Feasibility of new thresholds for coronary artery calcium score using low-tube voltage protocols in postmortem computed tomography1

Objective

To validate whether low tube voltage scans of 100 kilovolt-peak (kVp) and 80 kVp for measuring coronary artery calcium score (CACS) using computed tomography (CT) yield comparable results to the standard protocol of 120 kVp using postmortem CT (PMCT).

Materials and Methods

We obtained scans for cadavers where CAC was observed on PMCT scans. In addition to the standard protocol, tube voltage scans were also obtained under conditions of 100 kVp and 80 kVp. We obtained a newly adapted threshold under low tube voltage and compared them with the standard protocol.

Results

The CACS was 851±1421 (p=0.99) and 861±1433 (p=0.99) for the 120-kVp and 100-kVp scans, respectively, and 845±1390 (p=0.99) for the 80-kVp scan using the newly adapted threshold. The 120-kVp and 100-kVp scans demonstrated an almost perfect correlation (r=0.99996, p<0.0001). In the Bland–Altman analysis, the 9 5% limits of agreement ranged from -44 to 25. Similarly, the CACS obtained using the adapted threshold for the 80-kVp scan also demonstrated an excellent correlation with the standard 120-kVp scan (r=0.99993, p<0.0001). In the Bland–Altman analysis, the 95 % limits of agreement ranged from -62 to 75. The effective radiation dose was 2.21±0.064 mSv (p<0.0001) for the 120-kVp scan, 1.35±0.070 mSv (p<0.0001) for the 100-kVp scan, and 0.72±0.48 mSv (p<0.0001) for the 80-kVp scan.

Conclusion

This study suggests that PMCT can be used to measure CACS at low tube voltages and that significant dose reductions in patients can be expected in clinical practice.