3047 - A Comparative Study on the Determination of Gross Tumor Volume for Hepatocellular Carcinoma Radiotherapy based on Multi-Phase Contrast-Enhanced Magnetic Resonance Imaging

K. Meng¹, G. Gong¹, X. Yin², and Y. Yin³; ¹Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, shandong, China, ²Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China, ³Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China

Purpose/Objective(s): To perform a quantitative analysis of the differences in determining the gross tumor volume (GTV) for hepatocellular carcinoma (HCC) radiotherapy using multi-phase contrast-enhanced magnetic resonance imaging (CE-MRI).

Materials/

Methods: This retrospective study analyzed 99 HCC patients (145 lesions) who underwent MR simulation and radiotherapy. T₁-weighted imaging (T₁WI), contrast-enhanced T₁WI (CE-T₁WI) at 15s, 45s, 75s, 150s, and >10min after contrast agent injection were performed, comprising a total of six imaging sequences. The GTVs identified through different sequence images were grouped and fused together. The six sequence GTVs were fused as the internal GTV (IGTV), serving as the reference standard. Mean signal intensity (SI), volume, shape, and fibrous capsule (FC) thickness among GTVs were compared.

Results: (1) Compared with patients without TACE, the mean SI for the GTV_-T1WI, GTV_-15s–GTV_-10min in patients with TACE decreased from 14.09% to 31.31%. (2) The volumes of GTV_-T1WI, GTV_-15s–GTV_-10min ranged from 32.66 cm³ to 34.99 cm³. The volume differences between GTV_-45s and the other GTVs were statistically significant (p<0.05), excluding the GTV_-T1WI. (3) Compared with the IGTV, 2 GTVs exhibited a volume reduction rate of <5%, accounting for 3.51%, and 9 GTVs with dice similarity coefficients (DSC) >0.95, accounting for 15.79%. They were all fused GTVs. (4) In the CE-T₁WI sequences (except for CE-T₁WI_-15s), FC measurement was possible in 39.31% of lesions (57/145), with the largest mean thickness observed at 75s.

Conclusion: Although single-phase CE-MRI introduces uncertainty in HCC GTV determination, combining different phases CE-MRI can enhance accuracy. The CE-T₁WI_-45s emerges as a reliable conventional scanning modality.