Medison remains a small player, so there is very little chance that somebody would take the time to analyze their file format and develop an open-source reader for it. See some more information in this post: Could not load ultrasound from .mvl (Medison Volume) format
You may buy an option for your Medison software that allows export to standard file formats (this option may or may not exist, if it does not exist then let the vendor know that you would need it), buy software that can convert the data (I think TomoVision can do it), offer funding for developing an open-source reader, or use an ultrasound system that can readily export in open file formats.