Medical applicafions of physics

Question 1

CCDs

Answer 1

charge-coupled decides

detect X-rays and produce electronic signals to form high-resolution images

Question 2

CT scanners

Answer 2

X-ray fired through patient
detected by detectors on opposite side
beam+detector slowly rotate around patient
computer interprets signals, forms image
lots of patient exposure to X-ray

Question 3

fluoroscopy

Answer 3

patient stands between X-ray source and fluorescent screen
many images taken to form short film
intensity of X-rays depends on structures inside body
fluorescent screen absorbs X-ray and gives off light to show live image

Question 4

ultrasound uses

Answer 4

prenatal scanning (safer than x-rays as not ionising but images fuzzy)
shatter kidney stones into small particles
investigate blood flow (identify blockages in veins, artistries, heart)
cleaning and control quality in industry

Question 5

how ultrasound used to measure distance between boundaries

Answer 5

ultrasound partially reflected at boundary between 2 materials
part of ultrasound travels back through material to detector at first boundary
rest of wave continue to travel through second material until reaches another boundary
wave reflected back and detected by detector
distance = speed x time

Question 6

endoscope uses

Answer 6

instrument used to see inside patients body without cutting open
helps in diagnosis and keyhole surgeries

Question 7

endoscope structure

Answer 7

one bundle of optical fibres carries light into body
other bundle collects light reflected off internal body surfaces using lenses
reflected light sent along fibres seen by computer screen/eyepiece
see full-colour moving image

Question 8

pulse oximetre

Answer 8

measure percentage of oxygen carried by haemoglobin
passes two beams of light (one red, one infrared) through patient to sensor that measured light
amount of light absorbed by blood depends on oxyhaemoglobin content (it absorbs light)
normal = at least 95%

Question 9

PET scan

Answer 9

position emission tomography
multiple images taken to build 3D of image of body
radioactive isotope (tracer) emits position in body of patient (injected or swallowed)
collides with electron (annihilation converts mass to gamma rays)
detectors take images of radiation emitted

Question 10

how tumour cells detected by PET scan

Answer 10

more active so will take up more tracers

more annihilation occurs detected by detectors

Question 11

Einstein’s equation

Answer 11

E = mc^2

energy (J) = mass (kg) x speed light (3x10^8 ms^-1)