Comparative study between radiation exposure in common urological procedures

Background Fluoroscopy has become essential to urological surgery since advancement of endourology. Fluor-oscopy use has increased, placing urologists as well as staff members at risk for occupational radiation exposure and related dangers. This study compared radiation exposure for staff personnel in percutaneous nephrolithotomy (PCNL), ureteroscopy (URS) and extracorporeal shock wave lithotripsy (ESWL). Then, study determined the maximum number of PCNL, URS and ESWL cases that staff members can handle safely each year. Results Radiation exposure in PCNL group was higher than URS and ESWL especially for surgeon. Dose of radiation exposure in ESWL for surgeon, assistant and nurse was 2.4 microsievert (μSv), 0.9 μSv and 0.8 μSv, respectively. Dose of radiation exposure in URS for surgeon, assistant and nurse was 18.5 μSv, 14.3 μSv and 13.1 μSv, respectively. Dose of radiation exposure in PCNL for surgeon, assistant and nurse was 73 μSv, 51.3 μSv and 47.6 μSv, respectively. Conclusion Increased stone size and increased fluoroscopy time were associated with high radiation exposure. PCNL procedure was 8.8 times more likely to exhibit high-dose exposure than other procedures. Urologists can perform: 274 PCNL case, 1081 URS case and 8333 ESWL case per year within safe radiation exposure limits advised by International Commission on Radiation Protection (ICRP).


Background
PCNL, URS and ESWL, currently, considered the first line of management for urinary calculi.Retrograde pyelography (RPG) is an essential part of urology predominantly as a diagnostic procedure and an adjunctive to other urologic interventions such as PCNL, URS and ureteric stenting.This increased use of fluoroscopy has raised the possibility of occupational exposure of the urologist and assisting staff to radiation and its hazards [1].Fluoroscopy utilizes X-rays which are high-energy ionizing radiations.Ionizing radiation enters the human body, causing cellular damage and even cell death due to their energy.Damage amounts vary according to total dose, duration of exposure and site of exposure.Such damage may result in biological consequences that could be stochastic (independent of the dose received) or deterministic (dose-dependent effects) [2].
Direct or indirect radiation exposures are both possible.Direct exposure occurs when a person is directly in contact with radiation rays from the fluoroscopy machine.Indirect exposure occurs from scattered rays resulting from the interaction of the primary beam with the patient who disseminates in all directions [3].
Renal stones can be treated either by ESWL or PCNL.PCNL is an endoscopic surgical intervention for treating large renal calculi more than 2 cm for which ESWL has failed [4].Low morbidity and early return to work are advantages that have popularized PCNL for the treatment of renal calculi [5].
Although ultrasonography has been used to gain renal access in some institutions, in most centers worldwide, PCNL is carried out under fluoroscopy to gain renal access, since it has the benefit of being a single-stage procedure.Fluoroscopy has been used at almost every step of the PCNL.Long use of fluoroscopy for calculus localization and for making the tract to the calculus during PCNL necessitates measuring the radiation dosage for workers and patients [6].
Fluoroscopy predisposes health workers to ionizing radiation.Ongoing efforts have been made to raise the efficacy of fluoroscopy and reduce radiation exposure in surgical centers [7].
Hazards associated with high radiation exposure among medical staff in urology field have received little attention among studies.Providers carry out hundreds to thousands of procedures throughout their careers, raising cumulative radiation dosage to them and probability of stochastic consequences.Adverse effects of radiation exposure, even at low doses, are possible.So recognizing the basic rules of radiation safety is essential for urologists in order to protect both patients and medical professionals [8].

