The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government for governmental purposes without payment of any royalties thereon or therefor.
1. Technical Field of the Invention
The present invention relates in general to the field of sensors and instruments, and it particularly relates to medical diagnostic, prognostic, treatment and surgical instruments. This invention further relates to a system which heuristically provides tissue identification in neuroendoscopy and minimally invasive brain surgery.
2. Description of the Prior Art
Existing medical instruments provide general diagnoses for the detection of tissue interface such as normal tissue, cancer tumor, etc. However, such detection has been limited clinically to tactile feedback, temperature monitoring, and the use of a miniature ultrasound probe for tissue differentiation during surgical operations. Stereotactic computed tomography (CT) scanners, magnetic resonance imaging (MRI) devices, and similar other instruments provide guided brain biopsy and preoperative scans for use. in neurosurgical surgeries. These scans allow samples of brain tissue to be obtained with some degree of accuracy.
However, existing devices provide diagnostic data of limited use, particularly in neurosurgery, where the needle used in the standard stereotactic CT or MRI guided brain biopsy provides no information about the tissue being sampled. The tissue sampled depends entirely upon the accuracy with which the localization provided by the preoperative CT or MRI scan is translated to the intracranial biopsy site. Any movement of the brain or the localization device (e.g., either a frame placed on the patient""s head, or fiducials/anatomical landmarks which are in turn related to the preoperative scan) results in an error in biopsy localization. Also, no information about the tissue being traversed by the needle (e.g., a blood vessel) is provided. Hemorrhage due to the biopsy needle severing a blood vessel within the brain is the most devastating complication of stereotactic CT or MRI guided brain biopsy.
Several other drawbacks are associated with existing devices in stereotactic CT or MRI guided brain biopsy. For instance, this procedure is labor intensive and requires the transfer of localization coordinates from the preoperative scan to the localization device. The depth to which the needle is passed within the brain is also subject to human error. No real-time information is gained about either the tissue being biopsied or the tissue being traversed en route to the biopsy site. The biopsy information is not provided on a real-time basis, and may take a day or more for various staining procedures to be performed by the neuropathologist on the sampled tissue. The non-simultaneity of the sampling, analysis and use precludes existing stereotactic CT and MRI guided brain biopsy from being performed remotely, such as in space missions, long term space exploration travels, or hospitals that are not staffed with a neurosurgeon.
CT and MRI scans allow neurosurgeons to identify anatomical regions of the brain with an accuracy on the order of one or two millimeters. As presented later, these scans are not adequate for the precise localization needed by neurosurgeons to perform optimally safe surgery.
CT and MRI scans are obtained pre-operatively. In a conventional stereotactic CT or MRI guided brain biopsy, a frame is applied to the patient""s head and the scan obtained. The coordinates of the desired targets on the scan are then translated to corresponding coordinates of the frame. The patient then undergoes the biopsy through a small hole drilled in the skull (three or four millimeters in diameter) using a plastic or metal biopsy xe2x80x9cneedlexe2x80x9d that most commonly aspirates a very small core of tissue (on the order of one or two millimeters in diameter by three or four millimeters in length). Any movement of the brain, such as can be due to changing the position of the patient from the position in which the scan was obtained, can introduce error into the biopsy coordinates.
A much greater practical problem arises when the pre-operative scan is used to guide the removal of a tumor deep within the brain. As the tumor is removed, or the brain retracted to permit access to the tumor, the coordinates from the pre-operative scans become somewhat invalid. This error is especially troublesome with recently developed systems that use an optically-encoded xe2x80x9carmxe2x80x9d in an electro-optical camera system for localization during neurosurgical operations.
Another significant problem with using CT and MRI scans for localization is that they do not provide functional localization. As neurosurgical procedures become more precise, the need increases for knowledge of the functional organization of the brain. The localization necessary to perform pallidotomy procedures for Parkinson""s disease is one example where anatomical localization based on CT or MRI scanning is inadequate for optimal treatment, since electrophysiological mapping intraoperatively is important to maximize the benefit of the operation for a given patient.
There have been a few recent advances in preoperative scanning that provide some information about the functional organization of the brain. Functional MRI and PET (Positron Emission Tomography) are two examples of such recent scanning techniques. However, these scanning techniques are hampered either by their limited range of functions which can be utilized (e.g., functional MRI) or their relatively poor resolution, for example on the order of one half to one centimeter (e.g., PET).
It is an object of the present invention to enable the placement of multiple neurosurgical sensors and/or effectors (or tools), such as a biopsy probe in any desired region of the brain with extreme accuracy.
Another object of the present invention is to enable the localization of the neurosurgical sensors and/or effectors based on the characteristics of the local brain environment, taking into consideration the anatomical and functional variability among human (and non-human) brains.
