Summary of "GCSE Physics - Using Radiation in Medicine"

GCSE Physics: Using Radiation in Medicine

Ionizing radiation removes electrons from atoms/molecules, which can:
- Damage cells generally and mutate DNA, potentially causing cancer.
- Kill cells outright at sufficiently high doses — the basis for radiation sickness and for therapeutic uses (radiotherapy).

High doses can destroy many cells (radiation sickness); controlled doses can be used to kill cancer cells (radiotherapy).

Results from large whole-body doses.
Common symptoms: vomiting, tiredness and hair loss, caused by widespread cell destruction or severe damage.

Uses the cell-killing effect of ionizing radiation to destroy cancer cells.
Two main delivery methods:
- External radiotherapy
  - Typically uses gamma rays.
  - Beams are aimed at the tumour from multiple angles so the tumour receives the highest cumulative dose while surrounding healthy tissue receives less.
- Internal radiotherapy (brachytherapy)
  - Radioactive source is placed inside or next to the tumour.
  - Often uses beta radiation, which causes strong local damage but has limited penetration compared with gamma.
Side effects
- Healthy cells near the treatment area can be damaged or killed, causing patients to feel unwell.
- Patients and clinicians weigh the likely benefits against possible side effects.

Radioactive isotopes are introduced into the body (injected or swallowed); emitted radiation is tracked to follow movement and uptake.
Purpose: assess organ function by checking whether an organ absorbs the tracer as expected (example: radioactive iodine to check thyroid uptake).
Typical choices
- Gamma-emitting isotopes are commonly used because gamma rays penetrate the body and are suitable for external detection; beta emitters are sometimes used.
- Prefer isotopes with short half-lives so they emit radiation only while measurements are taken, then decay and stop being hazardous.

Use of radiation in medicine requires balancing benefits against harms.
Medical tracers: diagnostic value generally outweighs the small, short-term radiation risk; doses and half-lives are minimized.
Radiotherapy: can be life‑saving and often justifies side effects, though some patients decline treatment when expected benefits are limited.

External radiotherapy
1. Select a gamma-emitting source/beam.
2. Plan beam directions so the tumour receives the highest dose (multiple angles).
3. Monitor and adjust to minimize dose to surrounding healthy tissue.
Internal radiotherapy (brachytherapy)
1. Choose an appropriate radioactive source (often a beta emitter).
2. Place the source inside or adjacent to the tumour.
3. Use the limited penetration of beta radiation to localize damage to the tumour area.

Choose a suitable radioactive isotope (prefer gamma emitters when possible).
Prefer isotopes with a short half-life to limit exposure.
Administer the tracer (inject or have the patient swallow it).
Use detectors/scanners to track emitted radiation and observe uptake by target organs.
Interpret tracer uptake to assess organ function or identify abnormalities.
Minimize dose consistent with diagnostic needs.