OBJECTIVE: We evaluated radiation exposure and image quality of a new coronary CT angiography protocol, high-pitch spiral acquisition, using dual source CT (DSCT).
METHODS: Coronary CTA was performed in 25 consecutive patients with a stable heart rate of 60 bpm or less after premedication, using 2 x 128 0.6-mm sections, 38.4-mm collimation width and 0.28-s rotation time. Tube settings were 100 kV/320 mAs and 120 kV/400 mAs for patients below and above 100-kg weight, respectively. Data acquisition was prospectively ECG-triggered at 60% of the R-R interval using a pitch of 3.2 (3.4 for the last 10 patients). Images were reconstructed with 75-ms temporal resolution, 0.6-mm slice thickness and 0.3-mm increment. Image quality was evaluated using a four-point scale (1 = excellent, 4 = unevaluable).
RESULTS: Mean range of data acquisition was 113 +/- 22 mm, mean duration was 268 +/- 23 ms. Of 363 coronary artery segments, 327 had an image quality score of 1, and only 2 segments were rated as “unevaluable”. Mean dose-length product (DLP) was 71 +/- 23 mGy cm, mean effective dose was 1.0 +/- 0.3 mSv (range 0.78-2.1 mSv). For 21 patients with a body weight below 100 kg, mean DLP was 63 +/- 5 mGy cm (0.88 +/- 0.07 mSv; range 0.78-0.97 mSv).
CONCLUSIONS: Prospectively ECG-triggered high-pitch spiral CT acquisition provides high and stable image quality at very low radiation dose.
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