Radiation Dose and Effective Risk Assessments in Adult Patient from a Common Radiological Procedure: A Comparative Study

doi:10.21203/rs.3.rs-5020394/v1

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Radiation Dose and Effective Risk Assessments in Adult Patient from a Common Radiological Procedure: A Comparative Study

https://doi.org/10.21203/rs.3.rs-5020394/v1

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Background: Generally, quantifying radiation risks associated with diagnostic radiology has been a subject of interest with the increased use of X-rays. So, pelvis radiography is used as a focus for dose monitoring with the need to balance the risks and benefits of a new diagnostic modality.

Objectives: This study assessed radiation dose and the risks at exposure age from pelvis examination.

Patients and methods: The study used an indirect dosimetric approach and PCXMC software to determine ESD, effective dose (E_D), and the equivalent dose to organs and then calculate risk based on the average percentage increase in LAR of cancer incidence.

Results: Pelvis lateral (LAT) with averagely low E_D (0.051mSv) recorded a lifetime risk coefficient (R_T) (2.693E-1 Sv-1) and high effective risk (E_R) (7.764E-4) against pelvis AP with E_D (0.226 mSv), R_T(5.90E-2 Sv-1) and low E_R (9.789E-5) in a single exposure for pelvis radiograph. Generally, among organs exposed during examinations, lungs with averagely low dose recorded moderately high R_o and E_R,Owhile pelvis bone recorded low E_R,O for pelvis radiography. The urinary bladder with high doses recorded low R_o (0.011Gy-1) and E_R,O (0.4985E-6). Prostate and pelvis bone recorded high and low E_R,O (males), and uterus and pelvis bone (females) for pelvis AP, while these were pancreas and pelvis bone (males) and colon and pelvis (females) for pelvis LAT.

Conclusion: Studies show that adult patients within the age group (40-49 yrs.) for pelvis radiography and their organs are averagely exposed to low and minimal risks of cancer induction, respectively.

effective dose

effective risk

lifetime risk coefficient

radiological procedure

risks of exposure

The motivation behind dosimetric methods for diagnostic imaging procedures lay basically in valuing health risks to patients subjected to a given type of examination using ionizing radiation. So, the need to balance the risks and benefits of a new diagnostic modality arises, to ensure that the chosen modality has the least potentially harmful effects on the health of the patient, surveyed. Therefore, an adequate comparison of the techniques and the probable risks of exposure to cancer inducement due to specific radiological procedures becomes necessary.

Radiation doses to patients from medical imaging have been widely examined to have contributed tremendously to increased cancer risks ^{[1, 2]}. One of the studies established an estimated average expected cancer incidence, which was quantified to be superficially 2% of the cancers diagnosed in the United States of America annually, in the year, 2007. Thus, compared with topical estimates of 0.015 to 0.02 ^{[3, 4]}. However, these facts and figures were linked to Computed tomographic (CT) studies. However, results confirmed a higher possibility of excess cancer risks being recorded equally from low level-radiation and so, accentuate the need to address the radiation dose and risks from identifiable common medical imaging procedures.

The technique of exposure has been branded to associate with quantities that account for risk, making the knowledge of organ dose and effective dose (E_D) become highly bossy ^{[5, 6]}. However, in 1977, the International Commission on Radiological Protection (ICRP) designed the concept of E_D to provide the quantity that is proportional to a radiobiological detriment for the specific radiological procedure, and thus represent a balance between carcinogenesis, life-shortening and hereditary risk of effects ^[7] which compared favourably, to the generic risk of exposure to different radiation risks ^[8]. In the understanding of this quantity, the technique accessible by ICRP to calculate effective dose was theoretically based on the use of multiplicative models of risk factors, applicable to some fundamental quantities as absorbed dose ^[9]. However, several limitations must be considered when quantifying medical exposure using E_D. This made its assessment and interpretation from planned exposure problematic, especially when organs/tissues receive partial or very heterogeneous exposure related to X-ray diagnostics ^[9]. So, the quantity of ‘E_D’ varies based on the patient's average body density, the procedure employed and the area of the body exposed to radiation. Thus, it depends on field size area (A) and the photon energy (h\(\:\nu\:\)) that relates to the collimator factor (CF) as a function of (A, h\(\:\nu\:\)) and the exposure in air, defined by ^[10]:

E_D (A, h\(\:\nu\:\)) = CF (A, h\(\:\nu\:\)) = REF (A, h\(\:\nu\:\)) (1)

Therefore, E_D as in Eq. 1, is population site-specific independent and can only compare the risk associated with different heterogeneous exposures and not measured. But, theoretically calculate the dose based on the organ exposed, radiation type, and the tissue-specific weighting factors ^[11], given by the relation:

E_D (d, r, A) = H_T (d, r, A)\(\:\underset{i}{\overset{f}{\int\:}}{W}_{T\:}\:d\text{T}\) (2)

Where A is field size area (beam size), H_T, is the specific equivalent dose to tissue T and W_T, as tissue-specific weighting factors while the alphabet (i-f) connote(s) the limit of the area exposed on the patient during an examination. Therefore, reducing beam size during examination minimizes the number of organs exposed and spontaneously reduces effective dose estimate. Thus, Eq. 2 can equally be as:

E_D = H_T\(\:\:\sum\:_{T}{W}_{T}\) (3)

