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Health Physics

QuestionAnswer
Health Physics Provides Radiation Protection for workers and public. (minimizing dose)ALARA
Cardinal Principles Of Radfiation Protection Keep the TIME of radiationn as short as possible, betweeen the source of rad and the person. Maintain as much DISTANCE and Insert SHIELDING material.
Time: Exposure Exposure rate X exposure time. Fluoro time shoulbe be kept at a minimum. Usually controlled by the Dr. The exposure in fluoroscopy does not follow the inverse Square Law because the pt. is an extended source of radiation.
Distance As the distance between the source and Pt./ worker increases, exposure decreases. This is calculted using the Inverse Square Law, except in fuoro.
Point Source Exposure comes from a single spot (in the tube). Scatter from a patient is not a point source until you are sufficient distance away (if the distance from source exceeds 5 X the source diameter)
Isoexposure lines Represents positions of equal radiation exposure in the fluoroscopy room.
Where techs and radiaologists stand during fluoroscopy is about? 300mR/hr. Two steps back is about 5 mR/hr. The inverse Square Law does not apply here.
Shielding Placed between source of rad. and person being exposed. Lead or concrete.
Half Value Layer (HVL) Thickness of the absorber to reduce dose to 1/2 its original value.
Tenth Value Layer (TVL) Thickness of absorber that reduces the radiation intensity to 1/10 its original value. 1 TVL = 3.3 HVL
Values of some protective gear. Aprons = 0.5 mm Pb(lead) = approx. 2 HVLs (should reduce exposure 25%, may be as low as 10%.Curtains = 0.5 mm PbGloves = .25 mm Pb
Dose Limits recommended by NCRP Occupational Exp. dose = Annual 50 mSv (5000mrem)Cumulative = 10 mSv X age (1000 mrem X age)
Equivalent annual dose for tissues and organ for occupational exp. Lens of eye: 150 mSv (15rem)Thyroid, skin, hands, feet = 500 mSv (50rem)
Public dose annually Less than workers; Lens of eye 15 mSv (1500 mrem), Skin, hands and feet = 50 mSv. Gen. Pop.(infrequent exp) = 500mrem/yr., Frequent exp. gen pop. = 1 mSv or 100mrem/yr. under 18= 100mrem/yr, lens, hand, feet 1/10th of occup. DL
Maximum permissible dose (MPD), now called DL (Dose Limit) Dose of radiation that should produce no harmful effects.
During pregnancy, DL =? 500 mrem per pregnancy or no more than 50 mrem / month. This is 1/10 of regular workers.
Risk of death for RT's if DL is recieved every year? 1 in 10,000; same as any occupation.
Patient DL There is no patient DL. Imposssible to track.
Occupational exp. is described as? Dose equivalent. DL are specified as effective dose.
Effective dose Factors in different types of radiation, tissue, radiosensitivity and lead apron.
Pregnant techs !st and 2nd week are all or nothing. Prg. Techs get a second monitor to wear on stomach, under apron.
Fetal dose and the ten day rule Fetal dose = 30 mrem (30% of abd. skin dose)Becoming obsolete the ten day rule was you could expose women of fertile age to exp. up to ten days after start of mentrual cycle.
For pregmant pt.s, the benefit should outweigh the risk we can take what actions to help minimize exp. Collimation, shielding, higher kVp in order to lower mAs.
What is the 10 - 25 Rad Rule? If patient was pregnant and didn't know it, she should contact Dr to determine fetal dose. Below 10, continue pregnancy; Above 25, terminate pregnancy, this depends on social status and beliefs.
Created by: sewwhat4