Patent Number: 
Section: claims

1. A method for producing high energy X-rays for radiation therapy at patient's level comprising the steps of:using a linear accelerator without a flattening filter to provide a high radiation dose having a dose distribution;wherein the radiation dose is high energy X-rays ranging from 6 MV to 25 MV;using inverse planning to shape the dose distribution, increase dose rate and shorten treatment time; andradiating a patient in need of radiation therapy with the shaped radiation field. 2. A method according to claim 1 including the step of improving patient radiation therapy by reducing radiation scattered to surrounding normal tissue and reducing electron contamination. 3. A method according to claim 1 including the step of delivering a less contaminated radiation beam at shorter treatment times. 4. A method according to claim 1 including the step of delivering a radiation beam with higher photon fluence at the patient's level. 5. A method according to claim 1 including the step of delivering a cleaner radiation beam at the patient's level. 6. A method according to claim 1 wherein the step of removing the flattening filter reduces lateral scatter. 7. A method according to claim 1 including the steps of:controlling planar fluence in the radiation source with a multi-leaf collimator (MLC); andinverse treatment planning to achieve uniformity within a target volume for the radiation beam without a flattening filter. 8. A method according to claim 1 wherein the linear accelerator is an IMRT capable radiation accelerator. 9. A method according to claim 1 wherein the MLC is used to achieve uniformity that conforms to convention 3D therapy treatments. 10. A method according to claim 1 including the step of varying fluence with a combination of MLC movements in and out of radiation field to produce beam modulation at the patient level. 11. A method according to claim 1 wherein the radiating delivers a 3D conformal gamma radiation dose to a treatment zone at the patient's level.