Individualized CT Angiography Protocols for the Evaluation of the Aorta: A Feasibility Study
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Purpose: Ionizing radiation and iodinated contrast media are potential drawbacks to repetitive follow-up CT angiography in current practice. The aim of the present study was to optimize radiation dose and contrast agent volume by using individualized CT angiography protocols. Materials and Methods: Eighty consecutive patients referred for CT angiography of the whole aorta were prospectively evaluated. Patients were divided into groups of patients with a body mass index (BMI) <28 kg/m(2) (group 1; n = 50) and those with a BMI >= 28 kg/m(2) (group 2; n = 30). A control group consisted of 50 consecutive patients who were retrospectively evaluated. CT angiography parameters on a second-generation dual-source scanner were 128 x 0.6-mm collimation, pitch of 0.9, rotation time of 0.33 seconds, tube voltages of 80/100/120 kVp (group 1/group 2/control), reference tube current of 400 mA, and image reconstruction at 1-mm/0.8-mm slice thickness (kernels, B30f [control] and I30f/strength 3 [groups 1/2]). The control group received 120 mL of contrast agent (300 mgI/mL) at 4.8 mL/s; groups 1 and 2 received 44 mL and 53 mL at 3.3 mL/s and 4 mL/s, respectively. Effective dose was evaluated for each patient. Image quality was determined by qualitative image analysis at the levels of the thoracic; abdominal, and pelvic aorta as nondiagnostic, diagnostic, good, or excellent, and quantitative image analysis was performed, including attenuation values and contrast-to-noise ratio (CNR). Results: Mean effective radiation dose values for CT angiography of the aorta were 3.7 mSv +/- 0.7 in group 1, 6.7 mSv +/- 1.4 in group 2, and 8.7 mSv +/- 1.9 in the control group (P <.001). Mean attenuation values and CNR levels were 334 HU +/- 66 and 16 8, respectively, in group 1, 277 HU 56 and 14 5 in group 2, and 305 HU 77 and 11 4 in the control group. Conclusions: Iterative reconstruction algorithms resulted in 23%-57% less radiation in combination with 55%-63% less contrast agent volume compared with standard CT protocols.