ABC/XYZ estimates intracerebral hemorrhage volume as a percent of total brain volume in children.

BACKGROUND AND
PURPOSE: Intracerebral hemorrhage volume (ICHV) as a percentage of total brain volume (TBV) is a strong predictor of outcome in childhood intracerebral hemorrhage with ICHV/TBV >2% associated with functional impairment. We aimed to determine whether easily performed approximations of intracerebral hemorrhage and brain volume can accurately and reliably stratify intracerebral hemorrhage by size.
METHODS: CT scans of 18 children with spontaneous intracerebral hemorrhage were independently reviewed by 4 neurologists. ICHV as a proportion of TBV was estimated as ABC/XYZ expressed as a percentage: A= largest axial hemorrhage diameter; B=largest axial diameter perpendicular to A on the same slice; and C=hemorrhage vertical diameter. Similarly, X=largest midline axial diameter of supratentorial brain; Y=largest axial diameter perpendicular to X; and Z=brain vertical diameter. Interrater reliability was measured with intraclass correlation coefficients. ICHV and TBV were measured using computer-assisted manual segmentation tracings to establish criterion validity. Each intracerebral hemorrhage was classified as small (< or = 2% TBV) or large (>2% TBV).
RESULTS: Estimates of ICHV, TBV, and ICHV/TBV using the ABC/XYZ method had outstanding interrater reliability (intraclass correlation coefficient, 0.95 to 0.99). These estimates were highly correlated with volumetric measures (R2=0.77 to 0.96). Sensitivity of the ABC/XYZ method for identifying an ICHV >2% TBV was 100% (95% CI, 89% to 100%). Specificity was 95% (95% CI, 83% to 99%).
CONCLUSIONS: The ABC/XYZ method accurately and reliably estimates ICHV and TBV in children. These values can be used to approximate quickly and easily ICHV as a percentage of TBV, which has important prognostic implications.