During the procedure, the patient’s progress is monitored in real time with ultrasound. The position of the ultrasound probe is also tracked electromagnetically and matched to the relevant slice of the pre-acquired CT image. And both images are brought together on one monitor, and can be viewed side-by-side or overlaid. According to Ramin Shahidi, head of the Image Guidance Laboratories at the Stanford University School of Medicine, this joining of the two imaging technologies helps to overcome a major problem in most minimally invasive procedures: disruptive movement.
In the past, Shahidi’s and other groups have introduced techniques for creating a model of the patient’s anatomy taken from CT scans before the surgery, which is then used to help guide the operation. This technique works well in surgeries of the head, neck, and knees, where the structures are rigid.
But Shahidi says that it fails when looking at soft tissue, such as the liver, intestines, breast, or prostate, where the anatomy can easily move or change. “The anatomical information that we use for guidance at eight in the morning doesn’t apply to a surgery at ten in the morning,” he says. “The dynamic nature of ultrasound, when married to CT, would address that huge limitation.”
Philips worked with the NIH team to complete a small pilot study of 20 patients testing the technology for radiofrequency ablation of soft tissue biopsies in the liver, kidney, lungs, and spine. They are now continuing to improve it in preparation for larger trials. Helen Routh, vice president of Philips Research, says that the workstation is still a few years away from the market.
Stanford’s Shahidi says Philips’ technique is the only one he’s seen “that has a really critical potential for minimally invasive soft tissue visualization.” He adds that the tool could become extremely useful for radiologists, who are increasingly performing minimally invasive procedures in place of surgeons.
Radiologists, Shahidi notes, are much more comfortable than surgeons with using and interpreting imaging technologies, yet they lack the surgeon’s knowledge of navigating the body. This kind of technology, he says, would increase their comfort level and “give the radiologists something that they’ve been missing: how to get from point A to point B.”