2508 - Time-Delayed Contrast-Enhanced T2-FLAIR and Accuracy of GTV Determination in Brain Metastases

S. Du¹, G. Gong², R. Liu², K. Meng², W. Ruozheng³, and Y. Yin⁴; ¹Shandong Cancer Hospital;Southwest Medical University, Jinan, Shandong, China, ²Department of Radiation Oncology Physics and Technology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, shandong, China, ³Tumor Hospital of Xinjiang Uygur Autonomous Region, wulumuqi, xinjiang, China, ⁴Department of Radiation Physics, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China

Purpose/Objective(s): Analyzing the effect of time-delayed contrast-enhanced (CE) T2-fluid-attenuated inversion-recovery (T2-FLAIR) on gross tumor target volume (GTV) determination of brain metastases (BMs), and exploring its feasibility for improving the accuracy of GTV determination in BMs. Materials/

Methods: We prospectively enrolled 76 patients with first diagnosed BMs (184 lesions). All patients underwent magnetic resonance (MR) simulation. CE T1-weighted imaging (T1WI) scans were performed at 1, 3, 5, 10, 18, and 20 mins after injection of contrast agents. And CE T2-FLAIR was performed after 10-min delayed CE T1WI scan. The GTVs were determined in the MR images of different sequences, named GTV_-1min, GTV_-3min, GTV_-5min, GTV_-10min, GTV_-18min, GTV_-20min and GTV_-T2-FLAIR, respectively. GTV_-1min, GTV_-3min, GTV_-5min and GTV_-T2-FLAIR were grouped and fused as fusion GTV. GTV_-1min~20min fusion was defined as GTV_-total, which was set as the reference GTV. The differences in signal intensity (SI), volume and shape of GTVs were compared.
Results: (1) In CE T2-FLAIR, the contrast ratio (CR) between GTV and brain white matter was reached 0.77 ± 0.39, which was 148.4%, 126.5%, and 126.5% higher than that of 1, 3, and 5-min delayed CE-T1WI. Except for GTV_-3min and GTV_-5min, the differences of CR between GTV and brain white matter were statistically significant (P < 0.05). (2) The volume of GTV_-T2-FLAIR increased by 11.5%, 8.6%, and 6.6% compared with GTV_-1min, GTV_-3min, and GTV_-5min; and decreased by 17.44% compared with GTV_-total (P<0.05). (3) Compared with GTV_-total, the fusion GTVs all had volume differences <0.08 cm³ and increase rates <5%. (4) Compared with GTV_-total, GTV_-T2-FLAIR had the smallest Dice Similarity Coefficient (DSC) of 0.858, and GTV_-5min had the maximum DSC of 0.903. The DSCs of the fusion GTVs ranged from 0.903 to 0.917.
Conclusion: Time-delayed CE T2-FLAIR could complement the display of the BMs GTV in CE T1WI, and its combination with CE T1WI improved the accuracy of GTV determination in BMs without increasing the MR scanning time.