Mohamed Abuzaid,Wiam Elshami,Baris Cavli,Ceren Ozturk,Ghada ALMisned,H.O. Tekin
A closer look at the utilized radiation doses during computed tomography pulmonary angiography (CTPA) for COVID-19 patients
COVID-19,Computed tomography,Radiation dose,Effective dose,Organ dose,Pulmonary embolism
Introduction CTPA stands for computed tomography pulmonary angiography. CTPA is an X-ray imaging that combines X-rays and computer technology to create detailed images of the pulmonary arteries and veins in the lungs. This test diagnoses and monitors conditions like pulmonary embolism, arterial blockages, and hypertension. Coronavirus (COVID-19) has threatened world health over the last three years. The number of (CT) scans increased and played a vital role in diagnosing COVID-19 patients, including life-threatening pulmonary embolism (PE). This study aimed to assess the radiation dose resulted from CTPA for COVID-19 patients. Methods Data were collected retrospectively from CTPA examinations on a single scanner in 84 symptomatic patients. The data collected included the dose length product (DLP), volumetric computed tomography dose index (CTDIvol), and size-specific dose estimate (SSDE). The organ dose and effective dose were estimated using VirtualDose software. Results The study population included 84 patients, 52% male and 48% female, with an average age of 62. The average DLP, CTDIvol, and SSDE were 404.2 mGy cm, 13.5 mGy, and 11.6 mGy\, respectively. The mean effective doses (mSv) for males and females were 3.01 and 3.29, respectively. The maximum to minimum organ doses (mGy) between patients was 0.8 for the male bladder and 7.33 for the female lung. Conclusions The increase in CT scans during the COVID-19 pandemic required close dose monitoring and optimization. The protocol used during CTPA should guarantee a minimum radiation dose with maximum patient benefits.
A closer look at the utilized radiation doses during computed tomography pulmonary angiography (CTPA) for COVID-19 patients

CTPA stands for computed tomography pulmonary angiography. CTPA is an X-ray imaging that combines X-rays and computer technology to create detailed images of the pulmonary arteries and veins in the lungs. This test diagnoses and monitors conditions like pulmonary embolism, arterial blockages, and hypertension. Coronavirus (COVID-19) has threatened world health over the last three years. The number of (CT) scans increased and played a vital role in diagnosing COVID-19 patients, including life-threatening pulmonary embolism (PE). This study aimed to assess the radiation dose resulted from CTPA for COVID-19 patients.

Data were collected retrospectively from CTPA examinations on a single scanner in 84 symptomatic patients. The data collected included the dose length product (DLP), volumetric computed tomography dose index (CTDIvol), and size-specific dose estimate (SSDE). The organ dose and effective dose were estimated using VirtualDose software.

The study population included 84 patients, 52% male and 48% female, with an average age of 62. The average DLP, CTDIvol, and SSDE were 404.2 mGy cm, 13.5 mGy, and 11.6 mGy\, respectively. The mean effective doses (mSv) for males and females were 3.01 and 3.29, respectively. The maximum to minimum organ doses (mGy) between patients was 0.8 for the male bladder and 7.33 for the female lung.

The increase in CT scans during the COVID-19 pandemic required close dose monitoring and optimization. The protocol used during CTPA should guarantee a minimum radiation dose with maximum patient benefits.

