1 The first radiotherapy devices used radium applicators that were positioned adjacent to the prostate gland. E. Teletherapy isodose plan is considered medically necessary for a given course of radiation therapy to a specific volume of interest. However, radiation treatments to the head/neck, prostate and Hodgkin’s disease may require eight or more calculations. We began treating skin cancers with superficial x-ray units before pioneering mobile HDR radiation therapy 3 years ago. Our experience over the past 10 years of mobile radiation therapy has given us the knowledge to provide effective mobile units and has proven that mobile radiation therapy is convenient, reliable, and cost effective. Absorbed dose is defined as the amount of energy deposited by ionizing radiation in a substance.Absorbed dose is given the symbol D.The absorbed dose is usually measured in a unit called the gray (Gy), which is derived from the SI system. At the reference depth, TMR is set to unity. In addition, the radiation oncologist is responsible for the design of the series of Most patients get radiation treatments daily, 5 days a week (Monday through Friday) for 5 to 8 weeks. In the older system of units, equivalent dose was described by the unit rem and 1 Sv equals 100 rem or 1 mSv equals 0.1 rem. There are several categories of treatment devices used in conjunction with the delivery of IMRT radiotherapy. The total dose of radiation and the number of treatments is based on: The total dose of external radiation therapy is usually divided into smaller doses called fractions. The isocenter dose in IMRT is irrelevant because this could be in the region of low dose or in an organ at risk and does not necessarily represent dose to the target volume as is required by the International Commission on Radiation Units and Measurements 50 for dose reporting in three-dimensional conformal radiation therapy. You can also express dose this in… Radiation is prescribed as a daily dosage to the prostate given for a certain number of days = the total dosage. Here are radiation doses for common procedures if you get a scan with contrast, and then one without contrast: Belly and pelvis: 20 mSv, equal to about 7 years of background radiation Since the amount of radiation exposure depends directly (linearly) on the time people spend near the source of radiation, the absorbed dose is equal to the strength of the radiation field (dose rate) multiplied by the length of time spent in that field. At this depth, the change in dose as field size, Sc,p, is increased is mainly due to two independent effects: The change in the amount of radiation from the head of the treatment unit and the change in amount of scattered radiation from the patient. Treatment Devices . •The unit of dose equivalent still appearing in U.S. regulations is the rem(rad equivalent man) •The SI unit is the sievert(Sv) •100 rem = 1 Sv •1 rem = 0.01 Sv •Dose equivalent is essentially a radiation protection quantity •There are a number of specific dose equivalent terms (see following slides) A typical treatment course I give is 180 centiGray each day, given for 45 daily treatments, = 8100 centiGrays total (180 cGy x 45 = 8100 cGy). In conventional units, it is measured in mSv/sec, Sv/hr, mrem/sec or rem/hr. A monitor unit (MU) is a measure of machine output from a clinical accelerator for radiation therapy such as a linear accelerator or an orthovoltage unit. Weekend rest breaks allow time for normal cells to recover. The non-SI unit rad is sometimes also used, predominantly in the USA.. Units of absorbed dose: Gray.A dose of one gray is equivalent to a unit of … radiation therapy dose plan . The typical course of radiation therapy will require from one to three isodose plans. Immobilization treatment devices are commonly employed to ensure that the beam is accurately on target. Monitor units are measured by monitor chambers, which are ionization chambers that measure the dose delivered by a beam and are built into the treatment head of radiotherapy linear accelerators. Radiation therapy (RT) for the treatment of prostate cancer (PCa) has been utilized in the United States and Canada since 1915.