Radiation protection

LNT

Linear nonthreshold

-No safe exposure amount

-Proportional, as amount goes up effect goes up

As mAs increase what happens to milligray of air?

I1= mAs1

I2= mAs2

As mAs increase so does miligray of air

Equation to remember

mGya / mAs

mAs = mA x time

HISTORICAL FACT

 Clarence Daly-First American fatality from radiation\
 Thomas Edison’s assistant
 Thomas Edison is credited for discovering…..
 Fluoroscopy

Find overall exposure for patient and worker

Exposure = Exposure rate X time

If a certain exam is calculated to have an exposure rate of 2.25 mGya per hour, what is the total exposure per 36 minutes?

 X(exposure) = 2.25 mGya x 36/60 0r 0.6
 x = 1.35mGya

Distance

-As distance increases, radiation intensities to the occupational worker and other personnel decreases
-X-ray tube target is considered a point source of radiation
-Scatter from patient is considered an extended area source
-Isoexposure lines —>

• 5mGya/hr = farthest

• 50 mGya/hr

• 500 mgya/hr = at foot or head of table
  

-exposure areas calculated at waist level
-patient an extended source of radiation bc of scatter

Distance and intensity equation

I1/I2 x (D2/D1)²

Shielding

Thickness or amount of shielding can be estimated if the HVL or TVL of barrier is
known
 TVL= tenth value layer
 1 TVL = 3.3 HVL

Tissue weighting factor

Highest to lowest - As tissue factor increases the sensitive increases

Gonad 0.2

Active bone marrow 0.12

Colon

Lung

Stomach

Bladder 0.05

Breast

Esophagus

Liver

Thyroid

Bone surface 0.01

Skin

Radiologic Terrorism

-Rescue and medical emergencies priority over radiologic concerns

• RED → Radiation exposure device, wont directly expose patient, sealed closed

• RDD→ radiological dispersal device, Release to public, can be exposed, dirty bomb

• IND→ Improvised nuclear device, catastrophic

NCRP

National council on radiation protection and measurements

How much lead in the protective aprons

0.5 mm Pb