Estimation of Lifetime Attributable Risks of Cancer Associated with Chest Computed Tomography Imaging

Shaiful Kabir; Md Zahid Hasan; Debashis Das; Muhammad Raihan; Afia Begum; Aleya Begum

doi:10.14316/pmp.2025.36.1.14

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Kabir, Hasan, Das, Raihan, Begum, and Begum: Estimation of Lifetime Attributable Risks of Cancer Associated with Chest Computed Tomography Imaging

Original Article

Progress in Medical Physics 2025; 36(1): 14-24.

Published online: 31 March 2025

DOI: https://doi.org/10.14316/pmp.2025.36.1.14

Estimation of Lifetime Attributable Risks of Cancer Associated with Chest Computed Tomography Imaging

Shaiful Kabir¹

, Md Zahid Hasan^1,

, Debashis Das², Muhammad Raihan³, Afia Begum⁴, Aleya Begum⁵

¹Department of Physics, Chittagong University of Engineering and Technology, Chattogram, Bangladesh

²Department of Physics, Noakhali Government Women’s College, Noakhali, Bangladesh

³Department of Electrical and Electronics Engineering, International Islamic University Chittagong, Chattogram, Bangladesh

⁴Department of Physics, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh

⁵Division of Health Physics, Atomic Energy Centre, Dhaka, Bangladesh

Corresponding author Md Zahid Hasan, (zahid1115@gmail.com), Tel: +880-1515628590

Received 18 December 2024 Revised 31 January 2025 Accepted 31 January 2025

(open-access):

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Purpose

The study aimed to measure the radiation-absorbed dose, effective dose, and associated risks of radiation-induced cancers during chest computed tomography (CT) imaging procedures at Square Hospital, Dhaka, Bangladesh.

Methods

A total of 23 patients were examined using a 64-slice CT scanner and thermoluminescence dosimeters. The dose-length product was recorded and converted into an equivalent effective dose using age-dependent conversion coefficients for multi-slice CT as provided by the European Guidelines. Organ doses were further converted into lifetime attributable risks (LARs) for cancer incidence and mortality based on data from the Biological Effects of Ionizing Radiation VII (BEIR VII) report.

Results

The effective dose ranged from 3.1 millisieverts (mSv) to approximately 35.3 mSv. The mean LAR for cancer incidence was 20.6 cases per 100,000 males and 69.3 cases per 100,000 females. The LAR for cancer mortality was 21.5 cases per 100,000 males and 62.0 cases per 100,000 females. Female patients were found to face significantly higher risks than male patients.

Conclusion

The results highlight a noticeable increase in LAR for both cancer incidence and mortality due to chest CT examinations, particularly for female patients. These findings underscore the importance of carefully evaluating the risks associated with CT imaging procedures.

Keywords: Computed tomography, Radiation dose, Effective dose, Lifetime attributable risk, Cancer

