|
(Continued from page 130)
involved intravenous dye, used far red light (690 nm), was undertaken In the rat glioma model and then the results were utilized in 8 patients undergoing primary glioma resection, yielding increased survival.
In addition to tumor specific dyes, naturally occurring hematoporphyrin and photofrin derivative fluorescence may help discriminate, rat glioma from normal brain (3) or brain tumor from normal tissue (4). A slightly altered compound oligomeric Hematoporphyrin accumulates in tumor tissue in higher concentrations than in non-tumor tissue when injected (5). If laser induction is employed it will excite any of the, natural or injected hematoporphyrin derivative at their natural fluorescence (610 and 675 nm) allowing the discrimination of the tumor, which absorbs the dye preferentially with respect to the normal tissue (6). This procedure has been replicated in colon and bronchial tissue (7).
Reflectance spectroscopy and in vivo autofluorescence spectroscopy, which measures the absorption and reflectance of light at a given wavelength from tissue, has also been applied to Isolate malignant specimens from normal tissue. This is the least invasive method. There is no need for tissue dyes or excitation with additional lights or lasers. Instead, the natural occurring reflectance can be enhanced through the use of lenses at a specific wavelength.
Many biological tissues contain chromophores, which are responsible for autofluorescence. The most common are NADH, flavins, riboflavins, pyridoxal phosphate, vitamins, porphyrins and proteins such as phenylalanine, tyrosine and tryptophan (8). The chromophores spectra are dependent upon the function metabolism and composition of the tissue.
Therefore, the spectra can aid in tissue separation (9). Bronchial tissue (7), skin (10), cervical tissue (11 and 12), and colonic tissue (13), have been studied extensively. These tissues reflect light differently from their malignant counterpart at 365, 405, 436, 480 and 680.
METHODS
Patients were selected pre-operatively. Each patient had radiographic evidence of a suspected lobar glioma. The patients were also candidates for lobectomy as the best surgical procedure. While in the operating room within 20 minutes after tissue removal the specimen was prepared. White matter was selected and cleaned of blood vessels and blood products. Specimens of tumor and tumor free brain from the lobectomy were separated. Tissue was sent to pathology from each site. If the pathologist in the surrounding normal brain saw tumor then additional specimen was separated and sent. All tissue was confirmed on frozen, specimen to be either tumor or normal white matter. These specimens were then placed in normal saline arid taker to spectroscopy. There were a total of five glioma specimens and five normal brain specimens. The normal brain specimens were free from gliosis as determined by the (Continued on page 132)
|
|
