X-rays ionize human tissue and deposit energy that can cause harmful changes within the body (break the DNA chain). Additionally, there is a cancer risk from exposure to x-rays. The dose of radiation is cumulative. X-rays are considered carcinogenic. The government is attempting to minimize the use of unnecessary CT scans and x-rays to prevent unnecessary exposure to radiation. It is important for doctors to pay close attention to the risks involved with the use of x-rays. The cancer risk associated with radiation exposure is documented in cases of atomic bomb survivors.
The risk for medical uses is controversial and usually played down by physicians. Radiation at a high level is carcinogenic but, the level of radiation from x-ray exposure is low. The effects of low level radiation is not known.
What is the safe radiation level?
The safe level of radiation is not known.
It is known that CT scans, fluoroscopy, mammography, and x-rays expose the public to high levels of radiation, especially in young females. The risk of exposure should balance the medical benefits.
Optimize radiation doses by only exposing the patient to enough radiation to get a clear image. There is a growing concern about the risk associated with giving a patient large doses of radiation. The use of CT scans has increased recently in adults and children, possibly exposing the patient to an unnecessarily high dose of radiation. A CT scan is often the method used to diagnose cancer, diseases, and fractures, exposing the patient to a much larger dose of radiation than x-rays. Radiation from a CT scan of the pelvis equals the same amount as 100 chest x-rays. Children are ten times more sensitive to radiation than adults. 3-4 million children receive CT scans and about 1,500 of them will develop cancer two decades later. Additionally, children should not be given an adult dose of radiation.
Radiation Dose Limits
A CT scan of the pelvis has the highest level of exposure to the skin, marrow, and gonads. A mini fluoroscopy C-arm should be used whenever possible. Fluoroscopy emits a lot of radiation. The closer the extremity is to the radiation source, the higher the dose of radiation the patient receives. When the distance from the beam increases, the dose of radiation is less. Attempt to decrease exposure time. Radiation intensity follows the inverse square law. It is all about distance!
If the intensity of radiation at 1 meter from the source is 100mR/hr, then the intensity of radiation at 2 meters from the source is ¼ or 25mR/hr in the same unit area. At 3 meters from the source, the intensity of radiation is 1/9 the original or 11.1mR/hr.
Units of Radiation
- Roentgen
- Unit of radiation exposure in the air
- Rad
- Energy absorbed per gram of tissue
- Rem
- Biological effect of a rad
There is less exposure to the physician when imaging a smaller body part. Larger body parts create an increased exposure to the physician when imaging a patient with the C-arm. It is important to not be in the direct path of the radiation beam.
Methods of protection include: monitoring, shielding, and position. A dosimeter badge records how much radiation you have received; however, it does NOT protect you from exposure to radiation. Lead gowns and aprons work to stop exposure to fluoroscopic radiation. Lead aprons attenuate scattered radiation by about 95%. Rapidly dividing cells are most sensitive to radiation exposure and include: sperm, lymphocytes, and cells inside the small intestine and stomach.
Radiation damage seldom appears at the time or irradiation. The first effects of radiation damage is usually seen as a drop in the white blood cell count. The first external sign of damage is usually a skin burn. Studies suggest that people who use fluoroscopy extensively have a higher rate of cataracts.
Early effects of radiation exposure include:
- Death
- Hematologic depression
- Chromosome aberration
- Skin erythema
- Epilation
My recommendations:
A CT scan examination is usually done without justification by most insurances. In my opinion, 1/3 of CT scan studies that are given could be avoided; they are an added cancer risk with no benefit. The CT scan study should be justified. There is no close oversight or uniform standard in place to eliminate radiation exposure, and this is something that should be taken seriously.
Patient education is important. The patient should ask if the study is necessary and what is the lowest dose possible that can be given without compromising the study. Additionally, there should be a universal x-ray bank where patient’s x-rays can be accessed by any medical facility. This would eliminate the unnecessary repeating of x-rays.
In summary, the bone marrow, breast tissue, gonads, and lymphatic tissue are susceptible to radiation induced tumors. It is important to shield the gonads from exposure. Always wear protective equipment such as lead aprons and monitor your radiation exposure with the dosimeter badge.
Dr. Nabil Ebraheim's Blog 