Aaron So, Presenter: Nothing to Disclose

Jiang Hsieh PhD, Abstract Co-Author: Employee, General Electric Company

Ting-Yim Lee MSc, PhD, Abstract Co-Author: Research grant, General Electric Company Consultant, General Electric Company

We investigated using prospective ECG gated dynamic CT scanning (snapshot pulse, GE Healthcare) for myocardial perfusion (MP) imaging.

A patient-sized cardiac phantom was scanned at different simulated heart rates with a GE Healthcare (GE) VCT scanner over 20 heartbeats using snapshot pulse (SSP) at 140kV, 80mA and 0.35s rotation time. Phantom images were reconstructed using half-scan data (HSR). Mean CT number of a water ROI in the lateral wall (LW) of the left ventricle of the phantom was measured at each heart beat and different heart rates. Three pigs were scanned twice each using the same SSP protocol as the phantom scan after injection of iodinated contrast at a dosage of 0.5 ml·kg-1 (225 mgI·ml-1). Cardiac images were reconstructed using both HSR and full-scan data (FSR). Aortic and myocardial attenuation time curves (ATCs) were measured and MP map calculated using CT Perfusion (CTP, GE) were compared. MP maps obtained with SSP were also compared with those measured by retrospective gating of a 30 s cine scan (CS) at 140kV, 80mA and 0.4s/rot on the same pig. Effective dose (ED) of SSP and CS was estimated from the dose length product of each protocol.

The LW of the left chamber in the cardiac phantom HSR images showed a low frequency beat-to-beat oscillation in enhancement of 2±3 HU. A similar fluctuation (10±20 HU) was seen in the ATC from the LW of LV of porcine cardiac HSR images but not FSR images. Compared to HSR, MP maps calculated from FSR showed a smaller percentage difference between the LW and apex of the normal LV myocardium (10% vs 52%), between repeated scans (16% vs 43%), and compared with the respective values measured by CS (6% vs 15%). Estimated ED of SSP was 75 % less than that of CS (2.9 vs 11.8 mSv).

The accuarcy of MP maps calculated by CTP from SSP images was improved by minimizing half-scan artifact with FSR. This was reflected by the fact that perfusion measured in the normal myocardium was more homogeneous and comparable with that measured by the conventional retrospective gated CS technique.

MP imaging with snapshot pulse and FSR is accurate, delivers a low radiation dose to patients and can be used for diagnosing coronary artery disease.

So, A, Hsieh, J, Lee, T, Prospective ECG-gated Dynamic CT Scanning for Myocardial Perfusion Imaging.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6009901.html