Patients and methods
The study was performed in the urology department of our hospital.Ninety-nine patients undergoing PCNL, URS and ESWL, which done under fluoroscopic guidance divided equally into three groups, were observed during all stages of the procedure, and data on personnel radiation exposure were prospectively obtained for all cases.Dose reported between August 2020 and April 2022.Doses of radiation exposure estimated and recorded for operating room personnel: surgeon, assistant and nurse.The dose of radiation exposure was measured by digital electronic personal dosimeter (DEPD).This study was approved by local ethical committee.
Dose of radiation collected in the form of the cumulative dose.Dose reported for each group separately and categorically divided into: high-dose group and low-dose group utilizing a safe dose threshold of 10 μSv per hour as recommended by ICRP.Predictors of increased radiation exposure more than 10 μSv were determined using multivariate analysis.DEPD applied on outer surface of apron near neck collar.As a conventional measure of radiation exposure prevention, all staffs wore lead aprons throughout every procedure.Data were recorded in surgical report for every patient then compared for PCNL, URS and ESWL.
The medical history was gathered before the procedure plain radiography of the kidney, ureter and bladder (PUT), CBC, physical examinations and noncontractenhanced computed tomography on urinary tract (NCTUT).According to the radiological results, stone characteristics such as stone size, position, hydronephrosis presence or absence and average HU for stone density were recorded.
Three types of dosimeters used: The first dosimeter is DKG-21 PERSONAL GAMMA RADIATION dosimeter (Ecotest CARD, Operating manual BICT.412118.031-02HE.UKraine).The second dosimeter is Dositec dosimeter (Dositec.INC.modelL36.MA.USA).The third dosimeter is direct reading dosimeter named pen dosimeter (Model W 138-S, 0-2 mSV.Arrow Tech.USA), serial number for third dosimeter is TC346964, TC346962 and TC346975.Dosimeters rotated regularly between staff members in different cases in three groups.Following each case, the amount of radiation recorded, and then, the dosimeter is resetted, enabling its reuse for each following case.
Our research utilized single electronic dosimeter device for each person placed on outer surface of apron (0.5-mm equivalent lead thickness) near neck collar.The dosimeter is positioned over the apron at neck collar level.The location typically can be used for estimating lens dose, thyroid dose, chest dose and waist dose but not accurate to measure radiation exposure of another parts of body like extremities.Because of the expectedly greater recorded doses if the dosimeter had been worn at the waist due to the typical radiation scatter pattern, so it worn at the neck collar.
Two multidirectional C-arm fluoroscopic units were used with an over-couch image intensifier and an undercouch X-ray tube (source of radiation waves).The first C-arm fluoroscopic unit was used during ESWL (EMD: NO 1806370 Ostim/Ankara TURKEY).The second C-arm fluoroscopic unit was used during PCNL and URS (Siemens: NO 12791052 Eriangen, Germany).Ureteroscope two types: Karl storz and Wolf, while nephroscope type: Karl storz.The ideal tube voltage and current were automatically set by the fluoroscope using a mode for automatic brightness adjustment.The study's ranges for tube voltage and current were 63-110 kV and 0.9-7.8MA, respectively.
During the fluoroscopic exposures in three groups, the anterior-posterior (AP) projection was mostly used, with some contributions from 30° left-or right-oblique projections, only in PCNL group.Location of each personnel was accurately fixed, distance between personnel and fluoroscopy tube was standardized 80 cm for surgeon, 100 cm for assistant and 150 cm for nurse.Factors which may increase radiation exposure, e.g., decreased distance between staff and tube, excessive tube angulation, continuous X-ray and excessive manipulation, were being avoided.
Variables that affect radiation exposure in each group were reported then compared between three groups.Type of procedure, fluoroscopy time, stone size, HU, K.V and M.A of calculi were correlated with dose.Calculating number of ESWL, URS and PCNL cases can be safely done over the course of a year, with respect for the annual safe permissible radiation dose by ICRP.
Staff personnel investigated every 6 months for TSH, CBC and fundus examination.The duration of the procedure was measured from the initial surgical maneuver such as inserting the cystoscope to the final maneuver such as inserting the catheter.All surgeons received information on their average recorded results after 6 months.Procedures with any missing data excluded from statistical analysis.
The inclusion criteria will be: Age is more than or equal 18 years.Stone density is less than or equal 1000 HU.PCNL for renal stone size is 20-30 mm and renal stone less than 20 mm if failed ESWL.ESWL for renal stone size is less than or equal 20 mm.ESWL for proximal ureteral stone is less than or equal 10 mm.URS for single ureteral stones is more than or equal 10 mm.
The exclusion criteria will be: Stone density is more than 1000 HU.Renal stone size is more than 30 mm.Patient has ureteric or urethral stricture.

Statistical analysis
In order to perform the statistical analysis, SPSS (SPSS Inc., Chicago, Illinois, USA) was used.The analysis of variance test (ANOVA) was used to determine the level of significance between the various exposed groups, for normally distributed data.Data that were not-normally distributed were tested by Shapiro-Wilk test of normality; Kruskal-Wallis test (the nonparametric test of ANOVA) was used, followed by Bonferroni post hoc analysis for pairwise comparison to examine the significance among the studied groups.For categorical data, Chi-square test was used.Differences among means were considered statistically significant at p values ≤ 0.05.
To identify the potential predictors of radiation exposure, univariate analyses with Mann-Whitney U or Chi-squared tests were used (P 0.05).In order to ascertain associations between radiation exposure and the potential predictors, multivariate analysis utilizing binary logistic regression models was then conducted.Significance was set at two-tailed p value of 0.05.Radiation exposure was transformed into a binary variable with ≥ 10 micro-SV, as significant for high exposure; radiation exposure below 10 micro-SV was regarded as low exposure.

