Occupational Radiation Protective layers through tearing layers of ignorance

Occupational radiation protection is the need of the hour given the high volume of fluoroscopically guided interventional procedures all over the world. For a similar procedure and dose each interventi onal radiologist/cardiologist can be exposed to varying orders of magnitude. - Dr Dilip Gude

Radiation-associated lens changes in interventional cardiology workers has been on the rise and effective awareness and protection programs help curb the incidence of cataract. There is also known to be a dose dependent increased risk of posterior lens opacities for interventional cardiologists and nurses when radiation protection tools are not used.

Patient radiation doses vary widely among the different interventional cardiology procedures and the differences in levels of exposure of the concluded studies are patien procedure, physician, and fluoroscopic equipment related. Occupational radiation risk is higher in pediatric interventional cardiology as cardiologists need to stay closer to the patient and the use of biplane systems increases scatter radiation.

A study showed that scatter dose rates increase 92 times from low fluoroscopy to cine acquisition with increase in phantom thickness rise from 4 to 20cm. Recommendations for occupational radiation protection suggest that the centers comply with local and national regulations and should also consider the ergonomic detriment caused by personal protective devices. Monthly monitor replacement is recommended for operators conducting interventional procedures to identify practices leading to high personal dose and implementation of work habit changes.

The International Commission on Radiological Protection (ICRP) recommends wearing of two dosimeters one under the apron and one at collar level above the lead apron with hand doses being monitored,using an additional dosimeter. Dose limits set by European Union suggest that the limit for effective dose is 20 mSv per year, average dover defined periods of 5 years and the effective dose not to exceed 50 mSv in any 1 year. Once pregnancy declared additional dose to the embryo/fetus is not supposed to exceed about 1 mSv during the remainder of the pregnancy. Pregnant workers are suggested to have an extra dosimeter under radiation protective garment to detect fetal dose although attenuation by mother’s tissue need to be extrapolated. Scatter from the patient is the most important and significant source of radiation exposure which in turn can be controlled by minimizing patient dose. Shielding can be classified roughly in to architectural shielding, equipment mounted shields, and personal protective devices.

Architectural shielding consists of that built into the walls of the procedure room and the rolling and stationary shields resting on the floor made of transparent leaded plastic. Equipment mounted shield includes protective drapes suspended from the table and from the ceiling. Tablesuspended drapes hang from the side of the patient table, between the under-table X-ray tube and the operator. Ceilingsuspended shields made of a transparent leaded plastic, also help significantly.

Disposable, protective patient drapes made of metallic elements (bismuth or tungsten-antimony) significantly reduce operator dose with reported reductions of 12-fold for the eyes, 26-fold for the thyroid, and 29-fold for the hands. Protective lead aprons with thyroid shields are the main radiation protection tool for in the radiation protection armamentarium. This wraparound style type aprons achieve double thickness a total of 0.5-mm lead-equivalence. Weightless aprons hung from a rolling device and similar aprons on a set of ceiling mounted rails which can be easily donned within seconds provides substantial protection to the wearer and improves ergonomics.

Leaded eyeglasses with large lenses and protective side shields provide more protection and help minimize scatter which approaches the operator from the side and scatter from the operator’s own head. Leaded gloves may spuriously seem useful for radiation protection but not recommended and it is always better to keep them out of the radiation field.

Fluoroscopy needs to be used only to observe objects or structures in motion. The last-image-hold for study or a loop can be reviewed instead of additional fluoroscopic exposure. Virtual collimation feature eliminates the need for Fluoroscopy to determine or adjust collimator blade positioning. Limiting the number of fluorographic images, using variable frame rates specific to the examination as opposed to a constant frame rate also help minimize radiation considerably. Lowfluoroscopydose- rate settings, low-frame-rate pulsed fluoroscopy removal of the anti-scatter grid, spectral beam filtration, and use of increased X-ray beam energy are a few strategies of patient dose reduction technologies. Also with better quality image processing, exposure levels can be decreased as opposed to poorer quality images.

Using anti-scatter grid only when absolutely necessary and use of highly radio-opaque catheter tips also help. Placing the patient as far away as possible from the X-ray tube and the image receptor as close as possible to the patient is another way of reducing radiation. Tighter collimation focusing only the area of interest, using pre-procedure imaging (ultrasound, MRI, CT) to define the relevant anatomy and pathology and to plan the interventional procedure accordingly measures in minimizing radiation exposure. Positioning oneself in a low-scatter area, appropriate training, wearing dosimeters and knowing one’s dose are a few strategies that curb radiation exposure.