Imaging: Principles

Question 1

4 types of imaging

Answer 1

X-Rays, US, MRI, nuclear medicine

Question 2

downsides to X-rays

Answer 2

if the pathology is of similar density to its surrounding tissues it wont be shown

Question 3

describe contrast studies

Answer 3

liquids containing dense elements (i.e. barium, iodine) can block X-rays, by putting these in spaces between tissues, the tissue outlines become visible

Question 4

describe CT scans

Answer 4

uses X-rays to create cross-sectional, all round body images that show soft tissue pathologies of similar densities

Question 5

downside of CT

Answer 5

lots of ionising radiation, soft tissues of very similar densities can’t be distinguished, can’t show bone marrow disease
(pelvic organs, muscles and tendons, joint cartilage and ligaments, some areas of the brain aren’t shown)

Question 6

describe US

Answer 6

transmitter emits sound which is either absorbed or reflected, that reflected is picked up by transducer and converted to electrical impulses fed to the computer
cross sectional images produced

Question 7

for a good US

Answer 7

good skin/transducer contact, superficial structures, slim patient, correct transducer selection
tissues with different acoustic properties

Question 8

US strengths

Answer 8

• quick, easy, cheap
• shows pelvic organs, muscles and tendons
• high spatial resolution - useful in MSK imaging
• abnormal fluid collections shown well as fluids transmit and body structures reflect
• soft tissues with different acoustic properties differentiated well

Question 9

US downfalls

Answer 9

• bone blocks - cnat see brain, spinal canalm inside joints or assess bone marrows
• gas blocks US - lung, bowels and ‘gassy’ patients difficult to assess
• fat patients make poor subjects

Question 10

MRI strengths

Answer 10

• most complete brain assessment
• assess acute muscle and tendon tears (esp. in deep tissues)
• shows spinal canal disease and interior of joints to be assessed (cartilage and ligaments)
• bone marrow disease can be assessed

Question 11

MRI downfalls

Answer 11

• frostbite, thermal burns and deafness
• disturbance of ferrous metals, missile injuries - can cause harm
• expensive, claustrophobic and takes time (pain, restless or monitored patients cant get)
• poor lung detail

Question 12

role of imaging

Answer 12

• make/confirm diagnosis or narrow down DD
• stage a known disease or inform treatment
• monitor treatment effects and follow up on disease
• aid intervention/deliver treatment