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The efficacy of coronal ZOOMit diffusion-weighted MR imaging at 3T MRI for differentiation of malignant distal bile duct stricture1Radiology, Korea University Anam Hospital, Seoul, Korea, Republic of
Synopsis
For the evaluation of distal bile duct, diffusion weighted imaging should be routinely included in MR protocol for detection and differentiation of malignant distal bile duct stricture. If possible, it would be better to be able to acquire images in a coronal plane.
Introduction
The current study aimed to investigate diagnostic efficacy on malignant stricture of distal bile duct by using coronal ZOOMit DWI comparing with conventional DWI.
Methods
The institutional review board approved this retrospective study and waived the requirement for informed consent. 71 patients (M:F = 29:42; 67.4 years) who underwent Magnetic Resonance Cholangiopancreatography (MRCP) with suspected distal bile duct stricture were consecutively enrolled in this study between Mar 2016 and Sep 2018. ZOOMit diffusion images were obtained as coronal plane along the bile duct course. One board-certified radiologist measured mean ADC value at sites suspected strictures and normal bile duct wall for the comparison in both coronal ZOOMit DWI and conventional DWI. Two observers independently reviewed two image sets—a coronal ZOOMit diffusion with T2WI set and a conventional DWI with T2WI set. Receiver operating characteristic (ROC) curve analysis was used to evaluate the possibility of malignant distal bile duct stricture. Pairwise comparisons of all ROC curves were performed to test the differences in the area under the ROC curve (AUC). For distal bile strictures, sensitivity, specificity, and accuracy were calculated, and a comparison was made between the image sets by using the McNemar test. Confirmation methods for the bile duct stricture included all available clinicopathological tests including surgery.Results
Among 71 patients, 26 patients were confirmed as malignant stricture and 45 patients were confirmed as benign. On quantitative analysis, mean ADC value using coronal ZOOMit DWI of malignant stricture was 1.124 x 10–3 mm2/s and benign stricture was 1.522 x 10–3 mm2/s, respectively (p < 0.001). Mean ADC value using conventional DWI of malignant stricture was 1.107 x 10–3 mm2/s and benign stricture was 1.519 x 10–3 mm2/s, respectively (p < 0.001). There was no statistical difference between ADC values of normal bile duct in two groups: malignant group, 1.826 x 10–3 mm2/s; benign group, 1.811 x 10–3 mm2/s, p = 0.849. There were no statistically significant differences in the AUC values between coronal ZOOMit DWI (AUC = 0.802) and conventional DWI (AUC = 0.797) (p = 0.94). The cutoff value for malignant stricture providing the best sensitivity and specificity in the ROC curve analysis for ZOOMit ADC value was 1.391 x 10–3 mm2/s (sensitivity, 92.31%; specificity, 57.78%). On qualitative analysis, for each observer, the AUC values for differentiating benign from malignant distal bile duct stricture were 0.928 and 0.939 for the ZOOMit diffusion set and 0.851 and 0.824 for the conventional diffusion set. For differentiating 26 malignant distal bile duct strictures, the sensitivities with the ZOOMit diffusion set (92.31% for both observers) were higher than those with the conventional diffusion set (76.92% and 69.23% for both observers). There were statistically significant differences in observer 2 (Figure 1).Discussion
Compared with conventional DWI, ZOOMit DWI can increase spatial resolution because of the only reduced FOV (zoomed) needs to be encoded. Thus, this technique is expected to be suitable for evaluating subtle changes in small structures, such as bile ducts, by selectively magnifying the desired area. In fact, in this study, we found that the AUC value and sensitivity were increased in the coronal ZOOMit diffusion with T2WI set compared with the conventional diffusion with T2WI. However, more number of patients should be studied for further verification.Conclusion
For patients with malignant stricture of distal bile duct, conventional and coronal ZOOMit DWI may be predictive of histopathologic change of stricture, and coronal ZOOMit DWI may be more effective in diagnosis and lesion conspicuity for small lesion, such as distal bile duct.Acknowledgements
No acknowledgement found.References
1. Park MJ, Kim YK, Lim S, el al. Hilar cholangiocarcinoma: value of adding DW imaging to gadoxetic acid-enhanced MR imaging with MR cholangiopancreatography for preoperative evaluation. Radiology. 2014;270(3):768-76.
2. Yoo RE, Lee JM, Yoon JH, et al. Differential diagnosis of benign and malignant distal biliary strictures: value of adding diffusion-weighted imaging to conventional magnetic resonance cholangiopancreatography. J Magn Reson Imaging. 2014;39(6):1509-17.
3. Park HJ, Kim SH, Jang KM, et al. The role of diffusion-weighted MR imaging for differentiating benign from malignant bile duct strictures. Eur Radiol. 2014;24(4):947-58.
4. Liney G, Holloway L, Al Harthi T, et al. Quantitative evaluation of diffusion-weighted imaging techniques for the purposes of radiotherapy planning in the prostate. Br J Radiol. 2015;88(1049):20150034.
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