IMRT or Intensity Modulated Radiation Therapy is the use of high tech powerful computer controlled Linear Accelerators which are outfitted with Multi Leaf Collimators and Imaging Capabilities.
Multi Leaf Collimators (MLC's) are used to control the intensity of the radiation beam at different moments during the treatment. The radiation beam is made to conform with the 3 Dimensional volume of the tumor and prostate and then modulated accordingly to control the intesity of the radiation beam. The MLC's are small leaves, usually 120 of them (shown in photo below), that move to shape and control the intensity of the radiation beam. This movement of the MLC's are planned and designed by powerful treatment planning computers under the direction of physicist and the radiation oncologist. By moving each leaf in a prediefined pattern in front of the beam of radiation the radiation oncologist is able to modulate (change) the intensity of the beam of radiation at different points.
The physics team along with the radiation oncologist decides how much of a radiation dose they want the prostate to receive. They also tell the treatment planning computer what they would like the surrounding organs (bladder and rectum) to receive. They basically take the CT scan of the patients pelvis and locate the prostate, seminal vesicles, bladder, and rectum. The radiation oncologist will tell the computer that he wants the Prostate and seminal vesicles to receive 100% of the dose and the bladder and rectum to receive no more than 30% of the dose. The computer will then try thousands of combinations to find the perfect way to achieve the requirements the radiation oncologist set. Once the computer finds the correct movements that will allow the MLC's to modulate the radiation so the Tumor recieves 100% of the radiation and the healthy structures recieve 30% or less the planning computers job is done. When the radiation oncologist is satisfied that their criteria has been met the treatment plan is reviewed and then a dry run is done with a special phantom.
Using the CT (computed tomography) scan along with treatment planning computers an exact dose can be given to the tumor while the surround healthy tissue receives a minimal dose. Usually the treatment is broken up into several treatment fields or portals which the radiation will be delivered from different positions around the patient at several points determined by the treatment planning computer to deliver the optimal dose to the tumor while leaving the healthy tissue untouched by the radiation.
In the past a patient was treated with very large fields because the radiation could not be controlled as precisely as with the MLC's and IMRT. Large fields had to be used to assure the tumor was receiving the dose necessary to eradicate the tumor. Large fields mean a lot of normal healthy tissue (bladder and rectum) was in the path of the radiation (treatment field) which lead to a lot of side effects. Now since we can target the prostate and the prostate alone and control the amount of radiation that the bladder and rectum receives we can treat with less side effects and with higher doses.
Because such a precise dose of radiation can be given without affecting the normal healthy tissue higher doses can be given which are more effective in killing the cancerous tissue. These high doses could not be achieved with tradition methods of radiation therapy. Also since the minimal amount of healthy tissue receives very little if any of the dose of radiation side effects are kept to the minimum.
Multi Leaf Collimators (MLC's) are used to control the intensity of the radiation beam at different moments during the treatment. The radiation beam is made to conform with the 3 Dimensional volume of the tumor and prostate and then modulated accordingly to control the intesity of the radiation beam. The MLC's are small leaves, usually 120 of them (shown in photo below), that move to shape and control the intensity of the radiation beam. This movement of the MLC's are planned and designed by powerful treatment planning computers under the direction of physicist and the radiation oncologist. By moving each leaf in a prediefined pattern in front of the beam of radiation the radiation oncologist is able to modulate (change) the intensity of the beam of radiation at different points.
The physics team along with the radiation oncologist decides how much of a radiation dose they want the prostate to receive. They also tell the treatment planning computer what they would like the surrounding organs (bladder and rectum) to receive. They basically take the CT scan of the patients pelvis and locate the prostate, seminal vesicles, bladder, and rectum. The radiation oncologist will tell the computer that he wants the Prostate and seminal vesicles to receive 100% of the dose and the bladder and rectum to receive no more than 30% of the dose. The computer will then try thousands of combinations to find the perfect way to achieve the requirements the radiation oncologist set. Once the computer finds the correct movements that will allow the MLC's to modulate the radiation so the Tumor recieves 100% of the radiation and the healthy structures recieve 30% or less the planning computers job is done. When the radiation oncologist is satisfied that their criteria has been met the treatment plan is reviewed and then a dry run is done with a special phantom.
Using the CT (computed tomography) scan along with treatment planning computers an exact dose can be given to the tumor while the surround healthy tissue receives a minimal dose. Usually the treatment is broken up into several treatment fields or portals which the radiation will be delivered from different positions around the patient at several points determined by the treatment planning computer to deliver the optimal dose to the tumor while leaving the healthy tissue untouched by the radiation.
In the past a patient was treated with very large fields because the radiation could not be controlled as precisely as with the MLC's and IMRT. Large fields had to be used to assure the tumor was receiving the dose necessary to eradicate the tumor. Large fields mean a lot of normal healthy tissue (bladder and rectum) was in the path of the radiation (treatment field) which lead to a lot of side effects. Now since we can target the prostate and the prostate alone and control the amount of radiation that the bladder and rectum receives we can treat with less side effects and with higher doses.
Because such a precise dose of radiation can be given without affecting the normal healthy tissue higher doses can be given which are more effective in killing the cancerous tissue. These high doses could not be achieved with tradition methods of radiation therapy. Also since the minimal amount of healthy tissue receives very little if any of the dose of radiation side effects are kept to the minimum.
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