Pal Suranyi MD, PhD, Presenter: Speaker, Siemens AG Consultant, Siemens AG

Heon Lee MD, PhD, Abstract Co-Author: Nothing to Disclose

Robin Brothers RT, Abstract Co-Author: Nothing to Disclose

Walter Huda PhD, Abstract Co-Author: Nothing to Disclose

Philip Costello MD, Abstract Co-Author: Research grant, Bracco Group Research grant, Siemens AG Research grant, General Electric Company

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

To explore the use of a low-dose calcium scoring scan prior to coronary CT angiography (cCTA) to identify the phase with the least cardiac motion; and to assess the effect on radiation dose at cCTA if the full dose ECG-pulsing window is only applied during this pre-selected cardiac phase.

We analyzed scan data of 30 patients who underwent both, low radiation-dose calcium scoring and contrast medium enhanced cCTA using retrospectively ECG-gated dual-source CT. During cCTA the full radiation dose ECG-pulsing window was applied between 35%-75% RR for heart rates (HR) > 65 bpm (n = 14) and between 55%-75% RR for HR ≤ 65 bpm (n = 16). During the remainder of the cardiac cycle the tube current was down-modulated to 20%. Using a preview function, two radiologists in consensus identified the phase with the least cardiac motion based on the low-dose calcium scoring scan and in a blinded fashion also at cCTA The agreement between phase selection based on calcium scoring and at cCTA was assessed. For each patient, the potential radiation dose savings was calculated by assuming the use of full tube current only during the phase (+/-5%) with the least cardiac motion as determined by the calcium scoring scan.

Average patient HR was 68.7 ± 13.6bpm. The mean Volume CTDI value at cCTA was 57.5 ± 13.5mGy, while the mean for the calculated CTDI with the calcium scoring guided, narrow ECG-pulsing window was significantly (P<0.01) lower at 40.8±10.5mGy. Thus, the mean dose savings would have been 16.7 ± 7.4mGy (29 ± 9.8%). Cardiac phase selection determined at calcium scoring coincided with phase selection at cCTA in 28/30 of the cases (93.3%). In 2 patients, the reconstruction at the pre-selected cardiac phase was diagnostic, although there was another phase (identified at cCTA) in the cardiac cycle with even better image quality.

A calcium scoring scan can reliably predict the phase with the least cardiac motion at cCTA and guide the positioning of the ECG-pulsing window.

There is potential for substantial radiation dose savings by narrowing the full dose ECG-pulsing window to only include the cardiac phase with the least motion as determined at calcium scoring.

Suranyi, P, Lee, H, Brothers, R, Huda, W, Costello, P, Schoepf, U, Use of a Calcium Scoring Scan to Guide ECG-Pulsing at Coronary CT Angiography: Potential for Radiation Dose Reduction.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6007173.html