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S8- Diagnostic Imaging > W2- CT, MRI, Nuclear Imaging > Flashcards

W2- CT, MRI, Nuclear Imaging Flashcards

1
Q

PART 1: CT

A

PART 1: CT

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2
Q

What is a CT?

A

X-ray beam and detector within circular scanner that moves around the patient.

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3
Q

What is the difference between X-ray and CT scan?

A

CT is a series of cross-section slices that can be reconstructed in sagittal and coronal planes, as well as 3D. Series of X-ray (up to 1000 projections)

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4
Q

CT Indications. (6)

A
  • Bone and soft tissue tumors
  • Fx
  • Intra-articular abnormalities
  • Bone fragment detection
  • Bone mineral analysis
  • Neuroimaging
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5
Q

What is a limitation of CT scans?

A

Inability to distinguish small areas of different tissues.

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6
Q

Scanning Process

  • ______ image (2D) taken to localize target structures.
  • ______ slices taken continuously with multiple-detector rows. (Structures can be made into 3D images)
A
  • Scout image

- Helical (spiraling)

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7
Q

Data Conversion

  • ________ for each cubic millimeter.
  • Converted from digital signals into matrix. (Each cell (pixel) assigned shade of gray)
  • Matrix transformed into an image.
  • Contrasts and window modifications.
A

Radiodensities

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8
Q

“Multiplanar Reconstruction: Images can be rotated in space on a computer screen.”

A

3D CT

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9
Q

“Contrast material allows visualization of structures that impinge on neurologic structures.”

A

CT Myelogram

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10
Q

What is a big advantage of CT over radiograph?

A
  • Radiodensity free of superimposed tissues.

- Can see slices as compared to averages of tissue radiodensity.

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11
Q

With a CT, denser structures appear more ______.

-What is a voxel?

A
  • white

- Voxel- Product of pixel and slice thickness. (Average density of different tissues represented from within the voxel)

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12
Q

With CT imaging, having a familiarity with cross-sectional anatomy is important. Viewers scroll through multiple images. What is an axial image?

A

Axial image is as if the patient were supine, viewer looking in caudocephalad direction.

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13
Q

What is an axial image?
What is a sagittal image?
What is a coronal image?

A

Axial Image = Patient were supine, viewer looking in caudocephalad direction.
Sagittal Image = View from left to right.
Coronal Image = View as if facing the patient.

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14
Q

When it comes to bone, what is CT helpful for?

A
  • Subtle Fx
  • Degenerative changes
  • Serious trauma
  • Spinal stenosis
  • IV disc pathology (push onto CNS)
  • Intra-articular loose bodies
  • Osseous alignment in any place
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15
Q

When it comes to neuroimaging, what is CT helpful for?

A
  • Acute Trauma
  • SPECT
  • PET
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16
Q

What are some benefits of CT? (3)

A
  • Less expensive than MR.
  • Less time than MR and US.
  • Benefits over problems related to physical barriers with MRI.
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17
Q

What are some limitations of CT? (2)

A
  • Given observation is based on radiodensity, tissues of similar radiodensity may not be distinguishable.
  • Radiation exposure.
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18
Q

PART 2: MRI

A

PART 2: MRI

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19
Q

What is an MRI?

A
  • Radiofrequency waves within a magnetic field interact with tissues.
  • Relies on detection of remitted radiofrequency waves that are absorbed.
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20
Q

What planes do we view MRIs in? (3)

A
  • axial
  • sagittal
  • coronal
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21
Q
  • Do different structures have different signal intensities with MRIs?
  • Can contrast be used with MRI?
A
  • Yes

- Yes

22
Q

What are some indications for MRI? (4)

A

-soft tissue trauma, internal joint derangement, tumors, subtle FX/stress Fx

23
Q

How many gradient coils are there with an MRI?

A

-3, one for each orthogonal plane

24
Q

What are some extra variants of MRI machines?

A
  • Open scanners

- Upright scanners

25
Q

How does an MRI scan work?

A
  • MRI uses protons, which spin creating a small magnetic charge.
  • When a magnetic field is introduced (MRI), protons align with the field.
  • MRI tech introduces radiofrequency pulse, disrupting the proton and forces it into either 90 or 180 degree realignment.
  • Once the pulse is turned off, it realigns with the magnetic field, releasing electromagnetic energy along the way.
  • MRI detects energy and can differentiate tissues based on how quickly they release energy after pulse it turned off.
26
Q
  • T1 Weighted: Images measure energy from structures that give up energy ______ = _____.
  • T2 Weighted: Images measure energy from structures that give up energy _______ = _____.
A
  • T1 = quickly = fat

- T2 = slowly = water

27
Q
  • With T1 weighted images, they show good anatomical detail. Tissues with high ______ content appear darker.
  • With T2 weighted images, they are good at recognizing inflammation. Tissues with high _____ appear darker.
A
  • water

- fat

28
Q

What is contrast MR good at looking at?

