1. A system, for treating a target tissue with x-ray radiation, comprising: an x-ray source that emits x-rays, the source configured to provide therapeutic x-ray treatment; a collimator that collimates x-rays emitted by the x-ray source into an x-ray beam, the collimator having a outer perimeter as the x-ray beam is emitted from the collimator; the collimator having at least one exit plane having a first cross-sectional pattern, coextensive with the outer perimeter, defined by a first cross-sectional dimension; and the x-ray beam having a dose distribution at a beam spot in the exit plane of the collimator such that the x-ray beam at a region within the plane is characterized by a region of maximal intensity encompasses a region of minimal intensity.