4. The equipment used in radiation oncology

From greek.doctor
  • 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