Unit 4: Wk 3 Flashcards
what are the principles of CT imaging?
how is CT similar to radiograph? how is it different?
similar: employs xrays attenuated by body tissues
different: CT creates images based on cross section/axial slices
what are the components of CT machine?
gantry: the tube (high voltage generator)
oporators console
the computer
3-D CT
CT myelogram
CBCT
how are they similar and different? pros/cons?
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
considerations of viewing CT images in terms of radiodensity, orientation of the image, windowing, image quality
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
what are the clinical uses of CT? indications? advantages? limitations? disadvantages
- 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)
role of CT in neuroimaging in terms indications, advantages, and CT examination
indication: ischemic stroke; cerebral hemorrhage, hematoma
what are the principles of MR?
MRI principles: based on measurements of energy emitted from hydrogen nuclei after their stimulation by radiofreq signals. CAN DISTINGUISH BETWEEN TISSUES
how does mri work?
Nuclei absorb and release energy based on signals from hydrogen nuclei (proton) in water molecules
what are the components of MRI equipment? different types of equipment set-up?
- main magnet
- gradient coils
- radiofrequency coils
- workstation
- computers
T1 and T2, and weighting in MRI.
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
advantages and disadvantages of T1 and T2 and weighting in MRI
advantage: T1 is fairly balanced;
disadvantage: T2 are granier and give less spatial resolution
what are MRI protocols?
no standard protocol
- plane, slice thickness 3-4mm
- T2 weighted
- T1 weighted
What are the two main sequences used in MRI; compare and contrast?
Spin Echo: 90 degree pulse flip followed by T1 relaxation and T2 decay; then 180 degree rephasing pulse
Gradient Echo:
how is contrast used in MRI?
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
considerations of viewing MRIs in terms of tissue characteristics, orientation, and image quality
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
what are the clinical uses of MRI? indications? advantages? limitations? disadvantages?
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
MRI vs CT
MRI: better contrast, view of organs, no ionizing radiation, less chance of missing disease
CT: cheaper, faster, thinner slices, easier imaging w metal implants
what is diagnostic ultrasound? what are the equipment components? how does it work to produce and image?
cross section imaging method based on sound waves reflected off soft tissues and tissue interfaces
- pulser
- transducer
- scan converter
- monitor
how can ultrasound imaging be used in rehab?
a form of biofeedback
what is doppler ultrasound and how does it work?
sound waves reflected off blood cells moving toward a transducer arrive at transducer at higher rate than corresponds to a freq of emitted waves
describe how DUS is performed. How is it unique?
its the only dynamic imaging modality
components of US that produce an image?
- amplitude, timing, and transverse location of reflected waves
How is an ultrasound image viewed? what are the characteristics of tissues? characteristics of abnormal findings? image quality?
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
clinical uses of US? indications? advantages? limitations? disadvantages?
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