Abstract
ObjectivesTo assess the sensitivity of stimulated echo acquisition mode diffusion weighted imaging (STEAM-DWI) to ischemic stroke in comparison to echo-planar imaging diffusion weighted imaging (EPI-DWI) in the infratentorial compartment.MethodsFifty-seven patients presenting with clinical features of infratentorial stroke underwent STEAM-DWI, high-resolution EPI-DWI (HR-DWI, 2.5 mm slice thickness) and low-resolution EPI-DWI (LR-DWI, 5 mm slice thickness). Four readers assessed the presence of ischemic lesions and artifacts. Agreement between sequences and interobserver agreement on the presence of ischemia were calculated. The sensitivities of the DWI sequences were calculated in 45 patients with a confirmed diagnosis of infratentorial stroke.ResultsMedian time from symptom onset to imaging was 24 hours. STEAM-DWI agreed with LR-DWI in 89.5% of cases (kappa = 0.72, p<0.0001) and with HR-DWI in 89.5% of cases (kappa = 0.68, p<0.0001). STEAM-DWI showed fewer intraparenchymal artifacts (1/57) than HR-DWI (44/57) and LR-DWI (41/57). Ischemia was visible in 87% of cases for LR-DWI, 93% of cases for HR-DWI, and 89% of cases for STEAM-DWI. Interobserver agreement was good for STEAM-DWI (kappa = 0.62, p<0.0001).ConclusionsCompared to the best currently available MR sequence for detecting ischemia (HR-DWI), STEAM-DWI shows fewer artifacts and a similar sensitivity to infratentorial stroke.
Highlights
Diffusion-weighted imaging (DWI) has a sensitivity exceeding 90% for detecting acute ischemia [1,2] and is routinely used for this purpose in clinical practice
Our results show that such artifacts are far less frequent in STEAM-DWI than in either of the echo-planar imaging diffusion weighted imaging (EPI-DWI) sequences
Very small areas of ischemia can be mistaken for artifacts on echo-planar imaging (EPI)-DWI sequences–this happened in several cases in our study and substantially contributed to the false negative rates of these sequences
Summary
Diffusion-weighted imaging (DWI) has a sensitivity exceeding 90% for detecting acute ischemia [1,2] and is routinely used for this purpose in clinical practice. Commonly used DWI sequences, which combine a pulsed gradient spin-echo sequence and an echo-planar imaging (EPI) readout, show anisotropic diffusion and susceptibility artifacts Such artifacts are prominent in the infratentorial compartment and can hamper the detection of ischemic lesions in this area. Despite taking longer to acquire and having a potentially lower signal-to-noise ratio, thin-slice DWI is considered the best available imaging tool in clinical practice for diagnosing cerebral ischemia. Both these sequences are acquired with an EPI readout and suffer from susceptibility artifacts. Despite their potential advantages, the utility of STEAMDWI sequences for diagnosing ischemic stroke has not yet been assessed
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