Purpose: The purpose of this study is to compare diagnostic performances of (18)F-fluorodeoxyglucose (FDG) visual score, maximum standardized uptake value (SUVmax), ratio of adrenal SUVmax to liver SUVmax (A/L SUVmax), apparent diffusion coefficient (ADC) from diffusion-weighted imaging, and SUVmax/ADC ratio to differentiate adrenal pheochromocytoma from other benign tumors.
Methods: Eleven pheochromocytomas and 22 other benign tumors in 30 patients were included. FDG-based indices, ADC, and SUVmax/ADC ratio were compared between groups using the Mann-Whitney U test, and sensitivity, specificity, accuracy, and area under the curve (AUC) for diagnosing pheochromocytoma by receiver operating characteristic analyses. The correlation between SUVmax and ADC was analyzed using the Spearman's rank test.
Results: Pheochromocytoma showed significantly higher visual score (2.8 ± 0.4 vs. 1.3 ± 0.9), SUVmax (11.0 ± 8.9 vs. 3.2 ± 1.4), A/L SUVmax ratio (3.96 ± 3.48 vs. 0.96 ± 0.51), and SUVmax/ADC ratio (10.6 ± 8.09 vs. 2.28 ± 0.98) (each P < 0.001) and significantly lower ADC (1.08 ± 0.23 × 10(-3) mm(2)/s vs. 1.43 ± 0.29 × 10(-3) mm(2)/s, P = 0.003) than other benign tumors. Sensitivity, specificity, and accuracy for diagnosing pheochromocytoma were 100, 73, and 82% for visual score, 100, 86, and 91% for both SUVmax and A/L SUVmax ratio, and 64, 100, and 88% for ADC and 82, 95, and 91% for SUVmax/ADC ratio. No significant differences in AUC were found between FDG-based indices, ADC, and SUVmax/ADC ratio. A significant negative correlation was noted between SUVmax and ADC (ρ = -0.36, P = 0.039).
Conclusion: FDG-based indices and ADC appear comparably useful for differentiating pheochromocytoma from other benign adrenal tumors.