Eye lens dose correlations with personal dose equivalent and patient exposure in paediatric interventional cardiology performed with a fluoroscopic biplane system

Medical staff dose estimation during pediatric cardiac interventional procedures

The purpose of this study is to evaluate the occupational doses (eye lens, extremities and whole body) in paediatric cardiac interventional and diagnostic catheterization procedures performed in a paediatric reference hospital located in Recife, Pernambuco. For eye lens dosimetry, the results show that the left eye receives a higher dose than the right eye, and there is a small difference between the doses received during diagnostic (D) and therapeutic (T) procedures. The extrapolated annual values for the most exposed eye are close to the annual limit. For doses to the hands, it was observed that in a significant number of procedures (37 out of 45 therapeutic procedures, or 82%) at least one hand of the physician was exposed to the primary beam. During diagnostic procedures, the physician's hand was in the radiation field in 11 of the 17 catheterization procedures (65%). This resulted in a 10-fold increase in dose to the hands. The results underscore the need for optimization of radiation safety and continued efforts to engage staff in a radiation safety culture.

Ratios of Eye Lens and Hand Equivalent Doses with Whole-Body Effective Doses for Operators Performing Interventional Radiological Procedures

ABSTRACT

Estimating radiation doses for operators performing interventional radiological procedures is crucial in the occupational radiation protection of medical staff. In this study, Monte Carlo simulations coupled with an anthropomorphic phantom were used to model various exposure scenarios during the procedures. Conversion coefficients of the dose-area product of x rays for the eye lens equivalent dose, hand equivalent dose, and whole-body effective dose of the operator were calculated. Accordingly, the relationships between these dose quantities in typical interventional configurations were established, considering various source locations, tube voltages, and use of protective equipment or not. The results are presented in a systematic way for easy comparison and use. Tables and figures of the data can be helpful to provide estimates of eye lens and hand equivalent doses when records of specific dosimeters are absent, such as in the retrospective assessment of operators' eye lens and hand equivalent doses in past practices.

The eye lens dose of the interventionalist: Measurement in practice

OBJECTIVE

Early 2018, the new eye lens dose limit of 20 mSv per year for occupational exposure to ionising radiation was implemented in the European Union. Dutch guidelines state that monitoring is compulsory above an expected eye lens dose of 15 mSv/year. In this study we propose a method to investigate whether the eye lens dose of interventionalists would exceed 15 mSv/year and to determine if the eye lens dose can be derived from the regular personal dosimeter measurements.

METHODS

The eye lens dose, Hp(3), of interventional radiologists (n = 2), cardiologists (n = 2) and vascular surgeons (n = 3) in the Máxima Medical Centre, The Netherlands, was measured during six months, using thermoluminescence dosimeters on the forehead. Simultaneously, the surface dose, Hp(0,07), and whole body dose, Hp(10), were measured using regular dosimeters outside the lead skirt at chest level. The dosimeters were simultaneously refreshed every four weeks. The eye lens dose was compared to both the body-worn dosimeter values. Measurements were performed in the angiography suite, Cath lab and hybrid OR.

RESULTS

A clear relation was observed between the two dosimeters: Hp(3) ≈ 0,25 Hp(0,07). The extrapolated year dose for the eye lens did not exceed 15 mSv for any of the interventionalists (average 3 to 10 studies/month).

CONCLUSIONS

The eye lens dose can be monitored indirectly through the regular dosimeter at chest level. Additionally, based on the measurements we conclude that all monitored interventionalists remain below the dose limit and compulsory monitoring limit for the eye lens dose.

Uncertainties in occupational eye lens doses from dosimeters over the apron in interventional practices

It is relevant to estimate the uncertainties in the measurement of eye lens doses from a personal dosimeter over the protective apron without using additional dosimetry near the eyes. Additional dosimetry for interventionists represents a difficulty for routine clinical practice. This study analyses the estimated eye doses from dosimeter values taken at chest level over the apron and their uncertainties. Measurements ofH_p(0.07) using optically stimulated luminescence dosimeters located on the chest over the apron and on the glasses (in the inner and outer part of the protection) were taken from ten interventionalists in a university hospital, in the period 2018-2019 during standard clinical practice. For a total sample of 133 interventional procedures included in our study, the ratio between theH_p(0.07) on the glasses (left-outer side) and on the chest over the apron had an average of 0.74, with quartiles of 0.47, 0.64, 0.88. Statistically significant differences were found among operators using the U-Mann-Whitney test. The average transmission factor for the glasses was 0.30, with quartiles of 0.21, 0.25, and 0.32. Different complexity in the procedures, in the quality of the scatter radiation and in the individual operational practices, involve a relevant dispersion in the results for lens dose estimations from the over apron dosimeter. Lens doses may be between a 64% and an 88% of the over apron dosimeter values (using median or 3rd quartile). The use of 88% may be a conservative approach.

