CLINICAL-APPLICATION OF ABDOMINAL ECHOPLANAR IMAGING (EPI) - OPTIMIZATION USING A RETROFITTED EPI SYSTEM

Objective: Echoplanar MRI (EPI) with data acquisition times as short a s 36 ms has been advocated for imaging body areas where gross physiolo gic motion degrades images. In this study we investigated the effect o f various operator-defined parameters on image quality in EPI of the a bdomen using a commercially available scanner. Materials and Methods: Specifically, we assessed the effect of breathholding, slice thickness , k-space coverage (raw data size), and high resolution EPI in volunte ers. The effect of these parameters on signal-to-noise ratio (SNR) and image quality of liver, spleen, kidney, and pancreas was evaluated to propose guidelines for clinical EPI of the abdomen. The requirements for contiguous imaging were analyzed in a phantom experiment. Results: Our study suggests that optimum clinical EPI requires a minimum slice thickness of 7 mm. Breathhold single shot techniques are preferred to avoid spatial misregistrations and to optimize the signal yield for s egmented techniques. Maximum k-space coverage at a given TE should be implemented. High resolution techniques (128 x 512) suffer from low SN R and are clinically not useful for routine EPI. Contiguous imaging re quires a scan time of >6 s to eliminate effects of cross-talk. Conclus ion: The results suggest that clinical EPI requires careful attention to the choice of imaging parameters. The practical recommendations may help other investigators to optimize their clinical EPI studies.