why do we wear lead vest during x ray
Titanium is used in aprons as the shielding material instead of lead. Other material used includes bismuth and barium. In evaluating the shielding properties of materials, their mass and linear attenuation coefficient need to be considered. Mass attenuation coefficients for various elements can be found through the
(NIST) Physical Reference Data website. First, consider the amount of material needed to provide the same amount of protection as 0. 5 mm of lead, which is protection provided by many leaded aprons. At 60 keV (6. 0 Г 10 MeV), the mass attenuation coefficient, В/П, of lead is 5. 021 cm. Multiplying by the thickness of 0. 05 cm and the density of lead, 11. 35 g cm, gives 2. 85.
The negative value of this coefficient is the exponent in the basic attenuation equation, I' = Ie -2. 85, where I is the intensity of the unshielded x-ray field and I' is the intensity of the shielded x-ray field. The amount of titanium needed to provide the same amount of shielding as 0. 5 mm of lead can be found by dividing the exponent 2. 85 by the density of titanium, 4. 54 g cm, and dividing by the mass attenuation coefficient of titanium of 60 keV, 0. 7661 cm. The result is 0. 82 cm of titanium. Thus, the thickness of titanium needed to provide the equivalent shielding of lead is 16. 4 times that of lead. This value may be misleading if one considers the weight of the apron.
The ratio of the weight of the titanium apron to a lead apron of the same size can be computed as the ratio of the density times the equivalent shielding thickness, i. e. , (density of titanium) Г 0. 82 cm/(density of lead) Г 0. 05 cm. A titanium apron would weigh about 6. 6 times a lead apron. The real advantage in using titanium is that it is not a hazardous material such as lead. Thus, if you are looking for a reduction in hazardous waste, the titanium aprons may be a good option. Alternate nonhazardous shielding materials include bismuth, as its mass attenuation coefficient for 60 keV photons is greater than that for lead, and it is less dense than lead. The advantage of lead is and will remain that it is inexpensive.
Any test that involves x-rays or radioactive isotopes exposes the people nearby to potentially harmful radiation. This is especially true for doctors, nurses and technicians who work around radiation day in and day out. Think about an interventional cardiologist who evaluates your coronary arteries by performing an angiogram, then does an angioplasty procedure to expand sections of your arteries that are narrowed with built-up atherosclerotic plaque. During these procedures x-rays are used to create pictures of the insides of your arteries and to guide a slender balloon-tipped catheter through your arteries. The special camera used in the catheterization laboratory may be continuously sending out x-rays and taking pictures for 20 minutes or more.
In an entire lifetime, you may have only one angiogram and one angioplasty procedure, if any. But your interventional cardiologist may perform hundreds of procedures a year. That represents a lot of radiation exposure. Lead is very thick and blocks x-rays. That is why radiology technicians routinely step behind lead-containing walls before pushing the button to take a patient s x-ray. Your doctor needs to be by your side during many types of procedures and cannot step behind a protective wall. By wearing a lead apron, your doctor is at least partly shielded from harmful radiation.
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