Variations in Activity and Dose Calculations in Pre-Treatment Planning for Hepatic Lobar Y-90 Microspheres Therapy When Using Anatomic Versus Functional Imaging Contouring Techniques
D Alvarez1*, L Rodriguez1, R Herrera1, T Kutuk1, E Saugar1, A Kaiser1, M Chuong1, A Gutierrez1, S Kim1, R Gandhi1,2, (1) Miami Cancer Institute, Miami, FL, (2) Miami Cardiac & Vascular Institute, Miami, FL
Presentations
WE-E-202-6 (Wednesday, 7/13/2022) 11:15 AM - 12:15 PM [Eastern Time (GMT-4)]
Room 202
Purpose: BSA and partition model (PM) activity calculations rely on liver, hepatic lobes, and GTV segmentation. Administered activity impacts absorbed dose to the patient. Left (LT) and right (RT) lobe division is critical in determining treatment volumes, thus tumor burden within, and can be visualized using either anatomic or functional imaging. Functional imaging provides more accurate lobar delineations by visualizing perfusion volumes (PV) compared to anatomic imaging. This is especially important in patients with variant arterial anatomy or after hepatic artery embolization performed for redistribution.
Methods: Liver, hepatic lobes, and aggregated LT/RT GTVs were drawn on 85 Y-90 cases using PV method with CBCT from angiography and anatomical landmark (AL) method using contrast CT/MRI. PV visualizes blood flow pattern while AL technique uses the middle hepatic vein to determine LT/RT lobe division. BSA and PM activities were calculated using AL- and PV-guided volumes. Dose estimates to GTV, normal liver, and lungs were calculated using both AL- and PV-guided volumes.
Results: Comparing AL vs. PV methods, BSA activities differed in 83 cases for the RT lobe and 73 cases for the LT lobe. Significant differences (p<0.05) were observed for LT lobe using a Wilcoxon signed rank test with absolute median difference (AMD)=15.6%. In 58% of cases, there was an increase in LT lobe activity using AL vs. PV. Significant dose differences were observed in LT lung (AMD=26.0%) and LT GTV (AMD=19.8%). Similar trends were observed with PM activities. Whether using AL or PV methods, PM yielded higher activities vs. BSA in >92% of RT lobes and >63% of LT lobes.
Conclusion: Significant differences in LT lobe activities and doses in LT GTV/LT lung were observed between contouring techniques, regardless of activity model used. Functional CBCT imaging likely yields more accurate LT/RT lobe delineations, directly impacting activity calculations and estimated doses.
Funding Support, Disclosures, and Conflict of Interest: D Alvarez: Partial research funding from Sirtex Inc; M Chuong: Consultant for Sirtex Inc.; R Gandhi: Proctor and Consultant for Sirtex Inc.
Keywords
Nuclear Medicine, Functional Imaging, Segmentation
Taxonomy
IM/TH- Radiopharmaceutical Therapy: Localization Imaging
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