Clinical Implementation of a Contour-Consistent Workflow for Activity Calculation and Post-Treatment SPECT/CT...

Area of Science:

• Medical Physics
• Nuclear Medicine
• Radiology

Background:

• Image-based dosimetry is crucial for Yttrium-90 (Y-90) radioembolization, allowing quantitative assessment of absorbed dose in liver tumors and normal tissues.
• Accurate dosimetry ensures optimal treatment efficacy and minimizes toxicity in Y-90 radioembolization procedures.

Purpose of the Study:

• To describe the clinical implementation of a contour-consistent workflow integrating cone-beam CT (CBCT) segmentation with post-treatment SPECT/CT for voxel-based dosimetry.
• To evaluate the feasibility and clinical interpretability of segment-level dosimetry in Y-90 glass microsphere radioembolization.

Main Methods:

• A retrospective analysis of five Y-90 glass microsphere cases using a contour-consistent workflow.
• Contrast-enhanced CBCT for hepatic segment contouring and activity calculation via Medical Internal Radiation Dose (MIRD) formalism.
• Rigid and deformable registration of post-treatment SPECT/CT to CBCT, with contour transfer for voxel-based dose reconstruction and dose-volume histogram (DVH) analysis.

Main Results:

• Segment volumes derived from CBCT were generally comparable between planning and post-treatment.
• Delivered mean segment doses varied relative to prescription, with instances of underdosing observed (e.g., 87.66 Gy vs. 130 Gy).
• DVH analysis revealed heterogeneous absorbed-dose distributions, consistent with Y-90 glass microsphere radioembolization characteristics.

Conclusions:

• The implemented contour-consistent workflow enables clinically interpretable, segment-level post-treatment dosimetry in Y-90 radioembolization.
• Integration of CBCT segmentation with SPECT/CT dosimetry provides valuable insights into absorbed dose distributions for improved treatment assessment.