The dimensionless quantity W_T defined in Equations 2 and 3 is seen as hypothetical and does not relate to the epidemiologic strands of the disease, cancer. However, quantity W_T undergoes periodic changes nearly every decade or more due to merely committee discretion ^[11] and this contributes vastly to the noticeable changes in E_D estimate ^{[9, 12]}. However, this can be more useful clinically to provide data that allows for decision-making during the justification or optimization of medical imaging procedures ^[13]. However, for the risk of exposure calculation to an individual, the E_D concept is not anticipated to be used ^[14–17] since W_T has been averaged over all ages and sexes. So, to avoid vindicating E_D norms and follow the principle of limitation for occupationally exposed individuals, minding uniform whole-body exposures that make E_D more complex for risk evaluation ^{[9, 18]}, it was replaced by more scientific-oriented, non-committee defined but lifetime tissue-specific cancer risk, made age and gender-specific pinpointed called effective risk (E_R) ^{[15, 19]}. So, E_R as risk index is defined as a function of age at exposure(e), dose(d), radiation type (r), and gender (s) given by [20]:

E_R (e, d, r, s) = H_T (d, r, A) \(\:\underset{e}{\overset{a}{\int\:}}{\text{R}}_{\text{T}\:}\left(\text{e},\:\text{s},\:\text{d},\:\text{r}\right)\text{d}\text{a}\) (4)

In the Equation, R_T is the lifetime tissue-specific cancer risks (per unit equivalent dose to tissue T), H_T is the specific dose for tissue T, ‘e’ is the patient age at exposure, and ‘a’ is the attained age. Here, ‘a’ is seen as the summation of two variables (i.e. age at exposure and the latency period (L) for the cancer type). Subsequently, E_R as the number of risk of exposure to cancer inducement at exposure age to a specific time, considered along the patient lifespan (attained age), can be estimated at exposure age using Eq. 4 given by ^{[15, 20, 21]} as:

E_R = \(\:\sum\:_{T}{R}_{T\:}{H}_{T}\) (5)

Where R_T, as tissue-specific radiation-induced cancer risk replaced W_T. The probability of cancer risks and risk models ^{[9, 22, 23]} compared favourably with the authoritative report proposed nominal lifetime radiation risk (2–10 x 10^− 2 Sv^− 1), assessed as a function of age and sex ^{[9, 13]}. Therefore, this study aims to evaluate and compare the quantity ‘E_D’ and the risks of exposure-induced cancer (E_R) due to pelvis radiographs.

2.1 Study area

Lagos state, one of the smallest and fastest developing states within the Southwestern region of Nigeria, with a total area of 3577 km², was created on the 25th of May 1967 and lies within Latitude 6⁰ 52’ North of the equator and longitudes 3⁰ 38’ East, and has a population of about 25 million with a gender ratio of 53.6: 46.4 for males and females and an estimated growth rate of 8.3%, which exceeds the national growth rate of 2.8% ^[24]. The state consists of 20 local government areas and 37 local development councils with 30 government hospitals, all within secondary and tertiary health sectors, and more than 70 accredited private radio-diagnostic centres that generate a sizeable quantum of patients for different types of radiological procedures. Thus, this may contribute to a possible increase in radiation-induced health-related diseases, especially for those within the lower abdomen. Hence, the study data focused on the adult age groups.

2.2 Study sample and sampling technique

This study was conducted in six(6) selected centres within the state (5 publics, coded as OGH, LSTH, IGH, AGH and GBGH and one private diagnostic centre, tagged FANICR), with appropriate Health Research and Ethics Committee approval from Lagos State University Teaching Hospital, Ikeja, Lagos State (Reg.no. NHREC 12/02/2024 and Ref. no: LREC. 06/10/799) issued. The criteria for the choice of diagnostic centre studied include a good representation of the X-ray procedure studied, geographical location, and commendable hospital workload ^[25]. Also, all the centres except FANICR are secondary referral hospitals. Exposure parameters used during clinical examinations were observed and recorded. So, a population of 278 adult patients exposed to both Anteroposterior (AP) and Lateral projections of pelvis radiography were considered for the study ^[26]. Respective patient's characteristics information were observed and the values, recorded. The patient doses were monitored and evaluated using an indirect dosimetric approach. All the parameters required for ESD and E_D estimates for each patient, including the exposure factors used during clinical examination such as tube loading (mAs), tube potential (kVp), focus to skin distance (FSD), focus to film distance (FFD) together with the X-ray machine beam output was obtained and slotted appropriately into the study model.

2.3 Patient dose assessment

The patient's ESD was calculated using ^[27]:

ESD = D_o (\(\:\frac{mGy}{mAs}\)). q (mAs). (\(\:\frac{y}{x}\))². (\(\:\frac{kV}{80}\))². f ^− 1 (6)

