Coronary CT Angiography With Low Dose And Low Contrast Agent

Part Ⅰ:Iterative Reconstruction to Preserve Image Quality and Diagnostic Accuracy at Reduced Radiation Dose in Coronary CT Angiography-An Intraindividual ComparisonObjectives This study sought to determine whether a50%reduced tube current time product protocol using iterative reconstruction (IR) preserves image quality and diagnostic accuracy at coronary computed tomography angiography (CCTA) as compared to a routine dose protocol using traditional filtered back projection (FBP).Methods Sixty consecutive subjects (45men,53.3±9.4years) prospectively underwent coronary catheter angiography (CCA) and two coronary computed tomography angiography scans from April2012to October2012. One coronary computed tomography angiography acquisition used routine radiation dose settings and was reconstructed with filtered back projection. For another scan the tube current-time product was reduced by50%and data were reconstructed with iterative reconstruction. Catheter coronary angiography (CCA) was perfomed within one week after coronary CT angiography. Studies were blindly and randomly interpreted. Image quality (1, non-diagnostic with blurred vessel wall or severe motion artefacts;4, excellent, free of artefact), radiation dose and diagnostic accuracy were compared using coronary catheter angiography as the reference standard.Results Sensitivity and specificity for diagnosing>50%coronary artery stenosis on a per-segment level were88.5%and92.1%with filtered back projection and84.2%and93.4%with iterative reconstruction. On a per-patient level sensitivity and specificity were100%and93.1%with filtered back projection and96.8%and89.7%with iterative reconstruction, respectively (all p>0.05). With filtered back projection versus iterative reconstruction, the area under the receiver-operating characteristic curve was0.903[95%confidence interval (CI),0.881-0.922] and0.888(95%CI,0.864-0.909) on a per-segment level, and0.966(95%CI,0.883-0.996) and0.932(95%CI,0.836-0.981) on a per-patient level, respectively (p=0.290and0.330). Compared with filtered back projection, iterative series showed no significant (p>0.05) differences in image quality analyses. Median dose-length product was52%lower for the iterative reconstruction protocol compared with the filtered back projection protocol [109.00mGy*cm (interquartile range,82.00-172.50) vs.52.00mGy*cm (39.00-84.00), p<0.001].Conclusions Compared with a routine radiation dose filtered back projection protocol,50%reduced dose acquisition using iterative reconstruction preserves image quality and diagnostic accuracy at coronary computed tomography angiography, and radiation dose decreased by52%. Part Ⅱ:Detection of Coronary Artery Stenosis with Sub-milliSievert Radiation Dose by Prospectively ECG-Triggered High Pitch Spiral CT Angiography and Iterative ReconstructionObjectives:To evaluate the diagnostic accuracy of sub-milliSievert (mSv) coronary CT angiography (cCTA) using prospectively ECG triggered high pitch spiral CT acquisition combined with iterative image reconstruction.Methods:Forty consecutive patients (52.9±8.7years;30men) underwent dual-source coronary CT angiography using prospectively ECG-triggered high-pitch spiral acquisition from May2012to December2012. Catheter coronary angiography (CCA) was perfomed within one week after coronary CT angiography. Tube current-time product was set to50%of standard-of-care CT examinations. Images were reconstructed with sinogram-affirmed iterative reconstruction. Image quality was scored by three radiologists (1, non-diagnostic with blurred vessel wall or severe motion artefacts;4, excellent, free of artefact.) and diagnostic performance for detection of>50%stenosis was determined with catheter coronary angiography as the reference standard.Results:CT angiography was successfully performed in all40patients. Of the601assessable coronary segments,543(90.3%) had diagnostic image quality. Per-patient sensitivity for detection of>50%stenosis was95.7%(95%confidence interval [CI],76.0%99.8%) and specificity was94.1%(95%confidence interval,69.2%-99.7%). Per-vessel sensitivity was89.5%(95%confidence interval,77.8%-95.6%) with93.2%specificity (95%confidence interval,86.0%-97.0%). The area under the receiver operating characteristic curve on per-patient and per-vessel levels was0.949and0.913. Mean effective dose was0.58±0.17mSv. Mean size specific dose estimate was3.14±1.15mGy.Conclusions:High pitch prospectively ECG triggered coronary CT angiography combined with iterative image reconstruction provides high diagnostic accuracy with a radiation dose below1mSv for detection of coronary artery stenosis. Part Ⅲ:Effect of Reduced X-Ray Tube Voltage, Low Iodine Concentration Contrast Medium and Iterative Reconstruction on Image Quality and Radiation Dose at Coronary CT AngiographyObjectives:To assess the effect of reduced x-ray tube voltage, low iodine concentration contrast medium and iterative reconstruction (IR) on image quality and radiation dose at coronary CT angiography (CCTA).Methods:231consecutive patients with suspected coronary artery disease were enrolled in this prospective, multi-center trial and randomized to one of two dual-source coronary CT angiography protocols from August2013to December2013:120kVp with370mgl/mL iopromide or iopamidol (n=116;44women;55.3±9.8years); or100kVp with270mgl/mL iodixanol (n=115;48women;54.2±10.4years). Reconstruction was performed with filtered back projection (FBP) and IR. Attenuation, image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured and image quality scored by three radiologists. Size specific dose estimates and effective doses were calculated.Results:There were no significant differences in mean arterial attenuation (406.6±76.7vs.409.7±65.2HU, p=0.739), image noise (18.7±3.8vs.17.9±3.4HU; p=0.138), signal to noise ratio (22.5±5.4vs.23.7±6.1; p=0.126), contrast to noise ratio (17.5±5.5vs.18.3±6.1; p=0.286), or image quality scores (4.1±0.9vs.4.0±0.9; p>0.05)between120kVp FBP reconstructed and100kVp IR reconstructed series. Subjective image quality scores, signal to noise ratio and contrast to noise ratio were highest for IR reconstructed120kVp and lowest for filtered back projection reconstructed100kVp series. Mean iodine dose was26.5%lower (18.3±0.5vs.24.9±0.9g; p<0.0001) and mean effective dose was34.9%lower (2.3±1.0vs.3.5±1.1mSv; p<0.0001) with the100kVp compared with the120kVp protocol.Conclusion:Using low x-ray tube voltage and IR allows for decreasing the iodine load and effective radiation dose at coronary CT angiography while maintaining image quality.