Introduction

Computed tomography (CT) scan is an effective diagnostic tool that uses X-rays to create two-dimensional cross-sectional images, which are combined to generate a detailed three-dimensional representation of an object [1]. The quality of the CT images is significantly higher than that of standard X-ray images. Therefore, CT is a non-invasive alternative to exploratory surgeries. As the immediate medical benefits for patients are considerable, the use of CT as a diagnostic tool has increased worldwide since its invention in the early seventies [2 -5]. However, CT carries an inherent risk of cancer as patients are exposed to significantly higher doses of ionizing radiation than standard X-ray procedures. Therefore, CT is associated with the highest radiation exposure in patients compared to other medical imaging procedures [6]. Upon exposure to X-ray radiation, the absorbed dose reflects the amount of energy deposited by the radiation in a mass (in mg), which is expressed in milli gray (mGy). The sensitivity toward radiation varies for different organs and tissues in the body; for instance, bones are considerably more radiosensitive than muscles. To evaluate the overall health impact, the equivalent dose, calculated for individual organs based on the absorbed dose, is adjusted for the effectiveness of the type of radiation. Then, it is adjusted by a factor that accounts for the risk associated with particular tissues or organs, providing the effective dose, also known as the whole-body dose. This dose is calculated as the sum of the equivalent doses for all organs, adjusted for their sensitivity to radiation, and expressed in millisieverts (mSv). Studies have shown that the risk of cancer increases when radiation doses from CT scans are similar to those experienced by individuals exposed to high radiation doses, such as long-term survivors of the Hiroshima and Nagasaki atomic bombings, who received doses between 10–100 mSv. A single CT scan can deliver a comparable radiation dose, and patients may undergo multiple scans over time. In 2007, a landmark study by Brenner and Hall in the New England Journal of Medicine estimated that CT scans might contribute to 1.50%–2.00% of all cancers in the United States [7]. In 2021, research at Harvard University showed that the effective dose for the chest X-ray test is 0.1 mSv, while that for a chest CT scan is 70 times higher, at 7 mSv. In 2009, a study conducted at Brigham and Women’s Hospital in Boston estimated the potential risk of cancer from CT scans in 31,462 patients over 22 years, which is alarmingly high [8]. In contrast, the average radiation dose experienced by an individual from natural environmental sources (e.g., air, earth, food) is approximately 620 millirems (mrem) or 6.2 mSv annually. Individuals undergoing radiological medical procedures are exposed to higher radiation doses than the average [9], which considerably increases their risk of cancer. Therefore, evaluating the impact of CT on public health is crucial, considering its medical benefits and the associated lifetime attributable risk (LAR) of cancer. This study, conducted at a private hospital in Dhaka, aimed to assess these factors in Bangladesh.

1. The theoretical concept of CTDI and other CT parameters

The computed tomography dose index (CTDI), a basic radiation-dose parameter in CT, is defined as the integral under the radiation-dose profile of a single rotation scan at a fixed table position divided by the nominal width of the radiation beam. The radiation dosage during a CT scan [10] is calculated using CTDI as the primary dose measurement concept. For a given scan protocol, CTDI calculates the average radiation output of a particular scanner [11], especially in the center of the scanning area when several consecutive CT scans are performed. Throughout the field of view, the average CTDI is calculated as follows:

(1)

C T D I_{W} = \frac{1}{3} C T D I_{100, c e n t r e} + \frac{2}{3} C T D I_{100, p e r i p h e r y}

The weighted CTDI (CTDI_w) is calculated using the measured CTDI for a 100-cm scan length (CTDI₁₀₀) for the center (CTDI_{100, center}) and girth areas of a cylindrical acrylic phantom (CTDI_{100, periphery}).

The CTDI_vol, which is the pitch-corrected version of the CTDI_w for multi-slice, non-contiguous scans, is shown on the CT scanner console for a particular scan protocol. The energy provided by a specific scan program is being calculated by the dose length product (DLP), which is given below:

(2)

D L P = C T D I_{v o l} \times s c a n l e n g t h L = C T D I_{W} \times \frac{L}{p}

The DLP, which is also shown on the console, represents the pitch in this situation. DLP is a proxy for the total absorbed dose in a phantom over the scan length. DLP, expressed in mGy-cm, is useful for comparing absorbed doses if the scan lengths are equivalent. The Effective Dose (E), obtained by multiplying the DLP by a conversion factor, k [12], takes into consideration the age of the patient and the sensitivity of the specific body part being scanned (Equation 3). Compared with the DLP alone, this number gives a more realistic picture of the health effects of a particular scan.

(3)

E = k \times D L P = k \times C T D I_{v o l} \times L = \frac{k \times L}{p} C T D I_{W}

The LAR represents the risk of cancer-related death due to exposure to CT scans. It is calculated using the Linear No-Threshold Model [13], and is much more significant. In addition to the DLP, other variables that affect LAR include the age and sex of the patient, and the specific body part or organ exposed to radiation.