Occupational radiation dose of personnel involved in sentinel node biopsy procedure

INTRODUCTION

Sentinel node biopsy is a procedure used for axillary nodal staging in breast cancer surgery. The process uses radioactive ^99mTc isotope for mapping the sentinel node(s) and all the staff involved in the procedure is potentially exposed to ionizing radiation. The colloid for radiolabelling (antimone-sulphide) with ^99mTc isotope (half-life 6 h) is injected into the patient breast. The injection has activity of 18.5 MBq. The surgeon removes the primary tumor and detects active lymph nodes with gamma detection unit. The tumor as well as the active nodal tissue is transferred to pathologist for the definitive findings. The aim of the study was to measure dose equivalents to extremities and whole body for all staff and suggest practice improvement in order to minimize exposure risk.

MATERIALS AND METHODS

The measurements of the following operational quantities were performed: Hp(10) personal dose equivalent to whole body and Hp(0.07) to extremities for staff as well as ambiental dose for operating theatre and during injection. Hp(0.07) were measured at surgeon's finger by ring thermoluminescent dosimeter (TLD) type MTS-N, and reader RADOS RE2000. Surgeon and nurse were wearing TLD personal dosimeter at the chest level. Anesthesiologist and anesthetist were wearing electronic personal dosimeters, while pathologist was wearing ring TLD while manipulating tissue samples. Electronic dosimeters used were manufactured by Polimaster, type PM1610. All TLD and electronic dosimeters data were reported, including background radiation. Background radiation was also monitored separately. Personal TLDs are standard for this type of personal monitoring, provided by accredited laboratory. Measurements of ambiental dose in workplaces of other staff involved around the patient was performed before the surgery took place, by calibrated survey meters manufactured by Atomtex, type 1667. The study involved two surgeons and one pathologist, two anesthesiologists and three anesthetists during two months period.

RESULTS AND DISCUSSION

The doses received by all staff are evaluated using passive and active personal dosimeters and ambiental dose monitors and practice was improved based on results collected. Average annual whole body dose for all staff involved in the procedure was less than 0.8 mSv. Extremity dose equivalents to surgeon and pathologist were far below the limits set for professionally exposed (surgeon) and for public (pathologist).

CONCLUSIONS

Although has proven to be very safe for all staff, additional measures for radiation protection, in accordance to ALARA principle (As Low As Reasonably Achievable) should be conducted. The recommendations for practice improvement with respect to radiation protection were issued.

ASSESSMENT OF WHOLE BODY, SKIN AND EYE LENS DOSES OF THE INTERVENTIONAL RADIOLOGISTS AT SELECTED HOSPITALS IN IRAN

High radiation doses to the body may lead to the stochastic/deterministic effects of ionizing radiation on the critical organs as well as causing the cataract in eye lens of the clinical staff in interventional radiology. In this study, the received doses of the eyes, skin and whole body of 38 clinical staff including physicians, residents, nurses and radiotechnologists in cardiac angiography departments in three selected hospitals were assessed using personal dosemeters during two bimonthly dosimetry periods. Moreover, the correlation coefficients among the measured dose components including eye lens dose, skin dose and whole body dose equivalent in both area of under and over their lead-apron were calculated for all these occupational groups. The results show that the occupational annual dose values of the clinical staff are below the annual dose limits recommended by International Commission on Radiation Protection. Furthermore, among the measured dose components, the highest correlation coefficient value was obtained between the eye lens dose and personal dose equivalent measured over the lead apron for all the occupational groups.

Occupational doses to the eye lens in pediatric and adult noncardiac interventional radiology procedures

PURPOSE

To assess occupational lens exposure in a mixed interventional radiology department, comparing pediatric and adult procedures. To analyze the correlation between the lens dose and the doses measured at the chest and collar level and the kerma-area product (P_KA ).

