If it were a game, your task would be to maneuver thin instruments through a bowl of gelatin and remove a hidden pea. To increase the challenge, you are not allowed to disturb any of the gelatin except that which is in your immediate path. Furthermore, you cannot actually see the pea but you have an X-ray of its location. And by the way, things have shifted since the X-ray was taken.
For neurosurgeons, removing a tumor from the brain is far more difficult and anything but a game.
Within the past decade, imaging systems have provided much clearer pictures of the brain’s structures, and navigational tools have helped physicians map direct approaches, minimize points of entry and spare healthy brain and function. But the value of even the most detailed images has been limited by the fact that brain matter moves, and a picture taken is a picture out of date.
Since the advent of MRI technology, attempts have been made to install large machines in operating rooms, but powerful magnetic fields caused numerous problems with instrumentation, other electronic equipment distorted the images, and the size and shape of the machines made them impractical for use during surgery. Some hospitals have since located large machines adjacent to surgical suites, but patients must be transported to the MRI and back during the surgical procedure at a cost of time and efficiency. The latest-generation intraoperative MRI (iMRI) technology recently installed at Cedars-Sinai’s Maxine Dunitz Neurosurgical Institute enables surgeons to update images in the operating room with real-time results.
The PoleStar N-10, developed by Odin Medical Technologies, is a compact iMRI system that can be brought into a standard operating room, stored under an operating table, and used as needed during surgery – usually once at the beginning of the procedure and once at the end. Leading neurosurgical centers are adopting the system, which resolves most of the problems encountered earlier. Because of the machine’s portability, small size and tightly focused magnetic field, the surgical team has direct access to the patient, less electronic shielding is needed, and many standard surgical instruments can be used. Hospitals can implement the system with only minimal retrofitting of existing surgical facilities.
Although the more portable system does not provide the same image quality as the large machines, neurosurgeons say the advantages outweigh this tradeoff.
“Previously, scans taken before surgery would be reconstructed by computer software into three-dimensional images. But the brain is made up of tissue that is very much like gelatin, so as you start to work in the brain, it can move by as much as five or 10 millimeters, which in neurosurgical terms is a huge difference. The new system allows us to get real-time imaging updates as we remove critical lesions,” says Keith L. Black, MD, neurosurgeon and Institute director.
“The beauty of the system is that it is very small and unobtrusive. It slips under the operating table and out of the way, but the magnets can quickly be raised to the operating field to produce an image. This allows the surgeon to work with relative ease,” according to Dr. Black.
The ability to update images during an operation enables surgeons to modify approaches as the landscape changes. This allows them to be more precise, making minimally-invasive surgery even more minimal. They can see the borders of a tumor with greater clarity at critical moments, a capability that spares healthy tissue and dramatically increases the possibility of complete tumor removal. For patients, this is expected to translate into better outcomes, shorter hospitalizations and recoveries, and less likelihood of having to return for a follow-up operation.
Boris Tam, 8, from Fremont near Oakland, became one of the first patients at Cedars-Sinai to benefit from the new iMRI technology when he underwent surgery on March 8 to remove a benign but recurring tumor that was pressing against his optic nerve.
According to his mother, Vivian Lee, Boris was diagnosed with a craniopharyngioma last year when vision problems did not respond to usual treatments and an MRI was ordered. The growing tumor was pressing on the optic nerve and affecting the pituitary gland, causing a “lazy eye” and such problems as poor bladder control, as well as headaches.
After consulting four other neurosurgeons, Boris’ parents brought him to Cedars-Sinai where Dr. Black and Moise Danielpour, MD, director of the Pediatric Neurosurgery Program, removed the tumor during a first operation in Oct. 2003, several months before the new MRI was installed.
“He definitely felt stronger,” says Vivian. “His appetite was much better after that. His health just improved. Before, he was pale, but after the surgery he was very strong.” A follow-up MRI, however, showed that even though the tumor had been completely removed, it was growing back.
“Because of this type of tumor’s location and attachment to the nerves and the pituitary, there is a significant risk of tumor recurrence. Intraoperative image guidance greatly enhances our ability to access the degree of resection in real-time. Although the Odin intraoperative MRI scanner is very new technology, intuitively we feel that its use may both improve our chances at a complete tumor resection and perhaps decrease the operative risk of injury to critical structures,” says Dr. Danielpour, who performed the March 3 surgery while Dr. Black observed. “Following his second resection, the intraoperative images confirmed decompression of the tumor away from the optic nerve. With the intraoperative MRI, we don’t find out the next day and have to bring the patient back into the operating room.”
Back home now, Boris is undergoing radiation therapy to reduce the risk of further recurrence, and Drs. Black and Danielpour say his prognosis is excellent.
Simi Valley resident Agripino Segovia, who celebrates his 80th birthday on June 23, also has an excellent prognosis following MRI-assisted surgery performed by Dr. Black on April 15. Like Boris, Agripino was urged by his ophthalmologist to schedule an MRI. A macroadenoma, or giant pituitary tumor, was diagnosed last September, but because it is a slow-growing tumor and Agripino and his wife were scheduled to be out of the country, he did not immediately seek treatment. By February of this year, however, his vision was becoming more blurred every day, he says.
“Among the challenges we have with these tumors when they’re very large is making sure we get the tumors off of important structures like the optic nerve and making sure that we remove the entire tumor,” says Dr. Black, who also directs the medical center’s Division of Neurosurgery and the Comprehensive Brain Tumor Program and holds the Ruth and Lawrence Harvey Chair in Neuroscience.
“The advantage we have with intraoperative MRI is that we can identify exactly where the tumor is located and we can visualize whether any of the tumor still remains after the surgery. Mr. Segovia’s tumor was compressing his optic nerve, causing him to lose vision. Following the surgery, he certainly should not lose any more vision and there is a good possibility that the vision he has lost will return over time. He should do extremely well.”
Cedars-Sinai is one of the largest nonprofit academic medical centers in the Western United States. For the fifth straight two-year period, it has been named Southern California's gold standard in health care in an independent survey. Cedars-Sinai is internationally renowned for its diagnostic and treatment capabilities and its broad spectrum of programs and services, as well as breakthroughs in biomedical research and superlative medical education. It ranks among the top 10 non-university hospitals in the nation for its research activities.