A.I. Kozel, S.T. Ismagilova, R.U. Giniatullin, V.Yu. Shakhmatov, L.V. Astakhova, D.V. Eremeev
Chelyabinsky State Institute of Laser Surgery, Chelyabinsk, Russia
Treatment of glial intracerebral tumors is one of the solution-proof problems of neurosurgery. The majority of these tumors cannot be removed radically due to their spread and localization in deep-lying areas of the brain.
Laser interstitial thermotherapy (LIT) is an absolutely original method of surgical treatment of intracerebral tumors, in which a photothermal effect of a laser beam is used. LIT is based on obtaining local hyperthermia by means of moderate increase of temperature up to 43-45o C during a limited period of time against a background of a controlled and dosed effect of laser radiation. Its goal is to achieve destruction of tumor tissue without damaging adjacent normal tissue.
We carried out experimental study with the purpose of determining optimum regimens of a laser radiation effect. ALTO (a diode laser) with a wavelength of 980 nm was chosen as a radiation source. Its operation mode was quasi-continuous.
Destruction of brain substance was carried out for revealing dependence of an area and form of a necrotic focus on preselected power and exposure to laser radiation. Temperature measurements were indicative of gradual and smooth heating of tissue to a necessary level.
It was found out, that a degree of morphologic thermodestructive changes within a tumor increased and reached its maximum in 24-48 hours after laser irradiation.
We operated 21 patients with glial intracerebral tumors. They were deep-lying glioblastomas (10 cases) and astrocytomas (8 cases). Three patients were operated for deep-lying single cerebral metastasis.
We used the OREOL stereotactic manipulator. Stereotactic navigation was carried out in compliance with MRI images.
The first stage of an operation was biopsy. It was followed by LIT proper. Two paths were determined: 1 - for insertion of a laser fiber, 2 - for insertion a thermal electrode. A laser light guide was located so, that a laser beam was in a geometric center of a target. Target points (1-4) were determined, depending on a tumor volume and size. When LIT was over and a sensor and light guide removed, a bioptic specimen was taken from a place, located between tumor and normal tissue. There were no complications and fatal outcomes, conditioned by LIT.
Morphologic studies, carried out at the end of LIT, were indicative of coagulation necrosis. The adjacent tissue was intact.
MRI examination in 5-6 and then 24 hours after LIT demonstrated marked changes both on T1 and T2-weighted images, which manifested themselves in sharp reduction of a tumor volume. Subsequent MRI-examinations were carried out in 3, 6 and 12 months.
The very first results make us agree with the opinion of other authors, according to which this method is an interesting alternative in treatment of deep-lying intracerebral tumors of a small size, including single cerebral metastases. This method allows to ensure an optimum volume of intervention, to make it less traumatic and to improve life quality of operated patients.
Today a method of photodynamic therapy of experimental malignant glial tumors is being developed at our Institute. We want to dwell on its experimental phase.
The experiment was carried out on mongrel rats of different sex and a mass of 150-200 g. An infiltrative growth of malignant glial tumors after their heterotransplantation from a man was watched in 20% of animals. Clinical manifestations included hemiparesis, epileptiform seizures and coordination disorders. The animals were divided into three groups, depending on a dose of absorbed laser energy.
The experiment consisted in partial removal of cerebral glial tumors with use of a stereotactic approach and subsequent photodynamic therapy. Radachlorine (a phototsensitizer) was administered into a cavity, which appeared after partial removal of tumor. Its volume was equal to that of a cavity. Laser radiation, generated by a diode laser with a wavelength of 660 nm, was used. A dose of absorbed energy was equal to 30. 60 and 90 J. Irradiation was carried out via a monofiber quartz light guide with a diameter of 0.6 mm. All the rats were excluded from the experiment on the 7th day.
Histological investigation showed, that use of a dose of 60 J/session resulted in complete destruction of tumor tissue and at the same time had no damaging effect on important intact cerebral structures (subcortical nuclei, choroid plexus, etc.).