Exam 1 - Image Quality

what are the 3 exposure settings which can be changed to alter the x-ray beam

kVp, mA, seconds

what is the name of the absorption which gives us our 5 radiographic densities

differential absorption

what are the two types of attenuation which are important to us in class

compton scatter

photoelectric effect

The x-ray interacting with the patient represents which form of attenuation

compton scatter

is compton scatter or photoelectric effect the more common interaction

compton (90%)

compton scatter occurs when a photon hits an outer shell electron, this electron then gets ejected, the photon gets deflected, and the photon loses energy. This creates (scatter or absorption?)

scatter

describe the relationship between scatter frequency and kVp

scatter increases with higher kVp due to the higher energy being forced out

Does compton scatter lead to more blacks, whites, or gray?

gray

photoelectric effect occurs when a photon hits the inner shell electron, the electron gets ejected, the photon disappears, and the outer shell electrons fill the hole and give off radiation. This process leads to the photon being (scattered or absorbed?)

absorbed

describe the relationship between photoelectric effect and kVp

increases with decreased kVp because there are lower energy x-rays produced

does the photoelectric effect produce a more white, black, or gray image

white

t/f

a goof image requires both compton scatter and photoelectric effect

true

a higher kVp increases the penetrating power of the x-ray beam, this results in less _____ and more ____ in the tissues which results in an x-ray with (higher or lower?) contrast

absorption, scatter

lower

describe thee relationship between kVp and contrast

inverse

increase one, decrease the other

a high kVp image would produce a low contrast image, this would be helpful for imaging of what structures

soft tissues

a low kVp image would produce a high contrast image, this would be helpful for imaging of what structures

musculoskeletal

WHICH OF THE FOLLOWING IS ASSOCIATED WITH AN ANODE INTERACTION? CHOOSE ALL THAT APPLY

A. Photodisintegration

B. Characteristic radiation

C. Bremsstrahlung radiation

D. Compton

b, c

a,d - patient interactions

WHAT IS THE MOST COMMON X-RAY PRODUCING INTERACTION AT THE ANODE?

A. Brehmsstrahlung

B. Compton

C. Photoelectric

D. Characteristic

a

INCREASING KVP INCREASES GRAY SCALE DUE TO:

A. Increased x-ray interactions and therefore scatter production

B. Decreased x-ray interactions and increased x-ray transmission

C. More x-ray absorption and less x-ray transmission

D. Decreased attenuation of x-rays

a

INCREASING KVP DOES WHAT TO THE X-RAY ENERGY SPECTRUM?

A. Increases the energy of the x-rays produced

B. Decreases the quantity of x-rays produced

a

PHOTOELECTRIC EFFECT IS ASSOCIATED WITH _____ CONSTRAST IMAGE CONTRIBUTION:

A. high

B. low

a

using a grid requires more or less mAs?

more

describe the relationship between mA and contrast

proportional

increase one increases the other

an increased mA will also increase what?

ionizing radiation

what is the Inverse Square Law

increase SID decreases intensity of x-ray beam

if you increase SID by 2x, how much will this decrease the intensity

4x

if you decreased the SID by 1/2x, how much will this increase the intensity

4x

If you move the X-ray tube further from the patient (increase SID), the intensity of the beam decreases (you have less x-rays to work with to produce your image). This would result in _______ of the image. To compensate and maintain the same image density, you need to increase the _____

underexposure, mAs

increasing mAs will do what to exposure

increase

when looking at an x-ray, there are bones floating out in space....does this represent an over or underexposure

overexposed

if your image is overexposed, what would you adjust

decrease mas by 2

a ___% increase in KVP has the same effect as ____ the mAs

15, doubling

mAs only alters film ____ while kVp controls the ____ of photons and the _____ of photons produced which leads to changes in the ____ AND ______

density

frequency, number, contrast, density

increasing kVp by 15% will ____ the density and decreasing it by 15% will __ the density

double, half

what is used to avoid mAs creep

exposure index

what two things is the exposure index dependent on

collimation and central ray

if an image is grainy in appearance, it is most likely over or under exposed?

under

what is the other word for underexposure

quantum mottle

t/f

collimation focuses x-rays

FALSE and she WILL ask this

collimation blocks x-rays to decrease scatter

if you increase collimation, this decreases the number of x-rays hitting the object being x-rayed, what would you need to adjust in order to keep the image quality good

increase mAs

what is the purpose of utilizing grids

reduces post-scatter

what is the recommended grid ratio

12:1