Technical aids for the flexible use of the Leksell stereotactic system.

As part of a multimodality therapy program for intracranial tumours, 105 stereotactic and implant procedures have been carried out utilizing the CT-compatible Leksell stereotactic system. In the iridium implant series, 86 catheters have been implanted for an average of 3.6 targets per patient. There have been no deaths or missed targets and only two incidential haemorrhages detected. In order to facilitate the reliability, safety and speed of multiple catheter insertion, several techniques have been developed including: (a) a standardized single-length catheter and flange system; (b) a ceramic catheter for microwave hyperthermia; (c) a mnemonic card for ease of calculation; (d) a radiation shield for nursing; (e) a stereotactic drill and surgical approaches to far lateral and posterior fossa targets. Principles for the use of these technical aids are discussed.

Technique and preliminary results of interstitial irradiation for primary brain tumors.

We have conducted a phase-I clinical trial of CT-guided stereotactic implantation of Ir192 in the treatment of malignant astrocytomas. During the past year, 16 patients have been implanted with two to four catheters in the residual enhancing portion of their tumor. These patients represent 50% of our total experience with the CT compatible Leksell frame. Each catheter contains three to six high intensity (2.0 to 2.5 mg Ra equivalent) seeds with 0.5 cm separation between the sources. The total activity of Ir192 per implant has been 30-65 mg radium equivalent. In the 16 patients, 49 catheters have been placed, an average of three targets calculated per patient and no targets have been missed. The radiation exposure to personnel has been surveyed in detail and drops off to less than 2 mr/h six feet from the patient when our custom-built radiation shield is employed. We have reserved permanent implantation of I125 for patients with tumors in unusual locations (e.g. pineal) or for individuals with slowly growing non-gliomatous lesions (i.e. meningioma). The tumor volumes have ranged from 12-120 cm3. Unique aspects of our implant procedure include the use of a Leksell frame already adapted to the GE-8800 scanner, the use of pre- and post-implant computerized treatment planning programs to determine the dose distribution profiles and the use of adjustable metal collars crimped to the outer catheters to provide ease of insertion, uniform pre-implant catheter length, and protection against source migration. Two of our patients have suffered from subacute radiation reactions, primarily due to delayed cerebral edema and both of these cases have largely resolved.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteriovenous malformations of the superior cerebellar artery: excision via an occipital transtentorial approach.

Arteriovenous malformations (AVMs) of the superior cerebellar artery (SCA) are unusual and difficult lesions to treat, representing less than half of all AVMs located in the posterior fossa. Traditional approaches for surgical extirpation include the subtemporal transtentorial and suboccipital supracerebellar routes. On the basis of our recent experience with three SCA-supplied AVMs, we advocate an occipital transtentorial approach similar to that used for neoplasms of the pineal gland. Exposure of the AVM from above and in the midline provides superior visualization of the deep veins, the SCA arborization in the retrocollicular space, and the rostral cerebellum, without exposing the temporal lobe and the 4th nerve to surgical trauma in a narrow, confined space. Superior cerebellar AVMs that arise from the caudal branch of the SCA on the superolateral aspect of the hemisphere are more easily handled by standard suboccipital methods.

The pharmacology of diaziquone given in intravenous or intracarotid infusion to normal and intracranial tumor-bearing puppies.

Diaziquone (also called "aziridinyl benzoquinone," or AZQ), an antitumor drug designed to penetrate the blood-brain barrier, has demonstrated activity against central nervous system (CNS) neoplasms. Four-hour infusions of carbon-14 (14C)-labeled AZQ (0.8 mg/kg) were given via the left common carotid artery or left brachial vein to two groups of puppies. A third group, harboring a transplantable canine glioma, received 14C-AZQ by intravenous infusion. Levels of chloroform (CHCl3)-extractable 14C (AZQ only) and total 14C (AZQ and metabolites) were determined in serial samples of plasma and cerebrospinal fluid (CSF). At the end of the infusion time, total and CHCl3-extractable 14C levels were determined in brain and tumor. Intra-arterial infusion of AZQ caused no histological abnormalities in the retina or brain. For the intravenous infusion group, the concentrations of CHCl3-extractable 14C (in nmol/ml or nmol/gm) were 0.68, 0.35, and 0.84 for plasma, brain, and CSF, respectively. For the intra-arterial infusion group, the concentrations were 0.25, 0.13, and 0.32 for plasma, brain, and CSF, respectively. Comparison of right and left hemispheres following intra-arterial infusion showed a slightly higher concentration of 14C in the ipsilateral (left) hemisphere, with concentrations (nmol/gm) of CHCl3-extractable 14C/total of 14C of 0.15/0.87 on the left and 0.12/0.65 on the right. Concentrations (nmol/gm) of CHCl3-extractable 14C/total 14C in brain and tumor were 0.60/1.24 and 0.58/1.65, respectively. In tumor-bearing animals, tumor and surrounding brain contained similar concentrations of AZQ, but there were higher concentrations of metabolites in tumor. This may reflect different metabolism of AZQ within brain and tumor or different permeability to metabolites. This study revealed that AZQ enters the CNS and brain-tumor tissue in substantial concentrations and that there is no significant advantage to intracarotid infusion of AZQ.

Primitive neuroectodermal tumor in a 57-year-old man.

Primitive neuroectodermal tumors are rare cerebral neoplasms previously described only in children and young adults. This report describes such a tumor arising in the left frontal lobe of a 57-year-old man. After surgical resection and radiation therapy to the primary site, the patient developed extensive central nervous system metastases that led to his death. The histopathologic, radiographic, and clinical features of this case suggest that future therapeutic protocols for primitive neuroectodermal tumor should be similar to those for childhood medulloblastoma or neuroblastoma.

CT characteristics of a transplantable canine glioma model: preliminary kinetic analysis.

Experimental brain tumors can be produced in dogs through the intracerebral injection of 3 X 10(6) live tumor cells in either neonates or adult animals. Tumors are visible by computed tomography on day 8 postinjection. Most tumors appear as ring lesions with central lucencies and shaggy borders. By postinjection day 12, tumor volumes increase more than 10 times; the cell cycling time is about 1-3 days. The initial doubling time is about 1-2 days and corresponds to the in vitro doubling time of about 24 hr. The use of computed tomography to perform noninvasive kinetic analysis deserves further study. The transplantable canine glioma model would appear to be ideal for this purpose.