If we’re talking the same thing then it’s someone that sells and maintains a picture archiving server.
[What is a PACS server](https://www.intelerad.com/en/2022/01/24/what-is-a-pacs-server/)
It can be used in human or veterinary medicine and each have their own vendors.
Picture are taken using a machine called a modality. That modality can be an xray or MRI scanner for example. They all communicate to a PACS server that then stores it for future access.
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