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Biomedical subjects

V Sturm

Publications and source records attributed to V Sturm.

At least 55 records · Page 3Linked to original sources
PubMed1996

Glucose consumption and methionine uptake in low-grade gliomas after iodine-125 brachytherapy.

We investigated whether 2-[18F]-fluoro-2-deoxy-d-glucose (FDG) and carbon-11 methionine are suitable tracers to monitor the effects of therapy for low-grade gliomas. Ten patients with low-grade glioma without previous treatment were studied with FDG positron emission tomography. Additionally, l-[methyl-11C]methionine uptake was measured in five subjects before and 1 year after computerized tomography (CT)-guided stereotactic and computer-assisted implantation of iodine-125 seeds. All scans were 3D-matched to CT, isodose volumes were determined, and changes in glucose metabolism and methionine uptake were evaluated in tumour and brain tissue as a function of radiation dose. After 1 year glucose metabolism was not significantly altered up to a radiation dose of 300 Gy, whereas methionine uptake showed a significant dose-dependent decrease. Higher rates of decline were found in tumours with high basal methionine incorporation activity before therapy. These data suggest that measurement of methionine uptake is more suitable than measurement of FDG uptake for monitoring therapeutic effects in low-grade gliomas.

Adult↗
PubMed1996

Ablation of neural tissue by short-pulsed lasers--a technical report.

The basis for most laser applications in neurosurgery is the conversion of laser light into heat when the incident laser beam is absorbed by the tissue. Irradiation of neural tissue with laser light therefore leads to its thermal damage. However, due to the diffusion of heat energy into the surrounding tissue, often there is thermal damage to neural tissue outside the area of the target volume. These are the characteristics of thermal laser/tissue interaction. In this paper we discuss how we used three different short-pulsed lasers to achieve non-thermal ablation of neural tissue. Three different short-pulsed lasers were used to generate ultrashort laser pulses in the picosecond to femtosecond range. The interaction of such laser pulses with tissue was predicted to be nonthermal. The short-pulsed lasers were used for the ablation of neural tissue using an in vitro calf brain model. The histopathological examination of the lesions revealed that the neural tissue had been removed very precisely without any sign of thermal damage to the surrounding tissue.

Animals↗
PubMed1995

Serum albumin (SA) accumulation by bronchogenic tumours: a tracer technique may help with patient selection for SA-delivered chemotherapy.

Systemic toxicity and inadequate tumour uptake of chemotherapeutic agents limit effective therapy of disseminated malignant disease. We seek to use macromolecules for improved delivery of therapeutic agents to tumours, and hope to use radiotracer procedures to identify those malignancies able to accumulate the transport molecule. A literature search identified in vitro and animal experimental data which indicated that serum albumin is taken up in malignancies. Selected cytostatic drugs can be bound to albumin, which suggests the suitability of the molecule as a potential transport vehicle. We therefore evaluated indium-111 labelled human serum albumin (HSA) to determine the frequency of its accumulation in bronchogenic tumours. Single-photon emission tomographic (SPET) images were obtained in 23 patients 48 h after intravenous injection of 1.5 mCi 111In diethylenetriamine penta-acetic acid (DTPA)-HSA. SPET imaging with technetium-99m labelled erythrocytes was included in the protocol to assess the influence which vascularity has on the HSA-based images. All patients went on to surgery. We documented the histological diagnosis, T-stage and differentiation grade. The scintigraphic examination demonstrated HSA uptake in three squamous cell carcinomas and four adenocarcinomas. Of these, six malignancies accumulating HSA had 2.2-5.4 times, the tracer concentrations observed in comparable background regions. Small cell carcinoma failed to accumulate the labelled HSA during the 2-day scintigraphic evaluation. The HSA images did not appear to represent tumour vascularity. T-stage and differentiation grade failed to predict which tumours would demonstrate HSA uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Antineoplastic Agents↗
PubMed1994

Photogrammetric accuracy measurements of head holder systems used for fractionated radiotherapy.

PURPOSE: We describe how stereo photogrammetry can be used to determine immobilization and repositioning accuracies of head holder systems used for fractionated radiotherapy of intracranial lesions. METHODS AND MATERIALS: The apparatus consists of two video cameras controlled by a personal computer and a bite block based landmark system. Position and spatial orientation of the landmarks are monitored by the cameras and processed for the real-time calculation of a target point's actual position relative to its initializing position. The target's position is assumed to be invariant with respect to the landmark system. We performed two series of 30 correlated head motion measurements on two test persons. One of the series was done with a thermoplastic device, the other one with a cast device developed for stereotactic treatment at the German Cancer Research Center. Immobilization and repositioning accuracies were determined with respect to a target point situated near the base of the skull. The repositioning accuracies were described in terms of the distributions of the mean displacements of the single motion measurements. RESULTS: Movements of the target in the order of 0.05 mm caused by breathing could be detected with a maximum resolution in time of 12 ms. The data derived from the investigation of the two test persons indicated similar immobilization accuracies for the two devices, but the repositioning errors were larger for the thermoplastic device than for the cast device. Apart from this, we found that for the thermoplastic mask the lateral repositioning error depended on the order in which the mask was closed. CONCLUSION: The photogrammetric apparatus is a versatile tool for accuracy measurements of head holder devices used for fractionated radiotherapy.

