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Lowering radiation dose for integrated assessment of coronary morphology and its functional consequences: First experience with step-and-shoot CT angiography in the PET/CT environment

¹ Johns Hopkins University, Baltimore, Maryland

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Objectives: Reduction of radiation exposure from CT coronary angiography (CTA) will be a key factor for more liberal use in cardiac hybrid PET-CT. We tested the feasibility of a new algorithm for low dose CT angiography based on a prospectively gated step-and-shoot technique. This limits acquisition to the diastolic phase and minimizes exposure time versus the previous standard of retrospectively gated helical acquisitions.

Methods: In 10 patients referred for biomorphologic workup by Rb-82 perfusion PET-CT, step-and-shoot CTA (SnapShot Pulse, GE Healthcare; 120kV, 600-800mA) was acquired on a 64-slice GE Discovery Rx VCT PET-CT scanner, and compared to patients with conventional helical CTA (120 kV, mA modulated), matched for clinical variables. Effective dose was estimated from dose length product. The AHA 17 segment coronary tree model was used to determine study interpretability. Potential for fusion with PET was tested using commercial software.

Results: Effective dose for helical and step-and-shoot CTA was 20.3±4.0 vs 5.6±1.1 mSv(p<0.0001). Evaluable segments for the best phase of helical CTA were 14.6±2.6(86±15%) vs 15.4±1.8(91±11%; p=ns vs helical) for step-and-shoot. Review of multiple phases increased the number for helical to 15.9±1.3(94±8%; p=ns vs step-and-shoot, where this was not an option). Fusion with corresponding Rb-82 perfusion PET was feasible for all studies.

Conclusions: Low dose prospectively gated CTA reduces radiation exposure by approximately 75% vs the previous standard of helical acquisition, without significant loss in interpretability and integrative potential with PET. This represents a first step towards a broad, routine integration of CTA and PET in cardiac PET-CT.

This Article Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Javadi, M. Articles by Bengel, F. PubMed Articles by Javadi, M. Articles by Bengel, F.