Chemical shift-encoded multishot EPI for navigator-free prostate DWI

Abstract

Purpose: DWI is an important contrast for prostate MRI to enable early andaccurate detection of cancer. This study introduces a Dixon 3-shot-EPI proto-col with structured low-rank reconstruction for navigator-free DWI. The aim isto overcome the limitations of single-shot EPI (ssh-EPI), such as geometric dis-tortions and fat signal interference, while addressing the motion-induced phasevariations of multishot EPI and simultaneously allowing water/fat separation.Methods: DWI data were acquired from 7 healthy volunteers using both Dixon3-shot EPI and standard fat-suppressed ssh-EPI with similar scan times for com-parison. Two readers evaluated image quality using a 5-point Likert scale regard-ing different aspects. The ADC values were quantitatively compared betweenprotocols. To show feasibility in a clinical setting, the protocol was applied totwo patients.Results: From the reader scores, Dixon 3-shot EPI significantly reduced geo-metric distortion compared with ssh-EPI (p < 0.01), with no significant dif-ferences in edge definition, SNR, or overall image quality. There was no sig-nificant difference in ADC values between the two protocols. However, theDixon multishot-EPI protocol offered advantages such as self-referenced B 0map–driven distortion correction, greater flexibility in imaging parameters, andsuperior fat suppression. In the patient data, the lesion could be clearly identifiedin both protocols and on the associated ADC maps.Conclusion: The proposed Dixon 3-shot-EPI protocol shows promise as analternative to ssh-EPI for prostate DWI, providing reduced geometric distortionsand improved fat suppression. It addresses common DWI issues based on EPIand enhances scanning flexibility, indicating potential for optimized imaging