Radiation dose to multidisciplinary staff members during complex interventional procedures

Introduction: Complex interventional radiology procedures involve extensive ﬂ uoroscopy and image acquisition while staff are in-room. Monitoring occupational radiation dose is crucial in optimization. The purpose was to determine radiation doses received by staff involved in complex interventional procedures performed in a dedicated vascular or neuro intervention room. Methods: Individual real-time radiation dose for all staff involved in vascular and neuro-interventional procedures in adult patients was recorded over a one-year period using wireless electronic dosimeters attached to the apron thyroid shield. A reference dosimeter was attached to the C-arm near the tube housing to measure scattered, unshielded radiation. Radiology staff carried shoulder thermo-luminescent dosimeters with monthly read-out to monitor dose over time. Results: Occupational radiation dose was measured in 99 interventional procedures. In many cases prostate artery embolization procedures exposed radiologists to high radiation doses with a median of 15.0 m Sv and a very large spread, i.e. 0.2 e 152.5 m Sv. In all procedures except uterine ﬁ broid embolization radiographers were exposed to lower doses than those of radiologists, with endovascular aortic repair being the procedure with highest median exposure to assisting radiographers, i.e. 2.2 m Sv ranging from 0.1 to 36.1 m Sv. Median radiation dose for the reference dosimeter was 670 m Gy while median staff dose for all procedures combined was 3.2 m Gy. Conclusion: Radiation doses for multiple staff were determined and the ratio between staff dose and reference dosimeter indicated proper use of shielding in general. Some high-dose procedures may need further optimization for certain staff members, especially those not primarily employed in radiology. Implications for practice: The study provides benchmark doses that may be used widely in audits and in the ongoing effort to optimize radiation protection for staff in interventional radiology. © 2024 The Author(s). Published by Elsevier Ltd on behalf of The College of Radiographers. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).


Introduction
The number of interventional radiology (IR) procedures is rising 1,2 and the length of fluoroscopy guided procedures involves high risk of occupational radiation exposure. 3Complex procedures involving multidisciplinary team efforts, such as endovascular aortic repair (EVAR), embolization treatment and transjugular intrahepatic portosystemic shunt (TIPS) procedures require extensive fluoroscopy and intra-operative image acquisition, sometimes using oblique views where protective lead shielding may be suboptimal. 4Even though the radiation doses received by staff is much lower than those of the patients, the cumulative dose to staff may be substantial over time. 5Therefore, interventional radiologists, radiographers and other staff involved face a higher cancer burden and increased risk of cataract and/or opacities in the eye lenses.6e8 Considerable variation in occupational exposure has been observed suggesting that radiation protection practice can be improved, this with the inclusion of additional lead-shielding both on the patient and freestanding in the room. 1,9,10Furthermore studies suggest, that complex procedures completed without protection of extra lead shields might lead to operators exceeding the recommended maximum annual eye lens radiation dose. 11,12revious studies assessed radiation dose to the main operators during EVAR in a hybrid room setting, but only few also accesses dose for floor radiographers and anesthetic staff who often sit in a potentially more exposed place close to the patient. 2,11,13A study assessing radiation dose to anesthetists during prostatic embolization revealed that eye doses may exceed 500 mSv with one weekly procedure. 14Relatively high occupational doses during TIPS was previously reported, 15e17 but no studies focused on other than radiologist dose and most studies are of older date supposedly using less advanced, less dose efficient equipment.Regarding trans-arterial chemoembolization (TACE), only one study of older date (2006) and thus supposedly not comparable to current equipment was identified. 18he purpose of this prospective evaluation was to determine radiation doses received by staff involved in complex interventional procedures performed in a dedicated vascular or neuro intervention room.

Methods
Ethical approval for this prospective, observational single-center study was waived by The Regional Committees on Health Research Ethics for Southern Denmark (Journal No. S-20232000e132).
Before each procedure verbal consent was obtained from all staff involved.
We prospectively measured personal real-time radiation dose for all staff involved in vascular and neuro-interventional procedures in adult patients, i.e. radiologists, radiographers, vascular surgeons, surgical and anesthetic nurses, and occasionally a gastro-enterologist.Radiation dose was recorded using Raysafe I2 wireless electronic personal dosimeters (EPD) (Fluke Medical, Cleveland, US).Dosimeters were attached to the apron thyroid shield, i.e. above the apron to obtain an estimate of the eye lens dose. 3The reliability of the dosimeter in terms of angular dependence, linearity, dose-rate dependence and reproducibility was proven by Inaba et al. (2014). 19Before each procedure the dosimeter equipment was reset.Radiation dose was measured for all involved staff who were blinded to the dose measurements during procedures.Mobile phones were kept away from the dosimeters to avoid interference.Furthermore, Radiologists and radiographers carried shoulder thermo-luminescence (TLD) dosimeters which were routinely read-out monthly.Data collection was done during April 2022 to February 2023 and included the following procedures:
Scattered radiation was measured using a reference dosimeter attached to the C-arm near the X-ray tube housing as recommended by af Vano et al. (2020). 3taff were allowed to add and adjust radiation protection devices such as lead glass walls and screens, lead curtains, soft radiation protection pads etc. as they saw fit.

