List the 4 cardinal rules of health physics or radiation protection.

Time, Distance, Shielding and Monitor

How does Time effect occupational workers in radiation protection?

Exposure=Exposure rate x time

ex. 22mR/hr x 36min=

225mR/hr x (36min/60hr) =135mR/hr

Keep a large distance as possible between you and the source of radiation. The relationship is inverse square.

*The most effective means of protection for radiographers.

New Intensity=Old distance²

     Old Intensity   new distance ²   

ex. radiation intensity at 90cm is 1.3R/m what would it be at 270cm.

x/1.3R/m =90 ²  

                   270²

what direction does scatter go in?

0.1% (1/1000) of the entrance skin dose

ex. if the entrance skin dose is 820 mR, at 1 meter and at a right angle the intensity is 0.82 mR.

are with a high atomic number like lead Z=82

1. Thickness of material mm of Pb equivalence lead prefered but doesn't have to be the material used.

2. Tenth Value Layer (TVL)-amount of shielding material that will reduce the amount of intensity to 1/10 of the original amount.

How is monitoring involved in radiation protection?

uses a type of monitor to monitor the amount of radiation exposure received. required whenever radiation workers are at risk of receiving 10% or more of the annual total effective dose equiv of 5 REM (50mSv) per year.

1. pocket dosimeter or direct reading dosimeter.

2.Film badge dosimeter

3. Thermoluminescent dosimeter

4. Optically stimulated Luminescent dosimeter

give instantaneous reading of radiation received, reusable. bes used when there is a chance or high radiation. very accurate over short periods of time (day or less)

Disadv.no permenent record of the exposure exists, very fragile if you drop them looses data. charge on electroscope can leak and expensive 150-200 bucks

advantages: inexpensive, 1-4 dollars a month, fairly rugged, easily handling and processing and a permanent record of radiation received.

Disadv: limited range of exposure (10 - 1800mR)

limited k edge 50keV. doesn't record exposures less then 10mR, sensitive to heat and humidity, only be worn 1a month and accuracy is only 50%.

Describe a thermoluminescent dosimeter (TLD) or Tissue Equivalent dosimeter.

Better device to use.

Adv:Very accurate 99.9%, sensitive to wide band of energ, sensitve to wide range of radiatin 1 mR-1000R, small in size and not sensitive to heat and humidity and reusable. can be worn  up to 3 months.nuc med wears ring

Disadv: more expensive 20 bucks

useful or primary beam

leakage radiation

scattered radiation

stray or secondary radiation

radiation that passes through xray tube window and beam limiting device.

What is the most dangerous of radiation to a radiographer?

useful beam or primary beam

90%. Main source are patients

sum of leakage and scatter radiation together.

anything that isn't useful is secondary.

the protective cover over the x ray tube to prevent leakage radiation. must confine leakage radiation to under 100 mR/hour when measured at 1meter. 39.6 inches. close collimators put detectors 1meter away at different areas and measure radiation.

What is xray beam quality? energy,penetrating, hardness of beam.

affected by kVp usad and the amount of Aluminum

a. xray generator using 3 phase = higher ave. energy in beam not like single phase.

b. kVp =higher kVp =high beam energy. type of xray generator controls ave. energy

c. alum. filtration effects ave. energy of the beam. more filtration used at higher kVp

below 50kVp 0.5 mm Al HVL 0.3 mm Al

50-70kVp 1.5 mm Al HVL 1.2 mm Al

above 70 kVp 2.5 mm Al HVL 2.3 mm Al

must be a variable aperature collimator with 5 specifications

within 2% of SID

ex. if at a 40 " SID

40x0.02=0.8" margin of error exsist between the indicated value and the actual value

Light is used for indicating area being exposed.

distance from the illuminator bulb to the mirror must be the same as the distance form the focal spot to the mirror. area of light will be the same as the area hit by x rays

What is the minimum light field illumination

automatic collimation. senors in the bucky that measures size of image receptor and automatically adjusts the field size.

Accuracy 3% of SID.

Describe a controlled area

exposure can be 5mR/hr - 100mR/hr

ex. diagnostic room

radiation exposure greater than 100mR/hr -500R/hr

areas that are occupied by the general public not under the control of a radiatin safety officer.

ex. waiting rooms, offices, hallways.

Receive less then 10mR/hr.

how accurate does the SID indicator have to be?

How does the control panel accomplish indicating kVp, mAs and when the x-ray tube is energized?

by using meters,lights and audible sounds

What is the variation rate reproducibility can't exceed?

What is reciprocity in radiographic equipment?

any increase in mAs should produce the same increase in exposure rate (radiation output).

2 times more mAs should produce 2 times more radiation to be measured.

What is the purpose of the control booth in radiographic equipment?

what happens to the intensity as x ray scatters?

shielding requirement is like a lead shield, 1.5 Pb equivalent or 30% lead by wieght.

The size  must be at least 1 ft ²  and 5 ft from the floor.

What is the maximum tabletop thickness allowed by the FDA?

no more then 1.0 mm Al equivalent.

 they are designed to keep radiation from leaving the main x-ray room.

 types: primary and secondary.

to protect against useful or primary beam of radiation (full strength)

thicker in lead content.

installed perpendicular to the x-ray beam

ex. floor.

protect against secondary or stray radiation

include the control booth walls and ceiling of the x ray room

How does the distance affect the barrier thickness?

What is the occupancy Factor (T) that affect the barrier thickness?

