4. The equipment used in radiation oncology

Types of radiotherapy
- External beam radiation therapy (EBRT)/teletherapy
  - The radiation source is outside the patient
  - The source can be rotated around the patient, allowing the radiation beam to target the tumour from a variety of directions
  - Types
    - Conventional external beam therapy
    - Three-dimensional conformal radiotherapy (3DCRT)
    - Intensity modulated radiation therapy (IMRT)
    - Stereotactic radiosurgery/radiotherapy
- A multileaf collimator (MLC) is used to shape the radiation beam
  - Especially used in IMRT and 3DCRT
- Internal radiation therapy/brachytherapy
  - The radiation source is inside or very close to the patient, as close to the tumour as possible, or even inside the tumour
  - Can be temporary or permanent
    - Temporary brachytherapy – the radiation source is placed and then removed after some time
      - Most common
    - Permanent brachytherapy – a small radiation source is permanently placed into the patient
      - Also called “seed implantation”
      - The radioactive “seed” loses its radioactivity after some months, but won’t be removed
  - Can be high dose-rate (HDR), low dose-rate (LDR) or pulsed dose-rate (PDR)
    - HDR reduces the treatment time, and is most commonly used
    - HDR = dose rate of more than 12 Gy per hour
      - Treatment typically lasts a few minutes
    - LDR = dose rate of less than 2 Gy per hour
      - Treatment typically lasts 24 hours
    - PDR = short pulses of radiation are given
      - Treatment typically lasts 24 hours
  - Types
    - Intracavital brachytherapy
      - Into the cervix, bronchi, etc.
    - Interstitial brachytherapy
      - Into the breast, prostate, etc.
- Systematic radiation therapy
  - An isotope is injected into the patient, by itself or attached to a specific molecule
  - The isotope will travel to the tumour and irradiate it from inside
  - The isotope often gives off alpha or beta-waves, as these waves don’t travel far in the body
    - Alpha waves only travel 100 µm
  - Examples
    - Radioactive iodine given for thyroid cancer
    - Radium-223 given for bone metastases
Equipment used in brachytherapy
- Afterloading
  - The technique where a machine (an afterloader) is used to deliver the radiation source into the patient during brachytherapy
  - This eliminates the need for a person to deliver the radiation source, eliminating radiation exposure for that person
    - Manual delivery of brachytherapy is seldom used for this reason
  - Often used with HDR, sometimes called HDR Afterloading
  - 192Iridium is often used as radiation source
Equipment used in teletherapy
- Cobalt unit
  - Older type of teletherapy
  - The external beam is generated using 60Cobalt
- Linear accelerator (LINAC)
  - More modern than cobalt unit
  - Most commonly used device for external beam radiation therapy
  - The external beam is generated using linear acceleration
  - A multileaf collimator allows precise modification of the radiation field
  - Used for stereotactic surgery, intensity modulated radiotherapy, particle therapy etc.
- Gamma knife
  - Used for stereotactic radiosurgery in the brain
- Tomotherapy
- CyberKnife