imaging Flashcards
xrays
-produced in xray tube- radiographers charge current and voltage settings on xray machine to manipulate properties of xray beam produced (different beam spectra for diff parts of body)
- xray beams travel in straights lines. structures hit first will be magnified in relation to those nearer the detector–> reduce magnitude= move further away
-bone absorbs most radiation (white), air absorbs least (black)
-useful for: chest, abdomen, skeletal system (trauma, spine, joints, degen, metabolic & metastic disease), assessment of fracture healings
-usually xrayed from anteriorposterior or lateral (chest is posterioranterior to reduce mag of heart)
-kidneys, ureters and bladder= done with dye
-fluroscopy/ screening= continuous low power xray beam passed through patient to show dynamic images. used: barium studies gi tract, arteriography, manipulate a joint when being plastered, fracture traction, hip replacement
-dangers: radiation killing cells that divide quickly (when about to divide- dies). children worse off
-safety= sound clinical reason to justify exposure, follow local rules of xray department
-biological effects= skin damage (dose dependant), cancer development (random), some body parts are more susceptible, reproductive parts exposure can have potential risk to future gen
CT scan
-use xrays & a computer to create detailed images of inside the body (internal organs, blood vessels & bones)
-adv- done without damage to metal implants, bony structures are more clear and detailed, rapid, cheaper than MRI
-dis- xray risk, less soft tissue detail than MRI
MRI
-uses magnetic properties of certain nuclei in body. high intensity magnetic field displaces nuclei from their position–> when they return the nuclei release energy
-computer analysis processes the energy signals to a grey scale image
-pathological tissue returns different signals compared to normal
good for: brain and spinal imaging, internal derangement of joints, primary soft tissue and bone tumours, acute and chronic soft tissue injuries to tendons, ligs and muscle, osteomyelitis and soft tissue infection
-adv: can be taken in any plane, no documented side effects, detailed soft tissue
-dis: people with metal implants, longer to do, higher cost, need to hold breath
ultrasound
=utilises high frequency sound waves to produce images of soft tissue
-waves are transmitted from US probe/ transducer into soft tissues
-coupling gel= required on the skin (makes good contact)
-visualisation of soft tissue= dependant on differences in acoustic impendance of tissues and organisation of corrective tissues
-uses: imaging of neonatal brain, confirms pleural effusions and pleural masses, visualises liver, gall bladder, pancreasm kidneys etc, monitoring pregnancy (uterus and ovaries), assesses thyroid, testes and soft tissue lesions, identification of joint effusions and synovitis
-adv= cheap, high resolution of soft tissues, good extra articular visualisation, portable exam poss, can compare contralateral joints, can image dynamically (move part in exam)
-dis= limited intraarticular visualisation, cannot image through air filled spaces
