Evaluation of Patients’ Received Doses in Chest CT Scan Protocols for COVID-19 Diagnosis

Abstract

Purpose: This study aims to investigate and compare the doses received by Corona Virus Disease (Covid-19) patients on Computed Tomography (CT) scans by changing the scan parameters to diagnose the disease and evaluate its course and effects.

Materials and Methods: The total number of patients was 8290, with 4070 requesting a CT scan of the lungs. In 3512 cases, the purpose of the examination was to verify Covid-19. The remaining 558 scans were for other diseases. Two CT protocols were used for lung imaging: A low-dose protocol (kV=120 kVp and mAs=80ms) to screen for Covid-19 and a Smart protocol (kV=120 kVp and mAs = Smart) for other diseases. Each image was assigned a score from 1 to 5. The score reflects the quality of the image and Covid-19-related features such as Ground Glass Opacities (GGO), crazy paving, consolidation, Nodular Infiltrates (NI), Broncho Vascular Thickening (BVT), and Pleural Effusion (PE).

Results: In the low-dose protocol, the effective dose received by patients varied between 1.98 and 2.66 ± 0.1 milli Sievert (mSv) according to the different Dose-Length Product (DLP) values. The effective dose varies between 2.7 and 8.44 mSv for the Smart protocol. The maximum Size-Specific Dose Estimate (SSDE) was 11.97 ± 0.2 and 21.58 ± 0.9 milli Gray (mGy) for each protocol, respectively. The maximum carcinogenicity was 1.09 × 10⁻⁴ and 3.05 × 10−4, respectively. Radiologists gave an overall acceptance rate of 4.9 ± 0.1 and 4.8 ± 0.2 out of a possible 5-point for images with low-dose and smart protocols, respectively.

Conclusion: Decreasing the value of milli Ampere-seconds (mAs) decreases the effective dose, the size-specific dose estimate, and the carcinogenicity of radiation in patients requesting scans of the lungs CT. Images lose quality but are still good enough to determine the progression and impact of Covid-19.