Introduction to Radiology Flashcards
what part of the electromagnetic spectrum are x-rays in?
the high energy end
how do we get an x-ray image?
high energy allows x-ray to pass through body and reach a film those not absorbed (the remaining photons) expose the film
what is the order in which things stop x-rays?
bone>soft tissue>fat>gas
what are x-rays used for? (4)
to look at trauma, joint diseases, chest pathology, bowel obstruction
what are the problems with x-rays?
high energy -> free radicals -> genetic damage -> cancer risk increased
what is the ALARA principle?
as low as reasonably possible
who needs extra care when conducting x-rays? (3)
women of child bearing age, children, known pregnancy
length of background radiation for chest x-ray…
3 days
length of background radiation for lumbar spine/pelvis x-ray?
5 months
what does CT stand for?
computer tomography
what does a CT scanner do?
works out the densities of organs and structures to make up an image
what are the uses of CT? (4)
stage tumours, trauma, cerebrovascular disease, surgical emergencies
what are the problems with CT? (2)
expensive = £500,000 to buy, £300-500 thousand a year to run and radiation dose = CT abdomen/pelvis is 1200 days
what does PET stand for?
positron emission tomography
how does PET work? (physics)
unstable compound decays by emitting a positron (antimatter), positron hits electron resulting in mutual annihilation causing a 180 degree pulse of gamma radiation
how does PET work? (metabolism)
most cancers have high metabolism with the main metabolic agent being glucose so if an unstable compound is joined to glucose it will accumulate at sights of high metabolic activity
uses of PET?
staging of tumours - may detect occult spread, detecting recurrence after treatment
PET limitations… (4)
cyclotron (mini particle accelerator), short half life, expensive, radiation does = 750 days
ultrasound strengths… (2)
soft tissue detail, safe
main uses of ultrasound? (4)
heart, pelvis, abdominal solid organs, obstetrics
ultrasound weaknesses… (2)
cannot penetrate bone, ultrasound waves scattered by air = cannot view bowel and solid organs may be obscured by gaseous bowel
what does MRI stand for?
magnetic resonance imaging
how does MRI work?
short burst of radio waves applied at resonant frequency, protons give up energy which is detected to make a picture
what are uses of MRI? (4)
musculoskeletal system, pelvic neoplasms, angiography, cardiac imaging
what are the advantages of MRI? (4)
non-ionising radiation, few known side effects, good soft tissue visualisation, able to do functional studies
what are the disadvantages of MRI? (5)
expensive, dangerous = metal object in room or patient, very strong magnetic field, claustrophobic, noisy, can take a long time
what does angiography look at?
blood/lymph vessels
what is used to show up the lumen of the small bowel?
contrast media eg iodine compounds/barium