Head and Neck Neoplasms↗
PubMed1994

Linac radiosurgery in brain metastases.

Brain metastases are usually well-circumscribed and more or less spherical lesions. These conditions meet the criteria for radiosurgery (RS). A pilot study initiated by our group in 1983, demonstrated the effectiveness of Linac-RS in the treatment of solitary brain metastases with low radiosensitivity. A second trial including patients with 1-3 metastases started in 1990. By April 1993, 46 patients had been treated in this series. The radiation doses delivered to the tumour margin ranged from 10 to 25 Gy, and were chosen with respect to size, number and location of the tumours or previous whole brain radiotherapy (WBRT), decreasing mainly with increasing tumour volumes. 34/46 patients had a follow-up of more than 12 weeks. In 7/46 patients the disease progressed rapidly during the first weeks after RS and follow-up examinations were not performed. 5/46 patients had a follow-up of less than 6 weeks and follow-up CT/MR-examinations were not available. 14/46 patients received WBRT before RS. The regularly performed follow-up examinations (clinical status, CT-/MR-examinations in 6 or 12 weekly intervals) revealed tumour progression in 5/34 patients. Permanent cessation of the growth (11/34), tumour shrinkage (18/34) and decrease of surrounding oedema together with clinical amelioration have been observed a few weeks after radiosurgery. The median follow-up was 50 weeks. 14/46 patients died due to generalized progression of their disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Linac-accelerator-radiosurgery.

A survey is given of the actual possibilities and limitations of the use of linear accelerators (Linac radiosurgery systems) for intra = cranial radiosurgery. Depending on the collimator size, spherical fields from 5-54 mm in diameter can be irradiated with dose gradients from 10% (large fields) to 20% (small fields) per millimeter distance between surface and treatment volume. This is comparable to the possibilities of Gamma-Knife and Proton-irradiation. Optimal mechanical adjustment of gantry and linac table are necessary for the required stability of the isocenter. Mechanical inaccuracy should be smaller than 0.8 mm. Advanced computerized 3D-treatment planning systems are indispensable prerequisites for accurate treatment and use of the flexibility of the linac system. Future developments are outlined.

Brain↗
PubMed1993

Interstitial irradiation of cerebral gliomas with stereotactically implanted iodine-125 seeds.

Ninety-seven consecutive patients with primarily inoperable or only partially resectable gliomas have been analysed retrospectively. Mean tumour surface doses of 70 Gy (low grade gliomas) and 56 Gy (high grade gliomas) have been applied with stereotactically implanted Iodine-125 seeds at low dose rates. Patients with a glioma grade III or grade IV and permanent seed implantation additionally received a fractionated external beam irradiation. With mean follow-up times of 55.8 months (glioma grade I), 51 months (glioma grade II) and 59.6 months (glioma grade III) the estimated mean survival probabilities are 105 months, 102 months and 65.7 months respectively. In the glioma grade IV group the estimated mean survival time has been 15.6 months after continuous interstitial irradiation (response rate: 36%). Temporary interstitial irradiation in cases with a glioma grade IV (dose rate: 2.1 Gy/day) caused initial tumour shrinkage in 77%. Neurological deficits following radiation induced vasogenic oedema were reversible in 2 patients and irreversible in another 2 patients. 6 years after the Iodine-125 implantation and continuous interstitial irradiation 1 patient developed a severe localised radiation necrosis.

Adolescent↗
PubMed1993

CT-guided and computer assisted stereotactic biopsy. Technique, results, indications.

On the base of a stereotactic device originally described by Riechert and Mundinger a three-dimensional localization and treatment planning system for CT-guided computer assisted stereotactic procedures has been developed. The experience with 338 patients, in which image guided stereotaxy has been used for the assessment of various intracerebral lesions, is presented. In 54 of these patients the cannula was introduced with a 20 MHz Doppler-probe positioned at the tip of the needle. A comparison of tissue specimens taken stereotactically with tissue material after tumour resection and/or autopsy was performed in 35 patients. The accuracy of the histological diagnosis was 88%. Bleeding as a complication due to the stereotactic intervention occurred in 8 patients (2.4%). Two of these patients had a fatal outcome (mortality: 0.6%). The morbidity (transient and permanent deterioration of the clinical status) was 1.2%.

