.NET is pretty popular! We use a combination of Kotlin, Python, and Rust. Because of the V&V burden of extra libraries, we tend to only use standard libraries
Siemens, Philips use .NET. Although, I believe it is mostly due to their partnership with Microsoft rather than the technical side of things.
Are you sure? Philips' medical side have an in house GUI library (Qt-esuqe) called Sense and it's mainly implemented using C++.