L9 Equipment Specifications PDF

MRD441 Equipment Specifications Attenutation curve and HVL Equipment to Control Distance In case of X-ray equipment operating up to 125 kVp, the control panel can be located in the X-ray room. AERB recommends that the distance between control panel and X-ray unit/chest stand should not...

MRD441 Equipment Specifications Attenutation curve and HVL Equipment to Control Distance In case of X-ray equipment operating up to 125 kVp, the control panel can be located in the X-ray room. AERB recommends that the distance between control panel and X-ray unit/chest stand should not be less than 3 m for general purpose fixed x-ray equipment.  In mobile radiography, where there is no fixed protective control booth, the technologist should remain at least 2 m from the patient, the x-ray tube, and the primary beam during the exposure. In this respect, the ICRP (1982), as well as the NCRP (1989a), recommended that the length of the exposure cord on mobile radiographic units be at least 2 m long Shielding Shielding implies that certain materials (concrete, lead) will attenuate radiation (reduce its intensity) when they are placed between the source of radiation and the exposed individual.  Lead is used as a radiation shielding material as it has a high atomic number (i.e. 82) Atomic number of an element is the number of protons in the nucleus (which is equal to the number of electrons around the nucleus) For the photoelectric process, the mass absorption coefficient increases with the cube of the atomic number (z3)  0.25 mm lead thickness attenuates 66% of the beam at 75kVp 1mm attenuates 99% of the beam at same kVp. It is recommended that for general purpose radiography the minimum thickness of lead equivalent in the protective apparel should be 0.5mm. - Lead aprons: cut exposure by factor of 20 distant scatter: 0.25 mm Pb eq direct involvement: 0.5 mm Pb   ++ Paper Plastic Lead Concrete  Alpha −  − Beta    Gamma and X-rays   Neutron n Four aspects of shielding in diagnostic radiology 1. X-ray tube shielding 2. Room shielding (a) X-ray equipment room shielding (b) Patient waiting room shielding. 3. Personnel shielding 4. Patient shielding (of organs not under investigation) 1) X-ray tube shielding (Source Shielding) The x-ray tube housing is lined with thin sheets of lead because x-rays produced in the tube are scattered in all directions. This shielding is intended to protect both patients and personnel from leakage radiation. Leakage radiation is that created at the X-ray tube anode but not emitted through the x-ray tube portal. Rather, leakage radiation is transmitted through tube housing.  According to AERB recommendations manufacturers of x-ray devices are required to shield the tube housing so as to limit the leakage radiation exposure rate to 0.1 R/ hr at a distance of 1 meter from the tube anode. 2) Room shielding (Structural Shielding) The lead lined walls of Radiology department are referred to as protective barriers because they are designed to protect individuals located outside the X-ray rooms from unwanted radiation.  There are two types of protective barriers. (a) Primary Barrier: is one which is directly struck by the primary or the useful beam. (b) Secondary Barrier: is one which is exposed to secondary radiation either by leakage from X-ray tube or by scattered radiation from the patient. The shielding of X-ray room is influenced by the nature of occupancy of the adjoining area. In this respect two types of areas have been identified. Control Area: Uncontrolled areas: Is defined as the area Are those areas which are routinely occupied by not occupied by radiation workers who occupational workers. are exposed to an For these areas, the occupational dose. shielding should reduce For control area, the the exposure rate to shielding should be such