205 Diagnostic Imaging Midterm 1 & Written Lab Portion

The atomic theory states that _____________ orbit a nucleus that contains ________________ and _______________.

electrons

protons

neutrons

What is meant by the term ionization?

loss of an electron

unstable

creates a positively charged atom (ion)

T or F. Longer wavelength radiation has less energy than short wavelength radiation.

true

T or F. Electromagnetic radiation with higher frequency has less penetrating power through space and matter.

False

What are 4 properties of the electromagnetic radiation of x-rays that are useful in veterinary medicine?

create images on film

can penetrate objects

induce biologic changes

ionize materials

cause of fluorescence

how much of the energy used to produce an x-ray beam is actually lost?

more that 99%

T or F. electrons from the cathode are deflected to the patient by the anode because of the angle of the anode.

false

what parameter must be altered in the process of photon production to change the number of moving electrons?

mA or time

what is the advantage of a rotating anode in the x-ray tube?

it dissipates heat so its not all in one area

increases the size of the focal spot to a track that decreases heat damage

line focus principle

a smaller effective focal spot for a clearer image and a larger focal spot to help preserve the anode can by achieved by angling the anode target

the effects of ionizing radiation exposure are a minor concern for personnel and patients. T or F

FALSE

Off focus radiation creates a shadow like exposure outside of the collimation area by

electrons bouncing off the anode and then returning in a different location

what is the purpose of the collimator on an x-ray machine?

to limit the size of the beam of photons to a specific area

what are the 3 main principles of radiation safety?

time

distance

shielding

what is the MPD for non-pregnant individuals over 18 years old?

0.05 Sv or 50 mSv

4 basic interactions ionizing radiation can have on cells in the body

no damage

irreparable damage

repairable damage

destroy

in order to prevent wearer exposure to ionizing radiation, a dosimeter functions as a photon absorber. T or F

false. it only measures amount of radiation exposure

the primary beam is the most important when it comes to occupational exposure. t or f

false

how do we achieve ALARA ?

protective apparel

mechanical restraint

rotate personnel

use technique chart

increased distance from source

explain how quality of photons in an x-ray beam can be altered

change kVp

the quantity of photons in an x-ray beam can be decreased by

decreasing mA

decreasing time

what is the inverse square law relative to radiation?

the principle that x-ray beam intensity changes relative to distance

name the 5 basic tissue densities in order from least to most which can be seen on a radiograph

air

fat

water

bone

metal

define radiographic density

the degree of blackness of an image/film

3 ways to minimize scatter radiation

beam limiter

grids

filter

Rin Tin Tin has an abdominal thickness of 15 cm. What should the initial kVp setting be on the x-ray machine?

(2 x 15 cm) + 40 = 70 kVp

the measurement of dose equivalent is the REM or Sievert. How many REM in a Sievert?

100

what happens to the image when the screen in a cassette is not in contact with the film?

less clarity, blurry

what is the purpose of a screen in a cassette?

decrease amount of radiation needed to expose the film

how does foreshortening on a radiographic image occur?

the subject is not parallel to the x-ray receptor

radiographic density is the ___________ of film and can be altered by _____________ or _______________

blackness

changing mA or time

what are the requirements for a proper radiograph label?

patient ID

hospital/doctor

must be in image/emulsion

date

a grid is used to eliminate the effects of back scatter on a radiographic image. T or F

false

what effect does a grid have on the primary x-ray beam

it absorbs wanted x-rays as well as unwanted x-rays

it is important to match the screen speed and film speed as well as film color sensitivity with screen fluorescence. T or F

true

____________ and _______________ are 2 aspects critiqued when evaluating the quality of a radiograph

contrast

density

after determining what type of contrast is needed for a particular image, the first question to ask when evaluating a radiograph is?

is it too light or too dark?

after asking is it too light or too dark, the second question is?

is the penetration proper?

is the penetration proper? How do you determine the answer to this question?

if under penetrated or over penetrated

are silhouettes visible?

after an appropriate patient is available, what are the steps for formulating a technique chart?

measure patient thickness of abdomen and calculate starting kVp with sante's rule and grid factor

use highest setting for mA

take radiograph

make adjustments

calculate kVp for rest of areas

calculate mAs based on abdomen

set time so mAs is appropriate for screen/film

name 6 control tests that can be performed for any x-ray machine

9 penny test

screen/film contact

leak test in dark room

SID

perpendicularity

interlock

the mAs should be decreased by 50% in patients with internal effusions. T or F

false

___________________ is considered a disadvantage of digital radiography

interfacing PACS with hospital information system

What does DICOM stand for and what is it?

digital imaging communications in medicine

way to view an image from one system to another and prevent altering

the doctor reviews a radiograph that was just taken and request that it be repeated and it needs more radiographic density. give two methods to increase radiographic density.

increase mA

increase kVp

the lead equivalent in the protective apparel is sufficient to block a limited amount of x-ray photons. What is the lead equivalent and how much protection does it provide from the primary x-ray beam?

0.5 mm lead equivalent

25% protection

explain why it is not acceptable to place a glove or other piece of lead over your hand while you are holding an animal

it does not completely block the primary beam or scatter that comes from under and will hit the hand

gloves must be completely on

the x-ray machine can produce hard copy films and digital images. explain the steps required to obtain a digital image.

position the animal

set SID to cassette tray

switch machine to digital

determine measurements of area being radiographed

machine automatically sets mA, time, mAs and kVp

select species and view

take radiograph

explain process that we use to develop film. include steps that occur inside automatic processor

take cassette from exposed side

place on counter

turn off light and turn on safe light

take film straight up and place on photo imprinter

close until red light comes on

place film in processor until sound changes

in processor developer fixer and wash

refill cassette and place in unexposed box

explain how the starting settings for xray machine are determined when you are creating a technique chart

sante's rule for kVp

mA at highest setting

seconds selected so mAs is appropriate for screen/film

explain what effect tissue density has on a radiographic image

the higher the tissue density the lower the film density will be