Where, f is the average backscatter factor used and y, x, kV and q were respectively FDD used during reproducibility measurement on the X-ray machine, FSD, tube voltage and tube loading used during clinical examination. The beam output D_o (\(\:\frac{mR}{mAs})\) of the X-ray machine was measured using an X-ray test device (Noninvasive evaluation of radiation output, model 4000™ Victoreen Inc., USA), and at the time of this study, the calibration of the X-ray test device as issued by the manufacturer was still valid. The reproducibility measurements on the X-ray machines were carried out at 1m (focus to detector distance) with a constant tube voltage potential setting of 80kVp (voltage at which anode current was assumed stable) and tube loading of 10mAs. The measured beam output, averagely determined in \(\:\frac{mR}{mAs}\) was converted to\(\:\:\frac{mGy}{mAs}\) using a conversion factor of 8.73x10^− 3[28]. Then, the established beam outputs were used alongside others in Eq. 6 for the patient’s ESD estimate. Patient E_D was estimated by carrying out an analytical stimulation using a PC-based Monte Carlo program (PCXMC version 2.0) developed by STUK (Radiation and Nuclear Safety Authority in Finland) ^[29]. This software offered the most powerful tool for modelling radiation transport in different media and has extensively been used for this purpose with consistent and reliable outcomes. It was well-coded to automatically generate the required X-ray spectrum based on the input parameters (kVp, mAs, FSD, total filtration etc). During this process, the anode angle in the software was set to 14⁰ and the program software estimated the dose to organ and effective dose for an ample number of organs exposed during examination using anatomical data of the mathematical phantom model as developed and was made to estimate E_D based on the weighting factors of the ICRP publication 103 ^[9]. After inputting data as required by the software, the dose received by organs and the effective dose equivalent were obtained for different examinations. The patient’s cancer risk at exposure age for all cancers combined was calculated using Eq. 5 and the R_T (radiation-induced cancer risks per unit dose as a function of sex and age at exposure) determined, on average LAR (Sv^− 1) percentage increase in cancer incidence (all cancers combined) from a single exposure to radiation for different dose values by gender and radiological examination, in line with linear non-threshold (LNT) dose models ^{[22, 23]}. Therefore, attribute risk fraction (ARF) for cancer incidence, generated in the published studies for incidence cases based on genders, ages and population specific-site was employed ^[23]. Thus, the nominal lifetime radiation risk coefficient (R_T) calculated using ^{[22, 23]}:

R_T (Sv^− 1) = ARF. (E)⁻¹ (7)

Where ARF is the Attribute risk fraction for cancer incidence (all cancers combined), E is the mean E_D for each selected centre. So, E_R(a, s), the lifetime radiation risk (number of risk of exposure to cancer inducement) for the patient due to pelvis radiography, extrapolated to a significant population value of 10,000 made averaged over sexes and adult ages of the populations, were calculated by substituting Eq. 7 into Eq. 5 and multiplied by the patient ESD.

The effective risk to organs (o) exposed during exposure of patient of gender (s) to pelvis radiograph at exposure age (e) was calculated using ^[13]:

E_{R, O} (a, s, o) ₌ \(\:\sum\:{\text{E}}_{\text{o}}\left(\text{a},\text{s}\right){\text{R}}_{\text{o}}(\text{a},\text{s})\) (8)

Where E_{R, O}, the equivalent effective risk (organ lifetime radiation risk) to the organ (o) exposed due to patient of gender ‘s’ and age ‘a’ for pelvis examination by projection. The organ effective dose was estimated using the equivalent organ weighting factors from ICRP publication 103^[9] as generated from the software. These were used to evaluate the organ lifetime radiation risk coefficient. Consequently, the lifetime risk coefficient to the organ at age ‘a’ (Gy^− 1) was determined, where the organ is considered a material media as:

\(\:{\text{R}}_{\text{o}}\) (Gy^− 1) = ARF (H_T,_O) ⁻¹ (9)

Here, H_T,O represent the mean absorbed dose to organ/tissue (Gy). Thus, the average estimates from this work were limited to the data for average patient age ranges of (40 and 49) years ^[13].

Figure 1 shows the X-ray machine beam output at 80 kVp and the averaged exposure parameters used during examinations at different centres. In this study, the X-ray machines used were observed to belong to the twentieth-century manufactured type, identified with moderately high efficacy of between 35.70 and 50.11\(\:\frac{\mu\:Gy}{mAs}\) (Fig. 1). However, the machine-specific information was not transcribed, but can be observed as having their equivalent measured X-ray beam output falls within the accredited range for single phase X-ray machine ((4.5 ± 1.5) \(\:\frac{mR}{mAs}\) = (34.92 ± 17.46) \(\:\frac{\mu\:Gy}{mAs}\) ) ^[30], so may guarantee as low as reasonable practicable (ALARP), alongside others relevant radiographic/exposure parameters and equipment (film type, processing chemical etc.). The overall average measured efficacies of the X-ray machine used was (45.11 ± 5.59) \(\:\frac{\mu\:Gy}{mAs}\) which could still be well accommodated in the twentieth-century specified X-ray machine ^[31]. Therefore, it is expected that the dose to the patient from these X-ray machines with good radiographic technique in line with ALARA prescription ^[32] will yield better radiographic images.

The average exposure parameters recorded from this study ranged between 81–110 kVp and 20–40 mAs for tube voltage and tube loading, were in agreement with studies ^{[31, 32]} for pelvis examination (Fig. 1) and the difference in value when compared with other studies can be ascribed to either patient anatomical size and radiographic techniques employed during examination ^[31]. The FFD ranged from 100–120 cm and averaged for study as 109.5cm, while FSD ranged from (80.0–99.0) cm and (64.0-89.9) cm for pelvis AP and LAT. Therefore, FFD values from this study fall within the optimum FFD range of (80–210) cm reported in Sudan for good geometric image sharpness ^{[33, 34]}.

The Patient’s age and the estimated average entrance skin surface doses (ESD) by sex, averaged over sexes and examinations, are presented in Table 1. The average patient ages studied were (44.8 ± 3.74 yrs.) and (39.7 ± 3.61yrs.) for males and females and averaged over sexes as (42.3 ± 3.94 yrs.) with the approximate coefficient of variability determined as 8.35%, 9.09% and 9.31% for males, females and averaged over sexes respectively. So, an indication of more spread established among females age compared to males, deduced. Therefore, in line with the statistically established age group for radiation risk estimates ^{[13, 22]}, patient average ages in this study fall approximately within (40-49yrs) of working-class, reproductive and accredited adult age groups. However, the possibility of females in this age group being closer to their menopause is not completely nullified. Hence, an indication of distress in some organs such as the Ovaries and uterus may be suspected. Also, observation from studies (HPA) and (ICRP) and the postulate of the multiplicative risk projection model in line with linear non-threshold dose (LND) stipulated that the overall estimates of lifetime risks of all cancer incidence following whole body irradiation may be higher for females than for males, and decrease steadily with age at exposure by an approximate factor of 2 for every 30yrs ^[13]. These could be verified based on the study's limited but significant sample data of 278 patients (male-54. 6% and female- 45.4%) ^{[35, 36]}.

