Dosimetry and prescription in liver radioembolization with 90Y microspheres: 3D calculation of tumor-to-liver ratio from global 99mTc-MAA SPECT information.

This study presents a methodology to calculate the T/N ratio using global information from the SPECT. The T/N ratio is estimated by establishing uptake thresholds consistent with previously performed volumetry. This dose calculation method was validated against three-dimensional voxel dosimetry, and was also compared with the standard partition method based on freehand regions of interest (ROI) outlining on SPECT slices. Both comparisons were done on a sample of 20 actual cases of hepatocellular carcinoma treated with resin microspheres. The proposed method and the voxel dosimetry give very similar results. Differences are found in several cases when comparing with results derived from the ROI method. Differences in the T/N ratio imply more difference in tumor dose that in normal liver dose. Dispersion of values is greater in the ROI-based method than in the other two. The process is very simple and avoids the subjectivity inherent to manual distinction between tumor/normal liver tissue interfaces. Dosimetry results obtained with the new method are equivalent to those provided by voxel dosimetry. Compared to the use of ROIs, it also provides greater simplicity and - most importantly - greater reproducibility. PMID: 29057748 [PubMed - as supplied by publisher]
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research