Reverse Encoding Distortion Correction for Clinical Head Echo-Planar Diffusion-Weighted MRI: Initial Experience.

This study aimed to evaluate the feasibility of the recently commercialized reverse encoding distortion correction (RDC) method for echo-planar imaging (EPI) diffusion-weighted imaging (DWI) by applying clinical head MRI. This study included 50 consecutive patients who underwent head MRI, including single-shot (SS) EPI DWI and RDC-EPI DWI. For evaluation of normal structures, qualitative scores for image distortion, Dice similarity coefficient (DSC) values, distortion ratios, and mean apparent diffusion coefficient (ADC) values were assessed in the pons, temporal lobe at the skull base, and frontal lobe at the level of the lateral ventricles in 30 patients. To evaluate pathologies, qualitative scores for image distortion were assessed for 25 intracranial and 21 extracranial pathologies identified in 32 patients. Qualitative scores for image distortion, DSC values, distortion ratios, and mean ADC values of the pons and temporal lobe were significantly different between SS-EPI DWI and RDC-EPI DWI, whereas those of the frontal lobe at the level of the lateral ventricles were not significantly different between the 2 DWIs. The qualitative scores for image distortion and mean ADC values of extracranial pathologies were significantly different between the DWIs, whereas those of intracranial pathologies were not significantly different. RDC-EPI DWI significantly reduced image distortion and showed higher mean ADC values of the brain parenchyma in the skull base and extracranial pathologies.

Kashiwagi N ，Sakai M ，Nakamoto A ，Takahashi H ，Isogawa Y ，Suzuki Y ，Yamada S ，Tomiyama M ，Nakanishi K ，Tomiyama N ... -  《-》

Acquisition and reconstruction with motion suppression DWI enhance image quality in nasopharyngeal carcinoma patients: Non-echo-planar DWI comparison with single-shot echo-planar DWI.

To evaluate the impact of application acquisition and reconstruction with motion suppression (ARMS) technology on improving the image quality of diffusion-weighted Imaging (DWI) for nasopharyngeal carcinoma (NPC), compared to single-shot echo-planar imaging (SS-EPI). A total of 90 patients with NPC underwent MR examination, including ARMS DWI and SS-EPI DWI sequences. Both DWI sequences were acquired with b-values 0 and 800 s/mm2. Two radiologists evaluated the visibility of the lesion, geometric distortion, and overall image quality of the two DWI sequences. Signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), geometric distortion degree, and apparent diffusion coefficient (ADC) values of the nasopharyngeal lesions were assessed and compared for two sequences. The Wilcoxon signed-rank test was used to compare the quantitative and qualitative parameters of the two sequences. The lesion visibility, geometric distortion, and overall image quality scores were significantly higher in ARMS DWI (all P<0.001). Four small-sized lesions were not visible and four lesions were partially visible in the SS-EPI DWI sequence. Lesion detection rate of ARMS DWI is 100 %, while that of SS-EPI is 95.56 %, P<0.043. The mismatch distance between the fusion images of ARMS DWI and T2WI was smaller than that of SS-EPI DWI and T2WI (all P<0.001). The SNR and CNR of ARMS DWI were lower than that of SS-EPI DWI (114.48 ± 37.89 vs. 202.61 ± 78.84, P<0.001 and 1.81 ± 1.84 vs. 3.29 ± 3.71, P<0.003) while the ADC value was higher (839.19 ± 138.44 × 10-6 mm2/s vs. 788.82 ± 110.96 × 10-6 mm2/s, P<0.002). ARMS DWI improves the image quality by reducing geometric distortion and magnetic susceptibility artifacts. ARMS DWI is superior to SS-EPI DWI for diagnosing small-sized nasopharyngeal lesions, although it has lower SNR and CNR.

Xu G ，Liu H ，Ling D ，Li Y ，Lu N ，Li X ，Zhang Y ，He H ，Huang Z ，Xie C ... -  《-》

Evaluating Reproducibility of the ADC and Distortion in Diffusion-weighted Imaging (DWI) with Reverse Encoding Distortion Correction (RDC).

