Real Time Surgical Imaging

Summary

Vanderbilt researchers have developed a device that allows for a more accurate and precise detection of brain tumor borders in real time. This allows neurosurgeons to remove all tumor tissue without removing critical normal tissue in surgical brain resections.

Surgical removal of brain tumor is the most common initial treatment and is typically followed by radiation therapy and chemotherapy. Surgery aims to remove the maximum amount of the tumor mass without sacrificing the patients' neurological function. Aggressive surgery in the brain is not acceptable, yet residual tumor tissue left behind after surgery is believed to be the main cause of morbidity.

According to neurosurgeons, defining the margins of brain tumors can be very challenging, as the margins are often ill defined. In addition to visual appearance and/or tactile feel, margins are currently detected with ultrasound, computerized tomography (CT), magnetic resonance imaging (MRI) and surgical navigation systems. Studies have shown that neoplastic cells can be found in brain tissue outside the apparent tumor borders detected with CT and or MRI. Current navigation systems also do not account for post scan deformations of the brain. The spatial resolution of these techniques is also limited to several millimeters---resulting in removal of excess normal brain tissue.

Vanderbilt researchers have designed a novel and portable tool using optical spectroscopy for intra-operative brain tumor demarcation. By combining auto fluorescence and diffuse reflectance, spectra can be measured and used to guide the surgeon to the tissue for resection in real time. Intensities from normal tissue and cancerous tissue differ, and thus such spectra can be used to non-invasively detect alterations in tissue microstructure and biochemical composition associated with tumors. In addition, the spatial resolution of this optical spectroscopy is far less than 1 millimeter, eliminating the removal of excess tissue.

To date the inventors have constructed a prototype device and have tested it in approximately 150 patients with great success. When patient samples are measured 94-96% of tumor tissue and tumor margins are correctly identified as compared against histology, which is the current gold standard. Thus, this methodology is highly accurate and can be done in seconds rather than several minutes, allowing it to be used in real time during surgery

According to the American Brain Tumor Association, approximately 190,000 patients will be diagnosed with a brain tumor each year. For children and adolescents, these tumors are among the most common cancer related causes of death. Further, brain tumors are now the second fastest growing cause of cancer death among those over the age of 65.

Currently, preoperative MRI and CT scanning images, in conjunction with intra-operative biopsy, are used to determine brain tumor margins. Typically, prior to surgery, MRI or CT images are acquired, and surgeons then make calculations and judgments about the extent of tumor to remove, the location of critical structures and the amount of tissue shift that may occur during surgery. Tissue shift is a major challenge during surgery. Once tissue is removed, adjacent tissue can shift, and thus surgeons can become disoriented when comparing current tissue location to preoperative images. Often intra-operative biopsy is used to determine if the margin of the tumor has been removed. This requires the patient to remain on the operating table while the removed tissue is examined for cancerous cells.

Recently, an advanced intra-operative magnetic resonance imaging (MRI) scanner and an image guided surgical system were developed. Although it does provide surgeons with real time images during surgery, it has several disadvantages. The first is its cost. At $9.2M it is impractical for many hospitals to acquire. Furthermore, several challenges arise when working in close proximity to a magnetic field including surgical objects becoming projectiles.

Neurosurgeons will prefer this technology because it allows the surgeon to accurately and quickly define brain tumor margins during surgery. More complete brain tumor removal significantly delays the onset of reoccurrence and/or significantly reduces reoccurrence, considerably enhancing patient quality of life, as well as extending patient life.

Hospitals will prefer this technology over other available real time imaging suites because of reduced cost and portability, thus an entire surgical suite does not have to be dedicated for its use. Rather, this system can be moved from OR to OR. Taken together, this system allows many hospitals to be able to acquire state-of-the-art technology.

U.S. Patent # 6,377,841 filed on April 7, 2000 and issued on April 23, 2002