Single point imaging with radial acquisition and compressed sensing.

Abstract

To accelerate the Pointwise Encoding Time Reduction with Radial Acquisition(PETRA) sequence using compressed sensing while preserving the image quality for high-resolution MRI of tissue with ultra-short values. Compressed sensing was introduced in the PETRA sequence(csPETRA) to accelerate the time-consuming single point acquisition of the k-space center data. Random undersampling was applied to achieve acceleration factors up to Acc=32. Phantom and in vivo images of the knee joint of six volunteers were measured at 3T using csPETRA sequence with Acc=4, 8, 12, 16, 24, and 32. Images were compared against fully sampled PETRA data(Acc=1) for structural similarity and normalized-mean-square-error. Qualitative and semi-quantitative analyses were performed to assess the effect of the acceleration on image artifacts, image quality, and delineation of anatomical structures at the knee. Even at high acceleration factors of Acc=16 no aliasing artifacts were observed, and the anatomical details were preserved compared with the fully sampled data. The normalized-mean-square-error was less than 1% for Acc=16, in which single point imaging acquisition time was reduced from 165 to 10s, reducing the total scan time from 7.8 to 5.2min. Semi-quantitative analyses suggest that Acc=16 yields comparable diagnostic quality as the fully sampled data for knee imaging at a scan time of 5.2min. csPETRA allows for ultra-short imaging of the knee joint in clinically acceptable scan times while maintaining the image quality of original non-accelerated PETRA sequence.