SBIR-STTR Award

Accurate, noninvasive assessment of brain circulation is needed in numerous neurosurgical procedures, clinical diagnosis of cerebrovascular pathology (e.g., stroke), drug testing, and biological psychiatry. However, currently employed methods not only are very costly, but expose patients to radioactive materials. Further, no available methods provide second-to-second (e.g., real-time) dynamic measures of cerebrovascular function, greatly restricting the number of applications of these methods. The long-term goal of this project is the development of a microcomputer-controlled electrical impedance brain monitor capable of providing accurate, nearly continuous imaging of hemispheric and regional cerebral blood flow _ noninvasively_at less cost than radioisotope-based methods.Phase I is designed to provide two-dimensional spatial calibration of the nontraumatic rheoencephalographic (REG) method by comparing it with an established radiological procedure (gamma camera with 133-Xenon inhalation) in healthy volunteer subjects and patients with cerebrovascular disorders. At this stage, several accepted flow equations will be compared with the goal of calculating absolute flow values using impedance waveform parameters. Concurrently, a microcomputer-based software will be developed to automatically collect, analyze, and format impedance-derived data. This will simplify operation of the system so that it will be useful for clinical as well as experimental applications.Phase II will initially involve development of software to generate two-dimensional images of regional cerebral blood flow, based on Phase I calibration. Subsequently, the complete imaging system will again be compared to radiological methods (PET scans, CT scans) and tested in clinical populations. The successful implementaton of the proposed research would provide essential, basic data needed for commercialization .National Institute of Mental Health (NIMH)

In Phase. II, BioComp Systems, Inc. proposes to develop a new functional brain-imaging modality based on electrical impedance data provided by noninvasive, nonradiological rheoencephalographic (REG) technology. Tetrapolar REG impresses a small (lmA), high-frequency (100 Khz) field across the patient's head to derive region-specific, intracranial pulse-volume waveforms ((Z) as well as total impedance (ZO) parameters.A bimodal approach to REG imaging will be taken. In Method 1, a linear interpolation algorithm, developed at NIMH, will be used; it assumes equal area projection of cortical-scalp voltage values. Method 2 estimates cortical voltage values through a deconvolution-interpolation procedure requiring estimation of cortical current densities using a previously developed 4sphere model of the head. Evaluation and refinement of these algorithms will be based on statistical comparisons with simultaneously collected Xe133 data. The imaging process will then be field tested in patients with (1) NMR-confirmed focal cortical infarction (n=15); (2) NMR-confirmed focal cortical tumors (n=15); and (3) schizophrenics (n=10) and normal subjects (n=10). Schizophrenic patients and matched control subjects will be studied both at rest and during the performance of a cognitive task that induces differential cortical blood flow patterns. Impedance-based hemispheric blood flow patterns will be compared with simultaneously conducted single photon emission computed tomography (SPECT) blood flow patterns.National Institute of Mental Health (NIMH)