Evaluation of contrast agent reduction on the image quality of pulmonary Computed Tomography using a standard reconstruction available in the conventional CT system

Determination of the effect of contrast agent reduction on image quality of the pulmonary Computed Tomography, reconstructed by the standard algorithm in patients suspected of pulmonary thromboembolism

This study is a randomized clinical trial containing 40 samples. This double-blind study has two parallel groups. A table of random numbers will be used to allocate samples to control (standard protocol) and intervention (contrast agent reduction) groups randomly.

This randomized clinical trial with inpatients suspected of pulmonary embolism, will be conducted at the Namazi Hospital, Shiraz. The patients will be allocated into control and intervention groups. The image quality of pulmonary CTA of both groups will be evaluated by two radiologists blinded to the scanning parameters.

Inclusion criteria: Patients suspected of thromboembolism on the basis of clinical indications, Abnormal level of plasma D-dimer, lower extremity deep vein thrombosis Exclusion: creatinine>1.36 mg/dL, allergy to iodinated contrast, severe pneumonia and atelectasis, Confirmed pregnancy or suspicious of pregnancy, Body Mass Index>30 kg/m2, Critically ill patient or hospitalized in ICU

Intervention group: patients will be scanned with a 0.7 ml/kg contrast agent and 100kVp. Control group: patients will be scanned by a standard protocol containing a 1 ml/kg contrast agent and 120 kVp. CT images will be reconstructed by the standard algorithm (FBP) in both control and intervention groups.

Independent variables: The amount of contrast agent. Dependent variable: Image quality of pulmonary CT angiography

To allocate patients in intervention and control groups, simple random allocation method will be used. We asked the SPSS software to provide us 20 values randomly between 1 to 40. The software gave us the values 5, 3, 13, 18, 2, 14, 10, 1, 35, 37, 23, 32, 8, 16, 33, 36, 39, 9, 22, 28. By drawing lots between the control and intervention groups, we assigned these numbers to the intervention group. Then, the rest of the numbers, between 1 and 40, were assigned to the control group. In this way, we will assign the patients as control and intervention groups right from the beginning of the study, among the patients who were referred to the CT scan department of Namazi hospital, with the suspension of pulmonary embolism and having the inclusion criteria for entering the study. From the above random numbers, the first, second, and third patients are to be included in the intervention group. The intervention group will be scanned by reducing contrast agent protocol (pulmonary CT Angio). The fourth, fifth, and sixth patients referred will be allocated to the control group and they will be scanned by the standard dose of the contrast agent protocol (pulmonary CT Angio). Other referred patients who are candidates for the study will be placed in the intervention or control groups based on the serial number of their referrals and the matching numbers in the above-mentioned allocations.

In this study, the investigator (radiologists who evaluate the quality of pulmonary CTA) and patients will not be aware of the scanning protocol (they are blind to the amount of contrast agent). Only, technologists responsible for scanning patients and the students responsible for performing the study are aware of the amount of contrast agent.

Part of the data can be shared after unidentified

6 months after publication

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