Table 1

patient’s age and the estimated average entrance skin surface doses (ESD) by sex, averaged over sexes and examinations
Centre	Age(yrs.)			Radiological examination
	Age(yrs.)			Pelvis AP (mGy)			Pelvis LAT. (mGy)
	M	F	Both	M	F	Both	M	F	Both
OAGH	42.3(2.26)	44.8(2.45)	43.6(2.60)	2.120(0.250)	2.121(0.320)	2.121(0.00)	2.620(0.160)	2.649(0.270	2.635(0.020)
LSTH	47.6(2.73)	39.7(3.06)	43.7(3.94)	2.074(0.120)	1.845(0.190)	1.960(0.120)	3.511(0.180)	3.464(0.120)	3.488(0.024)
IGH	46.5(2.91)	44.3(2.50)	45.4(2.91)	1.213(0.030)	1.114(0.060)	1.164(0.050)	1.912(0.200)	1.652(0.230)	1.782(0.130
AGH	38.7(2.26)	27.1(1.86)	32.9(2.74)	2.640(0.390)	2.233(0.560)	2.437(0.200)	3.651(0.130)	3.646(0.050)	3.649(0.030)
GBGH	44.3(1.58)	41.8(2.03)	43.1(2.03)	1.809(0.011)	1.827(0.140)	1.818(0.010)	5.400(0.190)	7.105(0.100)	6.253(0.850)
FANICR	49.6(1.58)	40.3(2.60)	45.0(2.60)	1.391(0.090)	1.267(0.100)	1.329(0.060)	2.063(0.020)	2.086(0.100)	2.075(0.010)
ALL	44.8(3.74)	39.7(3.61)	42.3(3.94)	1.875(0.480)	1.735(0.410)	1.805(0.440)	3.193(1.190)	3.434(1.790)	3.314(1.480)
RF	1.23	1.65	1.39	2.18	2.01	2.09	2.82	4.30	3.51

Note: Values are presented in mean and SD (in brackets), M = Male, F = Female

In this study, the overall average ESD recorded ranges from (1.805 ± 0.440 mGy) and (3.314 ± 1.480 mGy) with percentage spread (24.38% and 44.66%) for pelvis AP and LAT. (Table 1). So, widespread noted in the dose to the patient due to pelvis LAT than for pelvis AP. Thus, the difference may be traceable to the patient's anatomy, radiation thickness of penetration by projections and technical factors selection. Here, the average estimated ESD for pelvis LAT and AP was approximately a factors (LAT: AP) of 1.70, 1.98 and 1.84 for male, female and averaged over sexes respectively, signifying dose to patient from pelvis LAT examination as almost twice that recorded for pelvis AP, and this may credibly result in a high collective dose at exposure age to patients exposed for both examinations. The high and low ESD values were recorded from AGH (2.437mGy) and IGH (1.164mGy) for pelvis AP and these were GBGH (6.253mGy) and IGH (1.782mGy) for pelvis LAT. The low ESD recorded generally from IGH may be ascribed to high FFD (120cm) and low tube loading of (20mAs) used throughout pelvis examination which gave an impression of good radiological practice. These may promote as low as reasonably achievable doses since image quality is not compromised. However, variation in ESD values for the same type of examination from the same centre/room is expected.

Comparison in the estimated average ESD (mGy) with other published values for pelvis procedure publicized in Fig. 2. The ESD from this study, when compared with published values ^{[31, 37, 38]} showed a good agreement while the difference in values is ascribed to patient anatomy and technical factors selection difference (Fig. 2). Therefore, about 92% of the ESD values from this study fall below the UK reference dose level of 4.0 mGy ^{[32, 37 ]} and almost 8% were higher than this dose value but lower than the IAEA dose of 10.0 mGy ^{[36, 39]}. The observable difference may be ascribed to patient thicknesses, population of the study, technical factors selection and the adopted model employed. However, doses generally from this study may be seen as low but still need further reduction as long as the image quality is not compromised.

The estimated average effective dose by sex, averaged over sexes, and examination, is presented in Table 2. The estimated E_D was significantly based on individual reference person (male and female) and reference person (averaged over sexes) values (Table 2) since the quantity in dosimetry studies is considered tempting due to its ability to describe the procedure in terms of the potential risk to the health of the subjects, studied. So, the average E_D for study reference persons of an approximate age (42yrs.) were 0.226 and 0.051 mSv for pelvis AP and LAT respectively with a factor of 4.43 (AP: LAT). Thus, an indication that the overall stochastic health effects due to pelvis radiograph was higher for AP than for LAT projection, contrary to the belief that radiation health effects are independent of the X-ray beam projections, concluded.