Materials and Methods

The Study was approved by Head, CT scan lab Square Hospital, Dhaka, Bangladesh.

1. Thermoluminescent chips

Among the different crystals that exhibit thermoluminescence (TL), lithium fluoride (LiF) is the most widely used in TL chips. LiF has an effective atomic number of 8.2, which is comparable to the effective atomic number of 7.4 for human soft tissues. Due to this similarity, the absorbed dose measured using these chips is close to the radiation dose absorbed by human tissues over a wide energy range.

CT scans obtained from 10 male and 13 female patients were used in this study. Fifty TL dosimeter (TLD)-100 chips (Thermo Fisher Scientific) were placed between a 34-cm and a 45-cm polyethylene sheet in an array of 10 rows and 5 columns for CT imaging. With the columns lined up parallel to the scan length, the sheet was positioned beneath the patient before the CT scan. The Harshaw TLD Reader (model 3500, Thermo Fisher Scientific) at the Health Physics Laboratory in the Atomic Energy Center in Dhaka, Bangladesh, was used to read each TL chip after the scan was completed. The measured doses are shown in Tables 1 and 2.

1) Irradiation of the TLD

The TLD-100 (LiF: Mg, Ti) chips were irradiated by exposing them to a controlled radiation field for dosimetry. Before irradiation, the TLDs were annealed at 400°C for 1 hour, followed by gradual cooling to eliminate the residual signals and ensure reproducibility. The dosimeters were then placed in holders to ensure uniform exposure and irradiated using calibrated sources: Cs-137, Sr-90, and X-ray beams for gamma rays, beta particles, and diagnostic energy studies, respectively. The radiation dose was monitored using reference instruments, such as ion chambers, and the exposure was conducted under controlled environmental conditions to avoid variability due to temperature or humidity. After irradiation, the dosimeters were stored in light-tight containers to prevent accidental exposure until the readout. The emitted TL signal, which is proportional to the absorbed dose, is measured to determine the radiation exposure, making TLD-100 suitable for medical dosimetry applications during CT scans.

2) TLD calibration

Before dose measurements, each TLD must be calibrated to produce consistent and accurate readings in meaningful dosimetric units. After exposing all TLDs to a known dose, their responses were measured using a TLD reader. As the dosimeter is heated and gives off the light, the photomultiplier tube converts the TL signal to electrical currents. These currents are then integrated over the acquisition time to produce a charge integral, expressed in nano Coulombs (nC), and displayed over 200 channels. This integral was converted to dosimetry units using the reader calibration factor (CF). The CF was determined using the following equation:

(4)

C F = K n o w n D o s e (c G y) / T L D r e s p o n s e (n C)

The individual calibration factor (ICF) for TLD-100 (Fig. 1) is a unique correction factor assigned to each dosimeter to account for variations in its sensitivity, which might arise due to manufacturing differences, physical properties, or previous usage. The ICF ensures accurate dose measurements by standardizing the response of each TLD-100 chip to a known radiation dose. To determine the ICF, the TLD-100 chips were first annealed to remove the residual signals and ensure a uniform starting condition. They were irradiated with a known dose from a calibrated radiation source, such as Cs-137. After irradiation, the TL signals from each chip were measured using a TLD reader. Then, the ICF was calculated as the ratio of the known delivered dose to the measured dose.

2. The dose report from the CT operating system

The CTDI_vol (CTDI for volume) and DLP values were obtained from the individual patient dose reports during CT. CTDI_vol is a standardized measurement of the radiation output of a CT scanner, which was calculated from this average measured dose (at the scanning region) using the following equations:

(5)

M e a s u r e d C T D I_{v o l} = \frac{A v e r a g e m e a s u r e d d o s e}{P i t c h}

The DLP is a measure of the CT tube radiation output/exposure (expressed in mGy.cm). Although it is related to CTDI_vol, CTDI_vol represents the dose through a slice of an appropriate phantom. The DLP accounts for the length of the radiation output along the z-axis (the long axis of the patient).

