MSK Imaging Flashcards
How much radiation from an X-ray gets scattered and could pose a harm to other individuals in the room (who are not the patient)?
10-20%
X-ray projection (aka the color that shows up on film) depends on what?
thickness of the material that is to be penetrate
When there is no tissue to penetrate (aka air), the corresponding picture on x-ray will be what color?
black
As tissue becomes more dense/thicker, how does the corresponding picture on x-ray correlate?
the greater the depth/density, the lighter the grey (bone shows up light grey, metal shows up white)
What is fluoroscopy?
it is a type of imaging format that uses continuous x-ray imaging to create a real time look into internal structures
When is fluoroscopy imging used?
useful for dynamic procedures such as injections (joint injections to see where the needle is, etc), biopsies, angiograms (intavascular such as procedures in the cath lab), and gastrointestinal evaluations.
How much radiation does fluroscopy imaging use?
uses continuous radiation, so be mindful of the duration of time you are using it for
What is a CT?
essentially a rotating x-ray
what is the advantage of using a CT?
Able to measure and display varying x-rays attenuations of the tissues in a section of the body by passing x-rays through the section from many different angles then using computers to reconstruct the image you see
what are the strengths of CT?
- fast
- good resolution of bony lesions
- less epensive than MRI
what are the weaknesses of CT?
- ionizing radiation
- expensive
- poor soft tissue contrast
- tissue densities behind vdry dense tissue distorted
What does “MRI” stand for and how does it work?
MRI= Magnetic Resonance Imaging.
Magnetized polarized photons release energy that gives the computer information on tissue densities and can translate that information into an image.
What is MRI best used for?
soft tissue imaging
What are “T1” weighted images?
- General rule: good for visulaizing normal anatomy.
- T1 refers to how quickly it can become magnetized
- results in
- fat relatively bright
- water relatively dark
What are T2 weighted images?
- General rule: good for detecting pathology (can better visualize edema in the tissue)
- How quickly it loses its magentization
- results in
- fat relatively dark
- water relatively bright
Mneumonic for T2 weighted images
World War 2
WW= “Water is White on T2”
What are the strengths of MRI imaging?
- Strengths
- no ionizing radiation
- entire cross-sections without interference
- superior soft tissue contrast
What are the weaknesses of MRI imaging?
- Weaknesses
- subject to motion artifact
- inferior to CT in detecting acute hemorrhage
- Inferior to CT in detection of bony injury
- requires prolonged aquisition time for many images (takes a long time)
What are MRI/CT arthrograms used for?
a contrats medium is injected into a joint to detect tears in labrum or cartilage
What is an ultrasound?
- type of imaging that works by sending sound waves out of a transducer, and creates an image based on the waves coming back
What does the term “echogenicity” mean when refering to ultrasound?
a measure in the qulaity/strength of reverberation/vibration that is coming back from those vibrations
hyper-echogenicity=”whiter”
hypo-echogenicity= “darker”
What is a DEXA scan?
- readiograph tube generates photon beams of two different energy levels, thus the term “dual-energy”
- the difference in attenuation (reduction in intensity) of the two photon beams as they pass through body tissue of variable composition distinguishes bone from soft tissue and allows quantification of bone mineral density (BMD)
- T-score, the value used for osteoporosis
- z-score, used to compare a patients BMD to a population of peers
When ordering an x-ray, how many views should you get?
multiple. you need more than one 2D picture to figure out what is going on.
what the difference between an “open” fracture vs a “closed” fracture?
- open fracture (compound)
- has penetrated skin
- think “open to air”
- closed fracture
- bone has been fractured yet has not penetrated the skin
What is the risk associated with an open fracture?
risk of infection to bone is increased (osteomyelitis)
Greenstick fractures are common in what patient population?
pediatrics
Describe the SALTER Harris classification system
- Describes the fracture in relation to the growth plate. This is important because the patient is still growing and this can cause limb length discrepancies if not treated correctly.
- See attached picture.
Which part of the bone is a Giant Cell Tumor found?
Epiphysis