Diffusion-Weighted MRI in Patients with Testicular Tumors—Intra- and Interobserver Variability

Abstract

In general, magnetic resonance (MR) diffusion-weighted imaging (DWI) has shown potential in clinical settings. In testicles parenchyma, the DW imaging helps differentiate and characterize benign from malignant lesions. Placement and size of the region of interest (ROI) may affect the ADC value. Therefore, the aim of this study was to investigate the intra- and interobserver variability in testicular tumors when measuring ADC using various types of regions of interest (ROI). Two observers performed the ADC measurements in testicular lesions based on three ROI methods: (1) whole volume, (2) round, and (3) small sample groups. Intra- and interobserver variability was analyzed for all ROI methods using intraclass correlation coefficients (ICC) and bland-altman plots. The two observers performed the measurements twice, three months apart. A total of 26 malignant testicle tumors were included. Interobserver agreement was excellent in tumor length (ICC = 0.98) and tumor width (ICC = 0.98). In addition, intraobserver agreement was excellent in tumor length (ICC = 0.98) and tumor width (ICC = 0.99). The whole volume interobserver agreement in the first reading was excellent (ICC = 0.93). Round ADC had an excellent (ICC = 0.93) and fair (ICC = 0.58) interobserver agreement, in the first and second reading, respectively. Interobserver agreement in ADC small ROIs was good (ICC = 0.87), and good (ICC = 0.78), in the first and second reading, respectively. Intraobserver agreement varied from fair, good to excellent agreement. The ROI method showed varying inter- and intraobserver agreement in ADC measurement. Using multiple small ROI conceded the highest interobserver variability, and, thus, the whole volume or round seem to be the preferable methods.

Apparent diffusion coefficient histogram in the differentiation of benign and malignant testicular tumors

“…Therefore, our results suggest that the VOI 1 placement method likely improved the ability to differentiate between benign and malignant tumors. Our results are similar to those of Pederson et al, which studied a group of malignant testicular tumors consisting of 26 tumors and pointed out the highest value of whole-tumor VOI placement in diagnosing testicular tumors 9 .…”

“…HA analysis is a quantitative method for evaluating the statistical parameters in each image based on VOI placement to cover the entire tumor. Therefore, the histogram's shape and asymmetry reflect microstructural differences in tumor composition corresponding to histopathological grade, distinguishing benign and malignant tumors 8 , 9 . Previous studies have shown that placing the VOI so that it covers the entire tumor volume allows for a better assessment than the previous approach of placing an ROI on a specific slice or localized tumor region, often avoiding its cystic, necrotic, and hemorrhagic portions, leading to limitations in reflecting its heterogeneity, especially for malignant tumors that have more necrotic and bleeding portions than benign tumors 8 , 14 .…”

“…According to Wang et al, ADC value ≤ 0.90 × 10-3 mm 2 /s suggests a malignant tumor 2 . However, ADC-map-based measurements vary according to ROI location and size 9 . Histogram analysis of ADC maps (HA) is a recent method applied in distinguishing two groups based on statistical indicators using volume-of-interest (VOI) placement to cover the entire tumor.…”

“…While biopsy is considered the gold standard in differentiating benign and malignant tumors, it is an invasive procedure with potential hemorrhage or infection risks and limitations in evaluating the extent of lesions [2]. Ultrasound with a high-frequency linear probe (7)(8)(9)(10) is the initial imaging diagnostic tool in screening testicular pathology, with undeniable advantages such as determining intra-or extra-testicular masses and discriminating tumors from non-tumor lesions such as infections or testicular torsions. However, the value of conventional ultrasound, contrast-enhanced ultrasound, and elastography in differentiating benign and malignant tumors and evaluating the extent of lesions remains controversial [4] [5] [6].…”

Correlation of Apparent Diffusion Coefficient With Proliferation and Apoptotic Indexes in a Murine Model of Fibrosarcoma: Comparison of Four Methods for MRI Region of Interest Positioning

“…All ROI methods (oval, freehand, small‐sample, and whole‐volume) showed excellent interobserver agreement, indicating that different ROI methods were objective and reliable for ADC measurements in fibrosarcoma. Previous studies have demonstrated good or excellent intraobserver or interobserver agreement for ADC measurements in hepatocellular carcinoma, 17 bladder cancer, 18 rectal cancer, 19 head and neck cancer, 20 testicular tumor, 21 and soft tissue masses 22 using different ROI methods, including the largest tumor slice, multiple small tumor samples, and whole tumor volume. Notably, the whole‐volume ROI method in the present study had the best reproducibility in ADC measurements, suggesting that the inclusion of the whole tumor volume method, which is not limited by the number and size of ROIs, leads to a decline in sampling errors and interobserver variability.…”