Region of interest demarcation for quantification of the apparent diffusion coefficient in breast lesions and its interobserver variability

Abstract

ORIGINAL ARTICLEPURPOSE We aimed to compare two different methods of region of interest (ROI) demarcation and determine interobserver variability on apparent diffusion coefficient (ADC) in breast lesions. METHODSThirty-two patients with 39 lesions were evaluated with a 3.0 Tesla scanner using a diffusion-weighted sequence with several b-values. Two observers independently performed the ADC measurements using: 1) a small fixed area of 10 mm 2 ROI within the area with highest restriction; 2) a large ROI so as to include the whole lesion. Differences were assessed using the Wilcoxon-rank test. Bland-Altman method and Spearman coefficient were applied for interobserver variability and correlation analysis.RESULTS ADC values measured using the two ROI demarcation methods were significantly different for both observers (P = 0.026; P = 0.033). There was no interobserver variability in ADC values using either method (large ROI, P = 0.21; small ROI, P = 0.64). ADC values of malignant lesions were significantly different between the two methods (P < 0.001). Variability in ADC was ≤0.008×10 -3 mm 2 /s for both methods. When using the same method, ADC values were significantly correlated between the observers (small ROI: r=0.990, P < 0.001; large ROI: r=0.985, P < 0.001). CONCLUSIONThe choice of ROI demarcation method influences ADC measurements. Small ROIs show less overlap in ADC values and higher ADC reproducibility, suggesting that this method may improve lesion discrimination. Interobserver variability was low for both methods. Diffusion-weighted imaging (DWI) of the breast has been used to improve lesion diagnosis. However, due to lesion heterogeneity, differences between acquisition protocols, and lesion demarcation strategies, there is some overlap in apparent diffusion coefficient (ADC) values of different lesion types (1).Regarding lesion demarcation, different strategies can be found in the literature. Pereira et al. (2) suggest delimiting the whole lesion area, whereas others consider only its most solid part representing viable tumor (3, 4).A study focusing on the use of ADC minimum, average, and maximum to characterize breast lesions (5) has indirectly investigated the influence of region of interest (ROI) on ADC quantification, but has not specifically compared these two methods of demarcation. Here, we compare these two ROI demarcation methods and determine their interobserver variability in ADC quantification. Methods Study populationDuring a five-month period, 38 women with clinical indications to perform breast magnetic resonance imaging (MRI) were studied following approval from the Ethics Committee (code number 276/13).Exclusion criteria were breast surgery within six months, chemotherapy or radiotherapy within 24 months, no lesions in dynamic contrast-enhanced (DCE) image, breast implants, and examinations presenting artefacts. Only lesions ≥7 mm in the DCE having histological results or a minimum two-year follow-up were included. MRI data acquisitionPatients underwent examinations at 3.0 T system (Mag...

Diffusion‐weighted quantitative MRI of pleural abnormalities: Intra‐ and interobserver variability in the apparent diffusion coefficient measurements

“…In a study of 81 patients with benign and malignant conditions of the anterior mediastinum, Priola et al found that ADC values of the OSR and MSR methods were significantly lower compared to all other methods that sampled the whole tissue on one or more transverse slices . However, both studies found excellent interobserver agreement in all methods . Notably, we obtained the highest repeatability in ADC measurements by using the WTV method.…”

“…Prior studies assessed the interobserver agreement of ADC quantification by using different methods in various tumors . However, none of the studies on DW‐MRI of pleural disease evaluated the measurement variability of the ADC between different readings or readers .…”

“…Similar results were found by previous investigators in different tumors. For example, Nogueira et al used manually placed ROI of different sizes in DW‐MRI measurements of 39 breast lesions and found significantly lower ADC values for small ROI compared to large ROI . In a study of 81 patients with benign and malignant conditions of the anterior mediastinum, Priola et al found that ADC values of the OSR and MSR methods were significantly lower compared to all other methods that sampled the whole tissue on one or more transverse slices .…”

“…However, several factors, which include also the manual method of region‐of‐interest (ROI) positioning for measuring the ADC, affect the measurement and can lead to unreliable values . Indeed, some investigators have found significant differences in ADC values by using different ROI methods in the same tumor, suggesting that the method of measurement significantly affects the ADC …”

Role of diffusion weighted magnetic resonance imaging in a rat model of testicular torsion

“…An ROI that covers all tumour volume minimizes the interobserver variability and differences between ADC calculations and ensures that the measurements are repeatable. 27,28 Therefore, we used the largest ROI which was not affected by artefacts.…”