Typically, electron beam radiation therapy aims at delivering a uniform dose to a target volume containing cancer cells. Electron sources typically impinge a spatially uniform flux across the beam onto the patient； however, irregular patient and bolus surfaces, the latter encountered in bolus electron conformal therapy (ECT), scatter electrons unevenly creating non-homogeneous dose distributions in the target. However, spatially-modulated beam intensities can restore target dose homogeneity, as well as enable utilization of other advanced ECT methods. Unfortunately, present methods, which have attempted to spatially-modulate beam intensities, have been either impractical or ineffective. Here, a novel, passive method has been developed to spatially-modulate electron beam intensities by taking advantage of multiple Coulomb scattering. The method utilizes Island Blocks or Island Apertures, strategically located in ‘；transparent’； or ‘；opaque’； substrates, respectively, which are placed in the beam's path. This method spatially-modulates electron flux across the beam with insignificant loss of electron beam energy. Thus, delivering a uniform, highly conformal dose distribution to the target volume is possible. Further, the method is inexpensive and can be easily incorporated into existing electron therapy machines.
