**4.**

**Table**  *Effective doses and their compliance with radiation risk levels in patient groups with a single CT scan of the chest on COVID-19.*

#### *Radiation Doses and Risk Assessment during Computed Tomography of the Chest in COVID-19 … DOI: http://dx.doi.org/10.5772/intechopen.100177*

#### **Figure 1.**

*Average doses, mSv (A), and radiation risk values by age groups of patients (B) with a single, double and triple computed tomography of the chest. On the ordinate axis: (A) – average effective dose and confidence intervals (p* ≤ *0.05), mSv; (B) – values of radiation risk per 100,000 people; on the abscissa: age groups. Legend: number of CT scans of the patient, single, double, triple. The dashed lines show the boundaries between the levels of radiation risk (\*).*

old), 3.43 0.08 mSv in group 3 (adults 19–64 years old) and 3.28 0.19 mSv in group 4 (older persons – 65 years and older).

These doses are comparable with the ED values shown in the report [16] on the evaluation of DRLs for adult CT in European countries and in studies of other authors [17–19]. The DRLs for CT of adult chest organs in European countries were: 4.7–6.31 mSv in Netherlands [11, 14], 5.1–5.95 mSv in Germany [16, 18], 6.8 mSv in Austria [16], 5.95–10.4 mSv in Great Britain [16, 19], 7.31 mSv in Finland [16], 8.5–10.5 in Denmark [16], as well as 7.65 mSv in Australia [20].

In our earlier study [21], with standard protocols on different CT scanners, the values of the ED were in the ranges of 2.4–6.04 mSv and 8.4–15.33 mSv, for a singlephase and multiphase with contrast CTs, respectively. The use of low-dose protocols (tube voltage from 80 to 100 kV with automatic modulation of current) made it possible to reduce the ED to 1.6 mSv, when applying the iterative reconstruction algorithm MBIR for single-phase CTs and to 4.41 mSv when applying the iterative reconstruction algorithm ASIR for multiphase CTs [22].

Based on the risk indicator value for exposure of 1 mSv with age and sex (**Table 3**) were calculations radiation risk values and radiation risk levels after chest CT radiation per 100,000 exposed persons (**Table 4**). The maximum radiation risk values for a single CT were observed (**Figure 1B**) in groups of children (24.1\*10<sup>5</sup> ) and adolescents (23.3\*10<sup>5</sup> ). As can be seen in **Figure 2B**, the radiation risk values for a single CT were 31.2\*10<sup>5</sup> in women children (12–14 years old) and 29.3\*10<sup>5</sup> in women adolescents (15–19 years old), which exceeds the risk values for men in these groups by 2.3 and 1.9 times, respectively. For the group of adult patients the

*Radiation Doses and Risk Assessment during Computed Tomography of the Chest in COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.100177*

#### **Figure 2.**

*Average doses for a single CT scan (A), radiation risk values for a single (B), twice repeated (C) and triple (D) CT, distribution by levels of radiation risk by age groups and depending on the sex of patients. On the ordinate axis: (A) – average effective dose and confidence intervals (p* ≤ *0.05), mSv; (B–D) – values of radiation risk per 100,000 people; on the abscissa axis: age groups. Legend: – men, – women. The dashed lines show the boundaries between the levels of radiation risk (\*).*

average risk was 14.4\*10<sup>5</sup> , (11.2\*10<sup>5</sup> ) in men and 17.4\*10<sup>5</sup> in women, which is 1.6 times higher than in men. Nevertheless, all these risk values are in the range of 10\*10<sup>5</sup> –100\*10<sup>5</sup> , which corresponds to the level LOW. For the group of older age patients, the radiation risk was 2.6\*10<sup>5</sup> , which corresponds to the leval rang of 1\*10<sup>5</sup> –10\*10<sup>5</sup> , VERY LOW.

We have compared the calculations with estimates of radiation risks in other studies.

For example, when planning the limits of exposure of astronauts [23], the risk of oncological diseases and genetic effects are rather low: 0.2\*10<sup>6</sup> for leukemia, 0.2\*10<sup>6</sup> for other types of malignant neoplasms, and 0.05\*10<sup>6</sup> for genetic effects, per year per dose of additional irradiation of 1 mSv. Spontaneous incidence are

50\*10<sup>6</sup> for leukemia, 1000–2000\*10<sup>6</sup> for other types of malignant neoplasms and 8000\*10<sup>6</sup> for genetic effects per year.

In publication 103 of the ICRP [11], new views of the ICRP on the principles and approaches to ensuring radiation safety, are formulated in comparison with the previous document - Publication 60 of the ICRP [15]. Epidemiological data obtained since the publication of Publication 60 of the ICRP served as a reason for revising the values of the nominal risk factors per unit dose for radiogenic cancers and hereditary effects (**Table 5**).

As we can see, the new risk values in Publication 103 are slightly lower as those specified in Publication 60. But, at the same time, for children compared with adults, they were increased in terms of Malignant neoplasms from 1.5 to 1.68, for hereditary defects from 2.25 to 3.0, and in the total number of negative effects from 1.61 to 2.0. Our results are comparable to these guidelines.