A

blood vessels: Magnetic Resonance Angiography (MRA) and MRI Arthrogram

29
Q

What is an axial image?
What is a sagittal image?
What is a coronal image?

A

Axial Image = Patient were supine, viewer looking in caudocephalad direction.
Sagittal Image = View from left to right.
Coronal Image = View as if facing the patient.

30
Q
  • MR is sensitive to changes in what in bones?

- What diagnosis can this lead to?

A
  • Bone marrow

- Can lead to Dx of bone tumor, stress Fx, and AVN

31
Q

MR can be used for _____ staging, but is not as effective as bone scan for screening purposes.

A

-tumor staging

32
Q

__________ = Arthrogram + MRI

A

-MR Arthrography

33
Q

__________ = View spinal canal and subarachnoid space with high resolution MRI + strong T2 weighting

A

-MR Myelography

34
Q

MR Limitations. (6)

A
  • Imaging of bone
  • Time for image
  • High cost
  • Contraindications (ferromagnetic metal)
  • Hardware can cause distortion of image
  • Physical limitations with procedure parameters (ability to stay still, claustrophobia)
35
Q

PART 3: NUCLEAR IMAGING

A

PART 3: NUCLEAR IMAGING

36
Q

What is nuclear imaging?

A

Produces images by detecting radiation from different parts of the body after a radioactive tracer material is administered.

37
Q
  • Is nuclear imaging used to target a body region or is it for the whole body?
  • Is nuclear imaging used for a static image of viewing over a period of time?
A
  • either

- either

38
Q

What is the difference between nuclear medicine and “Nuclear Imaging”?

A
  • Nuclear Medicine = Introduction of radioactive agents for treatment and Dx.
  • Nuclear Imaging = Nuclear medicine, though indicates intent of Dx.
39
Q

What is the general indication for nuclear imaging?

A

Testing function of tissues. (Dx by physiologic change (as opposed to structure)

40
Q

How does nuclear imaging work? (4)

A
  • Radionuclide (emits gamma rays) introduced.
  • Absorbed differently by tissues based on metabolic activity.
  • Gamma rays observed by special camera.
  • Computer converts to digital image.
41
Q

Methods

  • Static?
  • Whole body?
  • Dynamic?
A 
Static = single image of targeted body region.
Whole-body = AP
Dynamic = Timed sequence
42
Q

What are (2) other forms of nuclear imaging and what are they?

A

Single Photon Emission Computed Tomography (SPECT)

  • 3D (indications bone, cardiac perfusion, brain, liver)
  • Can produce thin slices

Positron Emission Tomography (PET)
-biologic function of cells (indications for CNS studies, tumors)

43
Q

Nuclear Imaging Indications. (3)

A
  • Cancer: staging, observation, and testing response to therapeutic interventions (screening pts with a high risk for metastasis to bone)
  • Detection of metabolic bone diseases and other osteopathies.
  • Detection of other bone abnormalities.
44
Q

MSK Indications. (7)

A
  • HO
  • Fx and Stress Fx
  • Inflammation/Infection
  • Complications of foreign hardware/prosthetic/medical device
  • CRPS
  • PFPS
  • AVN
45
Q
  • What is Scintigraphy?

- What typically indicates increased uptake with this imaging.

A
  • Nuclear imaging of skeleton.

- Black spots (hot spots) on image typically indicate increased uptake.

46
Q

Nuclear imaging (scintigraphy) is a good functional image used for what?

A
  • Confirm disease

- Identify extent of disease

47
Q

What is a bone scan?

A

Imaging study of the skeleton.

48
Q

With a bone scan, uptake depends on balance of osteoblastic and osteoclastic activity.

  • Increased uptake = ________
  • Decreased uptake = _________
A
  • Increased uptake = osteoblastic

- Decreased uptake = osteoclastic

49
Q

What are the 3 phases of bone scan?

A

1st Phase = flow study (immediate)
2nd phase = blood pool (30 minutes)
3rd phase = delayed (2-4hrs)

*See if tracers are being dispersed where they should and if they are collecting indicating altered function.

50
Q

What is an advantage of nuclear imaging bone scan?

A

High sensitivity for changes in bone metabolism.

51
Q

What are some disadvantages of nuclear imaging bone scan?

A
  • Low specificity

- Poor anatomic detail

52
Q

What are some contraindications to nuclear imaging?

A
  • Pregnancy

- Currently breast-feeding

S8- Diagnostic Imaging (21 decks)

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