principles of radiology exam one

what are the two primary parts of the x-ray tube?

cathode and anode

what is the cathode composed of?

filament and focusing cup

what is the filament made out of ?

tungsten

what is the purpose of the filament?

boil off electrons

what controls the heat of the filament?

mA

if the mA is increased what will happen to the temperature of the filament, the number of electrons produced, and the number of x-rays?

Increase

what is the purpose of the focusing cup?

to condense the electron beam

what is the focusing cup made of?

Molybdenum

what charge does the anode produce?

positive

what are the types of anodes?

stationary and rotating

what is the purpose of the rotating anode?

dissipate heat

what is the anode made of

Tungsten

what do anodes convert and what does it turn into?

kinetic electron; heat and x-rays

When the filament is heated and electrons are emitted what is this called?

thermionic emission

what is thermionic emission controlled by?

mA

potential difference is

The difference in positive charge on the anode and the negative charge on the cathode causing the electrons to driven over the anode at high speed

when electrons hit the anode the energy is converted into?

heat (99.8%) and x-ray (.02%)

the potential difference is controlled by?

KV

quantity or exposure of the x-ray beam is?

the quantity of radiation passing per second through a unit area of the surface perpendicular to the direction of the beam

what is quantity controlled by?

mAs

quality of the x-ray beam is?

the ability of the x-ray beam to penetrate matter

what is quality controlled by?

KV

what happens are the x-ray comes out the x-ray tube and enters the patient?

transmission (passes through), photoelectric (total absorption), and Compton's scatter (partial absorption)

where does the remaining radiation go after the x-ray comes out the tube?

the imaging receptor

what is an imaging receptor?

a device that receives the remaining radiation leaving he patient

what is the result of differential absorption?

image formation

differential absorption

the process whereby a radiographic image is created by variations in absorption and transmission of the exiting x-ray

variations in absorption and transmission represents what?

anatomic structure of interest

creating a radiographic image by differential absorption requires several processes such as

transmission, beam attenuation, and absorption

what is brightness?

amount of light seen on the monitor

no interaction or direct transmission is when

the radiation gets to the IR without interacting with tissue

tissue is what type of material

radiolucent material

it passes through tissue unaffected which makes the tissue?

dark

attenuation

the total reduction in the number of x-ray remaining in the beam after exiting the patient

how does attenuation occur?

through absorption and scatter radiation

the x-ray are absorbed what

photoelectric interaction

in order for photoelectric interaction (total absorption) to occur it depends on

energy of the radiation and the atomic number of the issue

if an area of the body has high x-ray absorption it is called?

radiopaque

what is the source of the majority of the patient's radiation dosage and subject contrast?

total absorption or photoelectric interaction

what is Compton's interaction ?

this is where the radiation changes direction which is also called scatter radiation and partial interaction

what does scatter radiation or partial interaction do to the imaging?

it fogs the imaging

if KV is increased, the amount of scatter will

increase

what direction can the scatter occur in ?

any direction

what is the source of most occupational exposure for techs?

scatter

what affects the intensity of scatter?

KV, collimation, and patient factor like density and thickness

what methods help control scatter radiation?

1. grids

2. beam restriction

3. air gaps

4. compressions

5. compensating filters

why must the x-ray be controlled carefully?

to produce the maximum differential absorption

the composition of the tissues affects x-ray interaction and is determined by:

1. energy of beam

2. tissue thickness

3. atomic number

4. density

what are the 5 major tissues that affect the characteristics of radiation exiting the patient

1. bone

2. muscle

3. fat

4. air

5. alterations in tissue density

what are the types of alterations of tissue density

1. additive pathology

2. destructive pathology

3. positive contrast media

4. negative contrast media

5. medical prosthesis

list the tissue in order of most dense to least dense

1. tooth enamel

2. bones

3. hollow organs (filled)

4. solid organs

5. muscles

6. hollow organs (empty)

7. cartilage

8. fat

9. gas

what is primary radiation?

it is produced in the tube but occurs before entering the patient

how does additive pathology affect tissue density?

it makes it harder to penetrate (ex: tumor)

how does destructive pathology affect tissue density?

easier to penetrate (ex: osteoporosis)

how does positive contrast media affect tissue density?

there is a higher atomic number with the concentrate (ex: barium iodine); attenuation is increased

how does negative contrast media affect tissue density?

air is used for imaging making it easier to penetrate. attenuation will decrease

how does medical prothesis affect tissue density?

it is metal and will make it harder to penetrate.

what is low optical density?

the light areas of a radiograph (heart)

what is high optical density?

the dark areas of a radiograph (lungs)

high tissue density or opacity is?

tissue in which cells are packed tightly together; they would be low optical density

low tissue density or opacity is?

tissue that are loosely packed together; they would be high optical density

remnant radiation is composed of?

scattered and transmitted

bone

atomic number: 14

tissue density: 1.87

interaction: photoelectric

muscle

atomic number: 7.46

tissue density: 1

interaction: photoelectric

fat

atomic number: 5.92

tissue density: .91

interaction: Compton's

air

atomic number: 7.64

tissue density: .0129

interaction: transmission

if tissue thickness increases, what will happen to absorption, attenuation, and transmission?

absorption = increase

attenuation = increase

transmission = decrease

what happens when photoelectric effect increases?

absorption = increase

transmission = decrease

what happens if the atomic number of tissue increases?

absorption = increase

attenuation = increase

transmission = decrease

if tissue density increase, what will happen?

absorption = increase

attenuation = increase

transmission = decrease

what happens when the beam quality (KV) increases?

absorption: decrease

attenuation: decrease

transmission: increase

what controls the speed of electrons?

KV

what controls the penetration of the beam?

KV