Dual-source CT in step-and-shoot mode: noninvasive coronary angiography with low radiation dose
Purpose: To prospectively investigate computed tomographic (CT) image quality parameters by using different protocols and to calculate radiation dose estimates for noninvasive coronary angiography performed with dual-source CT in the step-and-shoot (SAS) mode.
Materials and methods: This study was local ethics board approved; written informed consent was obtained from all patients. In the preliminary portion of the study, 40 patients underwent CT coronary angiography in the SAS mode: at 100 kV (protocol A) in 22 patients with a body mass index (BMI) of less than 25 kg/m(2) and at 120 kV (protocol B) in 18 patients with a BMI of 25-30 kg/m(2). Both protocols involved use of an attenuation-based tube current and 1 mL of contrast material per kilogram of body weight. The final portion of the study involved 50 additional patients: 21 patients with a BMI of 25-30 kg/cm(2) assigned to protocol B and 29 patients with a BMI of less than 25 kg/cm(2) assigned to protocol C, which was performed with 100 kV, an attenuation-based tube current, and a reduced contrast material dose of 0.8 mL/kg. Image quality was independently assessed. Attenuation in the aorta and coronary arteries and image noise were measured. Radiation dose was estimated.
Results: Mean image noise was similar with protocols A and B. Mean attenuation in the aorta and coronary arteries with protocol A (444 HU) was significantly (P < .001) higher than that with protocol B (358 HU). The reduced contrast material dose in protocol C yielded attenuation similar to that with protocol B. Diagnostic image quality was achieved with all protocols in 1237 (97.9%) of 1264 coronary segments. No significant differences in image quality between the 100- and 120-kV protocols were found. Mean heart rate had a significant effect on motion artifacts (area under receiver operating characteristic curve [AUC] = 0.818; 95% confidence interval [CI]: 0.723, 0.892; P < .001), whereas heart rate variability had a significant effect on stair-step artifacts (AUC = 0.79; 95% CI: 0.687, 0.865; P < .001). The mean estimated effective dose was 1.2 mSv +/- 0.2 for protocols A and C and 2.6 mSv +/- 0.5 for protocol B.
Conclusion: Dual-source SAS-mode CT coronary angiography yielded diagnostic image quality for 97.9% of coronary segments at a low radiation dose.
Authors:
Stolzmann P, Leschka S, Scheffel H, Krauss T, Desbiolles L, Plass A, Genoni M, Flohr TG, Wildermuth S, Marincek B, Alkadhi H.
Full text: Radiology. 2008 Oct;249(1):71-80.
I was reading up on the CT Siemens Daul Souce Technology and was quite impressed. I am actually a Toshiba fan and believe their 320 slice scanner is as good as it gets. So what scanner is best for brain perfusion and cardiac imaging. Dual Source vs 320 Slice
Thank you for your interest in the DSCT community.
Regarding your question on brain perfusion, I cannot really give you a good answer because of no experience in this body region.
In regard to cardiac imaging, I certainly can recommend the dual-source CT technology. It has proven more accurate at lower heart rates than 64-slice CT, it is – to my knowledge – the only scanner that is able to scan hearts in an accurate fashion also at higher heart rates, and finally, it must be considered very dose efficient. With a standard retrospective spiral protocol that is required in patients with high and/or irregular heart rates, you will end up with around 7-9 mSv. When you use a standard step-and-shoot protocol at 2-4 mSv (which can be used in patients with heart rates below 70 bpm), and when using the recently introduced Flash- (or high pitch) mode, you end up at a dose below 1 mSv for a coronary CT angiography examination.
I have no experience with the 320-slice CT scanner for cardiac imaging. So the only thing I can recommend is to review the (sparse) literature. Here you can see that the lowest reported radiation dose of a cardiac CT using this scanner is around 5 mSv (when using a protocol that requires lowering the heart rate with beta-blockers).
Best regards and good luck with your scanner choice.
Hatem Alkadhi
sir,
i am too working on a dual source siemens scanner and have done a lot of coronart angios with conventional step and shoot method and in most of the cases end up with radiation dose of 2 – 3mSV (including the calcium score). most of the times i do calcium scan with 80 KV and coronary angios with 100kv depending mainly on chest circumference and BMI.But have not yet tried reducing the effective mAS a lot since i do scans with care dose 4D on mAS will be selected automatically.if i do reduce mAS are there any standards so that the images will be not very noisy.