The computed tomography pulmonary angiogram (CTPA) is a gold standard diagnostic imaging examination to exclude pulmonary embolism (P.E.) (Zantonelli et al., 2022). The primary outcome of the procedure is to demonstrate the main pulmonary artery and its branches. The imaging technique used intravenous contrast media to fill the pulmonary arterial vasculature. Optimal results may be obtained when the contrast agent opacifies the pulmonary arteries. Image acquisition time is critical because delays make it difficult to discriminate between pulmonary arterial and pulmonary venous branches (Sakr et al., 2020). A typical CTPA scan would demonstrate that the pulmonary arteries are filled with bright contrast material. Deficiencies in the mass filling, such as an embolus, may look like a black filling or obstruct the region of the lungs where blood should flow (Fanous et al., 2012). Even though the actual scan may be done in less than a second, preparation of the contrast medium, patient posture, scan parameters, and scan planning should all be carefully considered (Zantonelli et al., 2022). CTPA patients have serious health concerns and need oxygen treatment and frequent monitoring; thus, this is crucial. The incidence of PE COVID-19 patients varies depending on the patient's condition, history, and population. Acute infection during COVID-19 was related to a higher risk of venous thromboembolic events (VTEs). Cytokine storms caused by VTEs result in hypercoagulability increases (Rotzinger et al., 2020). This uncontrolled immune response can result in systemic problems, including disseminated intravascular coagulation (DIC), which can be fatal (Čiva et al., 2022). Studies have shown that P.E. and VTEs might be likelier to occur due to this inflammatory response, which has been linked to the severity of the infection. Studies showed that 23–30% of patients who underwent CTA imaging had evidence of PE (6). Interestingly, patients with P.E. and those without had similar clinical illnesses (Ameri et al., 2021; Hauguel-Moreau et al., 2021). Therefore, PE might be connected, at least in part, to the severity of COVID-19 and not just to the physiologic state before infection. Furthermore, patients with COVID-19 infection and P.E. had greater d-dimer levels than those without P.E., indicating a more severe disease and robust immune response (Sakr et al., 2020). The role of CT Imaging during COVID-19 case management is essential. When a CT scan is indicated, and it should be carried out with care to reduce the risk of radiation and contrast media if indicated (Rotzinger et al., 2020). The purpose of this research is to analyze the above-mentioned circumstances, which are of great importance, by analyzing a large number of patients and to improve radiation dose monitoring, particularly in extreme scenarios such as the COVID-19 pandemic (Sakr et al., 2020; Rotzinger et al., 2020; Al Hassan et al., 2019; Ghetti et al., 2020). The study's results may provide a more significant picture of utilized radiation doses during Computed Tomography Pulmonary Angiography (CTPA) for COVID-19 patients, which is still on the global agenda, and other pandemics may occur in the future and require similar diagnostic radiological procedures.

A retrospective descriptive study was conducted for COVID-19 symptomatic patients who conducted CTPA between January and September 2021 in Turkey. CTPA procedures are performed on eighty-four adult patients with three scans: scout, pre-, and post-contrast media. The Affidea approved the study and data collection; written informed consent was not required for this study and was waived due to retrospective data collection. All exams were conducted using an Optima CT660 MDCT scanner (G.E. Healthcare, Milwaukee, WI. The contrast injection method uses a bolus track by positioning the region of interest (ROI) on the significant pulmonary trunk. The patients were injected with 40–80 ml/s of iodinated contrast media and 30–50 ml of normal saline contrast at 5 ml/s. The scanning began automatically when the Hounsfield unit (HU) hit 100 at the ROI, about 3–12 s after injection. The scan protocol's acquisition parameters are presented in Table 1 . The source-to-detector distance is 949.15 mm, the source-to-patient distance is 541 mm, the focal spot (mm) is 1.2, the gantry detector tilt is 0°, and the body filter type is utilized for data reconstruction. Because most emboli are found in the lower lobes, and the lower lobes exhibit greater excursion during image acquisition than the upper lobes, the scan was carried out in a caudal-cranial direction. The best results are obtained using a multidetector CT (MDCT), which can acquire all images in a single X-ray exposure with a scan rate of up to 320 mm/s. In addition, short scan times during the study helped minimize motion artifacts from the respiratory and cardiac systems (Sauter et al., 2019).