Discussion
The dosage of various operating room personnel was measured to compare radiation exposure levels in several spatial areas during different three procedures.It is essential for urologists to know the factors that raise the risk of radiation exposure in order to safeguard themselves against radiation hazards [9,10].
Doses delivered to surgeon 73, 18.5 and 2.4 μSv higher than that for assistant that were 51.3, 14.3 and 0.9 μSv and nurse that were 47.6, 13.1 and 0.8 μSv during PCNL, URS and ESWL, respectively, this is in line with data from studies published by Hellawell, Majid pour, Giblin, Kumari and their colleagues: whom revealed that surgeons were more radiation exposed than assistants and nurses.Surgeon and assistants were exposed to increased radiation exposure more than nurses because of their proximity to the radiation source.Due to participation of assistant in the PCNL procedure as well as in fluoroscopy-guided retrograde passage of ureteric catheter, assisting urologist received more radiation than nurse [11][12][13].
The effect of tube staff distance on radiation dose has been shown by Hellawell and colleagues, who showed that the average space between the surgeon, assistant and nurse and radiation source was about 75, 90 and 150 cm (cm), respectively.So, nurse was exposed to lesser radiation than surgeon and the assistant [12].
Doses delivered to our surgeon, assistant and nurse in PCNL were higher than delivered for them in URS and ESWL, mostly due to increased fluoroscopic time in PCNL than other procedures: due to excessive manipulation to localize urinary tract and increased use of continuous fluoroscopy mode.Otas and colleagues found that using pulse mode rather than continuous mode fluoroscopy significantly decreased total fluoroscopy time and radiation exposure [14].
The scatter radiation experienced during C-arm fluoroscopy, which varies with the arm's rotating direction, is a significant factor in the radiation exposure.When the primary beam tilted 30 degrees, notably in the PCNL group, more dispersed radiation is produced toward the urologist's head than when it is oriented 0 degrees, as in URS and ESWL.Therefore, mean dose for staff personnel is higher in PCNL than URS and ESWL [15].
Angulation of C-arm in PCNL makes source of X-ray above table which called over-couch that makes excessive scattered radiation exposing staff to more dose.Majidpour compares dose for leg (0.1 μSv) that near fluoroscopy beam and for neck (0.01 μSv) found that table decreases scattered radiation 10 times, this study explains excessive angulation increase the radiation exposure in PCNL than ESWL and URS [11].
Our study median dose for surgeon 104.4 μSv in PCNL group was higher than that median dose reported by Wenzler and colleagues that was 40.7 μSv.Our dose for assistant 51.3 μSv and for nurse 47.6 μSv was higher than that reported by Wenzler and colleagues, which were 40.7 and 1.3 μSv, respectively.Cause for increased dose in our study may be due to smaller sample size (33 cases in our study versus 91 cases in Wenzler study).Nurse dose in Wenzler study was very low than our nurse dose who exposed to more scattered radiation waves, because our nurse was closer to source of ionizing radiation than      circulating nurse in operating room in Wenzler study [16].
Mean dose for our surgeon PCNL group was higher than that reported by Safak and colleagues that surgeon dose over apron collar was 12.7 μSv [17].Our mean dose for surgeon was higher than reported by Shrader for urologist that was 24 μSv [18].Mean dose for our surgeon PCNL group was higher than that reported by Jaco and Miller that was 16 μSv for surgeon [19].Mean dose for our surgeon was lower than that reported by Law and colleagues: for surgeon 250 μSv [20].
Dose range reported per URS cases in our study for assistant (0.15-52.2 μSv) was lower than reported by Hellawell and colleagues that was 1.6-180 μSv, but for nurse (0.15-52.2 μSv) was higher than reported in Hellawell study that was 0.4-30 μSv as he reported dose for circulating nurse [12].Annually dose for surgeon in ESWL procedure was 1800 μSv lower than that reported by Baldock and colleagues that was 4800 μSv may be due to decreased awareness of radiation safety and protection in this old study when compared with our recent study that done with more recent fluoroscopic units and recent protective methods [21].
Our study reported that doses were higher than similar studies probably due to highly sensitive and accurate DEPD dosimeter used in our study when compared with thermoluminescent dosimeter (TLD) that used for the estimation of dose in most of these studies [22].
Radiation exposure may also be influenced by the decrease in fluoroscopy time, which was noticeably higher in older research compared to more recent trials.Previously, a single case of PCNL required fluoroscopic guidance for about 20 min; now, it only takes 4-6 min.Our mean total fluoroscopy time in PCNL group was 4.8 min that was very low than reported by Franklin, was 27.8 min per procedure.Our mean total fluoroscopy time was lowest 4.8 min if compared with similar studies like, that reported by Kumari was 6.04 min and that reported by Hellawell 10 min, mostly due to that our study done recently if compared with these oldest studies increased awareness of radiation risks, increased experience in manipulations of procedures, advancements in instruments, techniques and recent C-arm [22].