METHODS

For 17 months, three radiologists performing both pediatric and adult interventions were monitored by means of 14 dosimeters per worker: 12 single-point optically stimulated luminescent (OSL) dosimeters calibrated in terms of H_p (0.07) were placed on the inside and outside of two pairs of lead glasses, one for pediatric procedures and one for adult interventions; another whole-body OSL dosimeter calibrated in terms of H_p (10) was placed over the thyroid shield; finally, an additional active solid-state dosimeter, also calibrated for H_p (10), was worn on the chest, over the apron. Furthermore, a database was created to register the demographic and dosimetric data of the procedures, as well as the name of the radiologist acting as first operator.

RESULTS

For the three radiologists, who performed 276-338 procedures/year (20% pediatric), cumulative annual doses to the left bare eye exceeded 20 mSv (21-61 mSv). Considering the glasses' protection, annual doses exceeded 6 mSv (13-48 mSv) for both eyes. No important differences were observed in lens dose per procedure between pediatric and adult interventions (0.16 vs 0.18, 0.12 vs 0.09, and 0.07 vs 0.07 mSv), although lens dose per P_KA was 4.1-4.5 times higher in pediatrics (5.8 vs 1.3, 3.3 vs 0.8, and 2.6 vs 0.6 µSv/Gy·cm² ) despite a similar use of the ceiling-suspended screen. Lens doses were highly correlated with collar readings (with Pearson coefficients [r] ranging from 0.86 to 0.98) and with chest readings (with r ranging from 0.75 to 0.93). However, slopes of the linear regressions varied greatly among radiologists.

CONCLUSIONS

There is real risk of exceeding the occupational dose limit to the eye lens in mixed interventional radiology rooms if radiation protection tools are not used properly. Regular monitoring of the lens dose is recommended, given lens exposure might easily exceed 6 mSv/yr. Using a collar dosimeter for this purpose might be suitable if it is preceded by an individualized regression analysis. The same radiation protection measures should be applied to interventional radiologists regardless of whether they are treating pediatric or adult patients.

Eye lens radiation exposure in paediatric interventional treatment of retinoblastoma

Retinoblastoma represents 3% of cancers in children under fifteen years of age. The standard paediatric treatment for saving the affected eye is supraselective intra-arterial chemotherapy performed in interventional rooms. In order to address the radiation toxicity due to the angiography, the aim of this study was to determine the typical dose value corresponding to the procedure, estimate the paediatric patients' eye lens dose and study the relationship between dose indicators and dose to the lens. An automatic dose management software was installed in two interventional rooms to obtain the distribution of the dose indicators kerma-area product and reference-point air kerma, getting a typical value 16 Gy·cm2 and 130 mGy, respectively (n = 35). The eye lens dose estimates were obtained with photoluminescent dosimeters placed on the patient's eyelids. In the left eye, the entrance surface air kerma was 44.23 ± 2.66 mGy, and 12.72 ± 0.89 mGy in the right eye (n = 10). There was a positive correlation between dose to the lens per procedure and dose indicators, with R2 > 0.65 for both eyes. Based on this information, the threshold for the onset of radiation-induce cataracts (500 mGy) will be exceeded if the treatment is performed for more than 8 sessions.

Radiation Dose to the Eye Lens Through Radiological Imaging Procedures at the Surgical Workplace During Trauma Surgery

Background: Due to the drastic reduction of the eye lens dose limit from 150 mSv per year to 20 mSv per year since 2018, the prospective investigation of the estimated dose of the eye lens by radiological imaging procedures at the surgical site during trauma surgery in the daily work process was carried out. This was also necessary because, as experience shows, with changes in surgical techniques, there are also changes in the use of radiological procedures, and thus an up-to-date inventory can provide valuable information for the assessment of occupationally induced radiation exposure of surgical personnel under the current conditions. Methods: The eye lens radiation exposure was measured over three months for five trauma surgeons, four hand surgeons and four surgical assistants with personalized LPS-TLD-TD 07 partial body dosimeters Hp (0.07). A reference dosimeter was deposited at the surgery changing room. The dosimeters were sent to the LPS (Landesanstalt für Personendosimetrie und Strahlenschutzausbildung) measuring institute (National Institute for Personal Dosimetry and Radiation Protection Training, Berlin) for evaluation after 3 months. The duration of the operation, occupation (assistant, surgeon, etc.), type of surgery (procedure, diagnosis), designation of the X-ray unit, total duration of radiation exposure per operation and dose area product per operation were recorded. Results: Both the evaluation of the dosimeters by the trauma surgeons and the evaluation of the dosimeters by the hand surgeons and the surgical assistants revealed no significant radiation exposure of the eye lens in comparison to the respective measured reference dosimeters. Conclusions: Despite the drastic reduction of the eye lens dose limit from 150 mSv per year to 20 mSv per year, the limit for orthopedic, trauma and hand surgery operations is well below the limit in this setting.

