PET Scanning And Radiotherapy

Question 1

what is a radioactive tracer used for

Answer 1

used to investigate a patients body without need for surgery

Question 2

how is radioactive tracer put in a patients body

Answer 2

• small amount of radiation is put in the body through a substance that the body can absorb
• a radiographer puts a detector around the body to detect and gamma rays that pass out of the body

Question 3

what are the 3 ways radioactive tracer can be put in the body

Answer 3

• drinking
• ingesting
• injecting

Question 4

what happens after the radioactive tracer enters the body

Answer 4

it’s given enough time to diffuse through the body then as radiographer positions a detector

Question 5

what does the detector do

Answer 5

produces the picture of a patients internal organs, outside the body

Question 6

what is special about gamma emitters and the tracers

Answer 6

• they pass through the body easily and cause little ionisation
• the half life of the tracers is manufactured to be short so the radiation the patient is exposed to is minimised

Question 7

explain how PET scanners work

Answer 7

• radioactive tracer molecules are injected into patient
• time given for it to diffuse through blood stream and reach organ
• easily absorbed by cells as it has a similar form to glucose
• more TM is taken up by more active cells
• part of TM contains short-lived radioactive isotope
• radioactive emissions from organ are detected
• differences in activity of different parts of the organ are examined

Question 8

in detail, explain how the radioactive tracer molecule works

Answer 8

• isotope undergoes b+ decay, releasing positron
• immediately collides with an electron
• collision releases 2 gamma rays in opposite directions
• PET scanner detects both gamma rays, calculating the position of the source
• tumour will lie along the path of each pair
• if at least 3 pairs of gamma rays are detected, position calculated by a computer by triangulation

Question 9

what does PET scanning stand for

Answer 9

positron emission tomography

Question 10

what is PET scanning

Answer 10

• a technique used to show tissue or organ functions

- or diagnose medical conditions

Question 11

how can PET scanning identify active cancer tumours

Answer 11

by showing metabolic activity in tissue

Question 12

what is a tracer molecule

Answer 12

a substance that can be used by the body, like glucose

Question 13

why is more tracer molecule taken up by active cells

Answer 13

• because they have a much higher metabolism than healthy cells
• as theyre growing at a much faster rate
• therefore need more energy (like glucose)

Question 14

what does the distribution of radioactivity match up with and why

Answer 14

• metabolic activity
• ## because more tracer molecule injected is used by more active cells doing more work

Question 15

what is used to create the images of a PET scan that the computers observe

Answer 15

the distribution of radioactivity

Question 16

how are tumours shown differently than other tissues while PET scanning

Answer 16

• because more active cells take in more tracer molecule
• more b+ decay would take place in the cell
• meaning more positrons are created
• so more positrons collide with more electrons
• creating more pairs of gamma rays
• making their own distribution of radiation to be processed