Michael Paul Recht MD, Presenter: Nothing to Disclose

Ricardo Otazo, Abstract Co-Author: Nothing to Disclose

Christian Geppert, Abstract Co-Author: Employee, Siemens AG

Christopher Glielmi PhD, Abstract Co-Author: Employee, Siemens AG

Mary Bruno RT, Abstract Co-Author: Nothing to Disclose

Esther Raithel PhD, Abstract Co-Author: Employee, Siemens AG

Guobin Li, Abstract Co-Author: Nothing to Disclose

Soterios Gyftopoulos MD, Abstract Co-Author: Nothing to Disclose

Catherine Niyada Petchprapa MD, Abstract Co-Author: Nothing to Disclose

Leon David Rybak MD, Abstract Co-Author: Nothing to Disclose

To develop and optimize a 3D FSE(SPACE) sequence using compressed sensing (CS) acceleration that demonstrates similar accuracy as 2D FSE sequences for the detection of internal derangement of the knee.

An accelerated SPACE sequence was developed using CS with undersampling of the two phase-encoding dimensions. The following parameters were optimized: acceleration factor, turbo factor(TF), TR, TE, voxel size, fat suppression, and the presence or absence of a magnetization transfer(MT) pulse. Following optimization, 49 consecutive patients undergoing knee MR examinations were imaged on a 3T scanner with a TxRx 15 channel knee coil using our standard MR protocol (sagittal PDW and FS T2W, coronal PDW and FS PDW, and axial FS T2W 2D FSE sequences, total scan time (TA)10:56) and the optimized SPACE sequence(TA 4:36). CS reconstruction was performed in the sagittal plane using a 3D wavelet transform. Images were then reformatted in all 3 orthogonal planes at 1.5 mm thickness. Three MSK radiologists evaluated the SPACE and 2D FSE images for each patient at two separate readout sessions.

Optimal parameters for the SPACE sequence were: TR 1200, TE33, TF45, variable flip angle evolution with PD weighting, CS undersampling factor of 6, fat suppression, presence of an optimized MT module, and 0.5x0.5x0.6 mm voxel size. Agreement between the SPACE and 2D FSE sequences for the three readers were: menisci- 93%,95%,96%; ligaments-98%,99%,99%;bone marrow edema-90%,94%,93%;cartilage-84%,88%,92%.

Clinical utility of 3D FSE images has been limited by several factors including long acquisition time, blurring, suboptimal resolution, and decreased contrast compared to 2D FSE images. Utilizing compressed sensing and an optimized MT module, an optimized SPACE sequence achieved similar contrast and resolution to 2D FSE images with a clinically acceptable TA of 4:36 min. This sequence demonstrated excellent correlation with 2D FSE images for the detection of meniscal and ligamentous tears, and bone marrow edema. There was greater discrepancy for the detection of cartilage abnormalities though the lack of arthroscopic correlation in this study precluded determination of true accuracy for chondral pathology.

An optimized 3D FSE sequence with CS acceleration has the potential to replace 2D FSE sequences for evaluation of internal derangement of the knee with significantly shorter MR scan times.

Recht, M, Otazo, R, Geppert, C, Glielmi, C, Bruno, M, Raithel, E, Li, G, Gyftopoulos, S, Petchprapa, C, Rybak, L, 3D FSE Imaging Using Compressed Sensing Acceleration: Optimization and Comparison with Conventional 2D FSE Imaging for Detection of Internal Derangement of the Knee.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14009509.html