Low dose dual-source CT angiography of the thoracic aorta

Abstract

The purpose of this study was to investigate the effects of a prospective ECG-gated, low kilovoltage and low mAs protocol on image quality and radiation dose when acquiring CT angiography of the thoracic aorta (CTTA). Sixty patients with a body mass index (BMI) of less than 30 and a heart rate of less than 100 beats per minute (bpm) were included in the study. Thirty consecutive patients were examined with retrospective ECG-gating and standard parameters (group A) (120 kVp, 340 reference effective mAs).The next thirty (group B) were examined with prospective ECG-gating, 100 kVp and 170 mAs. Quantitative analysis included measurements of image resolution of the thoracic aorta at three levels, mean attenuation in the aorta and signal to noise ratio (SNR). Qualitative analysis assessed image artifact and graded image quality on five point scales. Effective radiation doses were estimated. The radiation dose of group A was 26.2 ± 6.0 mSv (mean ± standard deviation). For group B it was 2.9 ± 0.5 mSv (P < 0.001). Mean aortic attenuation was significantly higher in group B than group A (487 ± 100 Hu and 372 ± 74 Hu) (P < 0.01).SNR was significantly higher in group A (21.7 ± 5.7 compared to 14.5 ± 5.3) (P < 0.01). Image resolution was significantly higher in group B at all measured anatomical levels (P < 0.01). There was no significant difference in the final subjective scores between group A and group B (Mann-Whitney U = 438, P = 0.79). High quality low dose CTTA is clinically achievable, in patients with a BMI less than 30 and a heart rate less than 100 bpm, using a prospective ECG-gated, low kilovoltage, low mAs technique.

Low kV settings CT angiography (CTA) with low dose contrast medium volume protocol in the assessment of thoracic and abdominal aorta disease: a feasibility study

“…[1][2][3][4]20 Two radiologists with 7 and 3 years' experience, respectively, in CTA and 3D vascular images interpretation, who were blinded to the two different scanning parameters, performed qualitative evaluations of the randomized 3D aortograms on VR and MIPreconstructed images, in a blinded manner. For qualitative evaluation, the diagnostic quality of images and the visualization of major aortic branches were evaluated using a three-point subjective scale, derived from ones previously proposed in literature: [1][2][3] (1) as "inadequate" (major artefacts, unsatisfactory delineation of the boundary or poor visualization of major branches); (2) as "diagnostic" (delineation of the boundary equivocal but within an acceptable range, minor artefacts and sufficient visualization of major branches); (3) as "good" (no artefacts and excellent visualization of boundary and major branches).…”

Seventy–Peak Kilovoltage High-Pitch Thoracic Aortic CT Angiography without ECG Gating

“…In our study, mean ED was 0.4 mSv for thoracic aortic CT imaging at 70 kVp, which represents a reduction in ED by 85% compared to the 100-kVp acquisition mode. In previous reports, the ED can be up to 26 mSv for aortic CTA with retrospective ECG gating (7). Even with a prospective ECG gating, 100-kVp, and 170-mAs protocol, the ED was 2.9 AE 0.5 mSv for aortic CTA (7).…”

“…ED was estimated by multiplying DLP by a conversion factor of 0.014 mSv/mGy$cm according to the standard methodology (7,20).…”

“…Several CTA protocols that reduce radiation dose without compromising diagnostic image quality have been described in the literature. These include using lower tube voltage (6,7), automatic tube voltage selection (8), highpitch (9)(10)(11)(12) or iterative reconstruction (IR) (13,14).…”

“…For example, the study by Farrelly et al (7) demonstrated a significant reduction of the effective dose (ED) from 26.2 AE 6.0 to 2.9 AE 0.5 mSv by performing a prospectively ECG-gated CTA of the thoracic aorta at 100 kVp instead of the standard retrospectively ECG-gated CTA at 120 kVp. In addition, CTA examinations at 70 kVp have recently been shown to provide diagnostic image quality with an ultralow radiation dose in selected patients undergoing imaging of peripheral, cerebral, and coronary arteries (15)(16)(17)(18)(19)(20).…”