Table 2

Estimated average effective dose (E_D = E) (mSv) by sex, averaged over sexes and examinations
Centre	Examination
	Pelvis AP			Pelvis LAT
	M	F	Both	M	F	Both
OAGH	0.244 (0.000)	0.298 (0.010)	0.267 (0.023)	0.042 (0.001)	0.039 (0.001)	0.041 (0.002)
LSTH	0.263 (0.010)	0.239 (0.000)	0.246 (0.007)	0.058 (0.002)	0.062 (0.003)	0.060 (0.002)
IGH	0.126 (0.000)	0.108 (0.000)	0.117 (0.009)	0.027 (0.001)	0.030 (0.001)	0.029 (0.002)
AGH	0.300 (0.010)	0.291 0.007)	0.296 (0.005)	0.037 (0.002)	0.051 (0.004)	0.044 (0.007)
GBGH	0.232 (0.006)	0.267 (0.003)	0.250 (0.018)	0.094 (0.004)	0.093 (0.002)	0.094 (0.001)
FANICR	0.193 (0.000)	0.165 (0.009)	0.179 (0.014)	0.046 (0.002)	0.038 (0.001)	0.042 (0.004)
ALL	0.225 (0.054)	0.227 (0.068)	0.226 (0.060)	0.051 (0.022)	0.052 (0.021)	0.051 (0.021)
RF	2.38	2.69	2.53	3.48	3.10	3.24

Note: Values are presented in mean and SD (in brackets) with range factor (RF) across centres

A comparison of the study estimated effective dose with some published values and their time to accumulate annual natural background dose is reflected in Table 3. Here, the estimated E_D from this study and its possible health effects were considered, a fraction of the annual natural background dose. So, the time for study E_D and its radiation health effect to accumulate equivalently to annual background dose calculated and compared with some published values. Therefore, study values demonstrate a reasonable degree of agreement. However, the observable difference may be ascribed to different tissue weighting factors, the adopted method and the area of beam collimation. So, in this study, estimated E_D were found lower compared to those reported in UK studies with an approximate difference of 0.05 ^{[11, 37]}, and almost 5 times lower than ICRP established values of 1.2 mSv using dual-energy X-ray absorptiometry ^{[1, 7]}. A comparison of study E_D values with a study with pelvis LAT shows that values recorded from this study were a little higher for pelvis LAT and lower for AP ^[38].

Table 3

Comparison of study estimated effective dose (E_D mSv) with some published values and their time to accumulate annual natural background dose
Studies	Radiological examination		Time to accumulate comparable natural background dose ^a
Studies	Pelvis AP	Pelvis LAT	Pelvis AP	Pelvis LAT.
This study	0.23(0.06)	0.05(0.02)	27dys, 11.9 hrs	6dys,2hrs
Balogun et al., ^[38]	0.27(0.00)	0.01(0.00)	1mth, 2dys. & 20.4 hrs.	1dy & 5.2hrs
UK ^[37]	0.28	--	1mth, 4dys &2hrs.	--
Canada ^[31]	0.16	--	19dys & 11.2 hrs.	--
Iran [31]	0.25	--	1mth & 9.9hrs.	--
Sebia Montenegro [31]	--	--	--	--
Note: a: Natural background dose (3mSv/yrs.) and ICRP established value of 1.2 mSv ^[7]

Other accredited ways to better understand and compare E_D were to relate obtainable values for specific diagnostic examinations studied to annual natural background dose (3 mSv per year) ^[1] and observe E_D estimates for individual patients as subjected to substantial levels of uncertainty. However, risks associated with medical imaging procedures refer to possible long-term or short-term side effects. Hence, the need to compare the time for the obtainable E_D to accumulate comparable to such background dose arises. Generally, E_D values from this study when compared to the background dose gave approximate factors of 13.27 and 58.82 for AP and LAT, and will accumulate substantially to measurable background dose in (27dys and 11.9hrs.) and (6dys and 2hrs.) for AP and LAT respectively. Therefore, patients exposed to average E_D values recorded from this study would have radiation health effects (if no further X-ray exposure) accumulated in approximately 13 and 59yrs respectively for AP and LAT compared to that expected for annual background dose equivalent. This confirmed the degree of health effects associated with low doses of ionizing radiation exposure. So, an indication of relatively low E_D and low lifetime risk estimates with possible longtime effects for reference person at exposure age predicted.

Estimated average nominal lifetime risk of cancer incidence (All cancers combined) (R_T(Sv^− 1)) and the lifetime risk of cancer induction (Effective risk ‘E_R’) by sex, averaged over sexes for examination, presented in Table 4. In this study, the average lifetime risks of cancer incidence (All cancers combined) (R_T(Sv^− 1) and the effective risk (lifetime risk of cancer inducement) equivalent, at the understudied age were estimated based on the available sample data over 10,000 population of the study area, using established attributable risks fraction(ARF) for cancer incidence ^{[22, 23]}. However, the ICRP estimates proposed nominal lifetime radiation-induced cancer risk coefficient ranged (2–10 x E-2 Sv^− 1), averagely specified for adult estimates as (4.0 x E-2 Sv^− 1) and for all age as (5.0 x E-2 Sv^− 1) ^{[9, 13, 14]}. So, the study estimated lifetime radiation-induced cancer risk coefficient (R_T (Sv^− 1) were recorded as 5.76 x E-2, 6.03x E-2 and 5.90 x E-2 Sv^− 1for male, female and averaged over sexes respectively for pelvis AP while these were 2.75 x E-1, 2.64 x E-1 and 2.69 x E-1 Sv^− 1 respectively for pelvis LAT. A comparison of the study’s values with ICRP's established range of values shows a good agreement. But, the observable difference may be ascribed to the extrapolated population or the estimated E_D values. The average effective risk per patient (E_R) at exposure age was observed as 1.01 x E-4, 9.51 x E-5 and 9.79 x E-5 for study individual reference male, female and the reference person respectively for pelvis AP while these were 7.89 x E-4, 7.63 x E-4 and 7.76 x E-4 for pelvis LAT. So, low and high E_R across centres studied, recorded from GBGH (0.88 x E-4) and IGH (1.20 x E-4) for pelvis AP and FANICR (0.60 x E-3) and AGH (1.02 x E-3) respectively for pelvis LAT. Conclusively, high risks per reference person within the age group (40–49 yrs.), exposed for pelvis radiograph recorded from pelvis LAT. Comparative studies of E_D and E_R, show that health effect is inversely related to the risk of exposure to cancer inducement. Therefore, the assumption that the long-time health effects recorded for LAT in a single exposure will attract a high risk of cancer inducement, made while reversed may be assumed for pelvis AP. Generally, in line with four broad risk bands for typical total lifetime cancer risk to patients ^[21], estimated risk at exposure age due to pelvis AP fall within a very low-risk profile category (1:100,000–1:10,000) while it was an averagely low-risk category (1:10,000–1:1000) for pelvis LAT.

