Matthias Renker BSc, Presenter: Nothing to Disclose

Thomas Henzler MD, Abstract Co-Author: Nothing to Disclose

John William Nance MD, Abstract Co-Author: Nothing to Disclose

Garrett W. Rowe BS, Abstract Co-Author: Nothing to Disclose

Joseph Anwar Abro MA, Abstract Co-Author: Nothing to Disclose

U. Joseph Schoepf MD, Abstract Co-Author: Speakers Bureau, Bayer AG Speakers Bureau, Siemens AG Medical Advisory Board, Bayer AG Research grant, Bayer AG Research grant, Bracco Group Research grant, General Electric Company Research grant, Siemens AG

To compare effective radiation doses from coronary CT angiography (cCTA) of 2665 consecutive patients investigated on four different CT scanner generations over a time period of 8 years.

All patients who received dedicated cCTA examinations at our institution between June 2003 and March 2011 were included in this retrospective data analysis. Patients were scanned on one of four generations of CT scanners: 16-slice single-source CT (SSCT), 64-slice SSCT, 64-slice dual-source CT (DSCT), or 128-slice DSCT. Scan protocols were individualized to the patient and scanner generation. Relevant CT dose parameters were collected from the patient protocol and the effective dose (ED) for each scan was calculated by the following equation: ED=DLP*conversion factor. Three different ED values were calculated for each patient by using three conversion factors proposed in the literature: Two chest-specific conversion factors (ED1: κ1=0.014 mSv*mGy-1*cm-1; ED2: κ2=0.017 mSv*mGy-1*cm-1) and one conversion factor specific for cardiac CT (ED3: κ3=0.026 mSv*mGy-1*cm-1). The results were subsequently compared between CT generations using the Kruskal-Wallis test with post-hoc Bonferroni-Holm correction for multiple comparisons.

A total of 2665 (1658 male, 59±13 years) consecutive patient cCTA examinations were included in this study (16-SSCT: 111; 64-SSCT: 953; 64-DSCT: 1102; 128-DSCT: 494). Average doses (ED1, ED2, ED3) per scanner were as follows: 16-SSCT (15.9±3.3; 19.3±4.0; 29.5±6.1 mSv), 64-SSCT (15.5±2.2; 18.8±2.7; 28.8±4.2 mSv), 64-DSCT (12.8±4.3; 15.6±5.2; 23.7±8.0 mSv), and 128-DSCT (5.5±3.0; 6.7±3.7; 10.3±5.6 mSv). Radiation dose reduction was not significant for 16- versus 64-SSCT (p=0.22), but significant for 64-SSCT versus 64-DSCT (p<0.01), and 64-DSCT versus 128-DSCT (p<0.01).

When interpreting reported effective radiation doses at cCTA, particular attention should be paid to the specific conversion factor used, since large variations in dose estimation are incurred by this variable. Regardless of the calculation method, our data suggest that successive advances in CT technology have provided substantial reductions in effective radiation dose to the patient.

With more advanced CT scanner technology, radiation exposure from cCTA compares rather favorably with other cardiac imaging tests and general body CT applications. 

Renker, M, Henzler, T, Nance, J, Rowe, G, Abro, J, Schoepf, U, Radiation Dose from Coronary CT Angiography: Eight-year Single-Center Experience.  Radiological Society of North America 2011 Scientific Assembly and Annual Meeting, November 26 - December 2, 2011 ,Chicago IL. http://archive.rsna.org/2011/11034373.html