Statistics
All results are presented descriptively using median, interquartile range (IQR) and min/max value.Relative exposure was determined as personal dose percentage of unshielded procedural DAP and correlation between personal dose and dose area product was assessed using linear regression analysis.Observations with dosimeter read-out ¼ 0 mSv were interpreted as dosimeter failure and were treated as missing.Statistical analysis was performed using STATA BE/17 (Statacorp, Texas, US).

Results
Occupational radiation dose was measured in 99 interventional procedures.In many cases prostate artery embolization procedures exposed radiologists to high radiation doses with a median of 15.0 mSv with a very large spread, i.e. 0.2e152.5 mSv.In all procedures except uterine fibroid embolization radiographers were exposed to lower doses than those of radiologists, with EVAR being the procedure with highest median exposure to assisting radiographers, i.e. 2.2 mSv ranging from 0.1 to 36.1 mSv.An overview of procedures and involved staff is presented in Table 1.
Median procedure time, fluoroscopy time and Dose Area Product for each procedure is presented in Table 2.
Median radiation dose for the reference dosimeter was 670 mGy while median staff dose for all procedures combined was 3.2 mGy; i.e. <1 % indicating proper use of shielding in general.Overall staff dose and procedural DAP as measured by unshielded reference dosimeter were highly correlated; Pearson's r ¼ 0.81, p < 0.0001.
Both groups had a slight negative trend over time with a mean monthly decrease of 0.03 mSv, p ¼ 0.051 for radiologists and 0.04 mSv, p ¼ 0.016 for radiographers (Fig. 1).

Discussion
In this prospective study we investigated occupational radiation doses to multiple staff during a variety of interventional radiology procedures.
In 2017 Sailer et al. 2 made a comprehensive clinical investigation on staff radiation in vascular interventional practice, which showed median radiation dose (33.4 mSv, range 1.2e614.0)for the operating radiologist measured at chest-high with real-time monitoring during 60 EVAR-procedures.Setup and procedure was comparable to our study, except that the procedures were performed in a hybrid operating theatre where additional shielding was not feasible.20e22 During TIPS procedures the gastro-enterologist stands very close to the radiation field while performing ultrasound and flouroscopy guided needle positioning resulting in very high dose (7.0 mSv).Improved shielding or alternative position should be considered.
Prostate artery embolization procedures exposed radiologists to very high radiation doses with a median of 15.0 mSv and a very large spread, i.e. 0.2e152.5 mSv.The procedure often encompasses difficult micro-catheter positioning resulting in elongated procedure and fluoroscopy time as indicated in a median fluoroscopy time of 42.2 min similar to that of neuro-intervention procedures that also encompass micro-catheter positioning.
Similarly, a large spread in neuro-radiology procedures partly caused by diversity of included procedures, i.e. arterio-venous malformation embolization (n ¼ 2), aneurism coil procedures (n ¼ 11), aneurism embolization (n ¼ 4), spinal angio (n ¼ 1), carotid stenting (n ¼ 1) and thrombectomy (n ¼ 1).The equipment used for other than neuro-interventions was equipped with vendor-specific protocols shown to reduce radiation dose. 23The lack of such protocols in the neuro-intervention suite may explain the relatively high DAP-values in neuro-procedures.
In all procedures except uterine fibroid embolization assisting radiographers were exposed to lower doses than radiologists, with EVAR being the procedure with highest median exposure to the assisting radiographer, i.e. 2.2 mSv ranging from 0.1 to 36.1 mSv.In EVAR procedures the collimated field is quite large compared with the remainder and probably the radiographer cannot to the same degree seek shielding behind the radiologist during fluoroscopy and image acquisition, which can occur even though it may not be viewed as best practice.During EVAR anesthetic nurses reached median dose higher than that of radiographers and occasionally reached a single-procedure dose almost twice as high as the maximum dose to the radiologist, i.e. 89.6 versus 57.8 mSv.The anesthetic nurse sits near the patient's head and may in some cases not have used additional shielding.This should be explored further in order to improve radiation protection for this group who does not have main responsibility for local staff safety.
A strong correlation between the overall staff dose and procedural DAP was demonstrated indicating that the protective measures were used consistently, as inconsistent use would have affected the ratio between staff dose and the reference dosimeter.
The overall dose as measured by TLD shoulder dosimeters showed a slight negative trend over the study period.Though only statistically significant for radiographers, the trend may be caused by increased awareness of radiation protection as a result of participation in the study.
The study has a few limitations.The actual position of each staff member was not recorded and thus dose differences caused by different distance to the patient could not be further explored.However, as demonstrated by Dorman et al. (2023)  24 increasing distance from the primary beam is a simple and effective protective measure.
In our study staff were blinded to the dose measurements during procedures.Presenting real-time results using an in-room monitor might be beneficial, 25e27 but this was not possible in our current setup.

Table 1
Median procedural radiation dose in units of mSv, IQR and range for different procedures and staff.

Table 2
Median procedure time, fluoroscopy time and Dose Area Product (DAP) for each procedure.IQR: Inter-Quartile Range.*Dosimeter data missing in one EVAR and one Neuro, thus total n ¼ 97.