The magnetic resonance imaging characteristics of radicular cysts and granulomas

Limited studies have differentiated radicular cysts and granulomas with magnetic resonance imaging. Therefore, we investigated the magnetic resonance imaging characteristics of the two lesions and clarified features for distinguishing between them. We collected data of 27 radicular cysts and 9 granulomas definitively diagnosed by histopathology and reviewed the fat-saturated T2-weighted, T1-weighted, and contrast-enhanced fat-saturated T1-weighted images. We measured the maximum diameter and apparent diffusion coefficient values of the lesions. We employed Fisher’s exact test, Mann–Whitney U test, and independent t-tests to compare the two lesions and created a decision tree for discriminating them. There were significant differences between radicular cysts and granulomas with respect to five imaging characteristics—signal intensity of the lesion centre on fat-saturated T2-weighted images; signal intensity, texture, and contrast enhancement of the lesion centre on contrast-enhanced fat-saturated T1-weighted images; and maximum diameter of the lesion. The cut-off diameter for radicular cysts was 15.9 mm. The area under the receiver operating characteristic curve, sensitivity, and specificity were 0.971, 85.2%, and 100%, respectively. From the decision tree analysis, maximum diameter, lesion centre contrast enhancement on contrast-enhanced fat-saturated T1-weighted images, and lesion centre signal intensity on fat-saturated T2-weighted images were important for discriminating between the two lesions.