1. To learn how occupational dose limits have been established by ICRP to reduce the probability of stochastic effects.
2. To appreciate the order of magnitude of additional risk of cancer induced by occupational exposures.
3. To understand how these risks should be properly communicated to workers.
Starting with a short overview of the development of occupational dose limits, this presentation will concentrate on the quantitative estimation of the risk of radiation-induced occupational cancer. While facts are often statistically solid in the higher dose range, below around 50 mSv of effective dose the linear-no-threshold (LNT) model of dose-risk relation has been questioned by a number of radiobiological studies; existing epidemiological data, due to limited power, do not differentiate between LNT, non-linear and threshold-based models. In other words, the LNT model might either overestimate or underestimate the risk. Furthermore, even for the same physical dose the gender, age at exposure, the temporal distribution of exposure, whole-body vs regional exposure, and individual radiosensitivity will modify the biological impact and, thus, the cancer risk. Known and unknown influences of these modifications will be discussed. Despite open questions, enough facts are established to give the exposed workers clear rules to protect themselves. The communication, therefore, has to show known and disputed risks and to clarify that a medical worker (above all an interventional radiologist) can avoid a lot of unnecessary exposure and reduce the risk to a low, tolerable level by his/her behaviour and skills that are based on a solid training, and the proper use of technical options of the equipment as well as of protective devices. In conclusion, while professional exposure to ionising radiation asks for our respect and a continuous ALARA culture, nonspecific fear of cancer is not justified.
1. To become familiar with published data on lens opacities among interventionalists.
2. To discuss current methods for monitoring of eye lens doses.
3. To learn how effectively lead glasses protect the eyes of interventional radiologists.
Several recent studies have shown a significant association between long-term exposure to low-dose radiation and increased risk of cataract formation. It is evident that the eye lens is more radiosensitive than previously estimated and thus protection of the eyes of occupationally exposed personnel is very important. Radiation-induced opacities and cataracts may take years or decades to develop. It is not entirely clear whether radiation-induced cataracts are stochastic or deterministic effects. However, it is known today that cataracts can occur after receiving radiation doses as low as 0.5 Gy. For this reason, the International Commission on Radiological Protection (ICRP) has accepted the dose threshold of 0.5 Gy for radiation-induced cataracts. The equivalent dose limit for the lens of the eye for occupational exposure has been reduced from 150 mSv per year to 20 mSv per year averaged over defined periods of 5 years, with no annual dose in a single year exceeding 50 mSv. Interventional radiologists may reach cumulative lens doses that put them at risk for developing cataracts. Eye lens dose monitoring methods will be presented and discussed. To keep lens doses as low as possible, exposed personnel must use radio-protective glasses.
1. To learn which technical factors contribute to occupational exposures from interventional radiology procedures.
2. To appreciate that optimisation of a patient's exposure is a way to also reduce occupational exposure.
3. To understand additional means to reduce the occupational exposures.
The occupational dose of the Operator in fluoroscopically guided interventions can be assessed by personal dosimetry using thermoluminescence Dosimeters and real-time dosimetry. Personal dosimetry is a very reliable tool to measure personal dose but suffers from the fact that the operator gets the dose information with a time delay of weeks or sometimes even months. Real-time dosimetry is less accurate but provides real-time dose data. Thus, the operator gets immediate feedback on dose rate and how the dose rate changes if certain protective measures are put in place. Real-time dosimetry is, therefore, very important for individual radiation protection and optimisation. Occupational exposure arises mainly from scattered radiation from the patient and the angiographic Equipment. Scattered Radiation is undirected. Thus, radiation protection equipment has to be used to protect the operator. The most important tools are aprons, neck collars, lead glass shields and curtains as well as lead glass goggles. Operators have to be trained how to apply these protective measures most effectively and that they have to be used in every procedure. In addition, decreasing dose to the patient using dose optimised angiographic protocols is another important step to decrease dose to the operator.
1. To learn which personal protective equipment is needed for specific radiological practices.
2. To become familiar with occupational dose reduction provided by personal protective equipment.
3. To understand that a correct selection, use and periodic check of personal protective equipment are needed to ensure radiation protection of healthcare personnel.
Workers can be exposed to significant scatter radiation during fluoroscopically guided interventions. Radiation-attenuating personal protective equipment (PPE) includes aprons to protect radiosensitive body organs, glasses to prevent cataract development, thyroid collars to protect a radiosensitive organ, lead equivalent surgical gloves and caps to reduce hands and head exposure. PPE can afford very different degrees of protection of different parts of the body during fluoroscopy and interventional radiology procedures. The concept of dose reduction factors (DRFs), equal to the ratio of the dose to the part of the body with no PPE, divided by that when PPE are worn will be introduced. The typical DRFs provided by the different PPE (Body, Thyroid, Eye lenses, Head, Extremities) will be reviewed. The need of wearing specific PPE will be discussed for the interventionalists, nurses and radiographers. Each worker involved in fluoroscopically guided interventions should wear garments that are appropriately protective for that individual's practice. Review of past personal dosimetry results and consultation with a medical physicist should guide this choice.