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Diagnostic Imaging > CT, MRI, and Nuclear Imaging > Flashcards

CT, MRI, and Nuclear Imaging Flashcards

1
Q

Briefly describe what CT-scans are and how they work

A
  • What it is → X-ray beam and detector within circular scanner that moves around the patient
    • computer interprets (reconstructs) image
    • tissues assigned different shades of gray
    • series of cross-section slices (axial); can be reconstructed in sagittal and coronal planes, as well as 3D
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2
Q

Give several example indications for CT-scans

A
  1. Bone and soft tissue tumors
  2. Fractures
  3. Intra-articular abnormalities
  4. Bone fragment detection
  5. Bone mineral analysis (i.e. metabolic disorders)
  6. Neuroimaging
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3
Q

limitation(s) of CT-scans

A

inability to distinguish small areas of different tissues

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4
Q

describe the scanning process in CT-scans

A
  1. Scout image (2D) taken to localize target structures
  2. Helical (spiraling) slices taken continuously with multiple-detector rows
    1. volumetric scanning possible with this, as structures can be made into 3D images
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5
Q

describe the data conversion process in CT-scans

A
  1. Radiodensities for each cubic millimeter
  2. Converted from digital signals into matrix
    1. each cell (pixel) assigned shade of gray
  3. Matrix transformed into an image
  4. Contrasts and window modification
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6
Q

list and describe 2 CT-scan variants

A
  1. 3D CT
    1. multiplantar reconstruction → images can be rotated in space on a computer screen
  2. CT Myelogram
    1. contrast material allows visualization of structures that impinge on neurologic structures
    2. distinguish osteophytes, ligaments infolding, and disc material
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7
Q

when viewing CT-scans, denser structures appear _________

A

more white

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8
Q

______is an advantage of CT-scans over radiograph

A

radiodensity free of superimposed tissues

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9
Q

what is voxel?

A

product of pixel and slice thickness

average density of different tissues represented from within the voxel

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10
Q

cross-sectional anatomy familiarity is important with CT-scans. List 3 different plane views and how to orient yourself with them

A
  1. Axial image → as if the pt were supine, viewing looking in caudocephalad direction
  2. Sagittal image → view form left to right
  3. Coronal image → view as if facing the pt
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11
Q

list CT-scan clinical applications pertaining to bone

A
  1. subtle fracture
  2. degenerative changes
  3. serious trauma
  4. spinal stenosis
  5. IV disc pathology
  6. Intra-articular loose bodies
  7. Osseous alignment in any plane
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12
Q

list CT-scan clinical applications for neuroimaging

A
  1. Acute trauma (initial assessments)
  2. SPECT
  3. PET
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13
Q

list benefits of CT-scans

A
  1. less expensive than MR
  2. less time than MR and US
  3. benefits over problems related to physical barriers with MRI
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14
Q

list limitations with CT-scans

A
  1. given observation is based on radiodensity, tissues of similar radiodensity may not be distinguishable (e.g. tumors and surrounding soft tissues)
  2. radiation exposure
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15
Q

what is nuclear imaging?

A

imaging that uses radiopharmaceuticals (tracers) for the purpose of diagnosis, therapy, and research

can be used for static image or viewing over a period of time

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16
Q

what is the general indication for nuclear imaging?

A

testing function of tissues

diagnosis by physiological change (as opposed to structure)

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17
Q

describe the mechanism of nuclear imaging

A
  1. radionuclide (emits gamma rays) introduced
  2. absorbed differently by tissues based on metabolic activity
  3. gamma rays observed by special camera
  4. computer converts to digital image
18
Q

list and briefly describe the 6 different methods of nuclear imaging

A
  1. Static → single image of targeted body region
  2. Whole-body → AP (example: bone scans)
  3. Dynamic → timed sequence
  4. SPECT → 3D
  5. PET → biologic function of cells
  6. Combinations with CT and MR
19
Q

list indications for dynamic nuclear imaging

A

cardiac, hepatobiliary, gastric studies

20
Q

what does SPECT stand for?

A

Single Photon Emission Computed Tomography

21
Q

list indications for SPECT

A

bone, cardiac perfusion, brain, liver

22
Q

what does PET stand for?

A

Positron Emission Tomography

23
Q

list indications for PET

A

CNS studies, tumors

24
Q

list clinical indications for Nuclear Imaging

A
  1. Cancer
    1. staging, observation, and testing response to therapeutic intervention
    2. screening pts with a high risk for metastasis to bone
  2. Detection of metabolic bone diseases and other osteopathies
  3. Detection of other bone abnormality
25
Q

list MSK indications for nuclear imaging

A
  1. HO
  2. fracture and stress fractures
  3. inflammation/infection
  4. complications of foreign hardware/prosthetic/medical device
  5. CRPS
  6. PFPS
  7. AVN
26
Q

what is scintigraphy?

A

nuclear imaging of skeleton

27
Q

what is the function of scintigraphy and how do you interpret it’s results?

A

function → confirm disease, ID extent of disease

black spots (aka hot spots) on image typically indicate increased uptake

28
Q

what is a bone scan?

A

a nuclear imaging study of the skeleton comprised of 3 phases

29
Q

list the 3 phases of a bone scan

A
  1. 1st phase → flow study (immediate)
  2. 2nd phase → blood pool (30 minutes)
  3. 3rd study → delayed (2-4 hours)

imaging occurs over the few hours post injection

30
Q

list advantages/disadvantages of bone scans

A
  1. Advantages
    1. high sensitivity for changes in bone metabolism
  2. Disadvantages
    1. low specificity
    2. poor anatomic detail
31
Q

list contraindications for bone scans

A

pregnancy

currently breast-feeding

32
Q

list indications for MRI

A
  1. soft tissue trauma
  2. internal joint derangement
  3. tumors
33
Q

list 2 variants of MRI scanners

A

open scanners

upright scanners

34
Q

give a brief explanation of how MRIs work

A
  1. MRIs measure the energy emitted by hydrogen nuclei as the respond to radiofrequency signals
  2. energy differs by tissue
  3. a radiofrequency wave pulse is applied at a right angle to align protons (hydrogen) in transverse plane which brings them to a higher energy state
  4. as the protons realign with the magnetic field they release absorbed energy which creates a current that is induced in receiver coil
  5. a contrast in image produced by different T1, T2 and # of hydrogen nuclei
35
Q

what does T1 and T2 mean?

A

technical terms that refer to the time taken between magnetic pulses and the image is taken

36
Q

describe T1 MRI

A

weighted images that measure energy from structures that give up energy quickly (like fat)

good for anatomic detail

tissues with higher water content appear darker

37
Q

describe T2 MRI

A

weighted images that measure energy from structures that give up energy slowly (like water)

fat appears darker

grainer, less spatial resolution

good for ID of inflammation

38
Q

list several clinical applications for MRI

A
  1. sensitive to changes in bone marrow → dx of bone tumor, stress frxs, AVN
  2. Soft tissue injuries
    1. ligament and tendon
    2. meniscus
    3. alternative to arthroscopic dx
    4. disc pathology/neurologic impingement
  3. Tumor staging
  4. MR arthrography → arthrogram + MRI
  5. MR Myelography → view spinal canal and subarachnoid space w/high resolution MRI + strong T2 weighing
39
Q

list limitations to MRI

A
  1. imaging for bone
  2. time for image
  3. high cost/expensive
  4. hardware can cause distortion of images
  5. physical limitations with procedure parameters
    1. ability to stay still
    2. claustrophobic
40
Q

list contraindications to MRI

A

ferromagnetic metals (surgical clips, shrapnel)

Diagnostic Imaging (15 decks)

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