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Updated: Jun 2, 2026
A Whole Body Dosimetry Protocol for Peptide-Receptor Radionuclide Therapy (PRRT): 2D Planar Image and Hybrid 2D+3D SPECT/CT Image Methods
Published on: April 24, 2020
Quantitative accuracy and total-body voxel-based dosimetry of 177Lu molecular radiotherapy using a ring-shaped 360°
Panattha Damthongsen1, Wuri Handayani2, Benchamat Phromphao3
1Medical Physics Program, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand; Chulalongkorn University Biomedical Imaging Group, Department of Radiology, Faculty of Medicine, Chulalongkorn University, Bangkok 10330, Thailand; Division of Nuclear Medicine, Department of Radiology, Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla 90110, Thailand.
Purpose:
This study aimed to determine 177Lu quantification accuracy and total-body voxel-based dosimetry using a ring-shaped 360° CZT-SPECT/CT in both phantom and patient studies.
Methods:
An IEC/NEMA body phantom containing six fillable spheres (10-37 mm) filled with 177Lu at a 10:1 target-to-background ratio was scanned on a VERITON-CT 200 series at 0.5, 24, 144, and 168 h post-injection (p.i.). Measured activity concentrations were compared with known values. For the clinical study, total-body SPECT/CT was acquired at 4, 24, and 48-76 h p.i. in 9 treatment cycles from 5 patients receiving 177Lu-DOTATATE (n = 6) or 177Lu-PSMA (n = 3). Images were reconstructed with quantitative OSEM and triple-energy window scatter correction. Absorbed doses to organs-at-risk and lesions were calculated using voxel-level dosimetry in accordance with the MIRD schema implemented through the MIM SurePlan MRT.
Results:
Phantom measurements showed good agreement, with percentage differences of -8% to 9% in the 37-mm sphere across all time points. In patients, dosimetric estimates were consistent with previously reported results using standard gamma cameras. The mean [range] absorbed dose (Gy/GBq) for 177Lu-DOTATATE patients were: whole-body, 0.14 [0.07-0.19]; liver, 0.75 [0.39-1.71]; kidneys, 0.73 [0.36-0.95]; spleen, 1.32 [0.42-1.88]; salivary glands, 0.16 [0.03-0.57]; bone marrow, 0.07 [0.02-0.11]; and lesions 1.04 [0.49-2.66]. For 177Lu-PSMA patients, corresponding values were: 0.06 [0.04-0.08], 0.18[0.08-0.25], 0.71 [0.45-0.98], 0.12 [0.10-0.13], 0.26 [0.12-0.45], 0.03 [0.02-0.04], and 0.78 [0.34-1.22], respectively.
Conclusion:
The 360° CZT-SPECT/CT system enables accurate 177Lu quantification and supports clinically feasible voxel-level dosimetry for molecular radiotherapy.
