Anatomy 2 - Introduction to Medical Imaging

Question 1

Characteristics of Radiography

Answer 1

• Generate x-rays
• Detect transmitted x-rays (on film or digitally)
• Use radio-opaque contrast such as barium to help visualize structures

Question 2

Characteristics of Fluoroscopy

Answer 2

• Type of radiography
• Real-time imaging, viewed on monitor
• Used for interventional procedures
• Higher doses of radiation

Question 3

Production of X-Rays

Answer 3

Question 4

How do bones, soft tissue, fat, and air look on an x-ray?

Answer 4

• Bone = white (high density)
• Soft tissue = gray
• Fat = dark gray
• Air = black

Question 5

Radiography Benefits

Answer 5

• Low dose and low risk
• Simple, fast, and inexpensive

Question 6

Radiography Drawbacks

Answer 6

• Need 2 or more projections (usually)
• Can’t see behind structures

Question 7

Radiography Contraindications

Answer 7

• Pregnancy

Question 8

How does Computed Tomography work?

Answer 8

• X-ray source (gantry) rotates around patient
• Multple projections
  
  • Hundreds of “films”
  • Ability to see behind structures
  • Digital detector

Question 9

CT Benefits

Answer 9

• Fast scanning with good resolution
  
  • Good for traumas, post-op/unstable patients
• Can see behind structures
• Good bone contrast

Question 10

CT Drawbacks

Answer 10

• Limited soft tissue contrast
• High patient radiation dose

Question 11

CT Use in the United States

Answer 11

• Rapid increase in use since 1970s
• Sharp increse in use due to
  
  • improved CT technology
  • Fast scan times
  • Emergency room use

Question 12

CT Characteristics

Answer 12

• White - denser structures (bone, blood, clot, calcium)
• Dark - less dense structures (air, fat, water)

Question 13

Density on CT is measured in _____

Answer 13

Hounsfield Units (HU)

Question 14

Air on CT: ___HU

Answer 14

-1000

Question 15

Fat on CT: ___HU

Answer 15

-250

Question 16

Water on CT: ___ HU

Answer 16

0

Question 17

White matter on CT: ___HU

Answer 17

20-30

Question 18

Gray matter on CT: ___HU

Answer 18

37-45

Question 19

Blood (in vessel) on CT: ___HU

Answer 19

40

Question 20

Muscle on CT: ___HU

Answer 20

40

Question 21

Blood Clot on CT: ___HU

Answer 21

70

Question 22

Bone on CT: ___HU

Answer 22

1000

Question 23

CT Relative Contraindications

Answer 23

• Pregnancy
• Contrast:
  
  • Low glomerular filtration rate (GFR)
  • Metformin (glucophage)
  • Allergic reaction
  • No IV access

Question 24

Characteristics of Nuclear Medicine (Emission)

Answer 24

• Medications attached to radioactive material (radioisotope)
• Provides information about structure and function
• Gamma camera captures emission image

Question 25

Iodine 123 is a radioisotope used to assess:

Answer 25

Thyroid function

Question 26

Thallium 201 is a radioisotope used to assess:

Answer 26

Cardiac function

Question 27

Gallium 67 is a radioisotope used to assess:

Answer 27

Infection

Question 28

Technetium-99m is a radioisotope used to assess:

Answer 28

Skeleton, heart, brain, lungs, liver, spleen, kidney, gall bladder, infection, parathyroid

Question 29

PET Imaging

Answer 29

* Positron emitter: short half-life * Internal uptake (IV or oral) * Positron annihilates with electron to form 2 photons traveling in opposite directions * Photons interact in tissue and then a detector ring

Question 30

PET Benefits

Answer 30

* More sensitive than transmission imaging * Functional imaging

Question 31

PET Drawbacks

Answer 31

* Limited resolution * Requires CT for anatomy and attenuation correction * Patient dose * Radiotracers are expensive

Question 32

Magnetic Resonance Imaging

Answer 32

* Uses non-ionizing radio frequency * Proton spins to align with external magnetic field * RF pulse tips proton spins by 90 degrees

Question 33

MRI T1,T2 sequence is used to assess:

Answer 33

Structural

Question 34

MRI Spectroscopy Sequence is used to assess:

Answer 34

Metabolites

Question 35

MRI Diffusion Weighted Sequence is used to assess:

Answer 35

Water Motion

Question 36

MRI Susceptibility Sequence is used to assess:

Answer 36

Iron deposition

Question 37

MRI Functional Sequence is used to assess:

Answer 37

Brain activity

Question 38

MRI Perfusion Sequence is used to assess:

Answer 38

Blood flow

Question 39

MRI Angiography Sequence is used to assess:

Answer 39

Vessels

Question 40

MRI Benefits

Answer 40

* Good soft tissue detail * No ionizing radiation

Question 41

MRI Drawbacks

Answer 41

* Expensive * Some patients may require sedation * Several contraindications

Question 42

MRI Contraindications

Answer 42

* Older aneurysm clips * Pacemakers * Certain implants * First trimester of pregnancy

Question 43

How does Ultrasound (Sonography) work?

Answer 43

* Most widely used imaging modality * Transducer produces high frequency mechanical pressure waves (sound) * Sound wave coupled to surface using gel * Sound is transmitted through tissue or reflected at interfaces * Reflected wave is detected by transducer * Time for reflection indicates depth of interface

Question 44

How does Doppler Ultrasound work?

Answer 44

Uses the Doppler effect to measure and visualize blood flow

Question 45

Ultrasound Benefits

Answer 45

* Inexpensive and fast * No radiation dose * Extremely portable

Question 46

Ultrasound Drawbacks

Answer 46

* Limited contrast * Difficult to see behind air-filled cavities and bone