Investigating the Use and Optimization of Low Dose kV and Contrast Media in CT Pulmonary Angiography Examination

Abstract

Background: Using a low volume of contrast medium and tube voltage may enhance the opacification of pulmonary arteries and thrombus detection without decreasing the image quality. In addition, this protocol can also ensure that exposure of the patient to the contrast medium and radiation dose may be significantly reduced. Objectives: The purpose of this study was to investigate the efficiency of low tube voltage and low dose iodine-based contrast medium in computed tomography pulmonary angiography (CTPA) and optimize its use in the diagnosis of pulmonary thromboembolism (PTE). Patients and Methods: We included a total of 100 patients undergoing CTPA with an initial diagnosis of PTE into two groups: group A (n = 50) was given a contrast medium (CM) dose of 0.5 mL/kg at 80 kV while group B (n = 50) was given a CM dose of 1 mL/kg at 100 kV. Bolus tracking technique was used. Attenuation values were measured from the center of different pulmonary arterial segments. Values over 350 Hounsfield unit (HU) were accepted as significant. Image qualities of all pulmonary arterial segments were sufficient for diagnosis. The mean and effective doses of radiation received by patients in the two groups were compared. Results: PTE was detected in twenty-one patients (21%) in both groups. Total mean attenuation values for pulmonary arteries were significantly higher in group A than in group B (532.7 ± 243 HU vs. 380.6 ± 232 HU respectively, P < 0.001). Total dose length product (DLP) (76.5 ± 17.3 mGy.cm vs. 162.1 ± 31.3 mGy.cm, P < 0.001) and effective dose values (1.2 ± 0.2 mSv vs. 2.4 ± 0.2 mSv, P < 0.001) were significantly lower in group A compared to group B. Conclusion: CTPA may be obtained using an imaging protocol with low kV and reduced volume of contrast medium in the diagnosis of PTE.