Introduction to Imaging - S1P2

Question 1

medical imaging techniques

Answer 1

x-rays - radiography
position emission tomography - PET
magnetic resonance imaging - MRI
ultrasound - sonography
computed tomography - CT
computed axial tomography - CAT

Question 2

x-ray

Answer 2

electromagnetic waves with short wavelength
when directed through body, some are absorbed and some pass through
absorbed - dense tissue/organ
not absorbed - soft tissue
patient in front of photographic film so x-rays passing through expose film and turn it black
where x-rays are absorbed in patient, film appears white

Question 3

most radiolucent to least radiolucent
least radiodense to most radiodense

Answer 3

air, fat, water and most tissues, spongy bone, compact bone

Question 4

how do dense tissues appear on x-ray

Answer 4

opaque - appear white

Question 5

common clinical uses of x-ray

Answer 5

bone fractures
bone disorders
hollow, soft organs visualised
with contrast reagent (absorbs x-rays) GI tract

Question 6

advanced x-ray techniques

Answer 6

angiography
CT

Question 7

disadvantages of x-ray

Answer 7

soft tissue not shown unless contrast agent used
quality/resolution not good - i.e. images can appear blurry
3D structures flattened to 2D meaning organs can appear stacked/dense organs can block other organs

Question 8

computed tomography - CT

Answer 8

patient lies on bed between x-ray tube and recorder
tube and recorder rotate taking multiple angles
produces detailed section of body
contrast agent used
images used as if standing at foot of patients bed (inferior view)
often used to diagnose internal organ/vessel damage, cancer etd
useful for planning operations

Question 9

advantages of CT

Answer 9

relatively cheap
fast
can produce good images of soft and hard tissue

Question 10

disadvantages of CT

Answer 10

radiation
not good for joints due to angles

Question 11

magnetic resonance imaging - MRI

Answer 11

can produce high contrast images of soft tissue
doesn’t use radiation
detects hydrogen levels - found in water
distinguishes between tissues by differences in water content
patient lies in chamber surrounded by large magnet
magnetic fields of up to 60,000x stronger than on earth
magnet on = hydrogen protons align
brief pulse of radio waves knocks protons out of alignment
protons emit waves as they return to position

Question 12

volume rendering of MRI

Answer 12

individual slices can be reconstructed into 3D images

Question 13

advantages of MRI

Answer 13

no radioactive tracers
no radiation exposure
high contrast images of soft tissue
faster than PET so often used for brain imaging

Question 14

disadvantages of MRI

Answer 14

high magnetic fields - metallic implants can malfunction
longer time to collect images than CT
sensitive to patient movement
not available for trauma situations - traction etc

Question 15

ultrasound imaging - sonography

Answer 15

body probed with high frequency (ultrasonic) sound waves
probe produces sound and picks up echoes
moved over skin to image from multiple planes
can detail outline of organs
not good for air filled structures or surrounded by bone
most common use - visualising developing embryo/foetus
also used to visualise gallbladder, kidneys etc
used in musculoskeletal imaging - tendons

Question 16

doppler ultrasound

Answer 16

can image flow within blood vessels and motion within

Question 17

advantages of ultrasound

Answer 17

safe
non-invasive
quick
inexpensive

Question 18

disadvantages of ultrasound

Answer 18

low resolution - blurry images
no hard tissue presentation

Question 19

position emission tomography - PET

Answer 19

detects radioactive isotopes injected into the body - sugar or water molecules
can be used to detect areas of high cellular activity
identifies most active cells/greatest blood supply - e.g. brain or tumour cells
radioactive material decays and gives off gamma rays that can be detected by scanner
location of isotope can be imaged
used in brain imaging studies and cancer treatment