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Comparative Effectiveness and Safety of Radiotherapy Treatments for Head and Neck Cancer

Slide: 10 of 36

Treatment Planning

External-beam radiation therapy modalities have been developed as an attempt to improve the conformality of the radiation being delivered. In other words, getting radiation just to the tumor and not to the normal surrounding tissue that could be harmed during treatment. Both 2DRT and 3DCRT use forward planning to create radiation dose distributions, in which radiation treatment fields are designated and the number, direction, and shapes of the radiation beams are defined. The treatment plan dose distribution shows how much dose is delivered to the tumor and normal structures. IMRT uses CT simulation images like 3DCRT; however, inverse planning is used to outline target volumes. Inverse planning requires the treatment planner to input the desired radiation dose to the tumor and the constraints for normal surrounding structures. Then, computer software is used to arrive at the radiation beam characteristics most likely to meet the requirements designated at the start of treatment planning. Proton beam therapy can be planned using 3D images; the technology for using inverse planning with proton beam therapy, however, is just emerging.