Xray Physics Flashcards by TanMan Magee

a unit of ionizing radiation that is 99% heat and 1% diagnostic

roentgen ( xray photon)

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REM

roentgen equivalent in man (tech dose)

5 REMs is safe dose per year

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MPD

maximal permissable dose (badges)

number of REMs a person can get in a lifetime without getting radiation poisoning

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RAD

roentgen absorbed dose (in anything)

used to identify radiation in patients
measures radiation being absorbed

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what are the different forms of primary radiation

bremsstrahlung
and
characteristic

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which primary radiation comprises the most photons and interacts with the NUCLEUS of the cell

bremsstrahlung

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which primary radiation contains the most energy and interacts with the INNER SHELL of the cell and an outer shell electron fills its spot

characteristic

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what are the different forms of secondary radiation

Compton
and
thompson

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which secondary radiation interacts with the OUTER SHELL and LOSES energy

Compton

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which secondary radiation has EQUAL energy exchange within the cell

Thompson

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which form of radiation is also called classical

Thompson

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filters are made up of what

aluminum

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grids are made up of what

lead strips

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what supports the emulsion with silver bromide and halide crystals

film base

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what light is considered safe for X-ray use

red light

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what is the X-ray process

develop
fix
wash
dry

(DFWD)
don’t forget wash/dry

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what tissues are most radiosensitive (mutate)

blood (WBC) , sperm

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what tissues are least sensitive (death)

nerve, thyroid, ovaries

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what does the developer do

brings out the latent image by developing the exposed silver halide crystals to metallic silver

reduces the amount of exposed silver crystals

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what does the fixer do

neutralizes developer
removes unexposed crystals
hardens the image

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brown or greasy discoloration to film is caused by what

poor washing

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brown or yellow film is caused by what

old developer

“old yeller”

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if film is unexposed and developed it will be __

translucent

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if film is exposed and developed it will be __

black

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spider appearance on the film is caused by what

static

small dots on the film are caused by what

water droplets

corner clipped off on the film is caused by what

copy of film

vertical lines on the film are caused by what

dirty rollers or static grid

scratchy border around the film is caused by what

old screen

contrast = ?

kvp

density = ?

mas

quality of X-rays is

kvp

quantity of X-rays is

mas

darkness of the film is controlled by

mas

if you change 15% of kvp, you must change mas by

30-50%

what is the inverse square law

the dose is proportional to the inverse of the square of the radius. Thus if you double the distance you reduce the dose by a factor of four FFD to mas

shades of the film are controlled by

kvp

what is the total amount of filtration

2.5 mm

what does SID, FFD and OFD mean

source image distance film focal distance object film distance

increased detail on film is noted with what

``` increase FFD decrease OFD umbra small crystals small focal spot ```

decreased detail on film is noted with what

``` decreased FFD increase OFD penumbra large crystals large focal spot ```

what is in the emulsion in the film

silver bromide and halide crystals

the protective housing of the xray tube is made of what

lead

cathode is positive or negative charge anode is positive or negative charge

cathode - neg anode - pos

what does the cathode consist of

large filament small filament focusing cup

what serves as the source of electrons in the production of X-rays

filament

filaments are made of what

tungesten

what occurs when a current is applied to the filament

thermionic emission

what is part of the cathode that encases the two filaments

focusing cup

where does thermionic emission occur

focusing cup

electrons move from __ to __ in the xray tube

cathode to anode

why does the anode rotate

dissipate heat

the focal spot on the anode is determined by what

size of filament

what is the line focus principle

makes the focal spot size appear smaller decreases the target angle which decreases the spot

what heats the filament causing a boiling off of electrons

it takes a minimum change of mas by ___% to see minimum change in density on the film

30%

if mas is doubled then the density is ___

doubled

what is the force applied to accelerate electrons from cathode to anode

KVP

low kVP means __ energy and __ penetration

low energy | weak penetration

what is the difference in density between to structures

contrast

what controls contrast

KVP

increase in KVP causes a __ in contrast

decrease

low KVP produces __ scatter and __ radiation to the patient

decreased scatter | increased radiation

what is another term for low contrast

long scale

to lower contrast, (__ scale of contrast)(more shades of __) you must do what

long scale more shades of grey increase KVP by 15% and decrease MAS by 50%

to raise contrast, (__ scale of contrast)(more shades of __) you must do what

short scale more shade of black and white decrease KVP by 15% and increase MAS by 100%

what is the 15% rule

increase in KVP by 15% doubles the density | decrease in KVP by 15% will cut density in half

what mainly controls density

MAS

what is the anode heel effect

rotating anode is angled that produces varying intensity of x-rays intensity and density decreases on anode side of film place thinner portion of what is being xray toward this end (example: you would place the anode end of the xray tube towards the toes and cathode end towards the ankles)

what is the inverse square law

intensity is inversely related to square of FFD 40 inch FFD is doubled to 80 in FFD, so intensity is 1/4 this means we must increase MAS by 4 times 80 inch FFD is reduced to 40 in FFD, so intensity is 4x this means we must reduce MAS by 1/4

what makes up the intensifying screens? why is this important what is the intensifying screens job

fluorescent crystals small crystals - less light - lower contrast large crystals - more light - more contrast increases density by intensifying xray photons converts xray photons to visible light

what is the picture made by the useful beam

umbra

what are the blurry halo parts of the image

penumbra

how do we decrease penumbra

increase FFD decrease OFD small filament small focal spot

scatter can be reduced by what 4 things

grids air gap technique collimators filters

what is the proper grid ratio

12:1

what is the best way to reduce scatter

collimation

1 RAD =

1 REM

which primary radiation is majority of useful beam

bremstralung

low energy photon is absorbed by the subject creating a latent image

photoelectric effect

what chemicals are used in the developer

hydroquinone and phenidione

what converts one form of energy to another

transducer

what steps up or steps down the power

transformer

what term is used when a beam of radiation loses energy as it passes through matter

attenuation