Numamoto H ，Fujimoto K ，Miyake KK ，Fushimi Y ，Okuchi S ，Imai R ，Kondo H ，Saga T ，Nakamoto Y ... -  《-》

Intravoxel incoherent motion diffusion-weighted imaging in nasopharyngeal carcinoma: comparison of the turbo spin-echo and echo-planar imaging techniques.

Traditional echo-planar imaging with intravoxel incoherent motion (EPI-IVIM) exhibits significant magnetic susceptibility artifacts and geometric distortions, which limits its application in nasopharyngeal carcinoma (NPC). This study aimed to compare the qualitative and quantitative indicators between turbo spin echo with intravoxel incoherent motion (TSE-IVIM) and EPI-IVIM in patients with NPC and to provide optimal scanning strategies based on the relationships among these indicators. A cross-sectional study was conducted between March 2022 and August 2022. Patients with pathologically confirmed NPC underwent pretreatment staging magnetic resonance (MR) examinations with both TSE-IVIM and EPI-IVIM. IVIM images were subjectively and objectively assessed for anatomical structures including nasopharyngeal lesions, nasal concha, the spinal cord, and the temporal pole. Subjective evaluation indicators (including susceptibility artifacts, geometric distortion, lesion conspicuity, and overall image quality on a five-point scale) were compared using the Wilcoxon signed rank test. Quantitative indicators, including signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), apparent diffusion coefficient (ADC), and IVIM-derived parameters (true diffusion coefficients, perfusion fraction, pseudodiffusion coefficient), were compared using the Wilcoxon signed rank test. Bland-Altman plots and coefficient of variation (CV) were used to compare the reproducibility and robustness of the ADC and IVIM-derived parameters between TSE-IVIM and EPI-IVIM. A total of 30 patients (24 males and 6 females) aged between 29 and 71 years (mean age 47.6±12.3 years) were included in the study. TSE-IVIM demonstrated significantly better subjective evaluation indicators for nasopharyngeal lesions, nasal concha, and temporal poles as compared to EPI-IVIM (all P values <0.001), with no significant difference observed in the spinal cord. The SNR of TSE-IVIM was significantly lower than that of EPI-IVIM in the spinal cord and temporal pole (SNR: P=0.027 and P=0.026, respectively). For nasopharyngeal lesions and nasal concha, TSE-IVIM showed no significant difference in SNR (P=0.926 and P=0.428, respectively) but had a significantly higher CNR compared to EPI-IVIM (P=0.003 and P=0.01, respectively). The perfusion fraction (f) value for TSE-IVIM in nasopharyngeal lesions was significantly lower than that for EPI-IVIM (P=0.004), while no statistically significant differences were found in the diffusion coefficient (D) or pseudodiffusion coefficient (D*) values (P=0.914 and P=0.644, respectively). The 95% limits of agreement (LoAs) in nasopharyngeal lesions and nasal concha were wider and had a larger CV compared to those in the spinal cord and temporal pole. TSE-IVIM provided better subjective image quality scores and a significantly higher CNR, with no significant reduction in SNR. It demonstrated superior image quality and more stable quantitative indicators for nasopharyngeal lesions and nasal concha although magnetic sensitivity artifacts were more noticeable. Due to the different f values and wide LoAs observed between the two sequences in nasopharyngeal lesions, TSE-IVIM is recommended for follow-up in patients with NPC.

Liu Y ，Hu L ，Qian L ，Chen M ，Xu S ，Sun P ，Huang J ，Lei Z ... -  《-》

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

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. 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. 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. TGSE-BLADE DWI appears more suitable than SS-EPI DWI for evaluating epidermoid cyst.

Otani S ，Fushimi Y ，Okuchi S ，Sakata A ，Yamamoto T ，Nakajima S ，Wang Y ，Ikeda S ，Ito S ，Yasumura S ，Takada S ，Sano N ，Ueno K ，Urushibata Y ，Zhou K ，Arakawa Y ，Nakamoto Y ... -  《-》