This is a new technique in IMRT and 3D conformal gamma radiation dose delivery using a linear accelerator with no flattening filter. The technique improves patient radiation therapy by reducing radiation scattered to surrounding normal tissue and reducing electron contamination. It increases dose rate to shorten treatment time. Linear accelerators have for decades come with a photon flattening filter to make the photon profile of planar fluence to make the dose distribution more uniform. These filters, however, resulted in fluence attenuation and contamination of the beam. Now in the age of techniques such as intensity modulated radiation therapy (IMRT) the function of the flattening filter becomes redundant. The flattening filter now merely reduces the efficiency of the beam by reducing the fluence and increasing scattered radiation. Our technique involves removal of the flattening filter for complex treatments. It uses inverse planning along with multi-leaf collimators to shape the dose distribution.

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