Table 4

Estimated average nominal lifetime radiation risk of cancer incidence (R_T (Sv ^− 1)) and lifetime radiation risk of cancer induction (Effective risk ‘E_R’) by sex, averaged over sexes for examination studied.
Centre	Radiological examination
	Pelvis AP						Pelvis LAT.
	Estimated parameters						Estimated parameters
	R_T (Sv^− 1)			E_R (x E-4)			R_T (Sv^− 1)			E_R (x E-3)
	M	F	Both	M	F	Both	M	F	Both	M	F	Both
OAGH	0.0492	0.0415	0.0449	1.0430	0.8806	0.9616	0.2857	0.3077	0.2927	0.7485	0.8151	0.7818
LSTH	0.0474	0.0502	0.0488	0.9831	0.9264	0.9551	0.2069	0.1936	0.2000	0.7264	0.6706	0.6985
IGH	0.0952	0.1111	0.1026	1.1553	1.2378	1.1966	0.4444	0.4000	0.4138	0.8498	0.6608	0.7553
AGH	0.0400	0.0412	0.0405	1.0560	0.9209	0.9885	0.3243	0.2353	0.2727	1.1840	0.8579	1.0210
GBGH	0.0517	0.0449	0.0480	0.9356	0.8211	0.8784	0.1277	0.1290	0.1277	0.6894	0.9166	0.8031
FANICR	0.0622	0.0727	0.0670	0.8649	0.9215	0.8932	0.2609	0.3158	0.2857	0.5382	0.6588	0.5985
ALL (SEM) RF	0.0576 (0.0181) 2.38	0.0603 (0.0251) 2.69	0.0586 (0.0213) 2.54	1.0063 (0.0927) 1.34	0.9514 (0.1332) 1.51	0.9789 (0.1047) 1.36	0.2750 (0.0981) 3.48	0.2636 (0.0886) 3.10	0.2654 (0.0902) 3.29	0.7894 (0.1992) 2.20	0.7633 (0.1042) 1.39	0.7764 (0.1283) 1.71

Note: ALL (Study individual reference and reference persons), presented in mean, Standard error of mean (SEM) and range factor (RF).

A comparison of the percentage dose reduction due to examination projections for the estimated parameters at exposure age is presented in Table 5. Comparatively, effective dose and radiation risk description would not be adequate without a simple analysis of dose reduction due to different projections of the radiological procedure involved. However, effective dose and radiation risk reduction analysis embarked due to the observable trend encountered in the study estimated parameters with specific reference to already identified situations statistically ^[40]. So, the only situation identified between AP and LAT (combined RLAT > LLAT) projections of pelvis examination showed that the lower effective doses recorded were generally caused by LAT projection [i.e. E_D dose reduction value of 77.43%] and so triggered the risk of radiation-induced cancers (-349.15%) recorded than for AP. Thus, established disagreement between effective dose and radiation risk reductions with no significant difference observed at p-value > 0.05 using t-test analysis. These noticeable dose reduction differences may be ascribed to different absorbed doses to patients, various organs exposed during this Lateral (combined) examination and the difference in the calculated risk of exposure-induced cancer per unit of the dose (R_T (Sv^− 1)) in the case of either patients or the organs. However, in all radiographic examination projections, the risk of radiation-induced carcinogenesis will be based on the position of the sensitive organ to the X-ray tube (i.e. far or near) and the situation where the organ is shielded by structures such as the pelvis bone. This is evident during either right or left lateral positions of the pelvis spine radiograph, with male testicles/prostate or uteri in females seeming more protected by the pelvis bones. Therefore, negative values recorded in dose reduction are an indication or applied confirmation of increased dose to the patient for pelvis LAT examination. So, a related instance revealed in this study shows bones of the pelvis (Pelvis) recording averagely a high dose during LAT (male = 526.60 µGy and female = 514.28 µGy) compared to AP (male = 484.91 µGy; female = 456.70 µGy). Conversely, a high dose to an organ does not necessarily mean a high risk of cancer induction to the organ (e.g. Urinary bladder). Subsequently, risks of exposure-induced cancer are estimated based on the organ sensitivity, cancer site, sex, age at exposure and the organ dose inclusive.

