Helical Prospective ECG-Gating in Cardiac Computed Tomography: Radiation Dose and Image Quality

Int J Cardiovasc Imaging. 2009; 11(4):1030

Defrance T, Dubois E, Gebow D, Ramirez A, Wolf F, Feuchtner GM

OBJECTIVES: Helical prospective ECG-gating (pECG) may reduce radiation dose while maintaining the advantages of helical image acquisition for coronary computed tomography angiography (CCTA). Aim of this study was to evaluate helical pECG-gating in CCTA in regards to radiation dose and image quality.

METHODS: 86 patients undergoing 64-multislice CCTA were enrolled. pECG-gating was performed in patients with regular heart rates (HR) < 65 bpm; with the gating window set at 70-85% of the cardiac cycle. All patients received oral and some received additional IV beta-blockers to achieve HR < 65 bpm. In patients with higher or irregular HR, or for functional evaluation, retrospective ECG-gating (rECG) was performed. The average X-ray dose was estimated from the dose length product. Each arterial segment (modified AHA/ACC 17-segment-model) was evaluated on a 4-point image quality scale (4 = excellent; 3 = good, mild artefact; 2 = acceptable, some artefact, 1 = uninterpretable).

RESULTS: pECG-gating was applied in 57 patients, rECG-gating in 29 patients. There was no difference in age, gender, body mass index, scan length or tube output settings between both groups. HR in the pECG-group was 54.7 bpm (range, 43-64). The effective radiation dose was significantly lower for patients scanned with pECG-gating with mean 6.9 mSv +/- 1.9 (range, 2.9-10.7) compared to rECG with 16.9 mSv +/- 4.1 (P < 0.001), resulting in a mean dose reduction of 59.2%. For pECG-gating, out of 969 coronary segments, 99.3% were interpretable. Image quality was excellent in 90.2%, good in 7.8%, acceptable in 1.3% and non-interpretable in 0.7% (n = 7 segments).

CONCLUSIONS: For patients with steady heart rates <65 bpm, helical prospective ECG-gating can significantly lower the radiation dose while maintaining high image quality.

PMID: 19898955

3 Responses

  1. Paul Schoenhagen, MD  on November 10th, 2009

    Interesting concept between prospective triggering and aggresive dose modulation.

  2. Jacobo Kirsch, MD  on November 13th, 2009

    And according to this numbers also very effective: 99.3% of the analyzed segments were interpretable, the majority of them (90.2%) with excellent image quality. This paper, in combination with a prior one by Alkhadi using dual-source CT, show that by using their recommendations on tube current modulation and scan protocol the radiation dose can be reduced UP TO 86%!
    Note that this is not your conventional step-and-shoot scan technique, but rather one preserving the helical spiral method of image acquisition.

  3. Paul Schoenhagen, MD  on December 20th, 2009

    I agree with Dr. Jacobo Kirsch that the aggressive dose modulation (down to 4%, “min-dose”), which has been implemented by one of the vendors, is very similar and very effective.
    On high-end scanner, the user can chose between aggressive dose modulation, prospective triggering, and recently high-pitch modes.

    See also the editorial comment by Dr. Dewey:
    Prospective helical acquisition for coronary CT angiography.
    Dewey M.
    Int J Cardiovasc Imaging. 2009 Nov 18.
    PMID: 19921461


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