The CTDI_w for each scan was calculated using the pitch value and the CTDI_vol. A linear relationship was observed between the average measured dose derived from the TL chip readings and the CTDI_w obtained from the scanner report. The current time product (mAs) is automatically adjusted using techniques like Automatic Exposure Control.

3. Measured DLP and effective dose from the average measured dose

The measured DLP and Effective Dose (E) were calculated using the following formulas:

(6)

D L P_{m e a s u r e d} = \frac{C T D I_{v o l}}{p (A v e r a g e m e a s u r e d d o s e)} \times L_{r e p o r t}

(7)

E = k \times D L P_{m e a s u r e d}

These k-factors depend on the age and body region of the patient, and the tube voltage of the CT scanner, which are available in the European guidelines for CT [14]. L_report represents the report of the scan length.

4. Organ dose calculation

We determined the organ dose in a subject with a given weight [organ dose (w)] using the following formula:

(8)

O r g a n d o s a g e (y) \times R (w) = O r g a n d o s e (w)

where y and w represent the height and weight of the patient and R (w) indicates the weighted correction factor. During continuous radiation exposure, this factor decreases and acts in the opposite direction as the size of the patient increases [15]. An adult patient weighing 70 kg would have an R (w) of 1.0. Each patient underwent a chest CT simulation because a weighting factor was applied to all irradiated organs. Applying the same scaling factor that was used for organ doses, we modified the effective dosages to account for patient size.

5. CT protocol

The data was obtained using a 64-slice CT scan. The patients were examined following the protocol based on their body mass index (BMI): pitch factor was set to 0.531, slice thickness was 5 mm, tube voltage was 120 kVp, slice collimation was 2.2 mm, and slice interval was 1.8 mm. In protocols 1 and 2 for patients with a BMI <25 kg/m² and BMI ≥25 kg/m², the tube currents were adjusted to 130 mAs and 260 mAs, respectively. The scanning range in the chest CT was from the upper.

6. LAR estimation

In this study, we calculated the LARs for various types of cancer, including colon, stomach, liver, bladder, and prostate (for males) and uterine and ovarian (for females) cancers. We used the methodology outlined in the BEIR VII Report (National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation, BEIR VII Report [13]) to estimate cancer incidence and mortality due to radiation exposure. The BEIR VII model considers factors such as radiation dose to specific organs and the age and sex of patients to calculate LARs (National Academy of Sciences Committee on the Biological Effects of Ionizing Radiation, BEIR VII Report).

The BEIR VII model relies on epidemiological data, primarily obtained from survivors of the Hiroshima and Nagasaki atomic bombings, populations near nuclear facilities with accidental radioactive releases, occupationally exposed workers, and patients exposed through diagnostic or therapeutic medical procedures. These data have been adjusted to reflect US population demographics [16]. The cancer occurrence and mortality rates per 100,000 people exposed to 0.1 Gy (100 mSv) were derived from the BEIR VII Report.

Sex- and organ-specific LAR values were obtained from these tables for different ages, using linear interpolation for patient ages between the tabulated values. After calculating patient-specific organ doses, we divided these doses by 100 mGy and multiplied the result by the normalized LARs from the calculations to determine the final LAR for each organ (Equation 8) [17]. The LAR for each organ at a given radiation dose was determined through linear extrapolation based on the BEIR VII table data [18]. The total LAR for each patient was calculated by adding the organ-specific LARs.

(9)

L A R O r g a n = L A R O r g a n (100 m G y) \times (O r g a n d o s e (w) / 100 m G y)

Where LAR_Organ (100 mGy) is the normalized risk based on the BEIR VII table for different patient ages.

