Introduction to Radiology

Question 1

what part of the electromagnetic spectrum are x-rays in?

Answer 1

the high energy end

Question 2

how do we get an x-ray image?

Answer 2

high energy allows x-ray to pass through body and reach a film those not absorbed (the remaining photons) expose the film

Question 3

what is the order in which things stop x-rays?

Answer 3

bone>soft tissue>fat>gas

Question 4

what are x-rays used for? (4)

Answer 4

to look at trauma, joint diseases, chest pathology, bowel obstruction

Question 5

what are the problems with x-rays?

Answer 5

high energy -> free radicals -> genetic damage -> cancer risk increased

Question 6

what is the ALARA principle?

Answer 6

as low as reasonably possible

Question 7

who needs extra care when conducting x-rays? (3)

Answer 7

women of child bearing age, children, known pregnancy

Question 8

length of background radiation for chest x-ray…

Answer 8

3 days

Question 9

length of background radiation for lumbar spine/pelvis x-ray?

Answer 9

5 months

Question 10

what does CT stand for?

Answer 10

computer tomography

Question 11

what does a CT scanner do?

Answer 11

works out the densities of organs and structures to make up an image

Question 12

what are the uses of CT? (4)

Answer 12

stage tumours, trauma, cerebrovascular disease, surgical emergencies

Question 13

what are the problems with CT? (2)

Answer 13

expensive = £500,000 to buy, £300-500 thousand a year to run and radiation dose = CT abdomen/pelvis is 1200 days

Question 14

what does PET stand for?

Answer 14

positron emission tomography

Question 15

how does PET work? (physics)

Answer 15

unstable compound decays by emitting a positron (antimatter), positron hits electron resulting in mutual annihilation causing a 180 degree pulse of gamma radiation

Question 16

how does PET work? (metabolism)

Answer 16

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

Question 17

uses of PET?

Answer 17

staging of tumours - may detect occult spread, detecting recurrence after treatment

Question 18

PET limitations… (4)

Answer 18

cyclotron (mini particle accelerator), short half life, expensive, radiation does = 750 days

Question 19

ultrasound strengths… (2)

Answer 19

soft tissue detail, safe

Question 20

main uses of ultrasound? (4)

Answer 20

heart, pelvis, abdominal solid organs, obstetrics

Question 21

ultrasound weaknesses… (2)

Answer 21

cannot penetrate bone, ultrasound waves scattered by air = cannot view bowel and solid organs may be obscured by gaseous bowel

Question 22

what does MRI stand for?

Answer 22

magnetic resonance imaging

Question 23

how does MRI work?

Answer 23

short burst of radio waves applied at resonant frequency, protons give up energy which is detected to make a picture

Question 24

what are uses of MRI? (4)

Answer 24

musculoskeletal system, pelvic neoplasms, angiography, cardiac imaging

Question 25

what are the advantages of MRI? (4)

Answer 25

non-ionising radiation, few known side effects, good soft tissue visualisation, able to do functional studies

Question 26

what are the disadvantages of MRI? (5)

Answer 26

expensive, dangerous = metal object in room or patient, very strong magnetic field, claustrophobic, noisy, can take a long time

Question 27

what does angiography look at?

Answer 27

blood/lymph vessels

Question 28

what is used to show up the lumen of the small bowel?

Answer 28

contrast media eg iodine compounds/barium