What is Permanent implant for brachytherapy are all except- and explain in detail?
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 (Californium)2) 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 temporary/removable or permanent.Removable/Temporary sources or implantsPermanent sources or implants* Iridium-192 (Ir-192)Cesium-131 (Cs-131)* Cesium-137 (Cs-137)Yttrium* Cobalt-60 (Co-60)Gold-198 (Au-198)* Californum125I* Radium-226 (Ra-226)Radon-222 (Rn-222)* TantalumPallidum -103 (Pd-103)Note : 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 (l31I)c) 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 Gy/hour. 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 Gy/hour.iii) High dose rate (HDR) Sources emit radiation >12 Gy/hour. 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