Adolescent↗
PubMed1993

Interstitial irradiation of a large, low grade ependymoma with stereotactically implanted iodine-125 seeds. Case report.

In this case report a patient with a large intraventricular benign ependymoma is presented. The tumour was treated with stereotactically implanted Iodine-125 seeds and interstitial irradiation. Extension (diameter: 6.5 cm) and volume (112.5 ml) of the lesion caused the application of an unusually low dose (tumour surface dose: 40 Gy). The tumour shrank significantly within a few weeks. Follow-up at nearly 5 years shows the patient to be tumour free.

Adult↗
PubMed1993

Correlation of glucose consumption and tumor cell density in astrocytomas. A stereotactic PET study.

To determine histological correlates of the variability of glucose consumption in astrocytomas, the authors performed positron emission tomography (PET) with 18F-2-fluoro-2-deoxy-D-glucose (FDG) and matched the PET scans three-dimensionally with computerized tomography scans obtained in a stereotactic frame before biopsy. Ten patients with astrocytomas of World Health Organization Grade 2 or 3 were studied; patients with glioblastomas, oligodendrogliomas, or oligoastrocytomas were excluded from the study to avoid any confounding effects of different cell types and necroses. In samples of pure tumor, glucose consumption correlated significantly with cell density, but not with nuclear polymorphism. It is concluded that tumor cell density is a major determinant of glucose consumption in astrocytomas. The use of PET with FDG may help to locate the highest cell density and thus improve the diagnostic yield of stereotactic biopsy.

Adult↗
PubMed1992

Intrathecal chemotherapy with ACNU for meningeal gliomatosis.

ACNU [1-(4-amino-2-methyl-5-pyrimidinyl) methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride], one of the chloroethylnitrosoureas (CENUs), is believed to be effective against malignant glioma when intravenously or intrathecally administered. A rat model with meningeal gliomatosis (MG) induced by an intracisternal inoculation of rat C6 or 9L glioma cells was intrathecally and intravenously treated with ACNU in order to test the feasibility of intrathecal chemotherapy with ACNU in the treatment of meningeal gliomatosis. The median survival time (MST) of the animals was significantly prolonged when ACNU was intrathecally administered at dosages of 0.5 to 1.5 mg kg-1 in the early stages of MG, i.e. within 3 days after the tumour inoculation, whereas intravenous therapy with ACNU at a dose of 15 mg kg-1 did not exhibit any efficacy in the rats inoculated with C6 glioma cells (C6-MG). Intrathecal ACNU, however, at dosages of up to 1.5 mg kg-1 failed to demonstrate any therapeutic effect in the late stage of MG, i.e. 5 days after the tumour inoculation, except in the rats inoculated with 9L brain tumour cells (9L-MG). Intravenous chemotherapy with ACNU at a dose of 15 mg kg-1 extended the MST of the 9L-MG rats more significantly in the late stage of MG than in its early stage. This points to the feasibility of intrathecal ACNU in the treatment of meningeal gliomatosis in its early stages, but not in its late stages in which intravenous ACNU might be more effective than intrathecal treatment against MG of which the parenchyma has already been deeply invaded by the tumour.

Animals↗
PubMed1992

Blinded evaluation confirms long-term asymmetric effect of unilateral thalamotomy or subthalamotomy on tremor in Parkinson's disease.

In the past, stereotactic surgery was a regular treatment for prominent unilateral tremor in Parkinson's disease (PD), but follow-up studies were usually short-term and always unblinded. We examined 17 PD patients in long-term follow-up (mean, 10.9 years after surgery) and used videotapes and the Unified Parkinson's Disease Rating Scale to blindly compare tremor ipsilateral and contralateral to the side of surgery. Since the patients were specifically selected for stereotactic surgery because of asymmetric tremor, and the surgical side chosen was contralateral to the predominant tremor, a sign of long-term efficacy would be current postoperative reversal of tremor side predominance. Upper extremity tremor was significantly better contralateral to the surgery compared with the ipsilateral side. We conclude that stereotactic surgery improved the absolute magnitude of tremor or ameliorated its rate of progression. Since asymmetric bradykinesia and dyskinesia were not a prerequisite for the choice of surgical side, we cannot make any conclusion about long-term impact of surgery on these features.

Aged↗
PubMed1992

Isolation and preliminary characterization of ACNU-resistant sublines of rat brain tumors in vivo.

