Estimating head and neck tissue dose from x-ray scatter to physicians performing x-ray guided cardiovascular procedures: a phantom study

Estimating brain and eye lens dose for the cardiologist in interventional cardiology-are the dose levels of concern?

OBJECTIVES

To establish conversion coefficients (CCs), between mean absorbed dose to the brain and eye lens of the cardiologist and the air kerma-area product, PKA, for a set of projections in cardiac interventional procedures. Furthermore, by taking clinical data into account, a method to estimate the doses per procedure, or annual dose, is presented.

METHODS

Thermoluminescence dosimeters were used together with anthropomorphic phantoms, simulating a cardiologist performing an interventional cardiac procedure, to estimate the CCs for the brain and eye lens dose for nine standard projections, and change in patient size and x-ray spectrum. Additionally, a single CC has been estimated, accounting for each projections fraction of use in the clinic and associated PKA using clinical data from the dose monitoring system in our hospital.

RESULTS

The maximum CCs for the eye lens and segment of the brain, is 5.47 μGy/Gycm2 (left eye lens) and 1.71 μGy/Gycm2 (left brain segment). The corresponding weighted CCs: are 3.39 μGy/Gycm2 and 0.89 μGy/Gycm2, respectively.

CONCLUSIONS

Conversion coefficients have been established under actual scatter conditions, showing higher doses on the left side of the operator. Using modern interventional x-ray equipment, interventional cardiac procedures will not cause high radiation dose levels to the operator when a ceiling mounted shield is used, otherwise there is a risk that the threshold dose values for cataract will be reached.

ADVANCE IN KNOWLEDGE

In addition to the CCs for the different projections, methods for deriving a single CC per cardiac interventional procedure and dose per year were introduced.

Evaluation of novel radiation protection devices during radiologically guided interventions

BACKGROUND

In radiologically guided interventions, medical practitioners are subjected to radiation exposure, which may lead to radiation-induced diseases. In this study, novel radiation shields for the head and neck were evaluated for their potential to reduce radiation exposure.

METHOD

An anthropomorphic phantom was exposed on its left side to scattered radiation from beneath to simulate the exposure of an operator in a x-ray operating room. Thermoluminescent dosimeters (TLDs) were positioned at different depths in five slices in the phantom, measuring personal dose equivalent. Two different set up situations were evaluated: a head protector designed to reduce radiation in the upper section of the head; and a novel thyroid protector prototype extended in the front and on both sides, designed to reduce radiation in the lower and middle sections of the head. A standard thyroid collar prototype and a ceiling mounted lead glass shield were used as comparisons. Furthermore, the head protector was evaluated in a clinical study in which TLDs were positioned to measure scattered radiation exposure to the heads of operators during endovascular interventions.

RESULTS

The extended thyroid protector reduced the scattered radiation in the throat, chin, and ear slices. Some shielding effect was seen in the brain and skull slices. The head protector showed a shielding effect in the skull slice up to two cm depth where it covered the phantom head. As expected, the ceiling mounted lead glass shield reduced the scattered radiation in all measuring points.

CONCLUSIONS

A ceiling mounted lead glass shield is an effective radiation protection for the head, but in clinical practice, optimal positioning of a ceiling mounted lead shield may not always be possible, particularly during complex cases when radiation protection may be most relevant. Added protection using these novel guards may compliment the shielding effect of the ceiling mounted lead shield. The head protector stand-alone did not provide sufficient protection of the head. The extended thyroid protector stand-alone provided sufficient protection in the lower and middle sections of the head and neck.

Application of liquid scintillation light guide (LSLG) to scattered X-ray measurement from dental panoramic radiography system

A 1.2 m flexible liquid scintillation light guide (LSLG) detector connected to a portable electric device was developed and applied to monitor X-rays scattered from a panoramic dental X-ray imaging apparatus. The X-ray absorption of the LSLG tube was simulated for 20 and 40 keV X-rays. The LSLG detector was calibrated by comparing doses measured by a 3-inch NaI(Tl) detector using Am-241 and Cs-137 sources. A linear relationship was obtained between dose rates (μSv/h) and count rates (cps). The elapsed time profile of scattered radiation from a panoramic dental X-ray imaging apparatus was determined. Local absorbed doses were measured with small OSL dosimeters on the LSLG tube suspended over the shoulder and the eyeglass. Behind the ears and neck (in the center of the LSLG tube) showed high doses. The LSLG detector was useful for real-time monitoring of scattered X-rays.

Modified design of x-ray protective clothing to enhance radiation protection for interventional radiologists

BACKGROUND

In interventional radiology procedures, the operator typically stands on the right side of the patient's right thigh to manipulate devices through the femoral sheath. Because the standard x-ray protective clothing is designed as sleeveless and scatter radiations from the patient are mainly incident from the left-anterior direction to the operator, the arm hole of the clothing may be a significant unprotected area, contributing to an increase in the operator's organ doses and effective dose.

