Yes. A diploma student of ultrasound can open a clinic. But there are some rules and regulation that a   candidate have to follow.
You can open but you need a doctor. How is certified MBBS Doctor with MD in  Radiology to head your centre.your job is to just remove Xrays images.

But if you can do your own all then you have to bsc in radiology . Or also you can go for higher study .After your radiology course you can do  required for opening the clinic. Then you will get the  proper approvals from authorities to run the clinic .

All the best . I hope this answer helps you.
Thank you.