Radiation Biology Chapter 15

Inverse square law

the intensity of radiation is inversely proportional to the square of the distance from the source

secondary protective barrier 

protects against leakage and scatter radiation

50 mSv

annual occupational effective dose in metric units for whole body exposure during routine operations V

Positive beam limition 

restricts the dimensions of the radiographic beam so that its margins do not extend beyond the IR

Primary protective barrier

prevents direct, or unscattered, radiation from reaching personnel or members of the general public on the other side of the barrier

0.5 mSv

monthly allowable equivalent dose to the embryo-fetus in metric units from occupational exposure of a pregnant technologist

use factor (U)

beam direction factor

1 mSv

annual effective dose (EfD) limit set for individual members of the general public

Workload (W)

specified either in units of mAs per week or milliampere- minutes (mA-min) per week

Bucky slot shielding dose 

During a standard fluoroscopic examination, when the bucky tray is positioned at the foot end of the table, this device automatically covers the bucky slot opening in the side of the x ray table. it protects the radiologist and radiographer at the gonadal level 

lead and concrete

most common materials used for structural protective barriers

Occupancy factor (T)

this is used to modify the shielding requirement for a particular barrier by taking into account the fraction of the work week during which the space beyond the barrier is occupied

Remote control fluoroscopic system 

permits the radiologist and assisting radiographer to remain outside the fluoroscopic room at a control console behind a protective barrier while the x ray beam is on 

High level control

mode of operation in which the exposure rate may significantly exceed the rate used in routine fluoroscopy

Protective curtain

during a fluoroscopic examination, this device should be positioned between the fluoroscopist and the patient to intercept scattered radiation above the tabletop

Control booth barrier 

a permanent protective barrier for the radiographer that is located in an x ray room housing stationary radiographic equipment 

CumEfD limit

a radiation workers whole body lifetime effective dose in mSv should not exceed 10 times the persons age in years

Scatter radiation

all the radiation that arises from interactions of an Xray beam with the atoms of an object in the path of a beam

ALARA concept 

principle that holds that occupational exposure of the radiographer and other occupationally exposed persons should be kept as low as reasonably achievable 

GSD

the average annual gonadal equivalent dose to members of the population who are of childbearing age

Secondary radiation

consists of radiation that has been deflected from the primary beam. this radiation is made up of leakage radiation from the tube housing and scatter primarily from the patient

protective eyeglasses 

glasses with optically clear lenses that contain a minimal lead equivalent protection level of 0.35 

mechanical restraining devices

should be used to immobilize patients during radiographic exposure, whenever possible, instead of people

protective apparel 

special garments that conventionally are made of lead impregnated vinyl and are worn during fluoroscopic and certain radiographic procedures 

C- arm fluoroscopic

a portable device for producing real time images of a patient. this device holds an x ray tube at one end and an image intensifier at the other end