A Radionuclide-Independent Deep Learning–Based Patient-Specific Dosimetry
Abstract
Purpose
Conventional image-based dosimetry models for radiopharmaceutical therapy are generally radionuclide-specific and require extensive nuclear medicine (NM) datasets for training. We developed a deep learning (DL) model trained solely on a single whole-body CT image that predicts radiation doses for previously unseen radionuclides.
Methods
The DL model was trained to predict voxel dose kernels (VDKs) for beta-emitters using CT–derived density map patches and energy spectra. The DL model-derived VDKs were convolved with time-integrated activity to generate patient-specific dose maps. Zero-shot prediction was tested on unseen radionuclides (Ho-166 and Lu-177). The performance of DL model was validated at kernel, phantom, and patient levels. The proposed DL model, a conventional DL model trained on Y-90 NM/CT images of 22 patients, voxel S-value method (VSV), and organ-level dosimetry (OLINDA/EXM) were benchmarked against Monte Carlo (MC) simulation.
Results
The proposed DL model-based VDKs showed strong correlation with MC-based VDKs (R²: 0.99 and 0.91 for unseen Ho-166 and Lu-177) and, at the phantom level, revealed overall lower errors than VSV in heterogeneous region. At the patient level, the proposed DL model maintained good agreement with the MC simulation-derived horizontal dose profile for the unseen Lu-177 (mean difference: 2.1 Gy, 11.6%), whereas the conventional DL model trained using Y-90 data exhibited large discrepancies (mean difference: 129.4 Gy, 657.4%). The proposed DL model also predicted organ doses with the smallest differences from MC while reducing computation time from 4.6 hours to 2.6 minutes. For the mean tumor dose averaged across the patient cohort for unseen Ho-166, the DL model achieved the most accurate results with a difference of only 1.1 Gy (2.9%), outperforming multiple VSV (3.8 Gy, 7.2%), single VSV (3.8 Gy, 7.3%), and OLINDA/EXM (1.4 Gy, 4.5%).
Conclusion
The proposed DL model enables dose prediction for unseen radionuclides without requiring patient NM images for training.