T=1 full occupancy 100%ex. control booth, office, corridors,waiting rooms, darkrooms

T=1/4 occupied by 25% of the time

t=1/16 occasional occupancy.

W=mA minutea/week

about 1000 mA-minure/week is considered a busy room. The busier the room the more shielding required.

use factor (U) U=1the percentage of time that the xray beam is on and directed towards a particular barrier. also known as beam direction factor

U=1 full use-beam is directed all the time . floors, doors, ceilings and walls.

U=1/4 partial use-doors and walls not routinely exposed to the primary beam

U=1/16 occasional use- ceilings of rooms not routinely exposed to the primary beam

Wha is the primary protective barrier in a general purpose radiographic room?

1.6mm Pb eq. (1/16)

when  xray tube is 5-7 ft. from barrier.

must be worn whenever the exposure rate could exceed 5mR/hr.

usually during flouro

composed of lead-impregnated vinyl or rubber.

newer models made of a composite of barium, tungsten, and lead.

what is the percent attenuation at

0.25mm thickness at 50kVp, 75kVp and 100 kVp?

wt in lbs is 3-10 at 50 kVp= 97%

75kVp=66% and 100 kVp=51%

7-12 lbs

50 kVp=99.9%

75kVp=88%

100kVp=76%

13-25 lbs in wt. at 50kVp=99.99%

75kVp=98.7 %

100 kVp= 95 %

minimum 0.25 Pb but preferred is 0.5mm Pb.

is in the tower assembly

FDA limits exposure to less then 2 mR/hr at 10 cm away. about 2.0 mm Pb equivalence

fluoro units equiped with this can reduce exposure up to 90%

rate as beam enter patient.

with ABS(automatic brightness stabilization)

max 10 R/min

without ABS max is 5 R/min

Its a metal flap cover must absorbe 1TVl

absorbs 90% of radiation

radiation comes from under the table and curtain absorbs scatter radiation from patient. must be there during exam and min. of .25 mm Pb equiv.

 and be a min 18x18" in size

what are the same 4 things that mobile equipment has as radiographic equipment.

they have the same leakage 100mR/h

reproducibility 5%, collimator 2% of SID, Linearity and reciprocity 10% margin of error.

What is the SSD in mobile radiography?

SSD has to be 30cm or 12 "

what must indicate the focal spot on mobile equipment?

a mark must be present for the focal spot housing. SID indicator must be within 2%

How much radiation comes from occasional exposure?

Describe radiation therapy.

Use of radiation to treat diseases.

uses radiation hormeis effect-beneficial effect from radiation.

270 kinds.

characterized as uncontrolled growth. spread of abnormal cells

increased amount of chromatin than normal cells

and

increased amount of nucleoplasm to cytoplasm ratio

28% of cancer deaths are from lung cancer.

20 caused by radon gas and 80% caused by smoking

what is the percentage of cancer cure after 5 years?

the earlier you detect the cancer the cure rate goes up.

less then 20% of all cancers caught early are fatal

what are the factors the being cured of cancer depend on.

Squamous cell carcinoma 96%

how is surgery a treatment for cancer?

drugs used to treat cancer

cytotoxins kill poison cell but bad side effects.

what is immunotherapy?

what are the three types of immunotherapy?

gene therapy

vaccines and monoclonal antibodies

what is gene therapy?

called carcinoma. 2 locations of epithelial cancers-

ectoderm epithelial tumor-outside of the body and endoderm epithelial tumor-on the inside of the body.

ectoderm ex. skin cancers and mouth tongue.

endorm ex. breast cancer, thyroid cancer of GI system

connective tissues of the body

called sarcomas

cancers of the lymphatic system

made up of 2 parts

list the 2 parts of mesenchymal tissues .

stroma- made of up normal tissue, support malignant cells, excrete hormones

parenchyma-actual cancer cells that are growing  and dividing.

group 1 cell-viable and actively proliferating

group 2 cell-viable but not actively proliferation

group 3 cell- non-viable but intact morphologically recently dead

group 4 cells- non-viable and non-intact

direct-radiation is directly killing cells. make sure to kill all group 2 cells because of sensitivity.

indirect radiation- to kill tumor radiation destroys tumor bed, nutrients that supply the tumor .

a treatment designed to cure patient of the disease

radiation incorporated into their body tissues.

ex. thyroid cancer-inject or swallow Iodine 131.

tiny seeds of radioactive material implanted into diseased organ or tissue.

ex. cervical cancer

what is external beam therapy or teletherapy?

distance source from body

like cobalt 60, linear accelerator,neutron accelerator, and proton accelerator.

more commonly used. create a bunch of electrons accelerate at a high speed and hit an anode or target.

create xray up to 60 meV

what is neutron accelorator?

similar to a neutron accelorator , goes to a specific depth and stops.

fewer side effects and can be focused more specifically.

uses powerful magnetic fields. transfer of vibrating energy from one system into another.

sends radiowaves.

can be cross sectional and 3D

when a pt. is put in the MRI what happens to its Hydrogen atoms?

they line up with the magnetice field and create radio waves (sent perpendicular to direction of mag. field). H atoms get knocked out of alignment. to get back to alignment use energy to so. energy released is RF (which is used for imaging)

when H atoms are spining on its axis. term is precussion.

 relaxation when atoms line up or when wobbling stops. T-1 time it takes to realign back with main magnet.

T-2 time it takes precussion to stop.

supplies main mag. field. superconductive electromagnet

can conduct with no resistance.