Christiane Kuhl MD, PRESENTER: Nothing to Disclose

Abstract: HTML Purpose: Diffusion imaging (DI) has become the cornerstone for the timely diagnosis of acute stroke. Still at 1.5T, diffusion imaging suffers from poor SNR. Moving from 1.5T to 3T significantly improves SNR, which may help improve sensitivity for subtle ADC changes. On the other hand, DI at 3T suffers from substantial image distortions, as susceptibility effects increase with field strength. An efficient approach to reduce susceptibility artifacts is by reducing echo train length in single shot DI by parallel imaging techniques such as SENSE (Sensitivity Encoding). We performed an intra-individual comparative trial to investigate the impact of parallel imaging on DI in patients presenting for work-up of suspected ischemic stroke. Methods and Materials: Ongoing study on so far 55 patients who underwent DI on a 3T whole body MR system. A 6-element SENSE-compatible receive-only surface coil was used; the body coil served for RF transmission and generation of the coil sensitivity profile. All patients underwent "regular" DI (ssh SE-EPI, 128x128 matrix, 24 sections, 4 mm thick, 2 b-values (0, 1000), with TE/TR 79/4462 ms), and DI with SENSE (the same ssh SE-EPI sequence with a SENSE factor of 3, yielding a TE of 67 ms). Image quality, visibility and conspicuity of ischemic lesions were rated by 2 neuro-radiologists on a 5-point scale; results were compared for the SENSE and the regular DI pulse sequence. Overall SNR and lesion-to-background CNR of ischemic lesions were calculated for both sequences Results: Mean quantitative SNR in Sense DI compared to "regular" DI was 70%. In spite of this numeric SNR reduction, SENSE DI scored consistently and significantly higher regarding image quality, owing to a substantial reduction of image distortions, particularly in areas close to the skull base or to the skull convexity, and a significant reduction of image blurring. Conspicuity of ischemic lesions was maintained at SENSE DI; in lesions close to the skull base or vertex, conspicuity was higher. In 4 patients, small microembolic lesions to fronto-dorsal and temporal cortex, were only diagnosed on the SENSE DI Conclusion: At 3.0T, DI with SENSE allows a substantial reduction of image artifacts. In fact, the degree of image distortions in the regions close to the skull base are comparable with DI at 1.5T, while the high sensitivity for ischemic lesion is maintained. SENSE may help to actually exploit High Field MRI for DI. We conclude that SENSE (or parallel imaging in general) should be considered an integral part of clinical diffusion imaging at higher field strength      

Kuhl MD, C, Sensitivity Encoding (SENSE) Improves Clinical Diffusion Imaging of (sub)acute Stroke at High Magnetic Fields (3T): An Intra-individual Trial.  Radiological Society of North America 2003 Scientific Assembly and Annual Meeting, November 30 - December 5, 2003 ,Chicago IL. http://archive.rsna.org/2003/3103273.html