Objectives: To evaluate diagnostic performance of apparent diffusion coefficient (ADC) heterogeneity index to differentiate brain metastasis (BM) from normal appearing brain parenchyma (NABP) and to find out the correlation between 2-[18F]-fluoro-2-deoxy-D-glucose (18F-FDG) standardized uptake value (SUV) and ADC heterogeneity index derived from hybrid PET/MRI. Methods: Brain sequences, which were dixon and diffusion weighted imaging (DWI) protocols with simultaneous PET were used to calculate coefficient of variance of the ADC (ADCCV) and SUVmax. Inter-rater reliability was tested by interclass correlation (ICC). The correlation of ADCCV and SUVmax and the differences in ADC values, SUVmax and combination of ADC values and SUVmax between BM and NABP were investigated. Results: The excellent consistency was found between raters at ADCmean (0.972) and ADCCV (0.995). There was a moderate correlation between ADCCV and SUVmax (r=0.585) and a slight inverse correlation between ADCmean and SUVmax (r=-0.154). A statistically significant difference between BM and NABP was determined for ADCCV (p<0.001) and SUVmax (p<0.001). An area under the curve (AUC) of 0.663, 0.966, 0.571, 0.696 and 0.971were obtained with ROC analysis of SUVmax, ADCCV, ADCmean, ADCmean+SUVmax and ADCCV+SUVmax respectively. Conclusion: ADCCV may be considered as a potential biomarker that quantitatively discriminates BM from NABP with excellent interrater reliability. Keywords: ADCCV, brain metastasis, PET/MRI
Corresponding Author: Bahattin Ozkul