Comparison of DWI techniques in patients with epidermoid cyst: TGSE-BLADE DWI vs. SS-EPI DWI

Abstract

[Purpose]To compare quantitative values and image quality between single-shot echo-planar imaging (SS-EPI) diffusion-weighted imaging (DWI) and two-dimensional turbo gradient- and spin-echo DWI with non-Cartesian BLADE trajectory (TGSE-BLADE DWI) in patients with epidermoid cyst. [Methods]Patients with epidermoid cyst who underwent both SS-EPI DWI and TGSE-BLADE DWI were included in this study. Two raters placed ROIs encircling the entire epidermoid cyst on SS-EPI DWI, and then on TGSE-BLADE DWI. Apparent diffusion coefficient (ADC) of the epidermoid cyst was measured within each ROI, then the intraclass correlation coefficient (ICC) between raters was obtained for each DWI. The areas of ROIs placed by the two raters were measured and compared using the Dice coefficient. In the selected slice analysis, one rater selected the most appropriate slice and carefully placed the ROIs slightly smaller than the epidermoid outline to avoid artifacts. Image quality analysis was assessed qualitatively for geometric distortion, susceptibility artifacts, lesion conspicuity, and diagnostic confidence. ADCs for both DWI techniques were compared with theoretical values derived from the diffusion phantom. [Results]Twenty patients with epidermoid cyst were included in this study. The ICC of ADC measured by the two raters for TGSE-BLADE (0.80) was higher than that for SS-EPI (0.59). Dice coefficient of ROI areas was significantly higher with TGSE-BLADE (0.78) than with SS-EPI (0.71, P = 0.007). Selected slice analysis showed that the ADC of epidermoid cyst was significantly higher with TGSE-BLADE DWI than with SS-EPI DWI (P < 0.001). ADCs measured from carefully selected ROIs avoiding artifacts with the two techniques correlated positively (r = 0.87, P < 0.001; ICC 0.75). TGSE-BLADE DWI rated better for image quality than SS-EPI DWI according to all raters. ICCs of measured ADC and theoretical ADCs exceeded 0.99 for both techniques. [Conclusions]TGSE-BLADE DWI appears more suitable than SS-EPI DWI for evaluating epidermoid cyst.