For CT dose management, patient data were collected using DoseWatch software by GE Healthcare (Milwaukee, Wis). In this investigation, no sensitive or private patient information was utilized. The software monitors, tracks, and analyses the dose data and consequently suggests strategies for dose reduction. Data from chest scans include patient information (age, gender, weight, height, Body Mass Index (BMI)), examination data (study description, protocol name, series name, series description, number of scans), acquisition data (scan region, distance source to detector, generator power (kW), reconstruction diameter, distance source to the patient, focal spot, slice thickness, spacing between slice, convolution length kernel, images per series, filter type, scan length), exposure parameters (KVP, tube current, pitch factor, exposure time per rotation, exposure time), radiation data (size-specific dose estimates for body examinations (SSDE) volumetric computed tomography dose index CTDIvol, dose length product DLP).

The mean effective and organ doses were calculated using VirtualDose software (Virtual Phantoms Inc., Albany, New York, USA) (Liang et al., 2017; Gao et al., 2018; Ding et al., 2015). VirtualDose is based on its comprehensive database of organ doses derived from Monte Carlo based on ICRP Publications. The ICRP publication 103 guidelines were used for dose calculations depending on the CTDIvol of the scanner to determine the organ and tissue doses (International, 2009; ICRP, 2007; Vañó et al., 2017). The scan parameters were used to determine the effective dose (ED) and organ dose. In addition, the organ dose for the following organs were reported: bladder, bone surface, brain, breast, colon, gonads, liver, lung, esophagus, salivary glands, skin, stomach, thyroid, and remainder tissues (ICRP 103).

IBM SPSS version 23.0 was used to analyze the data (IBM Corporation, Armonk, NY, USA). The data's mean, standard deviation, minimum, and maximum are reported in descriptive analysis.

Eighty-four patients who underwent CTPA were included in the study (44 males and 40 females). The mean age was 61.7 ± 11.6 years and between 33 and 78 years old. The patient's BMI mean was 29.6 ± 4.7, the maximum patient width was 416 ± 53 mm, and the maximum patient thickness was 256.5 ± 49 mm. The patient's demographic information in Table 2 included weight, size, BMI, maximum patient width, and thickness.

Table 3 shows the descriptive analysis of CT scan dosimetric parameters in terms of mean, SD, minimum, and maximum. The mean and SD for the total DLP, CTDIvol, and SSDE were 404.2 ± 92, 13.5 ± 3.5, and 11.6 ± 17.2, respectively. The data used to calculate the typical dose value as the median value of the dose distribution determined from patients' samples. The median DLP was 1007.4 mG cm, and CTDIvol was 71.4 mGy. The imaging facility can use a typical value to identify procedures amenable to further optimization.

Fig. 1 shows the organ doses and effective dose estimation using VirtualDose software. The estimation considers the ICRP publication 103 tissue-weighting factors and scan parameters for adult male and female phantoms. The software estimated the radiation dose for 14 organs sorted alphabetically. The maximum to minimum organ doses (mGy) between patients was 0.8 for the male bladder and 7.33 for the female lung. The lungs, breasts, and esophagus directly exposed to radiation were shown to have substantial radiation burdens. The mean effective doses (mSv) for males and females were 3.01 and 3.29, respectively, and the effective doses for females were higher than those for males.

