They were physical probes thru the back, thru the lung and into the tumor as it heated up the tumor to destroy it. That’s the interventional part. Not sure what the brain procedure would be for your sister but an IR is highly trained and skilled. They use imaging to guide the procedure. I was lying on a CT table during the procedure and went in and out of the CT machine many times to be sure the probes were properly placed in the tumor before heating whereas a surgeon either has a direct visual with an open incision or via camera inserted thru a small incision so IR is less invasive, faster healing.