7. Analysis

The age, measured dose, effective dose, organ dose, and LAR for 10 male and 13 female patients are provided in Tables 1 and 2. The mean CTDI_vol, DPL, and organ dose values were 15.7 mGy, 423 mGy.cm, and 23.3 mGy for male patients and 19.2 mGy, 850 mGy.cm, and 31.8 mGy for female patients, respectively. The highest organ doses for male and female patients were 98.6 mGy and 93.1 mGy, respectively, which were greater than those reported by Bagherzadeh et al. (24.36 mGy and 41.49 mGy for male and female patients, respectively) [19].

The mean effective doses for male and female patients were 5.9 mSv and 11.9 mSv, respectively. Furthermore, the maximum values of the effective dose for male and female patients were 11.42 mSv and 35.23 mSv, respectively, which were higher than the maximum effective dose values reported by Smith-Bindman (5.9 mSv and 11.9 mSv for male and female patients, respectively) [17]. The effective dose limit restricted by government regulatory agencies is 100 mSv every 5 years or 20 mSv annually with a maximum of 50 mSv in any given year [20,21].

The average LAR values of cancer incidence for male and female were 20.6 and 69.3 per 100,000 individuals, respectively, whereas the LAR values of cancer mortality were 21.5 and 62 cancers per 100,000 male and female, respectively. The LAR of cancer-related incidence for male and female are shown in Figs. 2 and 3, respectively, representing that the LAR of cancer incidence decreases with an increase in the age at exposure in both cases.

Fig. 2 shows the LAR of cancer incidence per 100,000 male patients.

Herein, the highest LAR value for cancer mortality was found to be 87.7 and 223 per 100,000 male and female patients, respectively, while the values reported by Bagherzadeh et al. [19] were 58.45 and 53.25 for male and female patients, respectively.

Fig. 3 shows the LAR of cancer incidence for female patients. The mean LAR values were 21.5 and 62 deaths per 100,000 persons for male and female patients, respectively. The highest LAR of cancer mortality were 91.7 and 197 for male and female patients, respectively. Meanwhile, the values reported by Bagherzadeh et al. [19] were 23.05 and 23.47 deaths per 100,000 male and female patients, respectively.

Fig. 4 shows the LAR of cancer mortality for females per 100,000 persons.

As shown in Figs. 2–5, the LAR of cancer incidence and mortality is not consistent with the age of the exposure for both male and female patients. The cancer incidence and mortality were higher for female patients than for males, indicating that female patients have a higher risk of developing cancer after CT scans.

Results

Fig. 2 shows the LAR of cancer incidence for males per 100,000 persons. The circular points and the blue line represent the experimental data and its linear, respectively. The equation of the linear fit is y=a+bx, where the radial sum of the squares is 5,101.98095, the value of intercept (a)=13.45391 with SE 48.72055, and the slope of the line is 0.12071.

Similarly, the LAR of cancer mortality for males per 100,000 persons is shown in Fig. 5. The circular points and the blue line represent the experimental data and its linear fit, respectively. The equation of the linear fit is y=a+bx, where the radial sum of the squares is 5,565.48975, the value of intercept (a)=12.51949, with a standard error of 50.88555 and the slope of the line is 0.15254 with a standard error of 0.84793.

Fig. 3 shows the LAR of cancer incidence for females per 100,000 persons. The circular points and the blue line represent the experimental data and its linear fit, respectively. The linear fit is calculated using the following equation: y=a+bx, where the radial sum of the squares is 35,026.17501, the value of intercept (a)=248.96859 with a standard error of 91.15931 and the slope of the line is 3.28215 with a standard error of 1.63971.

Fig. 4 shows the LAR of cancer mortality for females per 100,000 persons. The circular points and the blue line represent the experimental data and its linear fit, respectively. The equation of the linear fit is y=a+bx, where the radial sum of the squares is 27,502.09096, the value of intercept (a)=216.38691 with a standard error of 80.77696 and the slope of the line is 2.81886 with a standard error of 1.45296.

