Mirjam Wielema, Abstract Co-Author: Nothing to Disclose

Monique D. Dorrius MD, PhD, Presenter: Nothing to Disclose

Hildebrand Dijkstra MSC, Abstract Co-Author: Nothing to Disclose

Paul E. Sijens, Abstract Co-Author: Nothing to Disclose

Matthijs Oudkerk MD, PhD, Abstract Co-Author: Nothing to Disclose

To determine the influence of the size and position of the ROI in Diffusion Weighted Images (DWI) of breast lesions on the Apparent Diffusion Coefficient (ADC) values and on discriminating benign from malignant lesions.

Sixty-four patients with 72 breast lesions (52 malignant and 20 benign) underwent breast DWI. ADCs were calculated for b-value pairs: 0-1000, 0-800, 0-500, 0-200 and 0-50 s/mm2. In each lesion 4 oval regions of interest (ROI) were drawn, ROI1- ROI4. ROI1 encompassed as much of the lesion as possible, while avoiding surrounding tissue, ROI2 (0.5 cm2) was located in the middle of the lesion and ROI3 (0.5 cm2) and ROI4 (1.0 cm2) were selections within the lesion yielding the lowest ADC value. ROI3 and ROI4 were compared to determine the influence of the size of the ROI. ROC analysis was used to quantify the diagnostic accuracy of the ROI methods with the different b-value pairs Statistical significance was determined with an independent sample t-test for malignant lesions and Mann-Whitney U test for all and benign lesions.

Lower b-value pairs generally showed higher ADC values in the lesions. Benign and malignant lesions significantly differ for almost every b-value pair (p<0.001). There was a significant difference between ROI3 and ROI4 for malignant lesions (p=0.005) with a higher accuracy for ROI3 (0.943 versus 0.932), probably due to reduced partial volume effect. The ADC outcomes of b-values 0-1000 and 0-800 s/mm2 met a higher specificity than the lower b-value pairs, that is, up to 70-75% for ROI1 and ROI3 when choosing a sensitivity and negative predictive value of 100%. The AUC was highest for ROI3 using b values 0-1000 and 0-800s/mm2 (0.965 and 0.964, respectively).

The size and the position of the ROI influenced the ADC values of benign and malignant breast lesions in DWI. ROI3, a small volume selected for the lowest ADC within the lesion, had the highest accuracy in differentiating benign from malignant lesions, with b-value pairs 0-1000 and 0-800 s/mm2.

Different ROI methods influence the ADC in breast DWI, therefore a ROI (0.5 cm2) positioning at the lowest ADC value within the lesion with b-value 0-1000 or 0-800s/mm2 is recommended.

Wielema, M, Dorrius, M, Dijkstra, H, Sijens, P, Oudkerk, M, Diffusion-weighted Imaging Study of the Influence of Size and Position of the Region of Interest on the Apparent Diffusion Coefficient Values of Breast Lesions and on Discriminating Benign from Malignant.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14002645.html