Unit 4: Wk 3

Question 1

what are the principles of CT imaging?

Question 2

how is CT similar to radiograph? how is it different?

Answer 2

similar: employs xrays attenuated by body tissues

different: CT creates images based on cross section/axial slices

Question 3

what are the components of CT machine?

Answer 3

gantry: the tube (high voltage generator)

oporators console

the computer

Question 4

3-D CT

CT myelogram

CBCT

how are they similar and different? pros/cons?

Answer 4

3D CT: can be rotated in space on computer screen

CT Myelogram: injection of contrast material into subarachnoid space; not often used

CBCT: cone beam CT; acquires all the data in a single sweep of the scanner; allows for shorter scanning times and lower radiation

Question 5

considerations of viewing CT images in terms of radiodensity, orientation of the image, windowing, image quality

Answer 5

radiodensities= dense is lighter, less dense is darker (opposite of radiograph)

orientation: looking up from patietns feet

windowing: rande of radiodensities displayed in an image

image quality : good bc it could have good contrast?? but also you could havae too much sooo

Question 6

what are the clinical uses of CT? indications? advantages? limitations? disadvantages

Answer 6

• for subtle fractures and detailed degenerative changes (arthritis) , loose bodies in joint

advantage: less time consuming, osseous alignment

limitations: bad w/ histological makeup bc tissues may be the same shade if densities are similar (tumor same shade as muscle)

Question 7

role of CT in neuroimaging in terms indications, advantages, and CT examination

Answer 7

indication: ischemic stroke; cerebral hemorrhage, hematoma

Question 8

what are the principles of MR?

Answer 8

MRI principles: based on measurements of energy emitted from hydrogen nuclei after their stimulation by radiofreq signals. CAN DISTINGUISH BETWEEN TISSUES

Question 9

how does mri work?

Answer 9

Nuclei absorb and release energy based on signals from hydrogen nuclei (proton) in water molecules

Question 10

what are the components of MRI equipment? different types of equipment set-up?

Answer 10

• main magnet
• gradient coils
• radiofrequency coils
• workstation
• computers

Question 11

T1 and T2, and weighting in MRI.

Answer 11

T1: defines anatomy; short time to repetition and time to echo time

T2: detects fluid; long time to repetition and time to echo time
* shows energy late in decay
* granier

Question 12

advantages and disadvantages of T1 and T2 and weighting in MRI

Answer 12

advantage: T1 is fairly balanced;

disadvantage: T2 are granier and give less spatial resolution

Question 13

what are MRI protocols?

Answer 13

no standard protocol
- plane, slice thickness 3-4mm
- T2 weighted
- T1 weighted

Question 14

What are the two main sequences used in MRI; compare and contrast?

Answer 14

Spin Echo: 90 degree pulse flip followed by T1 relaxation and T2 decay; then 180 degree rephasing pulse

Gradient Echo:

Question 15

how is contrast used in MRI?

Answer 15

gadolinium renders a bright signal allowing small deficits in capsule, articular surfaces, or ligs to be seen

its injected into cerebrospinal fluid during magnetic resonance myelography

Question 16

considerations of viewing MRIs in terms of tissue characteristics, orientation, and image quality

Answer 16

characteristics: creates image based on hydrogen proton energy emission

orientation: Coronal image viewed from front; acial image viewed from below, sagittal from side

image quality: it depends on parameters

Question 17

what are the clinical uses of MRI? indications? advantages? limitations? disadvantages?

Answer 17

uses: sports injuries, changes in bone marrow, bone tumors, BEST FOR DISC HERNIATIONS, stages neoplasms

limitations: high cost; time to produce image

disadvantage, no metal/pacemakers

Question 18

MRI vs CT

Answer 18

MRI: better contrast, view of organs, no ionizing radiation, less chance of missing disease

CT: cheaper, faster, thinner slices, easier imaging w metal implants

Question 19

what is diagnostic ultrasound? what are the equipment components? how does it work to produce and image?

Answer 19

cross section imaging method based on sound waves reflected off soft tissues and tissue interfaces

• pulser
• transducer
• scan converter
• monitor

Question 20

how can ultrasound imaging be used in rehab?

Answer 20

a form of biofeedback

Question 21

what is doppler ultrasound and how does it work?

Answer 21

sound waves reflected off blood cells moving toward a transducer arrive at transducer at higher rate than corresponds to a freq of emitted waves

Question 22

describe how DUS is performed. How is it unique?

Answer 22

its the only dynamic imaging modality

Question 23

components of US that produce an image?

Answer 23

• amplitude, timing, and transverse location of reflected waves

Question 24

How is an ultrasound image viewed? what are the characteristics of tissues? characteristics of abnormal findings? image quality?

Answer 24

monitor displays intensity of signals returned from tissues

image quality: resolution discussed in terms of lateral resolution and axial resolution
- lateral: ability to differentiate between structures in plane perpendicular to beam
- axial: ability to differentiate between structures that lie one above another in longitudinal axis of the beam

Question 25

clinical uses of US? indications? advantages? limitations? disadvantages?

Answer 25

Indication: like mri (soft tissue, ligs, tendons, nerves)

Advantage: noninvasive, no known ill effects, real time, low cost, portability

limitations: operator depending; obese patients dont image well