Advanced Functional and Structural Brain Mapping for Neurosurgical Planning and Intra-operative Decision Making

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Alexandra J. Golby, MD Brigham and Women's Hospital, Harvard Medical School

Alexander J. Golby, MD
Brigham and Women’s
Hospital, Harvard
Medical School

Surgery remains the single most effective treatment for patients with brain tumors. For many types of tumors surgery is able to improve symptoms, relieve seizures, and provide a great decrease in the amount of tumor, making further therapies more effective. The work of the Golby Lab centers on using imaging to improve neurosurgical treatment of brain lesions. Dr. Golby’s work uses multiple imaging approaches to give the surgeon maximal information for pre-operative planning and intra-operative decision-making. The Golby lab is grateful to the Brain Science Foundation for supporting its work using multiple imaging approaches to optimize surgical resection in patients with brain tumors.

Tumors located near critical brain areas such as areas that control movement, speech, vision or other important functions, pose a great challenge as neurosurgeons must remove as much of the tumor as possible while sparing the critical brain structures. Unfortunately, the brain does not have any labels on it indicating the key areas. In fact neither conventional imaging nor visualization of the brain itself directly at surgery is able to differentiate which areas of the brain are responsible for performing which functions. In addition, it can be difficult to localize tumors and to define the optimal limits of resection due to the limited information available to the surgeon using only their eyes.

Dr. Golby and team have been developing imaging techniques which can begin to show surgeons functional maps of the brain and to integrate these with intra-operative navigation. These techniques use magnetic resonance imaging (MRI) which is non-invasive and can be readily acquired before surgery. Her group’s efforts have been focused on using two advanced MRI techniques: functional MRI (fMRI) and Diffusion Tensor Imaging (DTI). fMRI is able to show areas in the grey matter (the cortex, where the neurons are clustered), which are activated when the patient performs a certain task. These areas can be superimposed on standard MRI images to show neurosurgeons a detailed functional map which can help to guide surgical decision making. DTI is another technique which is able to show another aspect of brain organization which has previously been invisible to the naked eye. This technique is able to show the arrangement of the white matter in the brain. White matter contains all of the connections between neurons in the cortex and between the cortex and deeper parts of the brain. These connections, called tracts, also have to be spared during surgery in order to avoid causing harm to the patient. By showing the configuration of these connections DTI can aid the neurosurgeon in determining whether they have been displaced, infiltrated or destroyed by the tumor thus helping to guide the resection strategy. While these functional and structural brain imaging techniques provide an unprecedented view into the structure-function relationship of the human brain, there remain many unanswered questions as to the best approaches which are valid, reliable, and helpful to the surgeon.

With funding from the BSF, Dr. Golby has made some significant strides in addressing some of these problems, while at the same time introducing new questions. Her present work is focusing on two new goals: (1) to allow the demonstration of specific white matter tracts by selecting or seeding from key cortical regions and (2) translation of a new approach using connectivity analysis in fMRI data to allow definition of key cortical regions without requiring the performance of a behavioral task.

Beyond pre-surgical planning, intra-operative delineation of resection margins can be difficult because tumors resemble brain, often infiltrate brain tissue, may be immediately adjacent to critical functional brain tissue, and deformation of brain structures occurring intra-operatively renders pre-operative images less helpful. Dr. Golby’s lab is developing several systems which can be deployed intra-operatively to assist neurosurgeons in clearing margins of residual brain tumor tissue following bulk tumor resection.