Optimization of HU threshold for coronary artery calcium scans reconstructed at 0.5‐mm slice thickness using iterative reconstruction

Abstract

Purpose This work investigated the simultaneous influence of tube voltage, tube current, body size, and HU threshold on calcium scoring reconstructed at 0.5‐mm slice thickness using iterative reconstruction (IR) through multivariate analysis. Regression results were used to optimize the HU threshold to calibrate the resulting Agatston scores to be consistent with those obtained from the conventional protocol. Methods A thorax phantom set simulating three different body sizes was used in this study. A total of 14 coronary artery calcium (CAC) protocols were studied, including 1 conventional protocol reconstructed at 3‐mm slice thickness, 1 FBP protocol, and 12 statistical IR protocols (3 kVp values*4 SD values) reconstructed at 0.5‐mm slice thickness. Three HU thresholds were applied for calcium identification, including 130, 150, and 170 HU. A multiple linear regression method was used to analyze the impact of kVp, SD, body size, and HU threshold on the Agatston scores of three calcification densities for IR‐reconstructed CAC scans acquired with 0.5‐mm slice thickness. Results Each regression relationship has R2 larger than 0.80, indicating a good fit to the data. Based on the regression models, the HU thresholds as a function of SD estimated to ensure the quantification accuracy of calcium scores for 120‐, 100‐, and 80‐kVp CAC scans reconstructed at 0.5‐mm slice thickness using IR for three different body sizes were proposed. Our results indicate that the HU threshold should be adjusted according to the imaging condition, whereas a 130‐HU threshold is appropriate for 120‐kVp CAC scans acquired with SD = 55 for body size of 24.5 cm. Conclusion The optimized HU thresholds were proposed for CAC scans reconstructed at 0.5‐mm slice thickness using IR. Our study results may provide a potential strategy to improve the reliability of calcium scoring by reducing partial volume effect while keeping radiation dose as low as reasonably achievable.

Coronary artery calcium mass measurement based on integrated intensity and volume fraction techniques

“…29 Hou et al demonstrated good correlation between Agatston scoring on a 3 mm slice thickness image compared to Agatston scoring on a 0.5 mm slice thickness image. 30 Our simulation was limited to 0.5 mm slice thickness which is expected to provide more accurate and sensitive comparisons for Agatston scoring. Nonetheless, future studies might provide insights by varying the slice thickness, and this study is limited without a direct comparison to Agatston scoring at the gold standard slice thickness of 3 mm.…”

Computed tomography-based calcium scoring in cadaver leg arteries: Influence of dose, reader, and reconstruction algorithm

“…To overcome the problem of increased image noise, iterative reconstruction (IR) was used [24]. IR has been proven to substantially reduce image noise [25,26] and to reduce blooming artifacts [27,28] resulting in higher image quality.…”

An Analytic Method for Calculating Scanner-, Kilovoltage Peak–, and Patient Size–Specific Hounsfield Unit Scale Thresholds for Agatston Score

“…The proposed method could be applied for any site- or software-specific dose level and reconstruction method (eg, kernel, slice thickness, noise reduction algorithm, 24 or keV selection for a dual-energy CT reconstruction). All these factors impact the detected area for each HU scale threshold and should be explored in future work via both phantom study and patient scans to evaluate the clinical performance of the proposed method.…”

“…In addition, setting the model 2 thresholds on a scoring software could also benefit other quantitative calcium scores, such as volume score and mass score, which are based on the conventional 130-HU threshold and therefore suffer a similar interscanner variation because of the spectrum difference. 10,23 The proposed method could be applied for any site-or softwarespecific dose level and reconstruction method (eg, kernel, slice thickness, noise reduction algorithm, 24 or keV selection for a dual-energy CT reconstruction). All these factors impact the detected area for each HU scale threshold and should be explored in future work via both phantom study and patient scans to evaluate the clinical performance of the proposed method.…”