Rationale and Objectives
To investigate motion artifacts, image quality, and practical differences in electrocardiographic (ECG)-gated versus non-ECG-gated high-pitch dual-source computed tomography angiography (CTA) of the whole aorta.
Materials and Methods
Two groups, each including 40 patients, underwent either ECG-gated or non-ECG-gated high-pitch dual-source CTA of the whole aorta. The aortic annulus, aortic valve, coronary ostia, and the presence of motion artifacts of the thoracic aorta as well as vascular contrast down to the femoral arteries were independently assessed by two readers. Additional objective parameters including image noise and signal-to-noise ratio were analyzed.
Results
Subjective and objective scoring revealed no presence of motional artifacts regardless of whether the ECG-gated or the non-ECG-gated protocol was used ( P > 0.1). Image acquisition parameters (examination length, examination duration, radiation dose) were comparable between the two groups without significant differences. The aortic annulus, aortic valve, and coronary ostia were reliably evaluable in all patients. Vascular contrast was rated excellent in both groups.
Conclusions
High-pitch dual-source CTA of the whole aorta is a robust and dose-efficient examination strategy for the evaluation of aortic pathologies whether or not ECG gating is used.
Introduction
Various improvements in computed tomography (CT) technology are currently commonly used such as wide-detector, single-source, or dual-source systems, and have led to shorter image acquisition durations and less motion artifacts. With the introduction of the latest dual-source CT devices, CT angiography (CTA) of the aorta is feasible in seconds (e.g., a whole body aorta examination within 3 seconds) . Faster image acquisition has become possible because dual-source CT allows pitch values of up to 3.4 with or without electrocardiographic (ECG) synchronization . Other factors influencing image acquisition are the use of fast gantry rotation times, fast table movement, and wide detector systems. One major advantage of high-pitch dual-source CT imaging is its ability to virtually freeze motion for the evaluation of the thoracic aorta, as heart motion can lead to diagnostic difficulties .
Previous studies have been conducted on bolus timing in high-pitch dual-source CT, and there have been feasibilities comparing high-pitch CT to single-source CT techniques . Many of these studies showed advantages such as fast image acquisition, motionless imaging of the thoracic vessels, and the possibility of evaluating the coronary arteries without ECG gating .
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Materials and Methods
Patients and CT Protocols
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TABLE 1
Study Population and Evaluation of Examination Parameters
Group 1 Group 2P Value: Group 1 vs. Group 2 Patients 40 40 Male 23 29 Female 17 11 Age (years) 63 ± 21.1 (39–82) 64 ± 24.2 (29–88) 0.72 BMI (kg/m 2 ) 27.8 ± 3.9 (18.9–31.5) 28.3 ± 3.8 (18.3–32) 0.24 Scanning range (cm) 71.6 ± 9.3 (64.2–84.1) 71.7 ± 10.5 (40.2–83.9) 0.61 Scanning duration (s) 1.7 ± 0.2 (1.2–2.2) 1.8 ± 0.5 (1.1–2.1) 0.97 CTDIvol (mGy) 3.7 ± 0.5 (2.9–4.2) 3.8 ± 0.6 (3.2–4.3) 0.44
BMI, body mass index; CTDIvol, volume CT dose index.
Values in brackets represent ranges.
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TABLE 2
Examination Parameters
Group 1 Group 2 Imaging mode Dual-source Dual-source Machine Definition flash Definition flash Slice × collimation 2 × 128 × 0.6 2 × 128 × 0.6 Pitch 3.0 3.0 ECG gating On Off ROI Descending aorta Descending aorta HU threshold 200 200 Delay (s) 7 7
ECG, electrocardiographic; HU, Hounsfield units; ROI, region of interest.
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Image Analysis
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TABLE 3
Image Quality Rating Between the Different Groups
Group 1 Group 2P Value Overall image quality 1.0 (1.0–2.0) 1.0 (1.0–2.0) >0.1 Homogeneity of contrast enhancement along patient z-axis 1.5 (1.0–3.0 1.5 (1.0–3.0) >0.1 Evaluation of coronary ostia 1.0 (1.0–2.0) 1.0 (1.0–2.0) >0.1 Motion artifacts 1.0 (1.0–3.0) 1.0 (1.0–3.0) >0.1 Image noise (HU) 10.2 ± 6.1 (5.9–20.3) 9.9 ± 5.9 (6.1–20.1) 0.55 Median overall (HU) 384.2 ± 162.1 (229.1–616.9) 392.1 ± 168.6 (224.1–628.3) 0.43 SNR 38.7 ± 16.8 (18.9–71.8) 40.6 ± 22.9 (20.1–68.3) 0.73
HU, Hounsfield units; SNR, signal-to-noise ratio.
Values in brackets represent ranges.
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Radiation Exposure
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Statistical Analysis
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Results
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Discussion
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