Gonadal shielding was introduced into clinical practice over 70 years ago. What about pregnant women? Can’t even a very small amount of radiation harm a fetus? Since shielding can introduce these risks and provides little or no benefit to the patient, we have discontinued using shields as part of routine practice. Many times when a shield is used, there is a risk that it will cover and obscure anatomy that could be important for an accurate diagnosis. Collimation is still critical to ALARA and our current collimation standards will still be upheld.Īdditionally, as with other areas of medicine, the use of patient shielding should be evaluated from a risk-benefit perspective. This is true regardless of the patient’s age, sex, or pregnancy status. These advances have made patient shielding a practice that introduces more risk than benefit. However, some of the features of modern imaging equipment (such as automatic exposure control) do not perform as intended when lead shielding is in the path of the beam. Advances in medical imaging technology, such as better detectors, have greatly reduced the amount of radiation required to create a quality image. The change in practice is due to improvements in imaging technology and a better understanding of how radiation affects the body.
The most comprehensive explanation for this change of practices has been created by the CARES committee of the American Association of Physicists in Medicine. With advances in modern technology and a better understanding of radiation, we are now aware that the practice of lead shielding does not benefit patients. T hese advances in technology and knowledge have made patient shielding a practice that introduces more risk than benefit.
In fact, some of the features of modern imaging equipment do not perform as intended when lead shielding is in the path of the beam. Today's equipment and technology also use much less radiation and operate more efficiently. We now know much more about how radiation affects the human body, and studies have shown that the effects of radiation on fruit flies do not correspond with its effect on humans or other animals. During the past decade, prominent radiology and medical physics experts have researched and reassessed the practice of using lead shields. Patient lead shields were initially recommended during the 1950s when a study on fruit flies prompted concern that radiation might damage DNA and cause birth defects. For a patient, the radiation dose from scatter is a minimal fraction of the dose received from the primary x-ray beam.We are changing a decades-long policy of shielding patients with a lead apron during exams which utilize radiation, including X-rays. This discussion would include possible measurements by the physicist and following proper radiation safety procedures for the worker (protection by time, distance, and shielding). If a radiation worker is concerned about the amount of scatter radiation at any point in an x-ray room, the best solution is to discuss those concerns with the radiation safety officer or the medical physicist at the facility. Scatter radiation dose is much easier to measure than it is to calculate at any given point. This rule simply states that as you double your distance from a source, the radiation dose will drop by one-fourth. If you are interested in knowing the scatter radiation dose at another point along that plane, you would correct the dose at a known point to the point of interest using something called the inverse-square law. A general rule of thumb is that the amount of scatter radiation at 1 meter (m) from the side of the patient will be 0.1% of the intensity of the primary x-ray beam. The amount of scatter radiation at a given location can be determined by performing a measurement with a calibrated survey instrument. In other words, if the x-ray unit is above the patient, the highest scatter radiation at a set distance from the patient will be out to the side of the patient. The maximum scatter radiation occurs perpendicular to the x-ray beam. Scatter radiation is generated in the patient when an x-ray beam strikes the patient.
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