Radiation Therapy delivery:
Ionizing Radiation
For certain cancer treatment types, ionizing radiation is conducted in the form of external beam radiation. Simply put, a machine applies radiation over the surface level of the skin.
All external beam radiation therapies (EBRT) use high-energy radiation to target and kill tumours by either causing irreparable DNA damage within the cancer cells or by disrupting the vascular supply to the growing tumour. The most common radiation technique uses high-energy x-rays, which deposit a radiation dose in a path from the body surface to the location of the tumour. In most cases the x-ray beam will continue to travel through the tumour without stopping and continue to deposit the remaining radiation energy into healthy tissues and organs beyond the tumour. Any remaining radiation energy deposited beyond the intended target is called an “exit dose”.
Proton Beam Therapy (PBT) does not damage healthy tissues beyond the tumour, as proton beams stop precisely at the back edge of the tumour.
Body Mold or Head Mask
During external beam radiation therapy, a body or face mould may be required to assist the cessation of movement during the delivery of treatment.
For the treatment of cancer types that do not benefit from external beam radiation therapy, ionizing radiation is administered internally in the form of internal beam radiation, whereby, as the name suggest, the radiation is put internally in the body. This is more commonly known as brachytherapy.
Brachytherapy
Brachytherapy is the temporary or permanent placement of radioactive sources within, or near, a tumour (subdermally). Also known as internal radio therapy or implant therapy, the advantage of this form of treatment is that it can deliver a high dose of radiation to a specific tumour area, with a rapid falloff in dosage to adjacent normal tissues.
Permanent (low dose rate = LDR) Brachytherapy: Traditionally, this has been done through low-dose permanent radioactive seeds implanted into the cancerous and/or surrounding tissue. The seeds used for the implant are smaller than a grain of rice. The seed capsule itself is made from titanium, and the radioactive isotope is sealed in small beads that are placed inside the capsule.
Temporary (high dose rate = HDR) Brachytherapy: A new option is the placement of temporary sources of radiation, where higher doses may be utilised. Cancers of the breast, vagina, cervix, prostate, and bronchus are the most common sites for temporary brachytherapy. Thin catheters are first placed in the tumour. The catheters are then connected to an HDR after loader. A computer will control how long the pellet stays in each catheter (the dwell time), and at which point of the catheter it should pause to release radiation. After a series of treatments, the catheters are removed, and at which point, there are no radioactive seeds left in the body.
MammoSite Radiation Therapy System (RTS): This is a tumour site-specific radiation therapy system for breast cancer. The device is comprised of a balloon catheter that internally administers the prescribed dose of radiation to targeted breast tissue in a 1-5 day course of therapy.