Figs. 2–5, as summarized in Table 3, illustrate the LAR trends for cancer incidence and mortality per 100,000 persons for males and females, with the circular points and blue lines representing the experimental data and the linear regression fits, respectively, characterized by specific equations and statistical parameters.

Table 4 presents the average value of the radiation dose measurements and the associated LAR of cancer incidence and mortality for males and females.

The various dose parameters measured during imaging procedures and their potential health impacts were compared in Table 4. The measured dose for female patients (32.1 mSv) was significantly higher than that for males (21.7 mSv), indicating greater radiation exposure in females. The measured CTDI_vol for male (15.7 mGy) and female (19.2 mGy) patients indicated that females received a slightly higher dose per unit volume of tissue. For organ dose, female patients (31.8 mGy) received a higher organ dose than males (23.3 mGy), which may be due to differences in body composition and organ sensitivity.

The DLP of female patients (850 mGy.cm) was nearly twice of that in males (423 mGy.cm), suggesting a larger scanned area or higher dose requirements. Moreover, female patients (11.9 mSv) received almost double the effective dose compared to males (5.9 mSv), suggesting that their overall risk of radiation-induced cancer was higher. The values show that the current-time product required by female patients (4,190 mAs) is higher than that for males (3,480 mAs), likely due to anatomical or imaging requirements.

The LAR of cancer incidence for female patients (69.3 cases per 100,000 persons) indicates a significantly higher risk compared to males (20.6 cases per 100,000 persons), likely due to increased radiosensitivity of female organs, such as the breast and thyroid. Similarly, the LAR of cancer mortality for female patients (62.0 per 100,000 persons) is much higher than that for males (21.5 per 100,000 persons). The data in Table 4 is shown graphically in Fig. 6, where the pink and yellow bars indicate the average LAR values of cancer incidence per 100,000 male and female, respectively. The light green and blue bars represent the LAR of cancer mortality per 100,000 male and female, respectively.

Discussion

The LAR values for male and female are shown in Table 4 and Fig. 6. As shown in the histogram, the LAR value is greater for female than male, possibly due to several biological and epidemiological factors. Female are biologically more sensitive to radiation-induced cancers than male, mainly breast, thyroid, and lung cancers, which can be attributed to hormonal and tissue-specific factors. The smaller body size and organ positioning in female may result in higher radiation doses to specific sensitive organs (e.g., breasts) during CT scans, particularly if the imaging is not optimized for sex-specific anatomy. Moreover, the baseline incidence rates for certain cancers, such as breast and thyroid cancer, are higher in female than in male. These higher baseline rates, coupled with radiation exposure, elevate the overall LAR. Depending on the type of CT scan (e.g., chest, abdomen, or pelvis), the radiation dose may disproportionately affect the more radiosensitive tissues in female, such as those in breasts and reproductive organs. All these reasons contribute to the higher LAR observed for female than male. This is consistent with other studies, which have also shown higher LAR values for female than male after CT scans [5,22 -24]. In the following section, the LAR values have been compared with the reference values to clarify the risk categorically. From Tables 4 and 5 it is suggested that the risk of LAR of cancer incidence per 100,000 person is low.

By comparing the average LAR value of cancer [25] with the reference value, we obtain a value of approximately 20 for male, indicating that the risk of cancer is very low for male. In contrast, the LAR of cancer for female is around 70, which is considered low based on the reference for risk qualification. This means that the radiation doses used for CT tests are safe for both male and female. Our analysis also revealed that the LAR for female is higher than that of male, which is consistent with previous reports. In this study, the sample size was limited to 23 participants due to ethical considerations related to radiation exposure and the specific inclusion criteria that required participants to undergo a particular type of CT scan within a defined time frame. As a preliminary investigation, this study aimed to explore the initial trends and validate the methodology, laying the groundwork for future research with a larger cohort.