Still another object of the present invention is to perform minimally invasive surgery, for example the localized placement of the effector and treatment with minimal disruption of normal brain functions. An important method for minimizing invasiveness is miniaturization.
Yet another object of the present invention is the automation of part of surgical procedures. This objective is realized by incorporating two disciplines. The first discipline is robotics and remote control, and the second discipline is neural net (or artificial intelligence) learning. Remote control has been used by NASA scientists in missions either too dangerous or impossible for human performance, such as sending an unmanned submarine beneath the Antarctic ice cap and a robotic rover into an Alaskan volcano crater. Neural net learning allows a computer to gather information from repeated exposures to normal and abnormal brain tissue which can then be applied to a novel situation, in order to decide the type of tissue being encountered.
A further object of the present invention is to provide a heuristic robotic system with a multimodality instrument for tissue identification. This instrument will replace xe2x80x9cdumbxe2x80x9d metal needles used to perform exploratory surgeries such as biopsies. It will also help avoid certain complications associated with the translation of the lesion (e.g., tumor) coordinates from MRI/CT scans to the actual lesion using the inventive multimodality instrument. These complications include the inability to obtain tissue which will allow the neuropathologist to make a diagnosis, and the risk of severing a blood vessel which may result in a hemorrhage causing significant neurological injury or possibly death.
Briefly, the foregoing and other features and advantages of the present invention are realized by a robotics system with a multimodality heuristic instrument for tissue identification. The instrument includes a computer-controlled motor driven probe with a multisensory tip, e.g., a group of sensors may be selectively incorporated into the probe tip, or near the probe tip or as part of the probe.
In a preferred embodiment, the probe is driven by a computer-controlled actuator mechanism to the appropriate depth within the brain for obtaining a continuous and real time output of resistance or density of the tissue being penetrated. This output is received into a neural net learning program which is constantly learning not only the differences between normal brain tissue and abnormal brain tissue, such as tumors, but also the differences between various regions of the brain (e.g., gray matter versus white matter).
In another embodiment where robotic insertion is not advantageous, the probe can be a hand-held device and/or manually driven instead of motor driven.
The instrument further includes a micro laser-Doppler blood flow probe having a diameter of less than approximately 1 mm. This probe detects blood vessels before it can disrupt them, and it can further catalog the blood flow differences between either normal brain tissue, abnormal brain tissue, or various regions of the brain such as gray matter and white matter (which are known to have a roughly fivefold difference in blood flow). A micro ultrasound probe, also less than approximately 1 mm in diameter, can aid in blood vessel detection and tissue identification. A pO2 (partial pressure of oxygen) microprobe, less than 1 mm in diameter can aid in the detection of hypoxia which is an indication of turner malignancy.
Ion-selective micro electrodes can also be used to monitor such important parameters as pH, calcium, sodium, potassium, and magnesium. Additionally, optical fluorescence and/or optical absorbance probes with a diameter of less than approximately 1 mm can also be used to monitor oxygen and carbon dioxide levels and other parameters of the signal. The combination of optical reflectance sensors and neural net learning to characterize the tissue being penetrated by the probe yields a characteristic optical reflectance signature which is very valuable in distinguishing and identifying different tissues, such as blood vessels, tumors, grey matter and white matter.
The present multimodality instrument offers several advantages and can be used in various commercial applications. For example, the present instrument improves the diagnostic accuracy and precision of general surgery, with near term emphasis on stereotactic brain biopsy. It automates tissue identification with emphasis on stereotactic brain biopsy to permit remote control of the procedure. It also reduces morbidity of stereotactic brain biopsy. The present instrument may also be used in conjunction with various surgical tools to increase the safety, accuracy and efficiency of surgical procedures. For example, the use of the multimodality instrument for monitoring patients with severe head injuries would greatly enhance the surgeon""s capabilities in neurosurgery.
The present instrument may also be used in conjunction with endoscopes for tissue identification in various types of surgery, and can be adapted to a hand held device and/or manually driven instead of motor driven for procedures where the automated robotic aspect is not advantageous.
The present instrument may be used in a variety of applications including but not limited to tumor ablation in neurosurgery, general exploratory surgery, prostate cancer surgery, breast cancer surgery, spinal surgery automated tissue identification for general surgery use (e.g., detecting the interface between normal tissue, cancer, tumor, or other lesion), automated stereotactic biopsy for neurosurgery, continuous monitoring for patients at risk for cerebral ischemia and/or increased intracranial pressure (e.g., many patients with cerebrovascular disease, tumors, or severe head injury), and other surgical procedures that could be performed in an automated/robotic fashion for minimizing trauma to the patient because of decreased exposure time in comparison with procedures performed manually and/or more invasively.