Our study showed moderate positive correlation between dose and stone size, also positive correlation between dose and fluoroscopy time.This similar to that reported by Tepeler and colleagues, who also observed that the duration of the fluoroscopy considerably increased with the size of the stone [23].
Similar to our study, Mancini and colleagues retrospectively found that: Increased radiation exposure was correlated with larger stones, based on a survey of 96 individuals' radiation exposures that underwent PCNL.The reported data in our study were in line with the previous studies that reported by Wenzler, Cohen, Kumari and their colleagues [3,8,16].
The recommended dose for radiation workers during a 5-year period is 20 mSv for the entire body, according to the (ICRP 60) study.Our urologist can complete 274 PCNL cases, 1081 URS cases and 8333 ESWL cases per year while staying under safe radiation exposure limits which is lower number of PCNL procedures than that is reported by Safak and colleagues 416 (20 mSV/48 μSv) PCNL per year within safe radiation exposure limits [17].
We evaluated the predictors of radiation doses given to staff members during PCNL, URS and ESWL.In our The prospective measurement of radiation exposure, where radiation doses of each staff member were gathered after each case, is a significant strength of this study.In addition, we assessed radiation doses in relation to fluoroscopy time.In order to provide comparative data for the radiation risk of workers at different spatial locations in the operating room during a particular surgery, radiation doses from various operating room personnel, including the surgeon, assistant and nurse, were collected.Another point of strength for this study: It is the first study worldwide in published studies to compare the radiation exposure data between three urological procedures ESWL, URS and PCNL.Most published studies reported radiation exposure data in PCNL only, few studies reported radiation exposure data in URS only.Only two studies reported radiation exposure data in ESWL.Three of these studies compare radiation exposure data between URS and PCNL procedures [22].
This study has also another point of strength: use DEPD dosimeter to measure radiation dose unlike most of other studies use TLD.Our DEPD has more updated recent techniques, accurate, on time reading, highly sensitive and can detect very low doses when compared with (TLD) that used for the estimation of dose in most of these studies.Radiation dose was continuously observed, readed, informed and alarmed by DEPD dosimeter, unlike TLD that must need calibration before being utilized in typical dosimetry.To calibrate TLD, the chips are heated and read in the TLD reader after being subjected to known doses [22].
Our dosimeter has easy and rapid on time reading data unlike, the Instadose ™ device which used in Wenzler study that is only able to read data via: a USB-compatible detector that can be used to read data from a computer after each case.Our DEPD dosimeter has no limits of detection of small doses unlike Instadose TM used by Wenzler study that its lower limit 1 mrem with potential drawbacks in its capacity to quantify radiation doses exactly [16].
Our study is not without limitations.Electronic dosimeter was situated on the external surface of the lead apron, which raises doubts about the beneficial implications of our findings, considering how much radiation really reaches the urologist's skin compared to the anticipated 95% shielded by the lead apron.Fluoroscopic shielding roughly 70-fold cut the urologist's radiation exposure from scatter [13].Modified radiation shields lessen radiation level by an average of 96.1% at a distance of 25 cm and 71.2% at a distance of 50 cm [24].
In addition to the aforementioned limitations, C-arm systems were not standardized across all cases.Another limitation in our study is that study measures dose at neck collar only unlike Majidpour and Safak studies that included measurements for dose at multiple body parts of urologists [11,17].

Conclusion
PCNL procedure, increased stone size and increased fluoroscopy duration were associated with high radiation exposure.PCNL procedure was 8.8 times more likely to exhibit high-dose exposure than other procedures.Staff personals radiation exposure was substantially below the annual maximum permitted limits during urological procedures (20 mSV per year).Regarding our mean radiation dose per procedure of the whole body, urologists can perform: 274 PCNL case, 1081 URS case and 8333 ESWL case per year within safe radiation exposure limits as recommended by ICRP.

Table 1
Gender distribution according to the type of procedure

Table 2
Distribution of the stone side and location according to different procedures

Table 3
Cumulative dose according to the exposed personnel in each procedure

Table 4
Post hoc Bonferroni pairwise comparison of the dose in procedure

Table 5
Association between type of surgery and dose level among staff personnel

Table 6
Intraoperative characteristics according to the procedure

Table 7
Post hoc comparison of the intraoperative characteristics according to the procedure

Table 8
Association between stone characteristics among different procedures

Table 9
Correlation between doses among staff and stone characteristics and fluoroscopic time

Table 10
Perioperative characteristics of the studied patients in each procedure

Table 11
Predictors of high-dose exposure among surgeons