(Monday, 7/15/2019) 1:15 PM - 1:45 PM
Room: Exhibit Hall | Forum 5
Purpose: To achieve a high SBRT dose in the re-treatment of liver tumors while sparing more normal liver tissue from radiation dose above 15 Gy with deformable image registration.
Methods: This case study is to explore the application of DIR for patients undergoing the second treatment for new liver lesion(s). The patient experienced great weight loss after the first treatment. Liver volume change was also caused by using different respiratory motion management: abdominal compression used in the first treatment and respiratory (phase) gating used in the re-treatment. The two courses used 45 Gy and 30 Gy both in three fractions, respectively. Both plans used two coplanar-arc VMAT with Eclipse (Varian, Palo Alto, CA) and 10X FFF beams were used in the both plans. In the second treatment, Velocity was used to register the first planning CT to the second planning CT and the same deformable mapping was applied to the first dose matrix. We compared it with the plan without DIR.
Results: Without DIR, the volume of normal live was 615.6 cc and the mean dose was 8.97 Gy; With DIR, the volume of normal live was 785.8 cc and the mean dose is 7.6 Gy. The volume of PTV4_new was reduced from 46.3 cc (PTV4_orig) to 16.2 cc.
Conclusion: DIR can improve the accuracy of volume change between different treatment courses, which can impact the re-treat decision regarding dose, fractionation, et al. The most important goal to deliver the high SBRT dose to the targets while sparing normal liver from radiation dose above 15 Gy cab be achieved by using deformable image registration.
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