IMRT - 9/30/2009 Optimization in Intensity Modulated...

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9/30/2009 1 Optimization in Intensity Modulated Radiation Therapy (IMRT) Shabbir Ahmed ISyE, GA Tech OUTLINE Radiation therapy Intensity modulated radiation therapy Key planning problems – Fluence map optimization – Beam angle optimization – Multi-leaf collimator optimization
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9/30/2009 2 Radiation Therapy Radiation therapy (also called radiotherapy, x-ray therapy, or irradiation) is the use of ionizing radiation to kill cancer cells and shrink tumors. About half of all cancer patients are treated with radiation therapy About half of all cancer patients are treated with radiation therapy. Radiation therapy injures or destroys cells in the area being treated (the “target tissue”) by damaging their genetic material, making it impossible for these cells to continue to grow and divide. Although radiation damages both cancer cells and normal cells, most normal cells can recover from the effects of radiation and function properly. Radiation therapy may be external or internal. External radiation, the type most often used, comes from a machine outside the body. Internal radiation is implanted into or near the tumor in small capsules or other containers is implanted into or near the tumor in small capsules or other containers. Radiation therapy planning: Determine dose delivery so as to damage as many cancer cells as possible, while limiting harm to nearby healthy tissue. Radiation Oncology in a Nutshell CT Simulation Planning Delivery/Verification Anatomy Map Deliver the radiation plan over 6 weeks Create personalized treatment plan
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9/30/2009 3 IMRT A form of external beam therapy Radiation delivered from a linear accelerator Beam head can swivel and bed can move offering many degrees of freedom Beam head has a mask called a “multileaf collimeter” (MLC) which can be used to shape the beam •B y several deliveries overlaying different shapes with different intensities we can get desired dosage of the tumor
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9/30/2009 4 MLC Lesion MLC in Action Radiation critical organs
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9/30/2009 5 Beamlets Since the beam can be positioned at many different angles, we can imagine we have several “stationary” beams Conceptually MLC discretizes each beam into several small “beamlets” Furthermore, by possibly overlaying, we can control the intensity of each beamlet independently 0001 0331 0111 + + Desired dose intensity e.g. required intensity of beamlet (2,2) is 3 units.
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This note was uploaded on 11/27/2009 for the course ISYE 4803 taught by Professor Staff during the Spring '08 term at Georgia Institute of Technology.

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IMRT - 9/30/2009 Optimization in Intensity Modulated...

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