I really wanted to make a career in tomography. But had only one elective from another department and didn't know how to make it into this stream.

You still can! It looks like it is an amazing mix of physics, math, engineering, acoustics, biology, basically everything.

It’s difficult. Medical devices are not easy for a small business to break into and the big manufacturers don’t typically hire entry-level.

Everyone I know in the field has come into it laterally either from a prior software or hardware job in an unrelated field.