medical imaging

Question 1

exaplain how x-rays are taken

Answer 1

focus high energy beam of electrons
pass through body to receiver
electrons absorbed and scattered dependent on density and atomic number
more dense/increased atomic number= appear lighter

Question 2

How to read a chest x ray

Answer 2

A irways 'darker'
B reathing 'lungs'
C irculation 
D isability (bone)
E verything else

Question 3

how to read a abdominal x ray

Answer 3

A ir
B owel
Densities (bone)
O rgans

Question 4

advantages of x-ray

Answer 4

quick
portable
cheap
simple

Question 5

disadvantages of x ray

Answer 5

radiation
2d
can’t see pathology
poor soft tissue imaging

Question 6

explain fluoroscopy

Answer 6

use constant stream of xrays and contrast to look at anatomy and motion

Question 7

advantages of fluoroscopy

Answer 7

dynamic studies
cheap
interventional procedures

Question 8

disadvantages of fluoroscopy

Answer 8

radiation

clinical exposure must be minimised

Question 9

Explain CT

Answer 9

rotating gantry of x ray and detect either side
images put together by computer
feet up images therefore l=r r-l
transverse cross sections

Question 10

Explain hounsfield units

Answer 10

water = 0
less dense- neg –> fat/air
more dense- positive–> bone/ metal

Question 11

Advantages of CT

Answer 11

quick
good resolution
can scan most areas

Question 12

disadvantages of CT

Answer 12

radiation
affected by artefacts
must hold breath
over use –> incidental findings

Question 13

Explain MRI

Answer 13

atoms spin randomly in own magnetic field
apply magnetic field they align wither north or south
not 50/50 split some unmatched
radiofrequency pulse applied unmatched ions spin other way
raadiofrequency off–> unmatched ions return to position before
energy released creates signal with computer processes and produced an image

Question 14

What are the different MRI weightings

Answer 14

T1 –> fat white / water black

T2–> water white/ fat black

Question 15

advantages of MRI

Answer 15

no radiation

good resolution

Question 16

disadvantages

Answer 16

long time to do 
expensive 
claustrophobic 
loud 
no metal 
must lie still

Question 17

Explain PET

Answer 17

positron emission tomogaphy
inject radiopharmaceuticals which emit gama rays
high light certain regions by using camera that detect annihilations e.g tumours

Question 18

Explain ultrasound

Answer 18

high frequency waves from transducer probe
sound wave reflected back based on distance and density
prob detect reflected waves
computer generates image

Question 19

advantages ultrasound

Answer 19

lack ionising radiation 
portable 
cheap 
insertion into body cavity 
dynamic ( blood flow)

Question 20

disadvantages ultrasound

Answer 20

operator dependent
no bone or gas penetration
body habitus

Question 21

what is hyperchoic

Answer 21

increase reflection - white

Question 22

what is hypochoic

Answer 22

decrease reflection- balck

Question 23

what is anechoic

Answer 23

not reflective (pure fluid) - blaclk

Question 24

Explain an doppler ultrasound

Answer 24

movin onjects influnece sound waves
nearer = increase frequency
further-= reduced frequency
can look at blood flow dynamically

Question 25

Why are contrast media used

Answer 25

help differentiate between tissues

Question 26

name some positive contrast media

Answer 26

seen as white
barium
iodine
gadolinium

Question 27

name negative contrast media

Answer 27

seen as black
water
air
co2

Question 28

what are the ideal features if a contrast media

Answer 28

low osmolality and viscosity 
increased water solubility 
biologically inert 
safe 
heat and chemical stability 
cost effective

Question 29

how can contrast media be administrated

Answer 29

orally 
rectally 
IU 
IA 
filling space or cavity

Question 30

How are contrast media excreted

Answer 30

95% glomerular filtration –> must check kidney function
tubular excretion and protein bounding minimal
half life 30 -50 mins

Question 31

What can osmolality do

Answer 31

increase osmolality–> endothelial damage
thrombosis
pain vasodialtion

Question 32

What are rare and unpredictable reactions to contrast media called

Answer 32

idiosyncratic

Question 33

what are predictable reactions to contrast media called

Answer 33

non idiosyncratic reactions

Question 34

what is umbra and peumbra

Answer 34

umbra x rays that create image complete shadow

peumbra x rays that scatter partial shadow

Question 35

What happens if CXR taken A-P

Answer 35

heart appear bigger

Question 36

Name some radiosensitive organs

Answer 36

lens of eye
thyroid
gonads

Question 37

What is MR spectroscopy

Answer 37

can look at chemical concentrations in certain regions of the brain
e.g. biomarkers in hypoxic ischemic encephalopathy in neonates