation of sequential SPECT and CT for targeted radionuclide therapy dosimetry
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ORIGINAL ARTICLE
Evaluation of sequential SPECT and CT for targeted radionuclide therapy dosimetry Tiantian Li1 · Nien‑Yun Wu2,3 · Na Song4 · Greta S. P. Mok1,5 Received: 5 September 2017 / Accepted: 8 November 2017 / Published online: 15 November 2017 © The Japanese Society of Nuclear Medicine 2017
Abstract Purpose In targeted radionuclide therapy (TRT), a prior knowledge of the absorbed dose biodistribution is essential for pre-therapy treatment planning. Previously, we showed that non-rigid organ-by-organ registration in sequential quantitative SPECT images improved dose estimation. This study aims to investigate if sequential CT can further improve TRT dosimetric accuracy. Methods We simulated SPECT/CT acquisitions at 1, 12, 24, 72 and 144 h In-111 Zevalin post-injection using an analytical MEGP projector, modeling attenuation, scatter and collimator-detector response. We later recruited a patient injected with 222 MBq In-111 DTPAOC imaged at 3 SPECT/CT sessions for clinical evaluations. Four registration schemes were evaluated: whole-body-based registration performed on sequential (1) SPECT (WB-SPECT) or (2) CT (WB-CT) images; organ-based registration applied on organs individually segmented from sequential (3) SPECT (O-SPECT) or (4) CT (O-CT) images. Voxel-by-voxel integration was performed followed by Y-90 voxel-S-kernel convolution. Organ-absorbed doses, iso-dose curves, dose–volume histograms (DVHs) were generated for targeted organs for analysis. Results: In simulation study, organ-absorbed dose errors were (− 8.66 ± 2.83)%, (− 2.51 ± 3.69)%, (− 9.23 ± 3.28)%, (− 7.17 ± 2.53)% for liver, (− 14.81 ± 4.91)%, (− 3.60 ± 4.37)%, (− 18.13 ± 4.44)%, (− 11.34 ± 4.22)% for spleen, for O-SPECT, O-CT, WB-SPECT and WB-CT registrations, respectively. For all organs, O-CT showed superior results. Results of iso-dose contour, DVHs were in accordance with the organ-absorbed doses. In clinical studies, the results were also consistent which showed O-CT method deviated the most from the result with no registration. Conclusions: We conclude that if both sequential SPECT/CT scans are available, CT organ-based registration method can more effectively improve the 3D dose estimation. Sequential low-dose CT scans might be considered to be included in the standard TRT protocol. Keywords Targeted radionuclide therapy · Quantitative SPECT · CT · Dosimetry · Image registration
* Greta S. P. Mok [email protected] 1
Biomedical Imaging Laboratory, Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau SAR, China
2
Department of Biomedical Imaging and Radiological Sciences, National Yang Ming University, Taipei, Taiwan, Republic of China
3
Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan, Republic of China
4
Department of Nuclear Medicine, Albert Einstein College of Medicine, Yeshiva University, Bronx, New York 10461, USA
5
Faculty of Health Sciences, University of Macau, Macau SAR, China
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