Between 1974 and 1985, 89 patients suffering from histologically confirmed, nonresectable low-grade astrocytomas located in the brain stem were entered into a retrospective study. Iodine-125 (125I) was implanted in 29 patients and iridium-192 (192Ir) in 26 patients. Computerized tomography revealed that 78% of the tumors in these patients were located chiefly in the mesencephalic region, 70% were circumscribed, and 78% were contrast-enhanced. Thirty-four patients underwent biopsy without prior aggressive tumor-specific therapy such as chemotherapy or external beam irradiation. Among these, 70% of the tumors were located predominantly in the pons, 74% were diffuse, and 59% were hypodense or isodense after contrast enhancement. Long-term follow-up investigations indicated that life expectancy after interstitial radiation therapy with 125I implanted directly by catheter either permanently or temporarily showed a more favorable trend than that after treatment with 192Ir. Interstitial radiation therapy with 125I appears to be an effective treatment for slowly proliferating, differentiated, well-delineated, nonresectable brain-stem gliomas. This technique makes it possible to achieve radiosurgical tumor control and, when carefully applied, represents the least traumatic treatment. Reduction of the tumor mass brings about improvement of the clinical symptoms. Further investigations on the biological behavior of brain-stem gliomas and prospective randomized long-term follow-up studies are necessary to evaluate the different kinds of treatment available for these patients.
SummaryI~iechert and Mundinger's stereotactic apparatus (1956) has been modified and partly reconstructed so that the parameters of different target points, adopted during a single procedure, can be immediately calculated by a computer. The mathematicM foundations and derivations are given.The expansion of clinical information regarding stereotaetic brain operations employing multiple target points during one operation provides an opportunPuy to include computer calculations in the operative procedure 5. Moreover, Modell II. (developed in 1951) of the stereotactic apparatus of Rieehert and Mundinger 6, 7, s has boon so modified that a computer calculation of the focus parameters can be performed. The obvious advantages for clinical use are described elsewhere 1,3,3,4 Two points are fundamental: the target point, which will be reached by the probe, and the trepanation point where the probe will enter the skull.If the calculations are to be performed with the coordination of these two points, it is then necessary to appreciate the principles of construction of our current stereotactic apparatus (Figs. 1 and 2): G is the basal ring which is fixed temporarily onto the patient's head. B is the target arc which, by pivoting the X-axis, produces a partial sphere with radius R ----g. ~ and t are the target and the trepanation point; the angles ~, ~, 9, ~, and the penetration depth T have to be determined.The ~ point is next calculated, by an equation which relates the line of approach through ~ and t to the spherical shell:
The only possible treatment of non-removable tumors of the diencephalon or recurring tumors invading the diencephalon after partial resection or percutaneous radiotherapy is interstitial irradiation (Curie therapy). With the CT/MRI stereotactic method, biopsy for histological tumor classification can be performed and 125I or 192Ir implanted, provided the neuroimaging methods show the delimitation of the tumor, its diameter does not exceed 3 cm and, given the patient's condition, focal irradiation seems advisable. As of 31 August 1987, a total of 1883 cases had been stereotactically biopsied and interstitially irradiated. The indications and results are reported in 204 patients under 18 years of age with diencephalic and deep-seated astrocytomas, after a follow-up period of up to 10 years; the data were compared for tumor resection, percutaneous irradiation, and for interstitial irradiation. The latter proved to be the most effective treatment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.