3D Landmark scout imaging accurately assesses presence and extent of coronary calcification with lower radiation exposure.

Background: Cardiac CT for coronary artery calcium (CAC) scoring exposes patients to 1 ​mSv of radiation. A new CT scout method utilizing ultra-low dose CT (3D Landmark) offers tomographic cross-sectional imaging, which provides axial images from which CAC can be estimated. The purpose of our study is to analyze the association between estimated CAC burden on 3D Landmark scout imaging vs dedicated ECG-gated CACS.

Methods: Consecutive patients over a 9-month period undergoing non-contrast ECG-gated CACS planned with 3D Landmark scout imaging were included. Extent of CAC on 3D Landmark scout imaging was scored from 0 to 3 (none, mild, moderate, severe). Agatston CACS was converted to an ordinal score from 0 to 3, corresponding to absent (0), mild (1-99), moderate (100-400), or severe (>400). Fischer's exact test, weighted kappa coefficient, and paired t-tests were used for analysis.

Results: Of 150 patients, 51.3% were female with mean age 49.0 ​± ​16.8 and BMI 28.6 ​± ​12.3. Sensitivity of 3D Landmark in identifying calcium was 96.2%, with specificity of 100%. There was strong interrater agreement between 3D Landmark calcium scoring and CACS, with weighted kappa coefficient 0.97 ​± ​0.01(CI 0.95-0.99). Radiation dose-length-product was significantly lower for 3D Landmark imaging vs. dedicated ECG-gated CACS (9.7 ​± ​3.6 vs 43.8 ​± ​26.4 ​mGy ​cm, p ​< ​0.001) despite longer scan length (465.0 ​± ​160.8 vs 123.0 ​± ​12.7 ​mm, respectively).

Conclusion: Estimated coronary artery calcium on 3D Landmark scout images correlates strongly with Agatston CACS, demonstrating utility in assessing cardiovascular risk without introducing additional radiation or costs.