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Health Physics
| Question | Answer |
|---|---|
| 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
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