1. A method comprising: determining a first estimate of leaf positions for a plurality of leaves of a multi-leaf collimator (MLC) in a reference coordinate space based on an image generated by an image-based aperture verification system, wherein the leaf positions for the plurality of leaves define an aperture for the MLC; determining a second estimate of the leaf positions for the plurality of leaves in the reference coordinate space based on data from an additional source, wherein the additional source comprises an additional aperture verification system; generating a pictorial representation of the second estimate; displaying the image generated by the image-based aperture verification system; displaying an overlay of the pictorial representation over the image; verifying, by a processing device, the leaf positions for the plurality of leaves based on comparing the first estimate to the second estimate, wherein the leaf positions are verified if the first estimate deviates from the second estimate by less than a threshold value; determining a first sequence of updates to the first estimate of the leaf positions based on a sequence of images generated by the image-based aperture verification system; determining a second sequence of updates to the second estimate of the leaf positions based on a sequence of data from the additional aperture verification system; synchronizing the first sequence of updates and the second sequence of updates in time; generating a sequence of updated pictorial representations for the second sequence of updates; and displaying a video representation of the aperture showing the sequence of images and the sequence of updated pictorial representations.