Abstract 15815: Non-Contrast Computed Tomography Attenuation Measurement for Early Detection of Aortic Valve Microcalcifications

Abstract

Introduction: Calcific aortic stenosis (AS) is often diagnosed at its late stage. 18F- sodium fluoride (18F-NaF) PET can identify areas of active calcification before appearance of macrocalcifications. Hypothesis: We hypothesized that CT attenuation measurement could detect areas of microcalcification as determined by 18F-Na F PET. Methods: 18F-NaF PET/CT data were evaluated in 102 patients (age 71 ± 8 years, 21% female) with calcific AS at baseline and 2-year follow-up. Multiple 3 mm regions of interest were identified based on 18Na-F PET uptake and presence of macrocalcification (Hounsfield units, HU>130): PET-/CT-, PET+/CT- and PET+/CT+. Assessment of CT attenuation was also performed in 20 control patients with no AS at baseline and after 1 year. Results: At baseline, PET+/CT- regions had greater HU than PET-/CT- regions (median 50 [IQR 42-55] vs. 39 [IQR 32-46]; p < 0.001). Further, PET+/CT- regions showed greater 24-month change vs PET-/CT- (median 16 [IQR) 7-28] vs. 0.83 [IQR -2.56-6.91]; p < 0.001) (Figure 1). A cut off value of 48.76 HU yielded sensitivity/specificity of 57%/85% for detection of microcalcifications, AUC = 0.760. Applying this threshold to the control group the calculated 24-month increase in HU was greater in patients above the threshold vs those below (median 9.89 [IQR -2.92-29.82] vs. 0.57[IQR -7.16-4.31]; p < 0.001) (Figure 2). Conclusions: Aortic valve non-contrast CT X-ray attenuation value above 48.76 HU was able to identify regions of 18F-NaF uptake in patients with AS. Therefore, measuring X-ray attenuation on non-contrast CT has the potential to identify regions of developing microcalcification within the aortic valve.