TrackVis 0.6.1 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. The actual developer of this free Mac application is Ruopeng Wang, Van J. Wedeen.
TrackVis for Mac lies within Design & Photo Tools, more precisely Viewers & Editors. According to the results of the Google Safe Browsing check, the developer's site is safe. Despite this, we recommend checking the downloaded files with any free antivirus software.
From the developer:
TrackVis is a software tool that can visualize and analyze fiber track data from diffusion MR imaging (DTI/DSI/HARDI/Q-Ball) tractography. The program comes with various track filters allowing users to explore and locate specific bundles with ease. It also provides multiple rendering modes with customizable scalar-driven color codes, as well as statistical scalar analysis of tracks and ROIs.
You may want to check out more software for Mac, such as Diffusion Toolkit, which might be similar to TrackVis.