Two variant cells lines resistant to the nitrosourea derivative ACNU ((1-4-amino-2-methyl-5-pyrimidinyl)-methyl-3-(2-chloroethyl)-3-nitrosourea hydrochloride), namely C6/ACNU and 9L/ACNU, were selected in vivo from rat brain tumors. Stable resistance to ACNU proved to be a characteristic of these cell lines, whether they were grown in vivo or in vitro. These cell lines exhibited a different pattern of cross-resistance to a wide range of chemotherapeutic agents with dissimilar chemical structures and mechanisms of action as compared with that of other ACNU-resistant cell lines established in vitro. Distinct cross-resistance was observed in both the C6/ACNU and 9L/ACNU cell lines to chloroethyl-nitrosoureas such as BCNU (carmustine), CCNU (lomustine), and methyl CCNU and, additionally, to vincristine, vinblastine, Adriamycin (doxorubicin), and arabinosylcytosine, but not to bleomycin, methotrexate, cis-platinum, and 5-fluorouracil. This might point to a multifactorial mechanism of drug resistance in ACNU-resistant cell lines derived from rat C6 and 9L brain tumor cells.

Animals↗
PubMed1992

Intrathecal chemotherapy with ACNU in a meningeal gliomatosis rat model.

Intrathecal administration of ACNU ((1-4-amino-2-methyl-5-pyrimidinyl)methyl-3-(2-chloroethyl)-3-nitroso urea hydrochloride) had a remarkable chemotherapeutic effect in a rat model of meningeal gliomatosis. This effect was evaluated in rats with meningeal gliomatosis induced by an intracisternal inoculation of rat C6 glioma cells. The median survival time of the rats treated with a single dose of intrathecal ACNU (1 mg/kg) on Day 1 or Day 3 after tumor inoculation was significantly prolonged by 35.7% to 42.9% or 25.0% to 28.6%, respectively, as compared with that of the control animals. Meningeal gliomatosis rat models treated intrathecally with ACNU (1 mg/kg) 5 days after tumor inoculation or intravenously with ACNU (15 mg/kg) both failed to prolong the survival time of the animals. These findings suggest that intrathecal chemotherapy with a low dose of ACNU is effective in the early stages of meningeal gliomatosis, whereas intravenous chemotherapy with a high dose of ACNU is always ineffective.

Animals↗
PubMed1991

Radiosurgical treatment of cerebral metastases. Method, indications and results.

Stereotactically guided single-dose irradiation of brain metastases with low radiosensitivity has been performed in a series of 30 patients. Clinical symptoms improved in 18 of 27 evaluated patients and remained stable in another 7. Tumour regression was achieved in 13 of 22 patients, and arrest of tumour growth in 7 other patients. The treatment was usually well tolerated. The incidence of side effects was low. Thus, radiosurgery seems to be a valuable alternative to microsurgical extirpation of solitary brain metastases with low radiosensitivity.

Adult↗
PubMed1990

Interstitial chemotherapy of experimental gliomas.

Two new approaches of interstitial (intratumoral) chemotherapy of gliomas are presented. Using s.c.-transplanted rat gliomas (G616) the therapeutic activity of biologically degradable polylactide rods as carriers for methotrexate was investigated. Carrier-mediated intratumoral chemotherapy was superior both to a systemic treatment and an intratumoral treatment with the free drug. The activity of the alkyllysophospholipids Et-18-OCH3 and BM 41.440 and of the alkylphosphocholine He-PC was investigated in a human glioma xenograft (T 406). All three compounds were highly active following intratumoral administration.

Animals↗
PubMed1990

Stereotactic single high dose radiation therapy of benign intracranial meningiomas.

Seventeen patients with intracranial meningiomas were treated with single high dose irradiation at the German Cancer Research Center in Heidelberg. Indications for radiosurgery included unresected tumors, gross disease remaining despite surgery, and recurrences. Therapy was carried out by a technique using multiple non-coplanar arc irradiations from a 15 MeV linear accelerator. This technique coupled with secondary tungsten collimators allowed a high concentration of the dose in the target volume with an extremely steep dose gradient at the field borders. The patients were treated with a single irradiation dose ranging from 10 to 50 Gy (mean of 29 Gy). Four of 17 patients died: one death was tumor-related and not attributable to the treatment, one died of a treatment related complication, and two patients died of intercurrent diseases. The remaining 13 of the 17 patients with a median follow-up time of 40 months have no evidence of tumor relapse. Late severe side effects include five patients with a large area of brain edema, three of which were concurred with tumor necrosis. We conclude from these initial data that single high doses of irradiation concentrated to the tumor volume by stereotaxic methods can achieve local tumor control. It is also clear from these data that the effective therapeutic dose range must be better defined.

Adult↗