Abdominal Aortic Calcification Detection Using Dual-Energy X-Ray Absorptiometry: Validation Study in Healthy Women Compared to Computed Tomography

Abstract

Abdominal aortic calcification (AAC) is an independent determinant of cardiovascular events. Computed tomography (CT) is currently the gold standard measure of AAC but is limited by high radiation exposure. Lateral dual-energy X-ray absorptiometry (DXA) has the potential to detect AAC at a fraction of the radiation dose. Our objective was to determine the accuracy of lateral-DXA in detecting AAC compared to CT in healthy women. Women from the TwinsUK registry aged 52-80years (n=105) underwent noncontrast CT and lateral-DXA imaging of the abdominal aorta at lumbar vertebrae L1-L4. Presence of calcium on CT was scored using the volume method. Lateral-DXA images were scored using the previously validated semiquantitative 24-point score and simplified 8-point score. Calcification was present in 81% of women as determined by CT and 49% with lateral-DXA. The mean volume score and the 24- and 8-point scores of AAC were 0.20±0.41cm(2), 2.39±3.91 arbitrary units, and 1.47±2.13 arbitrary units, respectively. There was moderate agreement between CT and 24-point lateral-DXA (Spearman's rank correlation coefficient r=0.58, P<0.0001). The sensitivity of lateral-DXA for detecting AAC was 56% and specificity was 80%. Sensitivity and specificity of lateral-DXA improved to 64 and 84% when analysis was limited to calcium volumes ≥0.008cm(3) as detected by CT. Lateral-DXA imaging may provide a useful alternative to CT in detecting AAC with minimal radiation exposure, which may be used with concurrent bone mineral density assessment.