RETROSPECTIVE ANALYSIS OF PATIENT RADIATION DOSES IN DIGITAL CORONARY ANGIOGRAPHY AND INTERVENTIONS

This study sought to assess patient and operator eye lens doses in diagnostic coronary angiography (DCA) and percutaneous coronary interventions (PCI) in a University hospital in Oman. Kerma area product (PkA), cumulative air kerma (CAK) and fluoroscopic time (FT) were retrospectively recorded from the DICOM header for 264 patients. The median (interquartile range) of FT, PKA and CAK were: 5.3 min (2.6-10.5), 60.9 Gy cm2 (41.3-91.4) and 0.86 Gy (0.61-1.29), respectively, for DCA procedures, and they were 20.2 min (13.3-30.1), 174.0 Gy cm2 (113.7-253.3) and 2.6 Gy (1.8-3.9), respectively, for PCI procedures. The results revealed wide variability in patient doses among individual patients. Monitoring and recording patient dose data can be valuable for quality assurance and patient safety purposes. Feedback to the operator may help optimize radiation doses to patients and prompt further action, as needed.

The International Atomic Energy Agency action plan on radiation protection of patients and staff in interventional procedures: Achieving change in practice

INTRODUCTION

The International Atomic Energy Agency (IAEA) organized the 3rd international conference on radiation protection (RP) of patients in December 2017. This paper presents the conclusions on the interventional procedures (IP) session.

MATERIAL AND METHODS

The IAEA conference was conducted as a series of plenary sessions followed by various thematic sessions. "Radiation protection of patients and staff in interventional procedures" session keynote speakers presented information on: 1) Risk management of skin injuries, 2) Occupational radiation risks and 3) RP for paediatric patients. Then, a summary of the session-related papers was presented by a rapporteur, followed by an open question-and-answer discussion.

RESULTS

Sixty-seven percent (67%) of papers came from Europe. Forty-four percent (44%) were patient studies, 44% were occupational and 12% were combined studies. Occupational studies were mostly on eye lens dosimetry. The rest were on scattered radiation measurements and dose tracking. The majority of patient studies related to patient exposure with only one study on paediatric patients. Automatic patient dose reporting is considered as a first step for dose optimization. Despite efforts, paediatric IP radiation dose data are still scarce. The keynote speakers outlined recent achievements but also challenges in the field. Forecasting technology, task-specific targeted education from educators familiar with the clinical situation, more accurate estimation of lens doses and improved identification of high-risk professional groups are some of the areas they focused on.

CONCLUSIONS

Manufacturers play an important role in making patients safer. Low dose technologies are still expensive and manufacturers should make these affordable in less resourced countries. Automatic patient dose reporting and real-time skin dose map are important for dose optimization. Clinical audit and better QA processes together with more studies on the impact of lens opacities in clinical practice and on paediatric patients are needed.

Monte Carlo simulation of eye lens dose reduction from CT scan using organ based tube current modulation

PURPOSE

To investigate lens dose reduction with organ based tube current modulation (TCM) using the Monte Carlo method.

METHODS

To calculate lens dose with organ based TCM, 36 pairs of X-ray sources with bowtie filters were placed around the patient head using a projection angle interval of 10° for one rotation of Computed Tomography (CT). Each projection was simulated respectively. Both voxelized and stylized eye models and Chinese reference male phantoms were used in the simulation, and tube voltages 80, 100, 120 and 140 kVp were used.

RESULTS

Dose differences between two eye models were less than 20%, but large variations were observed among dose results from different projections of all tube voltages investigated. Dose results from 0° (AP) directions were 60 times greater than those from 180° (PA) directions, which enables organ based TCM reduce lens doses by more than 47%.

CONCLUSIONS

Organ based TCM may be used to reduce lens doses. Stylized eye models are more anatomically realistic compared with voxelized eye models and are more reliable for dose evaluation.