Another step toward minimally-invasive surgery

Image-guided intervention has pushed progress in minimally and non-invasive surgical procedures, which will gradually replace extensive surgery.

Dr Roderic Pettigrew, Director of the National Institute of Biomedical Imaging and Bioengineering, an institute within the National Institutes of Health, tells EHM why.

The National Institute of Biomedical Imaging and Bioengineering (NIBIB) is the newest Institute of the National Institutes of Health (NIH). Its mission, says Dr Roderic Pettigrew, NIBIB Director, is to improve health by leading the development and accelerating the application of biomedical technologies. This mission puts the NIBIB at the intersection of the quantitative and life sciences. Research projects funded by the NIBIB combine disciplines as diverse as mathematics, computer science, chemistry, physics and biology to generate innovative approaches, microfabrication techniques, tools for image analysis, and improvements in imaging technology such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US).

The broad mandate for NIBIB includes a wide range of technological development, from the nanoscale to the organ system scale. One of these areas is image guided intervention (IGI), which is the utilization of an imaging technology such as magnetic resonance imaging to assist a surgical procedure. IGI can be used in a real time intra-operative mode to reduce the invasiveness of many surgical procedures, minimize post-surgical trauma, and improve outcomes by providing the surgeon with more precise, detailed information about the area that is being treated. Using IGI, a surgical procedure becomes more accurate and efficient, the procedure is less invasive, and the cost of the procedure is reduced. Examples of image guided intervention in common practice today include laparoscopic and arthroscopic procedures. “When I was in medical school in the late 1970s,” says Dr Pettigrew, “a patient with an infected or an obstructed gall bladder that needed to be removed had traditional surgery that resulted in a long incision in the abdomen and a recuperation time in the hospital of approximately 10 days. Today, a patient receives two or three small incisions in the abdomen, an endoscope is placed in one of these incisions, the gall bladder is removed from the other using tools small enough to insert through a catheter or small tube, and the patient returns home in a day or two. These technological advances and the consequential benefits of image guidance are very clear.”

Non-invasive surgery

Technological advances contribute significantly to progress in the development of minimally and non-invasive diagnostic and surgical techniques. For example, promising results have been achieved with high intensity focused ultrasound as a therapeutic approach, delivered under the guidance of imaging in real time. Open surgery or hysterectomy to remove uterine fibroid tumors has largely been replaced by uterine artery embolization, in which the blood supply to the tumor is blocked by inserting a catheter to inject a gel that closes the vessel. However, an even newer procedure requires no surgery at all. Pettigrew explains: “The patient goes into the MRI scanner, where the fibroid tumor is identified. Using the image information and an ultrasound device, ultrasonic waves can be intensely focused directly on the tumor. The thermal energy that is created by the ultrasound heats the fibroid and causes it to shrink.”

Image guided interventions have had a tremendous impact on surgical treatment of epilepsy. In 2002, NIBIB awarded a grant to Yale University for a multidisciplinary team to develop intraoperative use of integrated 3D images for neurosurgical guidance. This team integrated multiple complementary datasets from different imaging and diagnostic modalities in the operating room to aid in the surgical treatment of patients with epilepsy. “The researchers acquire MR images,” explains Pettigrew, “that depict the brain structure in three dimensions and identify the probable lesion of interest. This information is used in conjunction with a related technique, magnetic resonance spectroscopy (MRS), to identify important biochemical features in the brain. These data are combined to create ‘signatures’ of epileptic loci based on the identified biochemical markers, and the signature data are then integrated with electroencephalographic (EEG) data. The MR signature/EEG data are integrated into a set of 3D images that the neurosurgeon can refer to while in the operating theatre. In addition, the surgeon uses binocular sensors that are trained on the brain so that when the surgeon opens the skull and begins to enter the brain, the 3D images are updated in real time as the surgery is being performed. Specifically, they can see shifts in the physical position of the brain tissue, which is also shown in the images.”

Diffusion tensor imaging

A variety of neural functional features can be identified with functional MRI (fMRI) technology. An MR imaging technology called diffusion tensor imaging, or diffusion spectral imaging, allows surgeons to identify the location of nerves in the brain. This information helps the surgeon to avoid cutting across nerve fibre tracks and unnecessarily injuring specific centers in the brain that control critical functions. “This technology has yielded a number of benefits,” says Pettigrew, adding: “Of special interest is that the group at Yale reduced the time necessary to perform surgery by about 90 minutes. In addition, the number of patients that are being operated on successfully has increased by 30-60 percent. In the past, it was difficult in many patients with seizures for the surgeon to accurately identify the seizure locus. But technological advances in imaging have significantly improved our ability to perform this surgery successfully. Now, many significant neurologic deficits that previously occurred after epilepsy surgery can be avoided, all as a result of this approach to surgery, which we call image guided intervention.”

At Mayo Clinic in Rochester, Minnesota, researcher Richard Robb is developing an intra-operative, real time, 3D dataset that can also show other functional data, such as electrical and contraction activity in the heart. This tool is used currently to enable cardiologists to treat a type of abnormal heart rhythms termed atrial fibrillation (AF). This condition is most commonly caused by the abnormal presence of electrical tissue in the veins entering the heart. Because there are four veins into the atria, or blood receiving chamber, it is not always clear where the site of the abnormality is. Pettigrew: “Traditionally, electrophysiologists use an electrical probe on a small catheter, which physically touches the atria, and takes electrical readings along the atria to identify the aberrant site. This can be a long and tedious procedure, because the problematic spot can be very small and difficult to detect. What Dr Robb has done is very valuable. He can create 3D images on a computer screen, and these images are then merged with others showing the cardiologist the location of the catheter within the heart. As the surgeon touches each spot along the atrium and gets a sample reading, the computer screen displays this electrical activity reading as a coded color. The colors allow the surgeon to make easy visual distinctions between normal and abnormal electrical activity. The surgeon uses this information to guide the placement of his probe. Once the defect has been treated, the surgeon can take a new reading immediately to determine if the procedure was successful and the electrical activity in that area is now normal.”

Pettigrew believes that minimally-invasive and non-invasive surgery eventually will replace traditional open surgery. In the next few years, for example, he predicts that hysterectomy for fibroids will be a thing of the past. The removal of other organs due to the presence of tumors or other defects also may become unnecessary. “The ability of robotics to pinpoint areas in the body accurately and routinely in three dimensions certainly exists. Robots can perform these tasks even better than the most skilled surgeon,” Pettigrew assures. This is not to say that robots will eventually replace surgeons. The focus, Pettigrew emphasizes, is on the role of robots in strictly mechanical tasks. “You still need the high level integration of a large database of knowledge, individual situation evaluation, subjective reasoning, and adaptation of tools to that specific situation, all of which require the human brain to be involved. Therefore, I do not see a replacement for human involvement. Rather, I see an augmentation of this role by robots performing tasks that are mechanical in nature and require high precision. Robots assist surgeons, and bioinformaticists assist decision making. The person, however, provides the critical integration of information and technological tools to achieve the best possible outcome.”

Dr Roderic Pettigrew: Appointed in September 2002, Dr Roderic Pettigrew is the first Director of the National Institute of Biomedical Imaging and Bioengineering, an institute within the National Institutes of Health. Prior to his appointment at NIBIB, he was a Professor of Radiology, Medicine (Cardiology) and Director of the Emory Center for MR Research, Emory University School of Medicine, and Professor of Bioengineering, Georgia Institute of Technology, Atlanta, Georgia.

“Robots assist surgeons, and bioinformaticists assist decision making. The person, however, provides the critical integration of information and technological tools to achieve the best possible outcome”