Stereotactic body radiation therapy planning for liver tumors using functional images from dual-energy computed tomography

Purpose: This study aimed to generate a functional image of the liver using dual-energy computed tomography (DECT) and a functional-image-based stereotactic body radiation therapy plan to minimize the dose to the volume of the functional liver (V-fl). Material and methods: A normalized iodine density (NID) map was generated for fifteen patients with liver tumors. The volume of liver with an NID < 0.46 was defined as V-fl, and the ratio between Vfl and the total volume of the liver (FLR) was calculated. The relationship between the FLR and Fibrosis-4 (FIB-4) was assessed. For patients with 15% < FLR < 85%, functional volumetric modulated-arc therapy plans (F-VMAT) were retrospectively generated to preserve V-fl, and compared to the clinical plans (C-VMAT). Results: FLR showed a significantly strong correlation with FIB-4 (r = -0.71, p < 0.01). For ten generated F-VMAT plans, the dosimetric parameters of D-99%, D-50%, D-1% and the conformity index were comparable to those of the C-VMAT (p > 0.05). For V-fl, F-VMAT plans achieved lower V-5Gy (122.4 +/- 31.7 vs 181.1 +/- 57.3 cc), V-10Gy (44.4 +/- 22.2 vs 98.2 +/- 33.3 cc), V-15Gy (22.6 +/- 20.3 vs 49.8 +/- 33.7 cc), V-20Gy (11.6 +/- 14.1 vs 24.9 +/- 25.1 cc), and D-mean (3.9 +/- 2.3 vs 5.8 +/- 3.0 Gy) values than the C-VMAT plans (p < 0.01). Conclusions: The functional image derived from DECT was successfully used, allowing for a reduction in the dose to the V-fl without compromising target coverage. (C) 2019 Elsevier B.V. All rights reserved.