Room: Exhibit Hall | Forum 6
Purpose: Post Y-90 liver radio-embolization analysis of the dose deposited by microspheres is a new clinical tool. Velocityâ„¢ (v4.0) software enables the calculation of dose within the liver by utilizing post Y-90 CT-SPECT data sets. The objective of this study was to retrospectively analyze Y-90 treatments so that dose to the target(s) and normal liver could be quantified.
Methods: Six radio-embolization cases were selected for retrospective analysis, each receiving two treatments (right and left hepatic lobe). Patients received a pre Y-90 CT and MAA study to determine perfusion paths within hepatic arteries. Contours of whole liver, right and left hepatic lobes, and GTVs were drawn in Velocity. Prescribed activity of SirspheresÂ® was calculated for each hepatic lobe using the pre Y-90 CT and was initially determined by the body surface area method and adjusted based on partition modeling. CT-SPECT scans obtained post-procedure were imported into Velocity and fused with the planning CT. Contours were then transformed to the post treatment CT. The local deposition method was applied to the SPECT study to calculate dose distribution. The resulting dose distribution was overlaid on the CT scan with the transformed pre Y-90 contours superimposed on it.
Results: Highly heterogeneous dose distributions within GTV and normal liver were observed. Max doses within right and left GTVs, and whole liver spanned between 48.2-123.7 Gy, 16.7-60.6 Gy, and 70.8-192.8 Gy, respectively. Apparently, there is no correlation between activity and dose. In one case, significant heart dose (~22Gy) was unintentionally delivered in a left lobe treatment.
Conclusion: Velocityâ€™s new microsphere dosimetry module appears to be a powerful clinical tool that can help evaluate the quality of liver radio-embolizations. The variability in GTV doses, the lack of correlation between activity and dose, and uncovering unforeseen radiotoxicity supports the need to establish a standardized post Y-90 dosimetry method.