10.6.5 Use of radioactive implants

Radioactive Implants for Tumour Treatment

Radioactive implants are a method of delivering beta radiation directly to a tumour to destroy cancerous cells. These implants are placed either next to or inside the tumour, allowing for targeted treatment. Beta radiation is chosen because it has ionising properties, meaning it can damage or kill cells in close proximity to the implant. Since beta particles have limited penetration depth, they release their energy close to the site of implantation, minimising the impact on surrounding healthy tissue.

How Radioactive Implants Work:

• Ionising Radiation: As the beta radiation is emitted, it causes ionisation, which is lethal to cells at the radiation's impact site. This makes it effective in targeting cancer cells near the implant.
• Energy Limitation: Healthy cells that are further from the implant remain largely undamaged. This is because beta particles lose energy relatively quickly, so they're absorbed before reaching distant tissues.

Implant Characteristics and Half-Life:

• Half-Life Consideration: The radioactive material used in these implants must have a long enough half-life to maintain therapeutic effectiveness. A commonly used isotope, Iridium-$192$, has a half-life of $74$ days, which provides sustained treatment over time.
• High Dose to Targeted Area: Radioactive implants can deliver higher doses of radiation to smaller, specific areas than external beam radiotherapy. This increases treatment efficacy while minimising risk to the rest of the body.

Benefits of Using Radioactive Implants:

1. Localised Treatment: By placing the radiation source close to or within the tumour, there's a reduction in damage to surrounding healthy cells.
2. Sustained Radiation Release: The longer half-life of materials like Iridium-$192$ means that treatment can continue without frequent re-implantation.
3. Effective Dose Distribution: This approach allows for a concentrated dose, increasing the likelihood of tumour reduction or eradication while reducing the potential for broader tissue damage.