Biomedical subjects
Publications and source records attributed to J Glen.
The attraction of hexagonal closed packed (hcp) iron to a magnet at 16.9 gigapascals and 261 degrees centigrade suggests that hcp iron is either paramagnetic or ferromagnetic with susceptibilities from 0. 15 to 0.001 and magnetizations from 1800 to 15 amperes per meter. If dominant in Earth's inner core, paramagnetic hcp iron could stabilize the geodynamo.
OBJECTIVE: This study sought to investigate the effects of implant dose/volume and surgical resection on survival in a rat glioma brachytherapy model. Two doses were investigated to determine a suitable therapeutic range. METHODS: We performed two experiments. Three treatment groups and one control group of male F-344 rats bearing 9L brain tumors 12 days after tumor inoculation were used in the first experiment. Day 12 tumors were an average of 4 to 6 mm in diameter. Animals treated with brachytherapy received a tumor dose of 80 Gy delivered to a 5.5-mm-radius volume. Total macroscopic tumor removal was achieved by microsurgical techniques. A subsequent experiment compared the survival of tumor-burdened rats treated with an implant dose of 60 Gy delivered to a 5.5-mm-radius volume with a control group. RESULTS: Surgery alone produced an increased life span of 28.6% over control animals treated with sham surgery and dummy seed implants, a statistically significant increase in survival (P = 0.0023, log-rank test). Brachytherapy alone produced the most significant increase in survival over control animals (P = 0.0001, log-rank test; median survival not attained with an implant dose of 80 Gy delivered to a 5.5-mm-radius volume; and P = 0.0001, increased life span 121% with an implant dose of 60 Gy delivered to a 5.5-mm-radius volume). This was not improved by the addition of surgical tumor removal. CONCLUSION: We have demonstrated a relationship between implant dose/volume and survival of tumor-burdened rats in this model that is not improved by the addition of tumor removal. Implications for brain tumor brachytherapy are discussed.
BACKGROUND: Acute and chronic brain injury are common sequelae of high-dose focused radiation, as in radiosurgery and brachytherapy. Development of protectors of radiation injury, which would work in brain but not in tumor, would help enhance the therapeutic ratio of focused-radiation therapy. METHODS: Radiation protection by a clinically available 21-aminosteroid, Tirilazad, was studied in a rat brain brachytherapy model, both in tumor and non-tumor bearing animals. For the tumor model, 9L Glioma/SF line cells were implanted stereotactically into the right frontal lobe of F-344 rats and grew to a sphere of 5.0-mm diameter after 12 days. Animals received a standard brachytherapy dose of 80 Gy to a 5.5-mm radius volume administered by a high-activity removable iodine-125 seed. Radiation damage was evaluated 24 hours after removal of the seeds in all animals and again at 3 months in non-tumor-bearing animals, by T1-weighted gadolinium-enhanced and T2-weighted magnetic resonance imaging (MRI) on a 1.5-T unit. Treated animals received Tirilazad 5 mg/kg intravenously 15 minutes prior to implant, 1 hour after implant, every 6 hours for the duration of the implant, and for 24 hours after removal of the seed. Control animals were administered vehicle only. RESULTS: In both non-tumor-bearing and tumor-bearing rats, no difference in the volume of lesions on enhanced T1 or T2 MRI was seen between the Tirilazad-treated and control groups. In the non-tumor-bearing rats, volume of both T1 enhanced and T2 MRI lesions was significantly reduced at 3 months compared to the values at 24 hours. CONCLUSIONS: In the present model, Tirilazad failed to reduce the volume of radiation brain injury from brachytherapy as seen on MRI, studied acutely in tumor-bearing and non-tumor-bearing animals and also at 3 months in non-tumor-bearing rats.
Over the last several decades in Europe and 15 years in North America, numerous centers have used stereotactic high-activity brachytherapy for patients with malignant brain tumors. A number of nonrandomized series have contributed information regarding the efficacy compared to historical controls for patients with de novo and recurrent malignant gliomas and metastases. Two randomized studies for patients with de novo malignant astrocytoma and glioblastoma are nearing completion. Based on the author's personal experience with 115 patients and the reported literature, we conclude that brachytherapy is appropriate for a minority of patients with malignant brain tumors, that reoperation is frequently required, and complications of therapy can be significant. However, a proportion of highly selected patients benefit significantly from this therapy.