Conclusions

In this study, the organ and effective doses and LARs of cancer incidence and mortality were evaluated for male and female during chest CT scans employing a 64-slice CT scanner. To our knowledge, this is the first report showing the LAR of cancer associated with CT imaging in Bangladesh. The high organ and effective dosage values observed suggest that the LAR of cancer incidence and mortality due to chest CT is significant and should be taken into consideration. The vast scan area, high radiation doses, and the numerous radiosensitive organs in the chest area all contribute to this increase. Therefore, the treatment planning for CT protocols should be optimized to reduce the radiation absorbed dosage and lower the LAR of patients.

Notes

FUNDING

This research did not receive any specific grant from funding agencies in the public, commercial, or not-forprofit sectors.

Conflicts of Interest

The authors have nothing to disclose.

Availability of Data and Materials

All relevant data are within the paper and its Supporting Information files.

Author Contributions

Conceptualization: Shaiful Kabir, Md Zahid Hasan, Afia Begum, Aleya Begum. Data curation: Shaiful Kabir, Md Zahid Hasan. Formal analysis: Shaiful Kabir, Md Zahid Hasan. Investigation: Shaiful Kabir, Md Zahid Hasan, Debashis Das, Muhammad Raihan. Methodology: Shaiful Kabir, Md Zahid Hasan. Project administration: Afia Begum, Aleya Begum. Resources: Shaiful Kabir, Md Zahid Hasan. Software: Shaiful Kabir, Md Zahid Hasan. Supervision: Md Zahid Hasan, Afia Begum, Aleya Begum. Validation: Shaiful Kabir, Md Zahid Hasan. Visualization: Shaiful Kabir, Md Zahid Hasan. Writing – original draft: Shaiful Kabir, Md Zahid Hasan, Debashis Das, Muhammad Raihan. Writing – review & editing: Shaiful Kabir, Md Zahid Hasan, Debashis Das, Muhammad Raihan, Afia Begum, Aleya Begum.

Ethics Approval and Consent to Participate

The study was approved by the Institutional Review Board of Square Hospital (IRB approval number; IRB-2020-1005).

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Fig. 1

Dose measurement using the thermoluminescent chip. (a) Schematic arrangement of thermoluminescence chips in the Polythene sheet. (b) The chips were being arranged from a sheet to a tray just before read out.

Fig. 2

Lifetime attributable risks (LARs) of cancer incidence per 100,000 persons plotted against the age of male patients.

Fig. 3

Lifetime attributable risks (LARs) of cancer incidence per 100,000 persons were plotted against the age of the female patients.

Fig. 4

Lifetime attributable risks (LARs) of cancer incidence per 100,000 persons were plotted against the age of the female patients.

Fig. 5

Lifetime attributable risks (LARs) of cancer deaths per 100,000 persons were plotted against the age of male patients.

Fig. 6

Lifetime attributable risk (LAR) value comparison for male and female.

Table 1

Dose and risk of cancer due to “CT Chest” for male patients

Age (y)	Measured dose (mGy)	Measured CTDIvol (mGy)	Organ dose (mGy)	Measured DLP (mGy.cm)	Effective dose (mSv)	Current time product (mAs)	LAR of cancer incidence per 100,000 person	LAR of cancer mortality per 100,000 person	Standard deviation of the cancer incidence	Standard deviation of the cancer mortality	CT protocol
35	15.0	9.68	16.7	246	3.45	5,420	17.6	17.9	0.866	1.05	Protocol-1
50	14.6	8.41	13.3	336	4.71	1,810	13.4	13.8	3.868	3.98	Protocol-1
54	13.5	9.19	15.9	339	4.76	2,180	16.0	16.5	4.619	4.76	Protocol-1
61	16.2	10.40	16.4	425	5.95	2,420	14.6	15.3	4.215	4.42	Protocol-1
62	24.6	8.14	11.7	353	4.95	2,570	10.4	10.9	3.002	3.15	Protocol-2
63	69.8	68.50	98.6	815	11.40	5,620	87.7	91.7	25.317	26.47	Protocol-2
65	14.7	11.00	15.9	466	6.53	3,020	14.1	14.8	4.073	4.27	Protocol-1
65	13.2	8.16	11.7	362	5.08	2,630	10.5	10.9	3.033	3.15	Protocol-1
67	10.7	5.84	8.4	233	3.27	2,360	5.5	6.0	1.588	1.73	Protocol-1
70	24.2	17.30	24.9	664	9.30	6,820	16.2	17.7	4.677	5.11	Protocol-1

