The influence of the size and position of the region of interest on the ADC value in discriminating between benign and malignant breast lesions in Diffusion Weighted Imaging.

Wielema, M. (Mirjam) (2014) The influence of the size and position of the region of interest on the ADC value in discriminating between benign and malignant breast lesions in Diffusion Weighted Imaging. thesis, Medicine.

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Abstract

Introduction: Diffusion Weighted Imaging (DWI) is a promising additional sequence in breast MRI. Diffusion is measured by the Apparent Diffusion Coefficient (ADC) value. Two or more b-values are needed to calculate the ADC value. A region of interest (ROI) is drawn inside a lesion to calculate the mean ADC of the lesion. In literature different methods are used to draw a ROI. Purpose: The main purpose of this study was to determine the influence of the size and position of the ROI on the ADC values in discriminating between benign and malignant lesions in DWI. Other purposes were to determine the accuracy of different ROIs and the influence of different b-values on the ADC values. Materials and methods: In this retrospective consecutive study 95 patients (108 lesions) have undergone a breast MRI including DWI, using b-value combinations 0-1000, 0-800, 0-500, 0-200 and 0-50 s/mm2. The final diagnosis was obtained by pathology or a diagnostic follow-up with MRI. In each lesion 4 ROIs were drawn. ROI1 encompassed as much of the lesion as possible, ROI2 (0.5 cm2) was located in the middle of the lesion and ROI3 (0.5 cm2) and ROI4 (1.0 cm2) were located acquiring the lowest ADC value. The mean ADC value was measured for benign and malignant lesions. The effect of necrosis, non-mass-like and moderate enhancement and mucinous tumors on the mean ADC values was studied. ROI3 and ROI4 were compared and the accuracy was measured to determine the influence of the size of the ROI. The influence of the position of the ROIs and the use of different b-value combinations were assessed by calculating the mean ADC of the breast lesions. The specificity for ROI1-3 with different b-value combinations was calculated by choosing a sensitivity and negative predictive value of 100%. ROC analysis was used to quantify the diagnostic accuracy of the ROI methods with different b-value combinations in the assessment of breast lesions. Significant differences were tested by using an independent sample t-test for malignant lesions and Mann-Whitney U test for all and benign lesions. Results: The mean ADC value of malignant lesions for ROI1-4 was significantly higher by including the lesions with necrosis, non-mass-like and moderate enhancement and mucinous tumors. There was a significant difference between ROI3 and ROI4 for malignant lesions with a higher accuracy for ROI3 (0.943 compared to 0.932). Therefore, we excluded the lesions mentioned above and the ROI4 method for further analysis. There was a significant difference between benign and malignant lesions for ROI1-3 with almost every b-value combination. The ADC values of ROI3 significantly differed from ROI1 and ROI2 (p<0.000) with b-values 0-1000, 0-800 and 0-50 s/mm2. Lower b-values showed significantly higher ADC values for almost all lesions in ROI1-3. The ADC outcomes of b-values 0-1000 and 0-800 s/mm2 did not significantly differ. Furthermore these b-values showed the highest specificity (70-75%) for ROI1 and ROI3. However, the AUC was highest for ROI3 using b values 0-1000 and 0-800s/mm2 (0.965 and 0.964, respectively). Conclusion: The size and the position of the ROI and the choice of b-values influenced the ADC values of benign and malignant breast lesions in DWI. This study showed that ROI3 had the highest accuracy in differentiating benign from malignant lesions, with b-value combinations 0-1000 and 0-800 s/mm2.

Item Type:	Thesis (Thesis)
Supervisor name:	Dorrius, Dr. M.D. and Oudkerk, Prof. dr. M. and Sijens, P.E. and Dijkstra, H. and Kappert, P. and Jansen, L.
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 10:52
Last Modified:	25 Jun 2020 10:52
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/1306

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