Diffusion-weighted quantitative MRI to diagnose benign conditions from malignancies of the anterior mediastinum: Improvement of diagnostic accuracy by comparing perfusion-free to perfusion-sensitive measurements of the apparent diffusion coefficient

Purpose

To compare perfusion-free to perfusion-sensitive measurements of the apparent diffusion coefficient (ADC) to diagnose benign conditions from malignancies of the anterior mediastinum.

Materials and Methods

Seventy-six subjects were divided into a "benign conditions" group (A, n = 44) and a "malignancies" group (B, n = 32), based on histological findings. diffusion-weighted magnetic resonance imaging (DW-MRI) was performed at b of 0/150/800 sec/mm². The ADCs were obtained on an ADC map by including (perfusion-sensitive = ADC_b0-800) and excluding (perfusion-free = ADC_b150-800) the b = 0 sec/mm². The Mann–Whitney U-test was used to detect differences in ADC_b0-800 compared with ADC_b150-800 values between all cases, benign conditions, and malignancies. The same test was used to evaluate differences in ADCs between the two groups for each type of measurement (ADC_b0-800 and ADC_b150-800), and receiver-operating characteristic (ROC) curves were obtained to evaluate discrimination abilities with comparison of areas-under-ROC-curves (AUROC). Optimal cutpoints for discrimination between groups were determined by the Youden-Index with computation of accuracy.

Results

The median ADC_b0-800 was significantly greater compared with ADC_b150-800 for all cases (P = 0.0014), benign conditions (P = 0.0412), and malignancies (P = 0.0001). The median percentage of increase was 5.30% for group-A and 22.39% for group-B (P < 0.0001). AUROC of ADC in discriminating between groups was significantly greater for ADC_b150-800 (0.932) compared with ADC_b0-800 (0.831) (P = 0.001). The optimal cutpoint for distinction between groups was 1.52 × 10^-3mm²/sec (sensitivity = 93.7%, specificity = 88.6%, accuracy = 90.8%) for ADC_b150-800 and 1.75 × 10^-3mm²/sec (sensitivity = 75.0%, specificity = 79.5%, accuracy = 77.6%) for ADC_b0-800.

Conclusion

The use of perfusion-free ADC measurements significantly improves diagnostic accuracy of DW-MRI in differentiating benign conditions from malignancies of the anterior mediastinum. J. Magn. Reson. Imaging 2016.

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