The invention comprises a method and apparatus for determining a radiation beam treatment path to a tumor, comprising the steps of: (1) delivering charged particles from an accelerator, along a first beam transport path, through an output nozzle, and along a treatment path to the tumor relative to a calibrated reference beam path from the output nozzle toward a patient position and (2) prior to the step of delivering, a main controller verifying an unobstructed linear path of the treatment path using a set of fiducial indicators positioned at least: on a first element physically affixed and co-movable with the output nozzle and on a moveable object in the treatment room. Optionally, voxels of the treatment beam path and potentially obstructing objects are defined in the treatment room using an axis system relative to the calibrated reference beam path and a reference beam point.