Martin J. Willemink MD, Presenter: Nothing to Disclose

Adriana Maria den Harder BSC, Abstract Co-Author: Nothing to Disclose

Wouter Foppen MD, Abstract Co-Author: Nothing to Disclose

Hendrik M. Nathoe MD, PhD, Abstract Co-Author: Nothing to Disclose

Pim A. De Jong MD, PhD, Abstract Co-Author: Nothing to Disclose

Ricardo P.J. Budde MD, PhD, Abstract Co-Author: Nothing to Disclose

Tim Leiner MD, PhD, Abstract Co-Author: Speakers Bureau, Koninklijke Philips NV Research Grant, Bayer AG Research Grant, Bracco Group

To find the maximally acceptable radiation dose reduction for accurate coronary calcium scoring (CCS).

This prospective HIPAA compliant study was approved by our local institutional review board. Fifteen patients (9 men, mean age 56.8±6.8 years) underwent 4 calcium scoring computed tomography (CT) scans in a single session. Image acquisition was performed with a 256-slice CT system (iCT, Philips Healthcare) at routine, 40%-reduced, 60%-reduced and 80%-reduced doses. A fixed tube voltage of 120 kVp was applied and radiation dose was reduced by lowering tube current. Raw data were reconstructed with standard filtered back projection (FBP) and iterative reconstruction (IR, iDose4 levels 1, 4 and 7). Agatston scores were assessed with commercially available validated software (Heartbeat CS).

Effective dose values were 0.85±0.07, 0.51±0.04, 0.33±0.05, and 0.17±0.01 mSv, respectively. Routine dose acquisitions with FBP resulted in Agatston scores of 0 (N=3), 1-10 (N =4), 11-100 (N =5), 101-400 (N =2), and >400 (N =1). At 40%-reduced dose FBP acquisitions, 2 subjects (13.3%) were reclassified into higher categories with FBP and IR. 1 subject (6.7%) had false negative scores with IR levels 4 and 7. At 60%-reduced dose FBP acquisitions, 3 subjects (20%) were reclassified into higher risk categories and 1 subject (6.7%) had a false negative score. At this dose level, IR resulted in only 1 reclassification (6.7%) to a higher category and 3 reclassifications (20%) to lower categories, under which 2 false negatives. At 80%-reduced dose FBP acquisitions, 3 scans (20%) were not interpretable due to overwhelming noise artifacts and 6 scans (40%) were incorrectly reclassified. With IR, all scans were interpretable. IR levels 4 and 7 resulted in less reclassifications, 3 subjects (20%) were reclassified into lower categories including 2 false negatives (13.3%). 

This within-patients analysis showed that 80%-reduced dose FBP resulted in non-interpretable scans or reclassifications in 60% of subjects, which decreased with IR to 20%. Therefore, CCS may be done at 0.17 mSv with medium to high IR levels. However, results should be validated in a larger population.

Coronary calcium scoring at a radiation dose as low as 0.17 mSv may be possible with medium to high iterative reconstruction levels.

Willemink, M, den Harder, A, Foppen, W, Nathoe, H, De Jong, P, Budde, R, Leiner, T, Finding the Optimal Dose Reduction and Iterative Reconstruction Level for Coronary Calcium Scoring: A Within Patients Analysis.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14010761.html