Purpose: Calcification is an independent prognostic factor in cardiovascular disease and especially in aortic valve stenosis. However, there is no ultrasound method available to quantify calcification to date. We aimed to validate a new calibrated integrated backscatter (cIB) method for measuring the amount of calcium in an in-vitro model, to study the effect of ultrasound (US) settings on cIB measurements and to compare it to computed tomography (CT), the actual imaging gold standard. Methods: A calcium-containing agar phantom (2% agar) was made, containing 9 different amounts of hydroxyapatite Ca5(PO4)3OH (2, 4, 6, 8, 10, 20, 30, 40 and 50 mg). The phantom was imaged with micro-CT and with a 10 MHz probe for US (Vivid 7, GE). For both imaging modalities, each calcium spot area (CSA) was delineated, and each calcium spot density (CSD) value was measured for each acquired image. These values were summed to calculate calcium scores (∑(CSA x CSD)) and volumes (∑CSA). Then, the calculated scores were compared for each amount of Ca5(PO4)3OH. Furthermore, US settings were modified to study the effect of frequency, focus position, frame rate, gain, power, compression, dynamic range and depth on cIB measurements. Results: There was a significant correlation between cIB and micro-CT measurements for calcium volumes (R²0.87, p<0.0001) and calcium scores (R²0.88, p<0.0001). Both techniques calcium scores were significantly correlated with the actual amount of calcium. (R²0.94, p<0.0001 and R²0.80, p<0.0001 for CT and US respectively). The US focus positioning, frequency, power and gain significantly influence the cIB measurements but only for the low amounts of calcium (< 40 mg). Conclusion: Quantification of the amount of calcium in an in vitro model using a new ultrasound cIB method is strongly correlated with the CT method. US settings may have an influence on the cIB results but only for low amounts of calcium. Therefore, this new US method represents an interesting alternative to CT for calcification quantification without any radiation and may be well suited for serial evaluations.
|Publication status||Published - 4 Dec 2015|
|Event||EuroEcho Imaging 2015 - Seville, Spain|
Duration: 2 Dec 2015 → 5 Dec 2015
|Conference||EuroEcho Imaging 2015|
|Period||2/12/15 → 5/12/15|