Full Length ArticleA novel quantitative approach to the measurement of abdominal aortic calcification as applied to the Canadian Multicenter Osteoporosis Study (CaMOS)

- A quantitative approach to measure abdominal aortic calcification (AAC) is developed.
- AAC severity quantified by pixel intensity in a user-defined region of the aorta.
- Internal standardization and background calibration to vertebral endplates and body.
- Quantified AAC has high inter-observer reliability.
- Significant negative association between quantified AAC and BMD in CaMOS cohort.

Background and aimsLateral spine radiographs provide an inexpensive resource for characterizing abdominal aortic calcification (AAC). A widely accepted measurement of AAC is the semi-quantitative technique generated by the Framingham Heart Study (F-AAC-24). We sought to develop an analytical method to quantify ACC (QAAC) on lateral spine radiographs and compare the finding to conventional subjective measurements.MethodsSeverity of AAC was quantified by measuring pixel intensities in the user-defined region of the aorta with internal standardization to the vertebral endplates and background calibration to the density of the vertebral body. The association between bone mineral density (BMD) measured by dual energy X-ray absorptiometry (DXA) and AAC measured by QAAC, F-AAC-24 and a modified Framingham score (F-AAC-12) was determined in 110 participants of the Canadian Multicenter Osteoporosis Study (CaMOS).ResultsThe inter-observer reliability for the QAAC was slightly higher than with the visual and semi-quantitative Framingham method and the pseudo-colored images illustrate the potential to meaningfully resolve severity of calcification. There was a significant negative association between QAAC and BMD measures of the hip and spine. This association remained significant after adjustment for age, sex, estimated glomerular filtration rate, phosphate and hypertension. Significant predictors of F-ACC-12 and 24 included age and hypertension.ConclusionsThe QAAC is a reproducible approach to measuring AAC. Whether it is capable of monitoring subtle calcific changes over time requires further study. This technique could be applied to large studies that seek to determine the impact of interventions that modify bone density as a treatment for vascular calcification and cardiovascular disease in the general population.