MSK imaging Flashcards
radiograph - plain film
cheap
indicated for bones, foreign objects and hardware
generally first line
cons: need multiple views - negligible to very low risk of cancer
radiograph- fluoroscopy
indicated for procedures - live action -iodine dye used to confirm accurate injection of structures (high penetration); cons: increase risk due to multiple x rays
what is the spectrum of absorption for X-rays
in decreasing density levels;white - high: metal, bone; intermediate: soft tissue ( muscles, fat, fascia); low: air filled organs _ black
define radiograph
high frequency/energy electromagnetic waves that penetrate soft tissue (form of ionizing radiation);can produce damage to tissue/DNA (low dose: cancer; high dose: radiation sickness)
radiography- digital subtraction angiography
iodine based contrast is injected IV, makes vessels termporarily visible to x rays; image via fluoroscopy- computer subtracts bone; cons: contrast can injure kidneys, radiation from fluoroscopy
radiography- DEXA- dual energy x ray absorptiometry
two energy levels x ray beams (compares bone absorption)
indication: bone density scan when concerned for osteoporosis/osteopenia; standard for bone density measurements - cons: ionizing radiation
radiography- computer tomography - CT/ CAT scan (computer aided tomography)
numerous XRs as cross sectional slices; 3d saggital and transverse views of the structures; can increase resolution by combining mult. images in a single plane; taking thinner slices, more images closer to each other
CT angiography
iodine based contrast used ot improve context between structures (IV) - vasculature/ organs
what are iodine (IV) contrast risks
can cause kidney damage and have rare but possible allergic reactions
CT indications
visualize boney structures - plain film radiograph can’t see ( OA/AA joint), its high resolution can fing hard to see fractures; soft tissue, other organs such as abdominal organs, brain and blood vessles.
what are pros to ct scan
affordable, quick, 3d image with good resolution
what are the cons
relative high risk of radiation and iodine contrast can cause kidney damage
MRI- magnetic resonance imaging
uses a powerful magnetic field and radiofrequency waves on protons abundant in water and fat, to generate images
what are the steps to MRI
- magnetic field lines up randomly aligned protons; 2. radiofrequency pulse–> changes proton alignment in magnetic field; 3. radiofrequency pulse deactivates–> protons realign with the magnetic field–> release energy which is read by the MRI machine
what is the interpretation for MRI/CT
3d (sagittal and transverse views) - common reading convention is the sagittal plane slices
MRI indications
excels in visualizing soft tissue structure (cartilage, tendons, etc) = best for joint injury. Can find missed/hard to see structures
MRI pros:
no ionizing radiation, highest resolution, can differentiate soft tissue ( ex. tumors )
MRI cons:
expensive, slow and time consuming; difficult for claustrophobic pts; cannot use in patients with metal implants
ultrasound
uses echolocation to produce image
low frequency - more penetration, lower resolution; higher frequency- less penetration, higher resolution; waves travel into body then reflect back to make a single live 2-d image
ultrasound interpretation
hyperechoic/dense - not able to penetrate (bone, metal); anechoic/black - fully penetrates (air, fluid-blood); hypoechoic/dark (organs, soft tissue)
ultrasound indications, pros, cons
indication: quick diagnosis and guiding procedures, able to differentiate soft tissue well; pros: cheap, fast, portable, no ionizing radiation; cons: not always available, user dependent, not able to visualize structures behind bone (waves blocked) and bigger anechoic structures (waves scatter)
nuclear medicine
used to measure physiology not anatomy - IV injected radiotracers will bind to targeted physiological process- produce high conc. of gamma radiation visualized by camera
nuclear medicine-positron emission tomography (PET)
radiotracer is a glucose analog and will aggregate in areas of most glucose storage; indications (cancer monitoring- increased use of glucose); pros: targeted absorption by physio; cons: radiotracers produce ionizing radiation
