Kolja Thierfelder MD, MSc, Presenter: Nothing to Disclose

Wieland H. Sommer MD, Abstract Co-Author: Nothing to Disclose

Olaf Dietrich PhD, Abstract Co-Author: Nothing to Disclose

Felix G. Meinel MD, Abstract Co-Author: Nothing to Disclose

Maximilian F. Reiser MD, Abstract Co-Author: Nothing to Disclose

Konstantin Nikolaou MD, Abstract Co-Author: Speakers Bureau, Siemens AG Speakers Bureau, Bracco Group Speakers Bureau, Bayer AG

Diffusion-weighted imaging (DWI) of the pancreas often suffers from susceptibility and distortion artifacts. Our aim was to evaluate the use of 2D-selective parallel-transmit accelerated excitation MRI for diffusion-weighted EPI (pTX-EPI) of the pancreas and to compare it to conventional single-shot EPI (c-EPI).

The MRI examinations of 32 consecutive patients were evaluated in this prospective and IRB-approved study. All examinations were performed on a 3-T MRI system equipped with two independent transmit channels. PTX-EPI was performed with a (zoomed) Field-of-View (FOV) of 230 × 118mm2, whereas c-EPI used a full-FOV of 380 × 285mm2. The 2D-RF pulse of pTX-EPI was shortened by a factor of 1.7 (TX-acceleration factor). In a qualitative analysis, two blinded and experienced readers evaluated 3 different aspects of image quality on 3- to 5-point Likert scales. Additionally, apparent diffusion coefficients (ADCs) were determined in both c-EPI and pTX-EPI in normal-appearing pancreatic tissue using regions of interests (ROIs). Mean ADC values and standard deviations were compared between the two techniques.

The zoomed pTX-EPI was superior to c-EPI with respect to overall image quality (3.10 ± 0.65 vs. 2.45 ± 0.77, p < 0.0001) and identifiability of the pancreatic ducts (1.03 ± 0.81 vs. 0.45 ± 0.69, p < 0.01). Artifacts were significantly less severe in pTX-EPI than in c-EPI (1.06 ± 0.77 vs 1.61 ± 0.84, p < 0.01). The mean ADC values of c-EPI (1.29 ± 0.19 × 10-3 mm2/s) and pTX-EPI (1.27 ± 0.17 × 10-3 mm2/s) did not differ significantly (p = 0.44). The variation within the ROIs as measured by the standard deviation was significantly lower in pTX-EPI (0.095 ± 0.035 × 10-3 mm2/s) than in c-EPI (0.135 ± 0.075 × 10-3 mm2/s), p < 0.05. 

TX-accelerated spatially-selective EPI leads to substantial improvements in DWI of the pancreas with respect to different aspects of image quality without significantly influencing the ADC values.

PTX-accelerated EPI has the potential to overcome some of the limitations of conventional DWI techniques in MRI of the pancreas. Further studies might show whether the use of parallel-transmit enables a more accurate differentiation of pancreatic lesions.

Thierfelder, K, Sommer, W, Dietrich, O, Meinel, F, Reiser, M, Nikolaou, K, Parallel-transmit-accelerated Spatially-selective Excitation MRI for Reduced-FOV Diffusion-weighted Imaging of the Pancreas.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14045547.html