RP Unit 4 test prep

CH. 1, 2, 3, 6, 8, 15, positioning

German scientist _________ ________ ___________discovered X-Rays in the year_______.

Wilhelm Conrad Roentgen; 1895

describe X-Rays

• invisible

• electrically neutral

• travel in straight lines

• fluorescent in certain substances

• can produce scatter radiation

what is scatter radiation also known as

secondary radiationwhat

what are the 3 parts of an atom

1. protons (+)

2. neutrons

3. electrons (-)

where are protons and neutrons located in the atom

in the nucelus

where are electrons located in the atom

in the rings on the outer edges

as the number of protons increase, the number of corresponding electrons _________

increase

as the number of rings increase, does electrical charge increase or decrease

decrease

what metal has the highest melting point of other metals

tungsten

what is frequency

the number of waves passing a given point per unit of time

higher frequency = _______ penetration

more

what does mA stand for

milliamperage

what does kVp stand for

killavolt peak

what is the current

mA is used to measure the electric current that activates the x-ray tube

what is the voltage

speed in which electrons transfer energy along the circuit

what is the time

timer controls the length of time that x-rays are produced

what does rectification ensure

that the current travels in the same direction as a direct current

what kind of animals is a single-phase circuit used for

small animals, birds, lizards

what kind of animals is a three-phase circuit used for

large animals, horses, elephants

what is the filament made of in a x-ray machine

tungsten

what is the first step in the process of taking a radiograph

mA heats the filament to take the electrons from it to produce an electron cloud

cathode

negative side

anode

positive side

2 varieties of anodes

• rotating

• stationary

what is the second step in the process of taking a radiograph

electrons released from the cathode hit the target to break the electrons, producing radiation

what controls how hard the electrons hit the target

kVp

describe the anode heel effect

radiation is more intense on the cathode side

what is Step-Up

volts to kVp, slamming electrons into the target

what is Step-Down

volts to mA, heating the filament (tungsten)

what does pressing the pedal halfway down do

rev the anode, heat the filament

what does pressing the pedal all the way down do

sends cloud to target, takes the radiograph

___% radiation to ___% heat

1% to 99%

changing the kVp level affects what

contrast, quality of the image; inside of the image

how much should you change kVp by at a time

10%-15%

changing the mA level affects what

density, quantity of electrons; degree of blackness

how much should you change mA by at a time

30%-50%

what is Sante’s Rule

2 times thickness + SID (source image distance) + GF (grid factor) = kVp

what is the common source image distance in stationary machines

40 in

what does high contrast show on radiographs

blacks and whites (extremities/bones)

what does low contrast show on a radiograph

many grays (thorax/abdomen)

what kinds of subjects does the contrast level depend on

• thickness

• body part

• bone/muscle/fat ratio

• contrast media

what is collimation

moves around the field of view (etch-a-sketch)

why should we collimate

allows for less scatter radiation

what does ALARA stand for

as low as reasonably achievable

stochasitc effects

occur in your lifetime

deterministic effects

genetic effects

may not show up for 2-3 generations

what thickness of led protects us from scatter radiation

0.5 mm

radiation can affect the cell in 4 ways

1. pass through with no damage

2. repairable damage

3. irreparable damage

4. kills the cells

what is a dosimeter

measures exposure levels

what is the absorbed dose

RAD or Gy amount of radiation absorbed per unit of mass matter

what is the dose equivalent

REM or Sv unit measured by dosimeter

1 Sv = ___ REM

1 mSv = ___ REM

100; 100

T or F; shielding protects you from the direct beam

False

what are the 3 Cardinal Rules

1. reduce time of exposure

2. increase distance between source of radiation and the subject

3. shield or barrier between operator and source of radiation

what is the number 1 issue when taking radiographs

motion of the patient

radiolucent means

cannot see on a film

radiopaque means

can see on a film

what is a part of the machine that helps to absorb scatter radiation

the Grid

ADC

analog to digital converter

CCD

charge-coupled device

CR

computed radiography

DI

digital image

DR

digital radiography

FOV

field of view

HIS

hospital info system

IP

imaging plate

IR

image reciever

Lp/mm

line pairs per mm

PSP

photostimuable phosphor

RIS

radiology info system

ROI

region of interest

TFT

thin-film transistor

what is pixel pitch

center of one pixel to the center of the one next to it

what are the 2 indirect steps

radiation to light to electric

what is the single direct step

radiation to electric

what are artifacts

items that effect how our image looks

if structures are not easily visible, what should you do

increase or decrease kVp by 10%-15%

if the surrounding area is too dark or too light, what should you do

change mAs by 30%-50%