Table 2

Dose and risk of cancer due to “CT Chest” for female patients

Age (y)	Measured dose (mGy)	Measured CTDIvol (mGy)	Organ dose (mGy)	Measured DLP (mGy.cm)	Effective dose (mSv)	Current time product (mAs)	LAR of cancer incidence per 100,000 person	LAR of cancer mortality per 100,000 person	Standard deviation of the cancer incidence	Standard deviation of the cancer mortality	CT protocol
42	18.6	10.7	18.5	823	11.5	2,650	44.3	39.2	7.19	6.58	Protocol-1
42	60.4	42.9	74.1	817	11.4	7,100	177.0	157.0	51.09	45.32	Protocol-2
44	23.6	5.8	9.9	247	3.5	2,540	23.9	21.1	6.89	6.09	Protocol-2
44	78.9	53.9	93.1	2,520	35.3	10,200	223.0	197.0	64.37	56.86	Protocol-2
50	68.7	11.1	19.2	528	7.4	2,810	44.2	39.2	12.75	11.31	Protocol-2
55	28.9	20.6	35.6	829	11.6	7,080	82.0	72.7	23.67	20.98	Protocol-1
55	35.0	24.3	42.0	959	13.4	7,000	96.5	85.6	27.85	24.71	Protocol-1
56	16.7	9.1	15.7	683	9.6	3,550	31.7	28.8	9.15	8.31	Protocol-1
59	18.3	18.7	29.6	729	10.2	2,550	59.5	54.2	17.17	15.64	Protocol-1
60	9.4	5.8	9.1	221	3.1	2,270	18.3	16.7	5.28	4.82	Protocol-1
67	19.3	12.9	18.6	691	9.7	2,430	27.4	26.1	7.91	7.53	Protocol-1
68	17.0	11.7	16.8	443	6.2	2,030	24.7	23.5	7.13	6.78	Protocol-1
70	35.8	22.3	32.1	835	11.7	2,220	47.2	44.9	13.63	12.96	Protocol-2

Table 3

LAR trends for cancer incidence and mortality by sex, detailing linear regression equations and key statistical parameters

Figure	Sex	LAR type	Intercept (a)	Slope (b)	Intercept standard error	Slope standard error	Radial sum of the squares
2	Male	Cancer incidence	13.45	0.12	48.72	0.81	5,101.98
3	Male	Cancer mortality	12.52	0.15	50.89	0.85	5,565.49
4	Female	Cancer incidence	248.97	−3.28	91.16	1.64	35,026.18
5	Female	Cancer mortality	216.39	−2.82	80.78	1.45	27,502.09

Table 4

Average doses and LAR values for male and female

Sex	Measured dose (mSv)	Measured CTDIvol (mGy)	Organ dose (mGy)	Measured DLP (mGy.cm)	Effective dose (mSv)	Current time product (mAs)	LAR of cancer incidence per 100,000 person	LAR of cancer mortality per 100,000 person
Male	21.7	15.7	23.3	423	5.9	3,480	20.6	21.5
Female	32.1	19.2	31.8	850	11.9	4,190	69.3	62.0

Table 5

The reference LAR values for risk analysis

Risk qualification	LAR of cancer incidence per 100,000 person	Reference
Negligible	<0.2	[25]
Minimal	0.2–2
Very low	2–20
Low	20–200
Moderate	20–400

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