X-ray

Question 1

what is ionising radiation?

Answer 1

radiation that causes ionisation when it interacts with matter (causes electrons to be knocked out of matter)

Question 2

where do gamma rays come from?

Answer 2

nucleus of the atom

Question 3

where do X-rays come from?

Answer 3

movement of electrons

Question 4

why do we use ionising radiation?

Answer 4

can penetrate through the body and be captured on image detectors

Question 5

indirect interaction of radiation with matter

Answer 5

radiation interacts with water in our bodies and splits up water molecules into free radicals, free radicals have an impact on the cell structure

Question 6

direct interaction of radiation with matter

Answer 6

radiation can directly impact on DNA strand, cause breaks, they have an effect on cell structure

Question 7

radiation damage (direct)

Answer 7

visible effects after a threshold is reached; erythema, hair loss

Question 8

radiation damage (indirect)

Answer 8

• risk of cancer induction
• risk of genetic change in subsequent population
• (effect is proportional to radiation dose but there is no threshold)

Question 9

what is dose?

Answer 9

the amount of radiation that has been imparted to the patient

Question 10

principles of positron emission tomography

Answer 10

patients injected with positrons; interact with electrons in our body, cancel each other out & penetrating gamma rays are detected

Question 11

attenuation of X-rays

Answer 11

attenuation increases with higher atomic number, higher density
X-rays are an attenuation map: bone stops X-rays that muscles and lungs wouldn’t

Question 12

Transmission imaging

Answer 12

• radiation directed through the patient
• transmission map collected
• good at showing structure between tissues of different densities or atomic number

Question 13

Emission imaging

Answer 13

• radiation is administered to a patient in the form of a tracer
• emitted radiation is detected outside the patient

Question 14

how are x-rays controlled?

Answer 14

• high voltage controls the energy of the x-rays

- current controls the amount of x-rays

Question 15

x-ray set up

Answer 15

x-ray and x-ray film detector, with the patient in between

• x-ray beam penetrates through the patient
• don’t see bony tissues, just bony structures

Question 16

uses of x-ray

Answer 16

• diagnostic x-ray: fracture
• dental radiology
• normal chest x-ray
• mammography

Question 17

how fluoroscopy is used in real-time x-ray

Answer 17

catheter fed inside artery & radio opaque dye is injected
shows the blood flow inside vessels (can show any areas that have been blocked)

Question 18

limitations of planar x-ray

Answer 18

• cant distinguish between overlying tissues

- overlying tissues reduce the contrast between different layers

Question 19

CT scanner

Answer 19

X-ray tube & detector rotates around the patient, obtain 3D slices

Question 20

gamma camera

Answer 20

• Uses single photon emitting radionuclides

- Can operate in 2D (planar) or 3D (SPECT)

Question 21

nuclear medicine imaging

Answer 21

• only shows function

- make an image distribution of the radioactive tracer

Question 22

half-life

Answer 22

time taken for radioactivity to reduce 50%

Question 23

metabolism of FDG

Answer 23

FDG is a glucose analogue which enters cells in the same way as glucose: good reflection of the distribution of glucose uptake

Question 24

PET scanner

Answer 24

ring of detectors, photos emitted and recorded

Question 25

what is hybrid imaging

Answer 25

Combination of nuclear medicine and X-ray
Get functional imaging from nuclear medicine, this is localized and pinpointed on the actual anatomy of the patient
Can define and localize where the actual function is taking place within the patient