<prompt> Permanent implant for brachytherapy are all except-Cesium-131Gold-198Radon-222Iridium-192  <response>: Ans. is d i.e. Iridium-192 There are three main types of radiotherapy depending upon the position of the source of radiation1 External beam radiotherapy EBRT or Teletherapy In teletherapy the source of radiation is distant from the patient. Teletherapy may be given by the following.i X-rays beams Linear acceleration Superficial x-rays : 40 to 120 KV Orthovoltage x-rays : 250 to 400 KV Supervoltage x-rays : 400 to 1000 KV Megavoltage : 2, 4, 6, 12 35 MeVii Gamma rays: - Cobalt - 60 beam or Cesium-137iii Particulate beams: - Electron Linear accelerator Proton Betatron or cyclotron Neutrons Californium2 Internal radiotherapy or brachytherapy: - In brachytherapy, the radiation source in close contact with tumor. The principle is to use an Intra or Juxta lesional radiation implant to irradiate the tumor in vicinity. Sealed source in placed within or near the tumor i.e., Short distance therapy. Brachytherapy may be of following types: -a Interstitial: - Artificial radioactive sources are inserted directly into tumor tissues. The radioactive sources implant may be either temporaryremovable or permanent.RemovableTemporary sources or implantsPermanent sources or implants Iridium-192 Ir-192Cesium-131 Cs-131 Cesium-137 Cs-137Yttrium Cobalt-60 Co-60Gold-198 Au-198 Californum125I Radium-226 Ra-226Radon-222 Rn-222 TantalumPallidum -103 Pd-103Note : Co-60 and Cs-137 are used for both teletherapy and brachytherapy.b Intracavitary: - Artificial radioactive sources are inserted into natural body cavities. Most important use of intracavitary radiation is in patients with the cancer of the cervix after external radiation. It is also used in cancer of uterus, esophageal cancer and lung cancer.RemovablePermanentRadiumColloidal radioactive goldCesium-137YttriumCobalt-60Radioactive iodine l31Ic Mould :- Source is used in mould form, as used in carcinoma of penis. Depending on the dose, Brachytherapy may be divided into : -i Low dose rate LDR;- Sources emit radiation at a rate of up to 2 Gyhour. LDR brachytherapy is commonly used for cancer of oral cavity, oropharynx, sarcomas and prostate.ii Medium dose rate MDR:- Sources emit radiation between 2-12 Gyhour.iii High dose rate HDR Sources emit radiation 12 Gyhour. The most common applications of HDR brachytherapy are in tumors of the cervix, esophagus, lungs, breasts and prostate. Most common radioisotope used for HDR brachytheray is iridium-192. Other isotopes which have been used are Cobalt-60 and cesium-137iv Pulsed-dose rate PDR :- Involves short pulses of radiation, typically once an hour, to simulate the overall rate and effectiveness of LDR treatment.Advantages of brachytherapy Maximum radiation effect in diseased tisue and microscopic residual disease. Relative sparing of adjacent normal tissues. Better oxygenation of the surgical bed. Reduced overall treatment time. Can be used for most of the malignancies where radiotherapy is the component of treatment.Disadvantages of brachytherapy Invasive Requires trained personnel: - Cancer control is operator dependent. Local symptoms, e.g., Burning sensation when used in prostatic cancer; diarrhea pain or proctitis when used in rectal carcinoma. Has to be performed under anesthesia Local or general.3 Systemic radiotherapy: - Radioisotopes are given systemically iv. Following are used Pure beta-emitters:- 32p in polycythemia rubra vera. 1311 in papillary carcinoma thyroid Strontium-89 In painful bone metastasis. Samarium -153 in painful bone metastasis Yttrium in medical synovectomy Rhenium 