SPECT/CT image-based dosimetry for Yttrium-90 radionuclide therapy: Application to treatment response

Area of Science:

• Nuclear Medicine
• Medical Physics
• Oncology

Background:

• Hepatocellular carcinoma (HCC) management often involves selective internal radiation therapy (SIRT) using Yttrium-90 (90Y) microspheres.
• Accurate dosimetry is crucial for optimizing treatment efficacy and minimizing toxicity in 90Y radioembolization.
• Predicting treatment response and complications requires precise dose distribution calculations.

Purpose of the Study:

• To demonstrate the efficacy of voxel-based 90Y microsphere dosimetry using post-therapy SPECT/CT imaging.
• To apply this dosimetry method to predict treatment response in HCC patients.
• To evaluate the clinical utility of patient-specific dose calculations for 90Y radioembolization.

Main Methods:

• Voxel-based dosimetry was performed using a dedicated navigator (RapidSphere) on a commercial platform.
• Post-therapy 90Y SPECT/CT imaging was optimized and registered to follow-up diagnostic MR/CT using deformable image registration.
• Dose distributions were computed using the local deposition method, and dose-volume histograms (DVHs) were calculated.

Main Results:

• Dosimetric analysis revealed high local doses consistent with brachytherapy.
• Complete HCC response correlated with 85% gross tumor volume (GTV) coverage by the V150 Gy isodose.
• Partial response correlated with 18% GTV coverage by the V470 Gy isodose.
• Extrahepatic activity predicted duodenal toxicity with a maximum dose of 178 Gy to the duodenum.

Conclusions:

• Voxel-based 90Y dosimetry with SPECT/CT and deformable image registration can predict treatment response in HCC.
• This method accurately predicts treatment-related toxicities, such as duodenal ulcers.
• Patient-specific dose calculations are clinically valuable for optimizing 90Y radioembolization planning.