Abstract:

Objectives: The aim of this study was to determine the ADC values of different orbital masses and to calculate the threshold ADC value for differentiation of benign and malignant masses. Materials and Methods: For this study, ADC values of 43 lesions located in and around the orbit were measured. The obtained ADC values were averageed. Results: The average age of the 43 patients included in the study was 49.3±16.6 (min-max = 17-76). Twenty-six (60%) of the patients were female and 17 (40%) were male. Forty-three lesions (28 benign and 15 malignant) were included in the study. The average ADC values of benign lesions were 1304.8±636.2x10-6 mm2/s (min-max= 423-2709 x10-6 mm2/s), and the average ADC values of malignant lesions were 785.6±264.1x10-6 mm2/s (min-max= 420-1357x10-6 mm2/s). The difference between the average ADC values of benign and malignant lesions was statistically significant (p=0.006). The area under the curve in the ROC analysis was 0.776 (p=0.006). The cut-off value for malignancy was 841.25x10-6 mm2/s (sensitivity: 75%, specificity: 77%). No cystic area was observed in any of the malignant lesions. The average ADC value of hemangiomas was significantly higher than meningiomas (1197.6±44.4 10-3 mm2/s vs 982.8±129.8 10-3 mm2/s; p=0.021). There was no statistically significant difference between ADC values obtained from leukemia/lymphoma involvement and abscesses (746±12.9 10-3 mm2/s vs 452.6±29.3 10-3 mm2/s, p=0.083). Conclusion: In literature, the threshold value in the differentiation of benign and malignant lesions of the orbit is controversial. In our study, the sensitivity and specificity values were found to be low. Therefore, diffusion images should be correlated with clinical and other imaging findings.

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