PURPOSE: To assess the efficacy of interstitial brachytherapy in the treatment of patients with recurrent malignant astrocytoma. METHODS AND MATERIALS: Forty-six patients with recurrent malignant astrocytoma were treated with stereotactic high-activity temporary iodine-125 implants between September, 1986 and October, 1992. All patients had been initially treated for malignant astrocytoma (44) or low-grade astrocytoma (2) with surgery and external fractionated radiation. The median time between initial diagnosis and recurrence treated with brachytherapy was 12.5 months. Twenty-five patients received chemotherapy prior to brachytherapy. RESULTS: All but four patients have died; median survival time following brachytherapy is 46 weeks. Twelve patients underwent reoperation for radiation necrosis at a median interval of 6.5 months after treatment (26%). Five patients incurred complications directly due to brachytherapy (11%). Forty-four patients are evaluable regarding pattern of failure following brachytherapy. Six of these 44 patients (13.6%) recurred at a distance from the treatment volume (4 in brain and 2 in spinal subarachnoid space). CONCLUSION: Brachytherapy confers modest but meaningful prolongation of survival in selected patients with recurrent malignant astrocytoma, but complications are significant, reoperation frequently required, and recurrence outside the treatment volume common.
Radiation protection was studied in a rat brachytherapy brain injury model. Radiation lesions were produced by stereotactic placement of high-activity iodine-125 seeds on the frontal lobe of F-344 rats. A minimum dose of 80 Gy was delivered to a 5.5-mm-radius volume. Radiation damage was evaluated 24 h after removal of the seeds by T1-weighted gadolinium-enhanced magnetic resonance imaging on a 1.5-T unit. Computerized three-dimensional reconstruction of the lesions seen on magnetic resonance imaging was performed to calculate the volume of radiation injury. Two experiments were performed with rats of different weights (mean, 300 g; mean, 180 g). All animals underwent surgical placement of an indwelling internal jugular catheter before brachytherapy. Treated animals received the 21-aminosteroid U-74389F 5 mg/kg intravenously every 6 hours during the implant and for 24 hours after the removal of the iodine-125 seed. Control animals were administered vehicle only. In both experiments, a statistically significant reduction in volume of radiation damage was observed in the U-74389F-treated group compared with the control group.
Changes in normal rat brain were studied acutely, and at 3, 6, 9, and 12 months following interstitial brachytherapy with high-activity 125I seeds. An 80-Gy radiation dose was administered to an area with a 5.5-mm radius. Effects were measured with magnetic resonance (MR) imaging (with and without gadolinium enhancement), leakage of horseradish peroxidase (HRP), electron microscopy, and light microscopy. Significant histological damage was seen at radiation doses above 295 Gy, and breakdown of the blood-brain barrier was observed only in tissue receiving a dose of 165 Gy or greater. Blood-brain barrier breakdown increased up to the 6-month time point, and thereafter appeared to stabilize or decrease. The area of blood-brain barrier disruption indicated by gadolinium-enhanced MR imaging was greater than that indicated by leakage of HRP.
We describe transfemoral cerebral angiography of New Zealand white rabbits used to study the cerebral circulation, electroencephalogram, and histologic correlates of selective internal carotid infusion during embolic stroke.
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PURPOSE: The synovium-lined apophysial joint is an important cause of back pain through facet arthrosis and nerve root pressure. The short-term results of two relatively noninvasive treatments--facet block and facet rhizotomy--have been better than their long-term results. The authors propose treatment with fusion of the posterior facet joints in the lumbar spine by means of a simple percutaneous procedure performed under local anesthetic with use of radiologic guidance. MATERIALS AND METHODS: In the first phase of this study the technical feasibility of the concept was established in human cadaver spine. In the second phase a canine model was tested in which bone grafts were surgically inserted into lumbar facet joints. Five male and two female mongrel dogs, weighing 18-25 kg (mean, 20.3 kg), were operated on. Each procedure was done in three steps: First, preoperative computed tomographic (CT) scans were obtained to measure facet depth. Second, surgery was performed under fluoroscopic guidance with use of a threaded guide wire, a small cannulated coaxial drilling system, and hydroxyapatite cancellous bone plugs. Third, early postoperative CT scans were obtained to verify bone plug location. CT was repeated at 4 and 6 months after surgery to check for fusion. The dogs were killed at 6 months, and histologic examination was performed. RESULTS: Successful insertion of the bone plug was achieved in 12 of the 14 facets (86%). One dog died as a complication of the procedure. Fusion occurred in five of the 12 surgically treated facets (42%). CONCLUSION: Drilling and surgical insertion of bone plugs into facet joints of dogs were feasible. The fusion results are promising and may improve with future modifications of the technique.
The angiographic anatomy of the external carotid artery system in the rhesus monkey is described. Similarities and differences between human and monkey anatomy are emphasized, as well as anatomic variations and potential collateral pathways. Superselective angiography and embolization in the external carotid artery system of the rhesus monkey proved to be technically feasible and potentially represents an excellent training model for surgical neuroangiographic techniques.