Ultra-low-dose chest CT protocol during the second wave of COVID-19 pandemic: a double-observer prospective study on 250 patients to evaluate its detection accuracy

Abstract

Background While the second wave of COVID-19 pandemic almost reached its climax, unfortunately, new viral strains are rapidly spreading, and numbers of infected young adults are rising. Consequently, chest high-resolution computed tomography (HRCT) demands are increasing, regarding patients’ screening, initial evaluation and follow up. This study aims to evaluate the detection accuracy of ultra-low-dose chest CT in comparison with the routine low-dose chest CT to reduce the irradiation exposure hazards. Results This study was prospectively conducted on 250 patients during the period from 15th December 2020 to 10th February 2021. All of the included patients were clinically suspected of COVID-19 infection. All patients were subjected to routine low-dose (45 mAs) and ultra-low-dose (22 mAs) chest CT examinations. Finally, all patients had confirmatory PCR swab tests and other dedicated laboratory tests. They included 149 males and 101 females (59.6%:40.4%). Their age ranged from 16 to 84 years (mean age 50 ± 34 SD). Patients were divided according to body weight; 104 patients were less than 80 kg, and 146 patients were more than 80 kg. HRCT findings were examined by two expert consultant radiologists independently, and data analysis was performed by other two expert specialist and consultant radiologists. The inter-observer agreement (IOA) was excellent (96–100%). The ultra-low-dose chest CT reached 93.53–96.84% sensitivity and 90.38–93.84% accuracy. The signal-to-noise ratio (SNR) is 12.8:16.1; CTDIvol (mGy) = 1.1 ± 0.3, DLP (mGy cm) = 42.2 ± 7.9, mean effective dose (mSv/mGy cm) = 0.59 and absolute cancer risk = 0.02 × 10-4. Conclusion Ultra-low-dose HRCT can be reliably used during the second wave of COVID-19 pandemic to reduce the irradiation exposure hazards.

Is it necessary to define new diagnostic reference levels during pandemics like the Covid19-?

“…Regarding the pitch number, some studies suggest a pitch of less than 1 to have an image with enough quality to detect the ground-glass nodules ( Niu et al, 2021 ). However, other studies used pitch numbers of 1.4 and 1.5 and slice thickness of 5 mm, satisfying the results ( Samir et al, 2021a ; Song et al, 2020 ), similar to the results of H4 in this study.…”

“…They reported that they could reduce the mean effective dose from 0.85 (low-dose protocol) to 0.59 mSv/mGy cm (ultra-low-dose protocol) by reducing mAs from 45 to 22. They also stated that ultra-low-dose CT did not affect the diagnostic efficiency ( Samir et al, 2021b ).…”

Inter-Observer Agreement between Low-Dose and Standard-Dose CT with Soft and Sharp Convolution Kernels in COVID-19 Pneumonia

“…A similar conclusion was reached by Samir et al in a prospective study comparing ultra-low-dose CT with a 22 mAs tube current and low-dose CT. The former had excellent inter-observer agreement (96-100%) and 90.38-93.84% accuracy in COVID-19 imaging [18]. Tabatabaei et al obtained similar results on a small sample of 20 patients with an intraclass correlation of 0.98-0.99 for detecting COVID-19 pneumonia using a 30 mAs low-dose chest CT protocol (effective dose of 1.80 ± 0.42 mSv) [17].…”

“…WHO issued recommendations on COVID-19 imaging, advocating the usage of a low-dose CT in adults with the disease [16]. Several studies confirm the applicability of low-and ultra-low-dose chest CT protocols for detecting typical COVID-19 pneumonia signs [17,18]. In practice, the effective dose given to COVID-19 patients may vary widely depending on the medical center, and it is generally higher than for patients with other pulmonary infectious diseases [19].…”

Standardization of a CT Protocol for Imaging Patients with Suspected COVID-19—A RACOON Project

“…Quite often, protocols vary with regard to the associated radiation exposure and the desired image quality (IQ). There are already few reviews and evaluations published that compare different protocols with regard to the sensitivity and specificity of the diagnosis of COVID-19 [ 9 , 10 , 11 , 12 , 13 ]. Discrepancies in CT protocols for a particular organ or diagnostic inquiry are frequently observed within a single hospital, which is contingent upon the quantity of CT scanners and the diversity of vendors involved.…”