Perceptual evaluation of artifacts in cardiac magnetic resonance imaging due to partial parallel imaging

Evaluation of images generated by new MR pulse sequences or reconstruction methods is traditionally done using subjective measures of image quality in a clinical study or by using quantitative measures such as local SNR or CNR to support the subjective findings. In order to accelerate evaluation of new candidate MR techniques, objective measures related to human perception and performance are desirable. Therefore, the goal of this study was to determine if the effects of parallel-imaging artifacts on subjective image quality could be predicted using the JNDmetrix vision model as a first step in developing objective measures to guide MR development. Single-shot fast spin echo images (HASTE) were acquired with increasing acceleration factors (0, 2, 3, and 4) and reconstructed with two algorithms, mSENSE and GRAPPA. Subjective quality ratings (0-10 scale) for these images were compared to spatial-frequency channel responses of the JNDmetrix model and to PSNR. Our results confirmed the anticipated degradation in quality for GRAPPA and mSENSE images with increasing acceleration factor. The mSENSE method yielded significantly lower quality ratings than GRAPPA for the higher acceleration factors (3 and 4). Full matrix images with no partial parallel acquisition (noppa) showed blurring due to longer shot time and T2 decay and were rated most comparable to the GRAPPA acceleration factor 4 images. There was a strong linear relationship between just-noticeable difference (JND) changes and observer ratings, while PSNR showed no correlation with observer ratings. The JNDmetrix results better reflected image degradation due to both blurring and noise. These results give confidence that the JNDmetrix approach may become a useful tool for the design and evaluation of MR pulse sequences and reconstruction methods.