The Intraoperative MRI For Brain Tumors
Being able to establish the margins of a tumor is extremely important, especially for intrinsic tumors such as low-grade gliomas, glioblastomas and anaplastic astrocytomas. Presently all available image guidance techniques involves preoperatively acquired images to carry this out. Recently, Brigham & Women's Hospital in Boston, in collaboration with general Electric, have developed an intraoperative MRI scanner that allows direct intraoperative evaluation of patients and their tumors. This is an important technology which may radically change the management of such diseases.
The intraoperative MRI is unlike and previous MRI machine. It has a magnetic field between two 'donuts' and allows the patient's head or other body part to be placed in this and freely accessed by the surgeon. This in turn allows imaging brain surgery, both for image guidance and for resection of tumor.
Applications that we have found particularly important for these tumors include:
These are all applications for establishing the extent of resection. We have considerable experience with this. Our group now (as of 2/98) has done over 100 craniotomies in this device, as well as 100 stereotactic biopsies and we feel that it is a remarkable improvement on other image guided surgical devices.
- Low grade gliomas such as all gangliogliomas, astrocytomas and DNTs.
- Malignant gliomas including anaplastic astrocytomas and glioblastoma multiforme.
- Recurrent gliomas where the margin of the tumor may not be clearly evident.
- Radiation necrosis.
- Skull base meningiomas.
- Pituitary adenomas.
3-Dimension Reconstruction For Brain Tumor Surgery
The capacity to work from 3-dimentionaly reconstructed images for brain tumor surgery is a major advance in this surgery. We have developed, at the Brigham & Women's Hospital, a system that allows 3-dinentional creation of a hologram model of the brain and then merging this image with the patient's head at surgery that then can be used as a guide for surgical resection. This is particularly useful for tumors around eloquent areas where the major issue is being able to remove tumor without harming the brain. This can be done with no difficulty by reconstruction from 3mm slices. The image is then fused using laser scanning technology with the patient's head and the result is the ability to operate within the 3-D model. This is especially useful for localizing skull base tumors and establishing their extent and in tumors around the motor / sensory strip.
Surgery Under Local Anesthesia For Brain Tumors
One of the most difficult problems in brain tumor surgery is working with tumors which are in and around eloquent cortex, that is, around the speech area, the movement area or the sensory area. We have established techniques for doing surgery with local anesthesia or with evoked potential mapping that allows this to be done with safety. In a recent paper, we have noted that of 156 patients operated on with this technique, the surgery was very safe. Only one out of 81 patients who had normal function preoperatively had a deficit postoperatively. Of the 75 patients who had some deficit preoperatively, approximately one third resolved the deficit, 50% stayed the same, and 8% had a worsening deficit. We believe this means that this kind of tumor should be resected early before there are new deficits.
Surgery under intravenous sedation is well tolerated by the patient with occasional problems with strength and sensation, but which risks no difficulties with capacity to tolerate the surgery.
X-Knife Radiosurgery For Brain Lesions
X-Knife radiosurgery provides a very important technology for destroying the intracranial metastatic tumors, recurrent gliomas and benign tumors such as meningiomas. For this technology non-coplanar arcs are used to target a lesion which is established by CT scanning and 3-Dimentional reconstruction. These are planned to give optimum isocenter coverage of the lesion and from that point of view, allow accurate and major destruction.
The technique is very simple. The patient has a stereotactic base ring applied and a CT scan is done which demonstrates the abnormality. The tumor is then targeted with planning that avoids any difficulty with eloquent structures. Usually there are no immediate side effects from this procedure. Later in the course there may be radiation changes especially with gliomas.
|For More Information, Contact:|
|Peter Mcl. Black, M.D., Ph. D.|
|Brigham & Women's Hospital|
|Chief Of Neurosurgical Oncology|
|Dana-Farber Cancer Institute|
|Boston, MA USA |
|Phone: 617-732-6810 |
|Fax: 617-734-8342 |