Whole brain apparent diffusion coefficient histogram: A new tool for evaluation of leukoaraiosis

Purpose: To test whole brain apparent diffusion coefficient histogram analysis as an alternative approach to visual score for the assessment of leukoaraiosis (LA). Materials and Methods: T2 and diffusion weighted images were obtained in 15 elderly patients. LA extension was assessed on T2 weighted images by two observers using a semiquantitative visual score. Apparent diffusion coefficient (ADC) maps of the entire brain were generated and, after exclusion of the skull with manual tracing and of the cerebrospinal fluid (CSF) by application of a threshold value, whole brain (WB)-ADC histogram was obtained. Moreover, a brain volume index (BVI) was calculated on ADC maps as (intracranial volume - CSFvolume)/intracranial volume. Results: The kappa inter-observer agreement for LA scoring was 0.69. Manual segmentation of the skull showed a mean inter-operator coefficient of variation below 3%. The median value of whole brain ADC histogram directly correlated with LA extension (P = 0.013). Moreover a significant inverse correlation (P = 0.002) was found between WB-ADC median value and BVI. Conclusion: WB-ADC histogram is a reproducible alternative tool for assessing LA extension and severity.