Provided herein are methods and systems for designing a radiation treatment for a subject using single arc dose painting. The methods and systems comprise an algorithm or a computer-readable product having the same, to plan the radiation treatment. The algorithm converts pairs of multiple leaf collimation (MLC) leaves to sets of leaf aperture sequences that form a shortest path single arc thereof where the pairs of MLC leaves each aligned to an intensity profile of densely-spaced radiation beams, and connects each single arc of leaf apertures to form a final treatment single arc. Also provided is a method for irradiating a tumor in a subject using single arc dose painting.