| Term | Description |
| 3-dimensional conformal radiotherapy (3DCRT ) | A form of external beam radiotherapy delivered by linear accelerators where a 3D CT data set and a 3D computer planning system are used to define and calculate treatment fields to deliver a conformal dose to a tumour. |
| Afterloading | Remote loading of the radioactive isotopes after positioning of the applicators during surgery; used for brachytherapy. |
| Beam's eye view (BEV) | An image generated by a 3D treatment planning system that is similar to a conventional simulator radiograph with the field dimensions (including shielding) added to the image. |
| Brachytherapy | The use of radioactive isotopes inserted into either tissue (interstitial) or body cavities (intracavity) to deliver radiation close to a tumour bed. |
| Computed tomography (CT) | A form of radiographic imaging whereby multiple axial sections of a patient are scanned. The images are displayed in a greyscale and are a useful tool for viewing cross sectional anatomy. These sections can be viewed slice-by-slice or combined to form a 3D image of the patient. |
| Dose | The amount of radiation in the form of Gys to be delivered to the target. |
| Digitally reconstructed radiograph (DRR) | An image generated from a 3D CT scan of a patient that looks like a conventional radiograph. |
| Electron | The smallest particle of negative electricity. Electrons have a useful property of limited penetration of tissue as opposed to the exponential absorption that occurs with x-rays. |
| External beam radiation therapy (EBRT) | Radiation therapy delivered at a distance from the body, most commonly by a linear accelerator. (Also called teletherapy.) |
| Field | An area treated by the radiation beam at a particular angle. A radiotherapy treatment can be delivered using a single field or multiple fields at different angles. |
| Fractionation | The total dose of radiation to be delivered is divided by the daily dose (daily fraction) which gives a cumulative effect to the tumour but enables normal surrounding tissue to repair. |
| Gamma radiation | A photon produced from radioactive material. |
| Gray (Gy) | The modern unit of radiation dosage, equivalent to the deposition of one joule of energy per kilogram of tissue. |
| Image guided radiation therapy (IGRT) | The use of imaging technologies on the linear accelerator to enable accurate daily treatment delivery. |
| Intensity modulated radiotherapy (IMRT) | A form of EBRT where each treatment field is designed to have a highly varied (or modulated) intensity to treat tumours to a high dose that are adjacent to or surround radiosensitive normal tissues. |
| Linear accelerator (Linac) | A radiation treatment machine which produces beams of x-rays or high energy electrons that are focused on to a tumour within the body. Linear accelerators deliver millions of volts of radiation (MeV), depending on the type of machine and output. |
| Megavolts (MV) | A megavolt (millions of volts) is the unit of measurement of photons greater than 1 MeV energy. These are produced by Cobalt-60 apparatus and linear accelerators. |
| Photon | Energy produced by either gamma or x-rays. Commonly used to treat deep-seated tumours. |
