19 Fundamentals of medical imaging

Question 1

X-ray

Answer 1

Xray emitter shoots xrays through a person and to the detector.
If dense like bone it absorbs more radiation. this is called attenuation.
can use contrast to add density to areas that arent normally dense. eg can see narrowing of tubes

Question 2

front back top bottom

Answer 2

anterier
posterier
superior
inferior

Question 3

towards midline?

away from midline?

Answer 3

medial

lateral

Question 4

different planes:
cut in half down the midline
cut in half like putting a headband on
cut in half at waist

Answer 4

sagittal plane
coronal plane
transverse plane

Question 5

issues with xrays

Answer 5

2D
radiation
poor for soft tissues

Question 6

CT: computed tomography

Answer 6

use xrays to create 3d image
very quick: minutes
give contrast to increased density
normally use transverse plane
good for bone study

Question 7

units of attenuation?

Answer 7

hounsfield units

Question 8

issues with ct

Answer 8

still using ionising radiation as xray

poor detail of soft tissues

Question 9

fluoroscopy

Answer 9

essentially an xray movie, take serial xrays in sequence.

Question 10

PET positron emission tomography

Answer 10

a scanning modality done by muclear medicine
radioactively labelled substance injected, normally glucose. then scan to show tissue with high glucose uptake aka metabolically active.
often in combo with ct scan to give 3d view
normally used for cancers, epilepsy and dementia

Question 11

MRI magnetic resonance imaging

Answer 11

the machine is concerned with the spin of hydrogen ions, which is normally random but the MRI machine is a massively powerful magnet which causes the orientation of the spinning to line up about half up and half down. there are some ions that are not matched together and point the same way. these are the important ones.
The MRI applies a radio frequency pulse which gives energy to the unmatched ions and they flip to spin the other way. after the ions return to the way they were before they release a bit of energy which is detected and turned into an image by the computer with the difference betweem tissues arising cus freq of energy is emitted.

Question 12

Colour of the fluids:
T1
T2

Answer 12

Black

White

Question 13

Issues with MRI

Answer 13

expensive
claustrophobic
noisy
slow test
not great for bones but good for soft tissues
cannot be used for people with metal implants

Question 14

Ultrasound

Answer 14

sonar principles. ultrasound freq emitted from probe, sound waves travel into tissue and reflect back off changes in density, the reflection is detected.
Probes work using the piezoelectric crystal effect.
Used for pregnancies, heart valves.
its quick and doesn’t use radiation.

Question 15

how can you improve the ultrasound

Answer 15

increase frequency waves for better resolution only if not deep. if deep then poorer resolution.

Question 16

Issues with ultrasound

Answer 16

poor detail
bad imaging of bones
can’t view past air which is why the jelly is used
user dependant results