3D T1-weighted turbo spin echo contrast-enhanced MRI at 1.5T for frameless brain metastases radiotherapy.

Abstract

Performance of 3D-T1W-TSE has been proven superior to 3D-MP-GRE at 3T on brain metastases (BM) contrast-enhanced (CE) MRI. However, its performance at 1.5T is largely unknown and sparsely reported. This study aims to assess image quality, lesion detectability and conspicuity of 1.5T 3D-T1W-TSE on planning MRI of frameless BM radiotherapy. 94 BM patients to be treated by frameless brain radiotherapy were scanned using 3D-T1W-TSE with immobilization on multi-vendor 1.5T MRI-simulators. BMs were jointly diagnosed by 4 reviewers. Enhanced lesion conspicuity was quantitatively assessed by calculating contrast ratio (CR) and contrast-to-noise ratio (CNR). Signal-to-noise ratio (SNR) reduction of white matter due to the use of flexible coil was assessed. Lesion detectability and conspicuity were compared between 1.5T planning MRI and 3T diagnostic MRI by an oncologist and a radiologist in 10 patients. 497 BMs were jointly diagnosed. The CR and CNR were 75.2 ± 39.9% and 14.2 ± 8.1, respectively. SNR reduced considerably from 31.7 ± 8.3 to 21.9 ± 5.4 with the longer distance to coils. 3T diagnostic MRI and 1.5T planning MRI yielded exactly the same detection of 84 BMs. Qualitatively, lesion conspicuity at 1.5T was not inferior to that at 3T. Quantitatively, lower brain SNR and lesion CNR were found at 1.5T, while lesion CR at 1.5T was highly comparable to that at 3T. 1.5T 3D-T1W-TSE planning MRI of frameless BM radiotherapy was comprehensively assessed. Highly comparable BM detectability and conspicuity were achieved by 1.5T planning MRI compared to 3T diagnostic MRI. 1.5T 3D-T1W-TSE should be valuable for frameless brain radiotherapy planning.