Table 5

Comparison of the percentage dose reduction in patient’s estimated parameters at exposure age for study reference person value by examinations
Examination/Projections	ESD (mGy) [X (SD)]	E_D (mSv) [ X (SD] (ICRP 103)	R_T (Sv^− 1) [ X (SD)]	Effective risk (E_R) [ X (SD)]
Pelvis AP	1.805 (0.440)	0.226 (0.060)	0.059 (0.022)	0.979 E-4 (0.105E-4)
Pelvis LAT	3.314 (1.480)	0.051 (0.021)	0.265 (0.091)	0.776 E-3 (0.128E-3)
Dose Reduction (%)	-83.601	77.434	-349.153	-702.313
p-Value	p > 0.05

Note: Values are presented in mean(X) and standard deviation (SD)

The estimated equivalent dose, effective dose (E_o), radiation risk coefficient (R_o) and effective risk (E_R,o) to organs for exposure age group (40-49yrs.) by sex and examination, extrapolated to 10,000 of the population established in Table 6. In this study, organ-specific lifetime radiation induced cancer risk per unit of the organ dose R_o (Gy^− 1) and effective risk (lifetime radiation risk of cancer-inducement) (E_R,o) values at exposure age, for average patient ages (44.8yrs.), (39.7yrs.) and (42.3yrs.) for individual male, female and study reference person respectively, approximated to a demographically accredited age group of 40-49yrs., were determined (Tables 6 and 7). Here, R_o values for organs exposed were calculated directly from the study data with established ARF value ^{[22, 23]} extrapolated to 10,000 of the Lagos State population. However, a comparison of these R_o (Gy^− 1) with published values, estimated using age adjustment factors ^{[9, 35, 41]} and sex-specific detriment values ^[14] was made. So, study estimates based on epidemiologic studies ^{[21, 35]} for the age group (40-49yrs.), showed good agreement. However, the difference is traceable to extrapolated population size or equivalent dose to the organs exposed during radiographic examination. Therefore, the estimated average organ-specific lifetime radiation attributable cancer risk per unit of the equivalent organ dose in the study shows that the prostate(1.465xE-6) and the bone of pelvis(1.23xE-7) for males and Uterus(1.459xE-6) and pelvis bone(1.19xE-7) for females were exposed to high and low radiation-induced cancer risks at exposure for AP while these were pancreas(1.444xE-6) and pelvis bone(1.21x E-7) for male and colon(1.447xE-6) and pelvis bone(1.18xE-7) for female for LAT projection of the examination. Vivid observation from the study showed that the high risk recorded from the pancreas may be due to a higher number of patients examined for RLAT than for LLAT. Otherwise, it would have been colon (1.443xE-6).

Table 6

Estimated equivalent dose, effective dose (E_D), radiation risk coefficient (R_o) and effective risk (E_R,O) to organs for exposure age group 40-49yrs.) by sex (extrapolated to 10,000 of the population)
Pelvis AP examination
Organs/Tissues	Mean Dose (H_T,o) (µGy)(2dp)		Effective dose (E_o) (µSv) (3dp)		R_o (Gy^− 1) (3dp)		Effective risks (E_R,o) x E-6 (3dp)
Organs/Tissues	M	F	M	F	M	F	M	F
ABM (RBM)	70.30	65.61	8.436	7.873	0.171	0.183	1.443	1.441
Breast	-	1.30	-	0.156	-	9.234	-	1.440
Colon	177.70	178.80	21.324	21.456	0.068	0.067	1.450	1.438
Kidney	1.46	1.98	0.175	0.238	8.219	6.061	1.438	1.443
Liver	1.15	1.17	0.046	0.047	10.435	10.256	0.480	0.482
Lungs	0.14	0.22	0.017	0.026	85.714	54.546	1.457	1.440
Ovaries	-	1229.59	-	98.367	-	0.010	-	0.984
Testicle	973.84	-	77.907	-	0.012	-	0.935	-
Prostate	581.13	-	69.736	-	0.021	-	1.465	-
Uterus	-	640.00	-	76.800	-	0.019	-	1.459
Pelvis bone	484.91	456.70	4.899	4.567	0.025	0.026	0.123	0.119
Stomach	2.17	2.54	0.260	0.305	5.530	4.724	1.438	1.441
Urinary bladder	1135.07	1244.72	45.403	49.789	0.011	0.010	0.499	0.498
Gall bladder	2.60	2.68	0.312	0.322	4.615	4.478	1.440	1.442
Pancreas	1.74	1.83	0.209	0.220	6.897	6.557	1.441	1.443
Small intestine	31.70	37.12	3.804	4.454	0.379	0.323	1.442	1.439

Note: ARF = 0.0012% = 1.2 E-5 (BEIR VII phase 2; 2006), (UNSCEAR, 2006) ^{[22, 23]}

Table 7

Estimated equivalent dose, effective dose, radiation risk coefficient (R_o) and effective risk to organs for exposure age group (40-49yrs.) by sex (extrapolated to 10,000 of the population)
Pelvis LAT. examination
Organs/Tissues	Mean Dose (H_T,o) (µGy) (2dp)		Effective dose(E_o) (µSv) (3dp)		R_o(Gy^− 1) (3dp)		Effective risks(E_R,0) x E-6 (3dp)
Organs/Tissues	M	F	M	F	M	F	M	F
ABM (RBM)	72.34	71.43	8.681	8.572	0.166	0.168	1.441	1.440
Breast	-	1.23	-	0.148	-	9.756	-	1.444
Colon	111.34	110.59	13.361	13.273	0.108	0.109	1.443	1.447
Kidney	1.46	2.13	0.175	0.256	8.219	5.634	1.438	1.442
Liver	0.68	0.86	0.027	0.034	17.647	13.954	0.477	0.474
Lungs	0.15	0.16	0.018	0.019	80.000	75.000	1.440	1.425
Ovaries	-	136.30	-	10.904	-	0.088	-	0.960
Testicle	152.74	-	12.219	-	0.079	-	0.965	-
Prostate	120.89	-	14.507	-	0.099	-	1.436	-
Uterus	-	132.26	-	16.351	-	0.088	-	1.439
Pelvis bone	526.60	514.28	5.266	5.143	0.023	0.023	0.121	0.118
Stomach	2.32	2.86	0.278	0.343	5.172	4.196	1.438	1.439
Urinary bladder	210.86	181.09	8.434	7.244	0.057	0.066	0.481	0.478
Gall bladder	1.71	2.42	0.205	0.290	7.018	4.959	1.439	1.438
Pancreas	0.64	1.37	0.077	0.164	18.750	8.759	1.444	1.437
Small intestine	25.70	30.50	3.084	3.660	0.467	0.393	1.440	1.438

