SP4g Radioactivity in Medicine Flashcards
How are radioactive medical tracers used? (3)
.they are injected directly into an organ, swallowed or inhaled
.they attach to molecules that are taken up by particular organs
.their progress is followed using an external detector - a gamma camera
Which type of emitters are suitable to be taken into the body and why?
only gamma or beta emitters are suitable because they can penetrate out of the body.
Explain how PET (positron emission tomography) scans work? (3)
.PET scanning uses tracers that emit positrons
.almost immediately the poistrons meet electrons in an organ and annihilate
.the high energy gamma ray pairs are then picked up by gamma cameras
Explain what occurs during PET scanning?
.the patient is injected with a radioactive isotope that undergoes β+ decay (the tracer)
.when nuclei in the tracer decay, they emit positrons
.when a positron meets an electron, they annihilate and two gamma rays are emitted
.the PET scanner detects the gamma rays and calculates where the radiation came from
.the PET scanner moves around the patient and detects lots of pairs of gamma rays
Why must isotpes used in PET scanners be produced nearby?
.Isotopes used in PET scanners have short half-lives, ensuring patients are affected by ionising radiation as little as possible
.They are produced in cyclotrons in the hospital and used within hours/minutes of production, otherwise their activity would be too low, rendering them useless
What is radiotherapy?
.the treatment of cancer using ionising radiation
.a radioactive source can be used externally by directing radiation from the outside, or internally by implant or injection
What occurs during radiotherapy? (3)
.cancer cells diving uncontrollably to form a tumour
.high dose of radiation directed at cancer cells only, ionisation causes lots of damage to the cells
.cancer cells die
What radiation does most radiotherapy use?
.beams of gamma as it can penetrate the body
.sources used can have long half-lives so don’t have to be replaced so frequently
What radiation is used in internal radiotherapy?
.alpha or beta emitters which are highly ionising. They are placed within or close to the tumour
.sources need to have short half-lives to limit radiation emitted in the patients’ bodies to reduce risk
What are 3 advantages of internal radiotherapy?
.works precisely targeting the tumour
.reduced risk of unnecessary damage to surrounding healthy tissues and organs so reduces the long-term side effects
.clinically proven to be effective
What are 2 advantages of external radiotherapy?
.does not require a hospital stay
.clinically proven to be effective
What is an disadvantage of internal radiotherapy?
.radiation stays in the body for a few days, so requires hospital stay, and avoidance of close contact for this time
What are 2 disadvantages of external radiotherapy?
.treatment course can be long (4-7) weeks with daily outpatient visits
.risk of long-term side effects as the radiation has to pass through healthy tissue
