Sensitivity encoding for diffusion-weighted MR imaging at 3.0 T: intraindividual comparative study

To prospectively evaluate whether diffusion-weighted (DW) magnetic resonance (MR) imaging with sensitivity encoding (SENSE) at 3.0 T can help to improve image quality and confidence in and accuracy of diagnosis of ischemic lesions, compared with DW MR imaging with conventional phase encoding, in patients.

Patients provided informed consent after the study had been explained, and the institutional review board approved the study protocol. Eighty-five patients (46 male and 39 female patients; age range, 13-86 years; mean age, 52 years) underwent single-shot spin-echo echo-planar DW MR imaging at 3.0 T twice, in a randomized order: once with conventional phase encoding (repetition time msec/echo time msec, 4283/79) and once with SENSE (3141/69, with a reduction factor of three). With both, 128 x 128 matrix, 24 4-mm-thick sections, and two b values of 0 and 1000 sec/mm(2) were used. An eight-element SENSE-compatible receive-only surface coil was used; the built-in body coil served for radiofrequency transmission and generation of the coil sensitivity profile. SENSE and conventional phase encoding were compared for image quality, signal-to-noise ratio, relative signal intensity (SI), and lesion contrast. Two neuroradiologists read images. Diagnostic accuracy of and confidence in detection of apparent diffusion coefficient (ADC) lesions with conventional phase encoding and SENSE at MR imaging were compared; matched-pairs Wilcoxon signed rank test was used to test statistical significance.

No major SENSE-related artifacts were seen. At MR imaging with SENSE, consistently and significantly (P < .001) higher image quality scores were achieved because of substantial reduction of image distortions and blurring. Lesion contrast was equivalent with both techniques. Diagnostic confidence for demonstration and exclusion of lesions was significantly (P < .001) higher at MR imaging with SENSE. In three patients, small microembolic lesions were only prospectively diagnosed at MR imaging with SENSE, whereas they were masked by adjacent susceptibility effects and therefore overlooked at MR imaging with conventional phase encoding.

Parallel MR imaging with SENSE is feasible at 3.0 T. It significantly improves image quality, particularly by reducing or even preventing susceptibility-induced SI changes and image blurring. There was a significantly improved diagnostic confidence with which ADC changes were identified or excluded.