PURPOSE

This study aimed to compare the organ doses and effective dose received by the interventional radiologist when wearing the standard x-ray protective clothing and when wearing the modified clothing with an additional shoulder guard.

METHODS

The experimental setup aimed to simulate actual clinical practice in interventional radiology. The patient phantom was located at the beam center to generate scatter radiation. An adult female anthropomorphic phantom loaded with 126 nanoDots (Landauer Inc., Glenwood, IL) was used to measure organ and effective doses to the operator. The standard wrap-around type x-ray protective clothing offered 0.25-mm lead-equivalent protection, and the frontal overlap area offered 0.50-mm lead-equivalent protection. The shoulder guard was custom-made with a material providing x-ray protection equivalent to lead of 0.50 mm thickness. The organ and effective doses were compared between the operator wearing the standard protective clothing and the one wearing the modified clothing with a shoulder guard.

RESULTS

After adding the shoulder guard, doses to the lungs, bone marrow, and esophagus decreased by 81.9%, 58.6%, and 58.7%, respectively, and the effective dose to the operator decreased by 47.7%.

CONCLUSIONS

Widespread use of modified x-ray protective clothing with shoulder guards can significantly decrease the overall occupational radiation risk in interventional radiology.

Collar badge lens dose equivalent values among U.S. physicians performing fluoroscopically-guided interventional procedures

PURPOSE

To describe the range of occupational badge dose readings and annualized dose records among physicians performing fluoroscopically guided interventional (FGI) procedures using job title information provided by the same three major medical institutions in 2009, 2012, and 2015.

METHODS

The Radiation Safety Office of selected hospitals was contacted to request assistance with identifying physicians in a large commercial dosimetry database. All entries judged to be uninformative of occupational doses to FGI procedures staff were excluded. Monthly and annualized doses were described with univariate statistics and box-and-whisker plots.

RESULTS

The dosimetry dataset of interventional radiology staff contains 169 annual dose records from 77 different physicians and 698 annual dose records from 455 non-physicians. The median annualized lens dose equivalent values among physicians (11.9 mSv; IQR=6.9-20.0) was nearly threefold higher than non-physician medical staff assisting with FGI procedures (4.0 mSv; IQR=1.8-6.7) (P<0.001). During the study period, without eye protection, 25% (23 of 93) of the physician annualized lens dose equivalent values may have exceeded 20 mSv; for non-physician medical staff, this value was may have been exceeded 3.5% (6 of 173) of the time. However, these values do not account for eye protection.

CONCLUSION

The findings from this study highlight the importance of mitigating occupational dose to the eyes of medical staff, particularly physicians, performing or assisting with FGI procedures. Training on radiation protection principles, the use of personal protective equipment, and patient radiation dose management can all help ensure occupational radiation dose is adequately controlled.

Effectiveness of Radiation Protection Caps for Lowering dose to the Brain and the Eye Lenses

PURPOSE

This work was designed to study the effectiveness of radiation protection caps in lowering the dose to the brain and the eye lens during fluoroscopically guided interventions.

MATERIALS AND METHODS

Two types of radiation protection caps were examined with regards to their capacity to lower the radiation dose. One cap is equipped with lateral flaps, the other one is not. These caps were fitted to the head of an anthropomorphic Alderson-Rando (A.-R.) phantom. The phantom was positioned aside an angiographic table simulating the position of the first operator during a peripheral arterial intervention. One of the brain slices and both eyes of the A.-R. phantom were equipped with thermoluminescence dosimeters (TLDs).

RESULTS

The analysis of the data showed that the cap without lateral flaps reduced the dose to the brain by 11,5-27,5 percent depending on the position within the brain. The cap with lateral protection flaps achieved a shielding effect between 44,7 and 78,9 percent. When evaluating the dose to the eye, we did see an increase of dose reduction from 63,3 to 66,5 percent in the left eye and from 45,8 to 46,8 percent in the right eye for the cap without lateral protection. When wearing the cap with lateral protection we observed an increase of dose reduction from 63,4 to 67,2 percent in the left eye and from 45,8 to 50,0 percent in the right eye.

CONCLUSION

Radiation protection caps can be an effective tool to reduce the dose to the brain and the eyes.

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.

Estimating brain radiation dose to the main operator in interventional radiology

The aim of this study was to estimate brain radiation dose to the main operator during interventional radiology procedures. Occupational brain doses from 19 interventional procedures were measured using thermoluminiscent dosimeters and an anthropomorphic RANDO woman phantom simulating a main operator. Results show that, interventional radiologists may receive minimum and maximum brain doses per procedure of 0.01 mGy (left temporal cortex) and 0.08 mGy (temporal lobe cortex), respectively. A radiologist who works without movable shielding devices during procedures and has a typical workload (for example 500 procedures per year), might exceed the new dose threshold of 0.5 Gy for circulatory disease in the brain working 12.6 years of his career.

