SU‐GG‐J‐181: The Role of Voxel‐Based T10 Calculations in Determining Correct Pharmacokinetic Parameters for Head and Neck Tumors

Abstract

Purpose: To determine the optimal flip angle combination (oFAc) that generates voxel‐based T10 values, the median T10 for primary and nodes , and its implications on vascular permeability (PERM) and extracellular volume fraction (EVF) in HN patients treated with targeted therapy and chemoradiation. Method and Materials: To generate voxel‐based T10, a gradient echo sequence was used on a 1.5 T scanner with TR=6.44 msec and FA of 10, 15, 20, 30, 45°. For different FA combinations, the voxel‐based values were calculated using CAD Sciences® (White Plains, NY). The average of the median T10 in muscle and fat regions of interest (ROI) in 3 patients was calculated. Criteria for oFAc included minimal variation from published muscle and fat values at 1.5T, and minimum number of FA used for fitting. To determine , values from ROIs delineated by 2 users (A,B) were calculated. For 3 patients, the PERM and EVF from primary and nodes ROIs were calculated using T10 maps and . Results: The 10–45° FAc was chosen for subsequent T10 mapping as it had the greatest percentage of fitted pixels (90% for muscle, 100% for fat, % 83 for primary, 72% for nodes) and a , and , compared to reported 0.870 and 0.260 sec for muscle and fat, respectively. From14 patients, . The difference between the PERM and EVF calculated with voxel‐based T10 versus ranged from 6–81% for PERM, and 2.5–23% for EVF. Conclusion. The 10–45° FAc is fast and accurately describes the known T10 of normal tissue. Voxel‐based T10 calculations are essential for correct Tofts‐based PA in heterogeneous tumors. For HN, primary and nodes is a good estimate for T10 in the absence of T10 mapping capability.