Apparent Diffusion Coefficient Mapping of Salivary Gland Tumors: Prediction of the Benignancy and Malignancy

Abstract

BACKGROUND AND PURPOSE: Preoperative prediction of tumor malignancy is clinically very important, because this information strongly influences the surgical plan. We evaluate the preoperative apparent diffusion coefficient (ADC) maps of benign and malignant salivary gland tumors.

MATERIALS AND METHODS: High-resolution MR imaging was performed on 31 patients with benign or malignant salivary gland tumors; ADC maps of the tumors were also obtained. Surface coils of 47 or 110 mm diameter were used to improve the image resolution. The ADCs were compared with histologic features of the excised tumors.

RESULTS: The ADC maps effectively depicted the histologic features of the salivary gland tumors, such as presence of cancer cells, myxomatous tissues, fibrosis, necrosis, cyst formation, and lymphoid tissues. The ADC maps showed that more frequent areas with high ADCs (≥1.8 × 10⁻³ mm²/s) were significantly greater in benign tumors than in malignant tumors. The sensitivity and specificity for high ADC occupying fewer than 5% of the area of a tumor was 89% and 100%, respectively, resulting in 97% accuracy, 100% positive predictive value, and 96% negative predictive value.

CONCLUSION: The ADC may provide preoperative tissue characterization of the salivary gland tumors.