Occupational eye dose to medical staff in various interventional cardiologic procedures: is the need for lead goggles the same in all groups of radiation workers?

Considering the increased use of interventional cardiologic procedures and concern about irradiation to the eyes, it is necessary to measure eye dose in radiation workers. The assessment of eye dose using collar dose is a routine but inaccurate method. Therefore this study was designed to measure eye dose in the radiation workers of various interventional cardiologic procedures. In this study eye dose was measured for left and right eyes in three groups of radiation workers in angiography ward of Afshar hospital in various procedures using TLD. Measurements were done separately for cardiologists, nurses and radio-technologists in 100 procedures. The nurses functioned as surgical assistants and were usually close to the table. The correlation of staff dose to exposure parameters was also investigated. Eye dose in physicians were higher than other staff in all procedures. Also the left eye dose was considerably higher than right one, especially for physicians. The median equivalent dose per procedure of left eye for physicians, nurses and radio-technologists were 7.4, 3.6, 1.4 µSv (PCI) and 3.2, 3.1, 1.3 µSv (Adhoc) and 3.2, 1.7, 1.1 µSv (CA), respectively. The annual left eye equivalent dose with (without) using lead goggles were 2.4 (15.3), 1.4 (2.2), 1.0 (1.1) mSv for physicians, nurses and radio-technologists, respectively. There were also a positive correlation between eye dose and KAP for procedures without lead goggles. The lead goggles showed lower protection effects for radio-technologists than other staff. Only 30% of physicians received a dose higher than 1/3 of the ICRP annual dose limit, therefor only physician eye dose should be monitored in catheterization labs.

A more accurate and safer method for the measurement of scattered radiation in X-ray examination rooms

Advancements in and increasing usage of complex diagnostic examinations with interventional procedures and surgeries has led to an increase in the occupational radiation doses received by physicians and other medical staff. Measuring the scattered radiation doses received by these staff is vital for the development-effective radiation protection programs. In this study, we measured scattered doses during angiography and digital breast tomosynthesis examinations with small-type dosimeters using our jungle gym (JG) method with measurement points at 50-cm intervals. The results were compared with measurements taken using the conventional ion chamber method. The JG method uses paper pipe tubes and a plastic joint structure and allows measurements at different points inside an examination room. The difference between measurements can be attributed to the radiation absorption characteristics of the components used in the JG method. A maximum radiation dose reduction of 20% was observed due to absorption by the JG components. This effect was smaller than the measurement error produced because of reproducibility issues and other limitations of the conventional method. The conventional measurement has disadvantages that are associated with the reproducibility of measurement points, equipment load, and the radiation exposure experienced by the measurer. The proposed JG method exhibits significant improvements in all these aspects. Furthermore, the measurer does not have to be present in the measurement room; therefore, the JG method is extremely safe and useful for radiation protection.

OPTIMIZATION OF A RADIOPHOTOLUMINESCENT GLASS DOSEMETER FOR OCCUPATIONAL EYE LENS DOSIMETRY IN INTERVENTIONAL RADIOLOGY/CARDIOLOGY

Hospital based workers that perform interventional radiology are at risk of reaching the eye lens dose limit of 20 mSv/y. These workers are exposed to the radiation scattered by the patient, which creates a complex field, with low radiation energy reaching the eyes of the medical staff from wide angles. Therefore, the dosemeter used in the assessment of the eye lens dose of interventional radiologists needs to respond accurately in such conditions. In this study, the angular response of a commercially available radiophotoluminescent glass dosemeter, GD-352M, was optimized via Monte Carlo simulations, aiming at its use as eye lens dosemeter in interventional radiology. The improved dosemeter was manufactured and then characterized in terms of Hp(3), the quantity recommended for eye lens dosimetry. Its response was compared to the IEC 62387:2012 requirements for Hp(3) and to requirements proposed specifically for eye lens dosemeters used in interventional radiology. The improved dosemeter meets the IEC 62387:2012 requirements for energy and angular response for Hp(3) and also shows good agreement with the more strict requisites proposed for eye lens dosemeters to be used in interventional radiology.

Always on My Mind

This article is focused on occupational radiogenic brain tumors and some radioprotective techniques used to manage this risk. Published case reports have stimulated concern among operators. The anatomical pattern of tumor locations is not consistent with measured radiation dose distributions at operators' heads. In addition, the lack of statistically positive findings in these reports, and a recently published survey on radiologist's mortality both indicate that the current level of fluoroscopists' radiation safety practices is likely to be adequate. This presumes that the rules of dose-management, time, distance, and shielding continue to be followed. These are briefly reviewed in this article. The use of radioprotective surgical caps is a current fashion. In clinical practice, these caps provide minimal reductions in brain dose and might induce operators to neglect applying the practical rules mentioned above. Appropriate management of personal, staff, and patient risk should always be on the radiologists' mind.