Brachytherapy: a form of radiotherapy in which the source of radiation is applied in or on the patient in one prolonged dose, using surface applicators, needles, seeds or suspensions for use in serous cavities.
Electron: A negatively charged sub atomic particle arranged in orbits around the nucleus of an atom.
Gamma (γ) Rays: high energy electromagnetic radiation emitted from the nucleus of a radioactive materiall. Gamma ray emission is one means by which an unstable atomic nuclei lowers its energy state.
Plesiotherapy: The word “plesios” comes from the Greek and means “near” or “close”. Plesiotherapy involves the administration of radiation therapy using a beta particle admitting Sr-90 applicator. This therapy is ideal for treating small and superficial tumors.
Systemic radionuclide therapy: a form of radiotherapy in which the source of radiation is administered directly into the patient. Methods of delivery include oral administration and subcutaneous or intravenous routes.
Teletherapy: a form of radiotherapy in which the source of radiation is applied from a distance from the body. Also called external beam radiotherapy.
What is radiotherapy?
Radiotherapy, or radiation therapy, refers to the use of ionizing radiation usually for the treatment of malignant tumors and occasionally selected benign diseases. Radiotherapy can be categorized into several different forms:
- brachytherapy - a form of radiotherapy in which the source of radiation is applied in or on the patient in one prolonged dose, using surface applicators, needles, seeds or suspensions for use inside body cavities.
- plesiotherapy - is a form of brachytherapy and involves the administration of radiation therapy using a beta-particle emitting Sr-90 applicator.
- systemic radionuclide therapy - a form of radiotherapy in which the source of radiation is administered directly into the patient. Methods of delivery include oral as well as subcutaneous or intravenous routes. This includes both systemic radioiodine (131I) therapy for thyroid disease as well as 153Sm-EDTMP therapy for bone cancer.
- teletherapy - a form of radiotherapy in which the source of radiation is administered from a distance from the body. Also called external beam radiotherapy. This form of radiotherapy involves the use of a machine to produce the radiation and aim it at the region of affected anatomy of the patient.
How does systemic radiotherapy work?
Systemic radionuclide therapy is a form of radiotherapy that involves administering the source of the radiation into the patient. With systemic radionuclide therapy the physiology of the disease provides a major contribution to the therapy ultimately resulting in the delivery of the radionuclide to the tumor. By using a radioactive material that will be delivered to the tumor by the patient's own physiologic processes, it is possible to deliver a large dose of radiation to certain tumors with a minimal amount of patient manipulation. The most commonly utilized forms of systemic radiotherapy performed in veterinary medicine include radioiodine (131I) for thyroid tumors and radioactive samarium (153Sm-EDTMP) for primary or metastatic bone cancer. Thyroid tissue has the unique ability to concentrate iodine. The nonspecific (by either oral or subcutaneous injection) administration of radioactive iodine to a patient with a thyroid tumor can result in the very selective delivery of a dose of radiation to that tumor. Similarly the intravascular administration of a phosphorus-like chemical (EDTMP), that is bound to a radioactive form of samarium (153Sm) can result in the delivery of a dose of radiation to bone tumors.
How is radiotherapy used at AVMI?
AVMI uses systemic radionuclide therapy in the following ways:
- Radioiodine (131I) therapy for benign thyroid tumors causing hyperthyroidism in cats
- Radioiodine (131I) therapy for malignant thyroid carcinoma in dogs and cats.
- Samarium 153Sm-EDTMP therapy for malignant bone tumors.
AVMI uses plesiotherapy in the following ways:
- Local treatment for both malignant and benign superficial tumors in areas, frequently on the face around the eyes or nose, where surgical excision could prove problematic.