I.A. Tsalafoutas, G.V. Koukourakis [24] emphasize that stochastic negative effects can be caused even by small doses of radiation, and give the following example of calculating the risk associated with radiation during CT. The assumption of a 5% probability of risk per 1 Sv (1,000 mSv) for the occurrence of cancer or hereditary effects means that the examination, which leads to patient exposure in ED = 10 mSv (typical for CT of the abdomen and pelvis), implies 0.05% chance of such risks. That is, for every 10,000 patients, who underwent CT with a dose of 10 mSv, five people can be expected, to develop cancer or hereditary effects as the result of radiation.

There was calculation individual of effective dose and risk of malignancy based on Monte Carlo simulations after whole body CT [25]. The Excess Relative Risk (ERRMC), as a measurement of the exceeding risk of an exposed person compared to a non-exposed person, calculated using the solid cancer mortality in the United States as baseline (female: 17,500/100,000; male: 22,100/100,000).

There was calculation individual of Effective Dose and estimation of organspecific additional Lifetime Attributable Risk (LAR) of cancer mortality after Whole Body Computed Tomography based on Monte Carlo simulations and report VII about Biologic Effects of Ionizing Radiation (BEIR VII). Considering the effective doses of 1.48 0.15 mSv for the lungs, the LAR for mortality from lung cancer [n / 100,000] was 13.25 4.24.

In our study, it was shown that with a single chest CT scan in patients with suspected COVID-19, additional (to a spontaneous level) cases of oncological pathology per 100,000 people may occur: 24.1 cases in children, 23.3 cases in adolescents, 14.4 cases in adults, 2.6 cases in older persons.

The average effective dose will increase in proportion to the increase in the number of CTs performed on the patient from 2.6–3.4 mSv with a single CT scan to the calculated values of 7.8–10.3 mSv with three times CTs. This will lead to a threefold increase in radiation risks to levels per 100,000 people may occur


#### **Table 5.**

*Comparison of the risk of negative effects of exposure from a dose of 1 mSv, number of cases per 10<sup>5</sup> people (ICRP Publication 103, 2007 [11]; ICRP Publication 60, 1991 [15]).*

*Radiation Doses and Risk Assessment during Computed Tomography of the Chest in COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.100177*

(**Figure 1B**): 72.3 cases in children, 69.8 cases in adolescents, 43.2 cases in adults, 7.9 cases in older persons. Due to the increased post-radiation risks in children; сcurrently, both the European and the American Society of Pediatric Radiology do not recommend the use of CT to diagnose COVID-19 pneumonia in children. CT is indicated only for severe, where concurrent pathology need to be excluded.

In men, the average radiation doses in the four age groups were slightly higher than in women (**Figure 2A**). However, with an increase in the number of CT scans from one (**Figure 2B**) to two (**Figure 2C**) and up to three (**Figure 2D**) in females, the increase in the calculated radiation risk compared to men is more significant, especially in women children (in 2.3 times) and among women adolescent (in 1.9 times). The radiation risk in men and women in all subgroups by age up to 65 years remains at the LOW level (10\*10<sup>5</sup> –100\*10<sup>5</sup> ), and in the older subgroup at the WERY LOW level (1\*10<sup>5</sup> –10\*10<sup>5</sup> ). However, with a three-fold CT scan in groups of children and adolescents, the radiation risk in women approaches the border of the MODERATE level (100\*10<sup>5</sup> –300\*10<sup>5</sup> ), and in the old group to the border of the LOW level (10\*10<sup>5</sup> –100\*10<sup>5</sup> ).

By evaluating the lung irradiation with the doses used in the ongoing clinical trials to treat COVID -19 patients, our data shows that a radiation dose 0.5 Gy provides an acceptable Risk Identification Checklist (RIC) estimate (LAR 1%), irrespective of sex and age at exposure [26]. However, a promising direction is the use of modern CT scanners, which allow the use of low-dose algorithms for CT diagnostics [27], while significantly reducing the radiation exposure to patients.

#### **4. Conclusions**

Because the study established effective radiation doses for chest CTs of patients with the diagnosis of COVID-19, the radiation risks for a single, double and triple chest CTs in different age and sex of patients were calculated. It has been found, that the radiation risk due to a single, double and triple chest CTs for patients under 65 years old is LOW, and for 65 years old and older patents is VERY LOW. Taking into account the radiation risk during CT is necessary to reduce the long-term consequences of radiation exposure on the population.

#### **Financing**

The study was performed without external funding.

#### **Conflict of interest**

The authors declare no conflict of interest.

#### **Conformity with the principles of ethics**

The study was approved by the local ethics committee.

#### **Abbreviations**


#### *Computed-Tomography (CT) Scan*


## **Author details**

Elena Ivanovna Matkevich and Ivan Vasilievich Ivanov\* Department of Occupational Health, I.M. Sechenov First Moscow State Medical University of the Ministry of Health of the Russian Federation (Sechenov University), Moscow, Russian Federation

\*Address all correspondence to: ivanov-iv@yandex.ru

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

*Radiation Doses and Risk Assessment during Computed Tomography of the Chest in COVID-19… DOI: http://dx.doi.org/10.5772/intechopen.100177*

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#### **Chapter 4**
