Principles of radiation therapy and Isotopes
Principles of radiation therapy and Isotopes in veterinary practices are used to treat animal’s various conditions like neoplasms.
Radiation therapy in veterinary practices is the use of X-rays or radioisotopes for the treatment of Neoplasms of domestic animals. First radiation therapy in veterinary practices reported by Dr. R.Eberlin of Berlin Veterinary School (1906-1912).
Principles of radiation therapy
Radiation therapy works by making small breaks in the DNA inside cells. These breaks stop cancer cells from multiplying and expanding, ultimately leading to their demise. Radiation can also damage nearby normal cells, but for the most part they recover and resume their usual functions.
Terms in radiation therapy
Radiosensitivity
Radiosensitivity refers to the susceptibility of the cells or tissue to the killing effect of absorbed radiation.
Radioresponse
Radioresponse is the degree to which a normal or neoplastic tissue visibility changes during or after radiotherapy.
Radiocurability
In vet practice, Radiocurability is a two-year patient survival after radiotherapy without further progress of the neoplasm and subsequent metastasis.
Radio Isotopes or Radionuclide in veterinary practice
Radio Isotopes or Radionuclide are unstable form of a chemical element that releases radiation as it breaks down and becomes more stable.
These unstable Radio Isotopes or Radionuclide undergo the process of spontaneous decay to form stable nuclides by the process of radioactive decay. During this process of decay, there is emission of radiation energy from the isotopes. Such isotopes are called as radioisotopes (or) radionuclides. Isotopes are those nuclides, which have same atomic number but different mass number. ie. Isotopes of a given atom have same number of protons but different number of neutrons.
Isotopes of iron and carbon are stable where as isotopes of cobalt, cesium etc. are unstable. Naturally occurring radioisotopes are radium, thorium, radium etc.
Radioactivity
Radioactivity is an exponential decay artificially produced by irradiation of stable nuclides by subatomic particles such as neutrons in an nuclear reactor. In this process nucleus of bombarded atom captures a neutron and thus becoming unstable and exhibiting the properties of spontaneous breakdown.
Radioactive half-life
Radioactive half-life is a length of time required for one half of the atom to be decayed in a given amount of radionuclide that ranges from 10 –9 seconds to 1010 years, depends on the radioactive element.
For examples- Uranium has half-life of 4.5 Million years and Radium has half-life of 1622 years. Radioactive half-life is constant for any given radionuclide.
Tissue tolerance to radiotherapy
Neoplasm’s radio sensitivity is based on three factors-
- Neoplasm Lethal Dose: Neoplasm Lethal Dose is the dose of radiation, which in vivo produces lethal effects on the neoplasm.
- Normal Tissue Tolerance Dose: Normal Tissue Tolerance Dose is the dose of radiation which normal tissue can absorb without any pathological effects. E.g Eye lens – 200 rads, Kidney and lungs – 2000 rad/2weeks and Brain – 4000 rads/4 weeks
- Therapeutic ration: Therapeutic ration is the ratio of normal tissue tolerance dose to the neoplasm lethal dose.
Tissue sensitivity is divided into three categories-
- Sensitive category – Squamous cell carcinoma
- Moderate sensitive – Mast cell neoplasm
- Resistant – fibrosacroma