Diagnostic Imaging

Question 1

Radiodensity:

Answer 1

• amount of radiation a material absorbs

Question 2

Radio-opaque =

Answer 2

ABSORBS MORE RADIATION

Question 3

Radiolucent =

Answer 3

ABSORBS LESS RADIATION

Question 4

List of materials found in the human body from most radiodense to least radiodense:

Answer 4

• foreign heavy metal (absorbs most radiation)
• enamel
• bone
• water density (muscle, cartilage, blood, etc.)
• fat
• air (absorbs least radiation)

Question 5

The more radiodense an object is, what color does it appear on XR and CT?

Answer 5

• Lighter/whiter

Question 6

What happens to the film as the thickness of the material that the x-ray passes through increases?

Answer 6

• more radiation absorbed
• less radiation reaches film
• object appears lighter/whiter

Question 7

How can you determine if an object is in the front or the back of another object in an XR/CT?

Answer 7

• Cannot tell from a single image.
• Need to take multiple projections.
• Perpendicular projections will give you 3D.

Question 8

Anterior projection acronym and description:

Answer 8

• PA
• Anterior side faces film.
• Posterior side faces XR source.

Question 9

Posterior projection acronym and description:

Answer 9

• AP
• Posterior side faces film.
• Anterior side faces XR source.

Question 10

Left lateral projection description:

Answer 10

• Patients left side faces film.

Question 11

Right lateral projection:

Answer 11

• Patients right side faces film.

Question 12

The four oblique projections:

Answer 12

BASED ON BODY PART CLOSEST TO FILM.
TYPICALLY AT 45°.

1. Left anterior oblique (LAO)
2. Right anterior oblique (RAO)
3. Left posterior oblique (LPO)
4. Right posterior oblique (RPO)

Question 13

How are diagnostic images always read?

Answer 13

• always as if the patient is facing/looking at you.

Question 14

If you are interested in a particular structure, how should the patient be oriented relative to the film?

Answer 14

• With the structure of interest closest to the film.
• Increases resolution of the structure.
  
  • e.g. if you want image of spine, order posterior projection since patients posterior side will be closest to the film.

Question 15

The closer a structure is to a film:

Answer 15

• the higher the resolution.

Question 16

Penumbra effect:

Answer 16

• further an object is from the film, the more blurry the edge will be.

Question 17

Magnification of an object/structure on a film increases:

Answer 17

• the further that object is from the film.

Question 18

How do you minimize the superimposition of structures on a XR/CT film?

Answer 18

• Use oblique projections.

Question 19

How to read a computed tomography (CT) and MRI scans:

Answer 19

• as if you are looking up into a supine patient from the patient’s feet.
• top film = anterior
• bottom film = posterior
• left film = right
• right film = left

Question 20

Label this image:

Answer 20

Question 21

What kind of images do CT and MRI scans take?

Answer 21

• Axial (cross-sectional) images

Question 22

Colors on CT scans (white and black):

Answer 22

• white = radiodense (bone, metal)
• black = radiolucent (fat, air)

Question 23

Colors on MRI scans (white and black):

Answer 23

• white = radiolucent (air, fat)
• black = radiodense (bone, metal)

Question 24

What do MRIs measure?

Answer 24

• Very strong magnet aligns hydrogen atoms.
• Radiofrequency pulse (RF pulse) causes hydrogen atoms to bend.
• RF pulse turned off, hydrogen atoms return to alignment and release energy.
• Amount of energy released is measured.

Question 25

What is ultrasonography good at imaging?

Answer 25

• interfaces between solids and fluids (i.e. embryo in amniotic sac)
• cheap and portable