Treatment through controlled deposition of ionizing absorbed dose. External beams and internal radiopharmaceuticals require different delivery and radiation dosimetry models.
An effect-equivalent dose derived from the linear-quadratic radiobiology model, with a subscript often indicating the tissue's assumed in gray. It is distinct from the physical total absorbed dose . Increasing fraction size at fixed tumour BED can increase the normal-tissue BED when the latter has smaller .
A model for surviving fraction after radiation dose . Independent fully repaired fractions add their logarithmic effects. For equal fractions and no repopulation, dividing the total log kill by gives the biologically effective dose . Comparing tissue types requires their own parameters and the same stated repair assumptions.
The variation of absorbed dose with depth for a specified beam, geometry and medium. A megavoltage photon beam has a secondary-electron buildup region followed by gradual dose reduction. A nearly monoenergetic proton beam instead exhibits a Bragg peak near the end of its range.
A specified geometry, beam configuration and dose prescription intended to cover a target while limiting normal-tissue dose. Robustness to setup, motion and anatomy changes is part of assessing a plan.
Treatment using proton beams with controllable finite range and a Bragg peak. Potential normal-tissue sparing must be assessed against range uncertainty, motion and biological-effect uncertainties.
Uncertainty in where a charged-particle beam stops because of material conversion, anatomy, motion or delivery errors. A steep distal dose gradient makes it particularly consequential for target coverage and nearby tissue.
External-beam treatment using photons that create secondary charged particles in tissue. Megavoltage depth-dose curves usually show build-up followed by an extended fall-off and exit dose.
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Radiation therapy, also known as radiotherapy, is a medical treatment that uses high doses of radiation to kill or damage cancer cells. It is a common treatment for various types of cancer and can be employed either alone or in conjunction with other treatments, such as surgery and chemotherapy. ### Key Points about Radiation Therapy: 1. **Mechanism:** Radiation works by damaging the DNA within cells. Cancer cells are generally more sensitive to radiation because they are dividing more rapidly than most normal cells.