W2- CT, MRI, Nuclear Imaging

Question 1

PART 1: CT

Answer 1

PART 1: CT

Question 2

What is a CT?

Answer 2

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

Question 3

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

Answer 3

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)

Question 4

CT Indications. (6)

Answer 4

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

Question 5

What is a limitation of CT scans?

Answer 5

Inability to distinguish small areas of different tissues.

Question 6

Scanning Process

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

Answer 6

• Scout image

- Helical (spiraling)

Question 7

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.

Answer 7

Radiodensities

Question 8

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

Answer 8

3D CT

Question 9

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

Answer 9

CT Myelogram

Question 10

What is a big advantage of CT over radiograph?

Answer 10

• Radiodensity free of superimposed tissues.

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

Question 11

With a CT, denser structures appear more ______.

-What is a voxel?

Answer 11

• white

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

Question 12

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

Answer 12

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

Question 13

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

Answer 13

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.

Question 14

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

Answer 14

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

Question 15

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

Answer 15

• Acute Trauma
• SPECT
• PET

Question 16

What are some benefits of CT? (3)

Answer 16

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

Question 17

What are some limitations of CT? (2)

Answer 17

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

Question 18

PART 2: MRI

Answer 18

PART 2: MRI

Question 19

What is an MRI?

Answer 19

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

Question 20

What planes do we view MRIs in? (3)

Answer 20

• axial
• sagittal
• coronal

Question 21

• Do different structures have different signal intensities with MRIs?
• Can contrast be used with MRI?

Answer 21

• Yes

- Yes

Question 22

What are some indications for MRI? (4)

Answer 22

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

Question 23

How many gradient coils are there with an MRI?

Answer 23

-3, one for each orthogonal plane

Question 24

What are some extra variants of MRI machines?

Answer 24

• Open scanners

- Upright scanners

Question 25

How does an MRI scan work?

Answer 25

- 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.

Question 26

- T1 Weighted: Images measure energy from structures that give up energy ______ = _____. - T2 Weighted: Images measure energy from structures that give up energy _______ = _____.

Answer 26

- T1 = quickly = fat | - T2 = slowly = water

Question 27

- 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.

Answer 27

- water | - fat

Question 28

What is contrast MR good at looking at?

Answer 28

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

Question 29

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

Answer 29

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.

Question 30

- MR is sensitive to changes in what in bones? | - What diagnosis can this lead to?

Answer 30

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

Question 31

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

Answer 31

-tumor staging

Question 32

__________ = Arthrogram + MRI

Answer 32

-MR Arthrography

Question 33

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

Answer 33

-MR Myelography

Question 34

MR Limitations. (6)

Answer 34

- 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)

Question 35

PART 3: NUCLEAR IMAGING

Answer 35

PART 3: NUCLEAR IMAGING

Question 36

What is nuclear imaging?

Answer 36

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

Question 37

- 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?

Answer 37

- either | - either

Question 38

What is the difference between nuclear medicine and "Nuclear Imaging"?

Answer 38

- Nuclear Medicine = Introduction of radioactive agents for treatment and Dx. - Nuclear Imaging = Nuclear medicine, though indicates intent of Dx.

Question 39

What is the general indication for nuclear imaging?

Answer 39

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

Question 40

How does nuclear imaging work? (4)

Answer 40

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

Question 41

Methods - Static? - Whole body? - Dynamic?

Answer 41

``` Static = single image of targeted body region. Whole-body = AP Dynamic = Timed sequence ```

Question 42

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

Answer 42

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)

Question 43

Nuclear Imaging Indications. (3)

Answer 43

- 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.

Question 44

MSK Indications. (7)

Answer 44

- HO - Fx and Stress Fx - Inflammation/Infection - Complications of foreign hardware/prosthetic/medical device - CRPS - PFPS - AVN

Question 45

- What is Scintigraphy? | - What typically indicates increased uptake with this imaging.

Answer 45

- Nuclear imaging of skeleton. | - Black spots (hot spots) on image typically indicate increased uptake.

Question 46

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

Answer 46

- Confirm disease | - Identify extent of disease

Question 47

What is a bone scan?

Answer 47

Imaging study of the skeleton.

Question 48

With a bone scan, uptake depends on balance of osteoblastic and osteoclastic activity. - Increased uptake = ________ - Decreased uptake = _________

Answer 48

- Increased uptake = osteoblastic | - Decreased uptake = osteoclastic

Question 49

What are the 3 phases of bone scan?

Answer 49

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.

Question 50

What is an advantage of nuclear imaging bone scan?

Answer 50

High sensitivity for changes in bone metabolism.

Question 51

What are some disadvantages of nuclear imaging bone scan?

Answer 51

- Low specificity | - Poor anatomic detail

Question 52

What are some contraindications to nuclear imaging?

Answer 52

- Pregnancy | - Currently breast-feeding