A comparison of simultaneous multislice and conventional diffusion tensor imaging techniques for ischemic stroke evaluation at 1.5T

Abstract

Objective: Diffusion tensor imaging (DTI) is a promising technique for ischemic stroke evaluation; however, acquisition time is longer than DWI. Simultaneous multislice (SMS) imaging acquires multiple slices together and reduces scan time. This study compared conventional and SMS DTI for ischemic stroke workup. Methods: Following IRB approval, the departmental stroke protocol was supplemented with SMS DTI on a clinical 1.5T MRI. Cases suspicious for ischemic stroke outside the treatment window were included. Standard DTI (STD-DTI, 20-direction, b = 2000 s/mm2), was followed by SMS-2-DTI (two slices simultaneously imaged). Two blinded neuroradiologists independently assessed image quality and DTI-trace status (positive/negative = stroke/other). Average image quality, interrater reliability (κ), receiver operating characteristic area under the curve (AUC), signal-to-noise ratio (SNR = DTI-source min/max/average), coefficient of variation (CV), mean diffusivity (MD), and fractional anisotropy (FA, of DTI-trace) were compared using two-tailed t-tests and a p < .05. Results: 41 patients were evaluated. SMS-2-DTI decreased DTI time by 132.17 ± 15.33 s, a 45% reduction. SMS-2-DTI reduced image quality (STD-DTI 4.7 ± 0.5 vs SMS-2-DTI 3.8 ± 0.6, p < .001). Diagnostic accuracy persisted, AUC was high for observer 1 (STD-DTI 0.95, 95%CI = 0.88–1.00 vs SMS-2-DTI 0.94, 95%CI = 0.87–1.00, p = .86) and observer 2 (STD-DTI 0.89, 95%CI = 0.79–0.99 vs SMS-2-DTI 0.86, 95%CI = 0.76–0.97, p = .66). Interrater reliability was high for STD-DTI (κ = 0.80, 95%CI = 0.61–0.98) and SMS-2-DTI (κ = 0.84, 95%CI = 0.67–1.00). SMS-2-DTI significantly decreased average SNR (STD-DTI 42.85 ± 4.44 vs SMS-2-DTI 32.58 ± 4.30, p < .001), and CV MD (STD-DTI 0.23 ± 0.03 vs 0.20 ± 0.04, p < .001). CV FA and CV DTI-trace were not statistically different. Conclusions: This study supports using SMS to accelerate DTI for ischemic stroke workup at 1.5T in the non-hyper-acute setting. Advances in knowledge: This study highlights the feasibility of accelerated multislice DTI for faster diagnostic DTI-trace images capable of ischemic stroke detection.