Jean Louis Sablayrolles MD, Presenter: Research support, General Electric Company

Jean Marc Treutenaere, Abstract Co-Author: Nothing to Disclose

Jacques Feignoux, Abstract Co-Author: Nothing to Disclose

Caroline Jardin, Abstract Co-Author: Nothing to Disclose

Fabio Becce MD, Abstract Co-Author: Nothing to Disclose

With the installation of 64-slice CT scanners, Cardiac CT is getting an important role in the cardiology management of the patient. However the radiation dose (between 10 and 20 mSv) remains a limit to the emergence of new indications and the increase of the number of exams.

During the four last months, Coronary CT angiography was performed on 690 patients referred for Coronary CT angiography with the new low-dose technique SnapShot Pulse, an axial step-and-shoot mode with prospective gating on LightSpeed VCT XT (GE Healthcare), where X-ray are only turned on during required heart phases and completely switched off all other times. This new mode is essentially used when heart rate is below 65 bpm in order to make sure that the best phase for coronary assessment is in diastole and when functional study is not required by the referring physician. Scan parameters were set based on the morphology of the patient (500-800 mA, 80-120 kV, 0.625 mm slice thickness, 40 mm coverage/rotation, 0.35 sec gantry speed) and the indications (105-280 coverage). The radiation dose was collected and the image quality was qualified versus the one obtained with the helical mode with retrospective gating.

Among these 690 patients, coronary assessment was required for 563 patients (105-170 mm) and aorta or bypass study for 127 patients (210-280 mm). In the case of coronary assessment, the radiation dose was 5.6 mSv average (0.8-8 mSv) and 10.4 mSv average (4-13 mSv) in case of aorta or bypass study. No difference in terms of image quality was noticed between SnapShot Pulse exams and the exams performed with the usual helical mode with retrospective gating.

With SnapShot Pulse mode on LightSpeed VCT XT, a coronary CT angiography can be performed now with about 5 mSv radiation dose or less and a bypass study at 10 mSv or less, which represents a dose reduction of about 70% compared to the usual helical mode with retrospective gating and without compromising image quality.

This new technique might open the door to new indications for Cardiac CT like asymptomatic patients with high risk factors, systematic bypass or stent follow-up.

Sablayrolles, J, Treutenaere, J, Feignoux, J, Jardin, C, Becce, F, Drastic Dose Reduction in Cardiac CT with SnapShot Pulse Mode on LightSpeed VCT XT.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5010775.html