Zoomed EPI-DWI of the head and neck with two-dimensional, spatially-selective radiofrequency excitation pulses.

OBJECTIVES

To evaluate the feasibility of zoomed diffusion-weighted EPI (z-EPI) in the head and neck in a healthy volunteer population and to compare to conventional single-shot EPI (c-EPI).

MATERIAL AND METHODS

Nine volunteers were included in this prospective, IRB-approved study. Examinations were performed on a 3 T-MR system equipped with a two-channel, fully-dynamic parallel transmit array. The acquired sequences consisted of a T2w-TSE, a c-EPI, and two z-EPI acquisitions. For quantitative assessment of distortion artefacts, DW images were fused with T2-TSE images. Misregistration of DW images with T2-TSE images was assessed in the cervical spine. For qualitative assessment, two readers ranked c-EPI and z-EPI sequences in terms of susceptibility artefacts, image blur, and overall imaging preference. ADC values of several anatomical regions were calculated and compared between sequences.

RESULTS

Mean maximum distortion with the c-EPI was 5.9 mm ± 1.6 mm versus 2.4 mm ± 1 mm (p < 0.05) with z-EPI. Both readers found more blur and susceptibility artefacts in every case with c-EPI. No statistically significant differences in calculated ADC values were observed.

CONCLUSION

z-EPI of the head and neck leads to substantial image quality improvements relative to c-EPI due to a reduction in susceptibility artefacts and image blur.

KEY POINTS

• Zoomed DWI is feasible in the head and neck. • Image quality improves substantially with zoomed DWI of the neck. • Zoomed DWI exhibits markedly reduced susceptibility artefacts.