Lecture 1

Question 1

list some pros and cons of radiographs

Answer 1

good because: cheap, fast, ubiquitos, good at spatial resolution if adjacent

poor because: poor detail due to limitied contrast, radiation risk, bad at spacial resolution if overlapping, need two views

Question 2

briefly describe how a radiograph is generated

Answer 2

a cloud of electrons is formed in the X-ray tube at the cathode, and these elctrons travel across to the anode. the electrons react with the anode to produce X rays, which then radiate out in a cone shape from the focal spot and interact with the patient

Question 3

what can be used to correct how to X rays radiate out from the focal spot at the anode?

Answer 3

collimation and shielding

Question 4

when electrons hit the anode and X rays are produced, what else is produced?

Answer 4

heat (byproduct), and lots of it!

Question 5

how is the heat production at the anode mitigated?

Answer 5

by rotating the anode, or by changing the focal spot size

Question 6

quantity and quality of X rays detected is controlled by many factors. List 4 factors that can change how the image is generated

Answer 6

mAs
kVp
distance
grids

Question 7

explain what kVp and mAs are

Answer 7

kilovoltage peak (kVp): the speed of electrons flowing across the tube, greater speed means greater penetration of X rays, think of a high pressure hose

milliamperage (mA): amount of current flowing through the tube, aka the amount or volume of X rays produced, think of a high volume hose

Question 8

what are “grids” and how do they help produce a radiograph?

Answer 8

the grid sits between the patient and the detector plate, and it’s role is to act like a strainer to reduce scatter radiation and allow for better contrast in the image. sort of like polarizing the scatter radiation/trapping it

Question 9

define contrast

Answer 9

number of shades of grey between black and white

Question 10

high contrast is better for_____ and low contrast is better for ______

Answer 10

MSK (better delineation of bone defects)

thorax (better for soft tissues)

Question 11

how does distance from the focal point impact a radiograph?

Answer 11

for any intensity, it is inversely proportional to the square of the distance, meaning the closer you are, the more Xray beams there are

Question 12

list the 5 different “shades” or densities as tissue types from most dense to least dense

Answer 12

1. metal/contrast media
2. mineral/bone
3. soft tissue/fluid
4. fat
5. air

Question 13

the higher atomic number, the more _______

Answer 13

absorption, creating a whiter image

Question 14

describe what summation is in regards to a radiograph

Answer 14

as multiple tissue types are exposed, the sum total of their density is represented on the radigraph, think of the ven diagram kidneys!

Question 15

explain what a silhouette sign is in regards to radiograph

Answer 15

as similar adjacent tissue types are exposed you are unable to differentiate their edges. in order to see the outline of tissue, it must be surrounded by a tissue of different density

Question 16

what happens if the patient or subject is NOT adjacent to the detector plate?

Answer 16

you get an increase in penumbra or a halo of fuzziness or unsharpness, the edges of the structures will be not nice lol

you also get magnification where the image appears bigger

Question 17

what is distortion?

Answer 17

one part of the patient or subject is closer to the tube than another part so they are “tilted” in a way

Question 18

how does the focal spot size effect the radiograph?

Answer 18

if the focal spot is bigger, it increases “penumbra”, or increasing the fuzziness of the image

Question 19

how does plain film (old radiographs) work?

Answer 19

it is a silver plated photographic film and the X rays deactivate the silver, converting to deposits which persist on the film after processing (dark areas). Unexposed areas lose the silver coating allowing transmission of light (light areas)

Question 20

motion is your worst enemy in regards to radiographs and it is exacerbated by

Answer 20

long exposure times (increase in mAs)

Question 21

long latitude is ____ contrast and short latitude is _____ contrast

Answer 21

low
high

Question 22

what are the two types of digital radiography?

Answer 22

computed radiography and direct radiography

Question 23

list some pros and cons of digital radiography

Answer 23

pros: can decrease exposure, faster more convienient processing, fewer retakes needed, much more detailed image produced

cons: costs more, more complicated, temperature sensitive, environmentally sensitive, difficult to troubleshoot