OBJECTIVES: To assess the image quality and radiation dose of low-doseÂ dual-sourceÂ CT (DSCT) coronary angiography reconstructed usingÂ iterativereconstructionÂ in image space (IRIS), in comparison with routine-dose CT using filtered back projection (FBP).
METHODS: Eighty-one patients underwent low-dose coronary DSCT using IRIS with two protocols: (a)100 kVp and 200 mAs per rotation for body mass index (BMI)Â <Â 25 (group I), (b)100 kVp and 320 mAs for BMIÂ â‰¥Â 25 (II). For comparison, two sex-and BMI-matched groups using standard protocols with FBP were selected: (a)100 kVp and 320 mAs for BMIÂ <Â 25 (III), (b)120 kVp and 320 mAs for BMIÂ â‰¥Â 25 (IV). Image noise, signal to noise ratio (SNR) and modulation transfer function (MTF) 50% were objectively calculated. Two blinded readers then subjectively graded the image quality. Radiation dose was also measured.
RESULTS: Image noise tended to be lower in IRIS of low-dose protocols: 22.0Â Â±Â 4.5 for group I versus 24.8Â Â±Â 4.0 for III (PÂ <Â 0.001); 20.9Â Â±Â 4.5 for II versus 21.6Â Â±Â 4.9 for IV (PÂ =Â 0.6). SNR was better with IRIS: 25.8Â Â±Â 4.4 for I versus 22.7Â Â±Â 4.6 for III (PÂ <Â 0.001); 24.6Â Â±Â 5.4 for II versus 18.7Â Â±Â 4.5 for IV (PÂ <Â 0.001). No differences in MTF 50% or image quality scores were seen between each two groups (PÂ >Â 0.05). Radiation reduction was 40% for I and 51% for II, compared to standard protocols.
CONCLUSIONS: Compared with routine-dose CT using FBP, low-dose coronary angiography using IRIS provides significant radiation reduction without impairment to image quality.