During COVID-19, the CT chest was the most appropriate imaging test for diagnosing COVID-19 symptoms and complications. There are multiple protocols for CT chest examinations in COVID-19, whereas (55%) of the procedures follow routine chest CT protocol, (43%) follow a low-dose protocol, and (3%) follow a high-dose protocol, as stated in IAEA (Harun et al., 2020). Pulmonary CTA is the gold standard procedure for suspected PE (Zantonelli et al., 2022). This paper summarizes radiation, organ, and effective doses for CTPA COVID-19 patients from a single institute. Women undergo more CTPA than men, yet they are diagnosed with PE (35%–55%) less frequently than men (Jarman et al., 2021). Our data showed no significant difference (p > 0.05) between the ratio of male (52%) and female (48%) patients in the study, which indicated that both genders could be affected by P.E. symptoms during COVID-19. With a patient sample that included 52% males and 48% females, our study concluded that there is no significant difference between the genders and their likelihood of being affected by P.E symptoms during the COVID-19 (p > 0.05); hence, both males and females are prone to be affected by it. Most of the DRL's available data is based on anatomical region (Abuzaid et al., 2020; Vassileva and Rehani, 2015). However, recent studies have highlighted the importance of establishing DRLs based on clinical indications due to using different protocols for the same anatomical area (Elshami et al., 2022). For example, CT thorax protocol differs according to clinical indications such as P.E., cancer, and calcium scoring, which vary in scan parameters, contrast usage, number of series, and scan length. Although our study does not aim to establish DRL because of a single center date, we evaluate our dosimetric results regarding DRLs as a guide for dose optimization (Ghetti et al., 2020). In addition, the results can provide up-to-date reference levels based on clinical indications (PE). The 75th percentile dosimetric results of the current study regarding CTDIvol and DLP are comparable with previous literature on radiation doses for CTPA (Table 4 ). The most recent study by Geryes et al.2019 reported a CTDIvol of 8 mGy, which was largely lower than the rest of the studies stated here, and a DLP of 310 mGy cm, which was lesser than the yields of our study. Our study reported dosimetric lesser than Kanal et al. (USA), which reported CTDIvol = 19 mGy and DLP = 557 mGy cm. Schegerer et al. (DE) 2017 reported CTDIvol of 15 mGy as similar to our study but a DLP of 300 mGy cm that was the lowest compared to recent studies mentioned in Table 4 (Paulo et al., 2020). The CTDIvol and DLP of our work are relatively closer to the values reported by Public Health England (UK) in 2016 and Foley et al. (IE) 2012 (Paulo et al., 2020). The study used the VirtualDose program for dosimetric calculations to assess the mean organ doses and, subsequently, the effective doses for various patients, including males and females, according to their body sizes. Ghetti et al. reported that the risk of developing lung cancer among COVID-19 patients in women was higher than for men by a factor between 1.9 and 2.5, varying according to age. The study shows the maximum organ dose of 7.33 mGy was for female lungs, raising concerns about the risk of developing cancer (Ghetti et al., 2020). Further, the dose to breasts for both men and women was only second to the dose to lung, but the mean age of the patients in this study was 62 years, and it is glandular breast tissue susceptible to cancer risk; the importance is relatively lower.

The significance of ionizing radiation to both diagnosis and treatment is unquestionable. Nevertheless, there is a risk associated with ionizing radiation since it may affect tissues and organs and promote carcinogenesis (Abuzaid et al., 2022). Computed tomography (CT) is now one of the most significant contributors to the public's radiation dose. It is a relatively high-dose examination, and many individuals are exposed to CT scans several times. Meanwhile, the present COVID-19 pandemic has shown that using CT is indispensable and relevant even in such exceptional circumstances. Even though using such high-radiation equipment is obligatory in complex procedures, monitoring doses and minimizing radiation-related risks to public health are paramount. This paper demonstrates the increment of the CT Chest number during the COVID-19 pandemic. In addition, the number of scans with P.E. indications increased for both genders compared to the previous period. The current protocol ensures that the radiation dose is within the international guidelines and published DRLs. Furthermore, it is essential to ensure the justification of chest CT procedures to reduce unnecessary radiation doses and maximize diagnostic benefits. The acquired findings may serve as a valuable benchmark for the present pandemic and for comparable scenarios that may arise in the future.

MMA: Conceptualization, Original Draft Writing, Project administration; WE: Methodology, Virtual software analysis, Visualization; BC: Resources, Data collection, and analysis; CO: Resources, Data collection, and analysis; GA: Validation Formal Analysis, Virtual software analysis; HOT: Resources Review & Editing.

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.