Note: ARF = 0.0012% = 1.2 E-5 ^{[22, 23]}

Meanwhile, it is clinically and study-wise established ^{[9, 13, 14]} that the equivalent lifetime risk of cancers recorded for gonads may be considered the equivalent risk for hereditary effects owing to radiation exposure. Thus, the equivalent hereditary risk of cancer induction recorded shows that the prostate (1.465 x E-6) and testicle (9.35 x E-7) were exposed to high and low hereditary risks for males and the uterus (1.459 x E-6) and ovary (9.84 x E-7) for female for pelvis AP while these were Prostate (1.436 x E-6) and testicle (9.65xE-7) for male and uterus (1.439xE-6) and ovary (9.60xE-7) for female respectively for pelvis LAT. However, the urinary bladder which recorded the high mean organ dose from this study, recorded a moderately low value for radiation-induced cancer risk while the lungs which recorded a very low mean organ dose recorded moderately high radiation-induced cancer risk for both pelvis AP and LAT. Therefore, an indication of the possible inverse relation between mean organ dose and risk of exposure-induced cancer risk to organs is deduced. Thus, established morbidity cancer inducement to tissue/organ is solely dependent on organ radio-sensitivity, its position and distance from the X-ray tube.

Comparison of the study estimated lifetime radiation risk to the organ (E_R,o) with published values for the same average age group (40-49yrs.) by gender, presented in Table 8. Values obtained from this study demonstrate good geometric agreement with values extrapolated from the US population ^[13] compared to Euro-American populations ^{[21, 35]}. So, the observable difference may be ascribed to sample size, populations of the area and the adopted method for evaluation. Generally, across all studies, the lifetime radiation risk to lungs and breasts was high compared to other organs but, much higher for this study. Closely related in values were organs such as the ovary, gonad/uterus and urinary bladder.

Table 8

Comparison of the study calculated lifetime radiation risk to organ (R_o) with published values for same average age group (40-49yrs.) by gender.
Organs	This Study (Gy^− 1)				(US Population) (Gy^− 1) ^{[13, 14]}		(Euro-America Population) (Gy^− 1) ^{[21, 41]}
	AP		LAT		(US Population) (Gy^− 1) ^{[13, 14]}		(Euro-America Population) (Gy^− 1) ^{[21, 41]}
	M	F	M	F	M	F	M	F
Colon	0.068	0.067	0.180	0.109	0.045	0.020	0.600	0.290
Lungs	85.710	54.546	80.000	75.000	0.041	0.082	0.800	1.780
Ovary	--	0.010	--	0.088	--	0.014	--	--
Gonad/ Uterus	0.020	0.020	0.099	0.088	0.023	0.000	--	--
ABM	0.170	0.180	0.166	0.168	0.048	0.036	0.780	0.770
Breast	--	9.230		9.756	--	0.109	--	0.840
Urinary Bladder	0.011	0.010	0.057	0.066	0.012	0.011	0.460	0.390

Variation in estimated organs lifetime risk of cancer induction (E_R,o) due to pelvis AP by sex at average exposure age group (40–49) yrs. for pooled Lagos State population, established in Fig. 3. An observable close relation in values obtained with parity ranged from 0.01–0.03 for organs such as breast, lungs, colon, gonad/uterus and ABM, compared to organs such as ovary and urinary bladder, established. Therefore, calculated E_R,o falls within the minimal category of risk (1:1,000,000 − 1:200,000). Hence, symptomatic of fewer risks at exposure age to each organ exposed during pelvis examination deduced.

Studies have evaluated radiation dose and risk of cancer induction to adult patients from pelvis radiographs in some selected hospitals in Lagos State using an indirect dosimetry approach. Therefore, the study findings showed that adult patients for the pelvis (AP and LAT) radiography within the age group 40–49 yrs. were exposed to very low and low categories of risk of cancers combined incidence and the organs were exposed to very minimal risks of cancer induction. However, the noticeable variation in the cancer incidence recorded from this study called for adequate precaution during the radiological examination of patients for this procedure. Hence, the need to adopt techniques that allow for As Low As Reasonable Practicable among diagnostic centres within the State is advised.

Author Contribution

Fredrick O. AdeyemiDepartment of Physical Science, Olusegun Agagu University of Science and Technology, Okitipupa, Ondo State, NigeriaCorrespondence author e-mail address: [email protected]; [email protected] of the author: FOA conceived and wrote the article, reviewed and edited it and equally analyzed the data. So, I single-handedly, as an author, agreed to the published version of the manuscript. So, I declare that your journal should proceed with its publication in the immediate next version for the year, 2024.AcknowledgementsThe authors would like to thank the radiology Dept. staff of the hospital for their cooperation and permission during sample collection. God bless you all.

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Radiation Dose and Effective Risk Assessments in Adult Patient from a Common Radiological Procedure: A Comparative Study

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1.0 Introduction

2.0 Materials and Methods

2.1 Study area

2.2 Study sample and sampling technique

2.3 Patient dose assessment

3.0 Results and Discussion

4.0 Conclusion

Declarations

Author Contribution

References

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