To answer your question simply, Medical Grade HIFU devices needs to be registered with the local HSA. To qualify for registration they need supporting documents of safety as well as efficacy. Such devices are usually US FDA, Medical CE, KFDA approved or have multiple approval authorities. The popular ones include Ulthera and Ultraformer III.
Secondly HIFU needs to be performed by a trained medical doctor to ensure safety and efficacy.
The beauty salon devices are usually not true medical grade HIFU and require multiple treatment sessions with either minimal results or results that are very temporary.
The other issue is of course safety concerns as one cannot be sure of the training and experience of the beauty therapist.
Therefore my advice is if you are looking for a HIFU treatment seek it out at registered medical clinics.
Regards
Dr Chew