Biomedical subjects

B Wowra

Publications and source records attributed to B Wowra.

45 records · Page 3Linked to original sources

PubMed1989

[Stereotactically targeted radiotherapy of cerebral arteriovenous malformations].

A report is given about radiotherapy in 41 patients suffering from cerebral vessel anomalies. A modified linear accelerator was used in a moving field technique with multiple pendulum planes to apply single doses between 8 and 28 Gy by means of stereotaxis into the angiographically determined target volume. The medium follow-up is 23 months. The latency of radiogenic effects is between one and two years. Radiological controls with an interval of more than 18 months after therapy are available in 17 out of 41 patients. Angiographic investigation showed complete obliterations of pathological vessels in six out of these patients and partial obliterations in six patients; five patients remained unchanged. There were no acute complications. Seven patients presented neurological deficiencies with a latency of 6 to 12 months, however, in all cases but one they regressed completely. Even taking into consideration the small number of patients and the short time of observation, a comparison with the results of other radiotherapeutical proceedings allows to draw the conclusion that the presented technique of stereotaxic convergent-beam irradiation represents a relatively simple, reliable and, in case of precise indication, efficient method for the therapy of cerebral arteriovenous malformations.

Adult↗

PubMed1989

In vitro release and depot effect after intratumoral application of metrizamide-containing liposomes.

The drug release and intratumoral residence time of small and large liposomes composed of saturated phospholipids and cholesterol were measured in vitro and in tumor-bearing rats by computed tomography. The in vitro release of metrizamide at 37 degrees C was higher in tissue fluid than in diluted serum and PBS-buffer. The extent of release was 20%/48 h for the 100 nm-liposomes and 10%/48 h for the 480 nm liposomes. The decrease of x-ray contrast after intratumoral application resulted in a half-life of t50 = 0.05 d for metrizamide solution and t50 = 0.42 d for small liposomes. Large liposomes showed a linear decrease in contrast, the half-life being t50 = 15 d. While small liposomes rapidly leave the tumor, large liposomes rest intact in the tumor for about 30 d. Therefore they fulfill a fundamental prerequisite for intratumoral depots of cytostatics with controlled release.

Animals↗

PubMed1988

Diagnostic value of the stereotactic approach to focal lesions in the deep brain of children and adolescents.

Since it is relatively harmless, stereotactic biopsy has become in recent years a useful method for the diagnostic assessment of lesions deep in the brain, which are not accessible to open surgery. With the aid of stereotaxis, focal lesions only a few millimeters in diameter can be approached in every location in the brain with high precision. Since stereotaxis does not require general anesthesia, or at most requires only a very shallow anesthesia, it can also be applied to young infants or persons of advanced age. Experience with stereotactic biopsy exploration of lesions of various kinds in the deep brain of 74 children and adolescents, out of a sample of 260 patients of all age groups who received stereotactic biopsy, is reported. Our aim is to demonstrate and discuss the advantage of this contemporary method for child neurology and neurosurgery. In many medical centers in the world where stereotactic tumor biopsy has been established, it has become an important criterion for the choice of treatment.

Adolescent↗

PubMed1988

[CT kinetics of intratumor liposome deposits].

CT follow-up studies of liposome-entrapped metrizamide after intraneoplastic injection into neurogenic s.c. rat tumors were performed. By closely resembling clinical examination conditions, the experimental design has proven suitable in determining the in vivo kinetics of these interstitial liposome deposits. When compared to free metrizamide which may be considered an analogue of water-soluble chemotherapeutics, the encapsulation of metrizamide in liposomes resulted in a retarded decline of the contrast enhancement. Diffusion of liposomes could not be detected and the X-ray attenuation values measured within the liposome deposits continuously decreased with time for both types of liposomes. In the case of multilamellar vesicles, this significantly corresponded to a zero order kinetics with a mean halflife of 300 h. An initial increment in the X-ray attenuation of the liposome deposits might be due to the interstitial absorption of the water component of the liposome-dispersion. Because of the pronounced retardation effect of multilamellar liposomes resulting in a 140-fold prolongation of the interstitial retention time of metrizamide and due to their release kinetics these vesicles may be an appropriate carrier system for a local interstitial chemotherapy modality. Small unilamellar vesicles having an interstitial half-life of 14 h may be used as a faster component of a composed therapy system.

Animals↗

PubMed1987

[Cystic craniopharyngiomas: computed tomography in the pretherapeutic evaluation and control of treatment results following intracystic contact irradiation].

A report is given on the treatment planning by computed tomography and monitoring in 37 cases of preponderantly cystic craniopharyngiomas with different solid tumor parts. Colloidal yttrium 90 silicate was used for the intracystic contact irradiation. Two pretherapeutic forms of the solid tumor parts were found in CT examination which correlated with different courses: 1. the polymorphic type and 2. the type with a smooth outline. A posttherapeutic decrease of the cystic volume was observed in 74% of type 1 cases (n = 19) and in 89% of type 2 cases (n = 18). An increase in volume was only found in type 1 (21%). An increase of the solid tumor part was also found exclusively in the polymorphic type (68%). An additional external irradiation should be considered for this CT manifestation of the tumor, as the solid tumor part is not exposed in intracystic contact irradiation.

Brachytherapy↗

PubMed1984

An immunoperoxidase study of a human pituitary adenoma associated with Cushing's syndrome.

A large endocrine active pituitary adenoma causing a Cushing's syndrome was investigated for the presence of subunits of the corticotropin-lipotropin precursor by immunohistology. A quantitative study revealed immunoreactivity (ir) for ACTH in 87.1% of the adenoma cells, beta-lipotropin-ir in 77.1%, beta-endorphin-ir in 75.3%, alpha-MSH-ir in 22.9% and methionine-enkephalin-ir in 7.8%. The adjacent distal pituitary gland showed a six-fold increase of prolactin-ir cells indicating the release of biologically active endogenous opiates. The strong alpha-MSH-ir within the adenoma cells in contrast to those of the distal pituitary may signify that alpha-MSH was being secreted by the adenoma. The proportions of other endocrine cell types within the anterior pituitary were normal (3.1% corticotrophs, 49.4% somatotrophs, 8.2% gonadotrophs and 7.1% thyrotrophs). 0.5% of the cells of the distal pituitary and 0.1% within the adenoma were VIP-ergic, which may be due to a vasoregularitory system and/or be involved in prolactin release.

Adenoma↗

PubMed1983

[Tumor recurrence and massive cerebral angiofibrosis 28 years after conventional high-dose radiotherapy of prolactinoma].

A fatal recurrence developed 28 years after conventional X-ray therapy of a hypophyseal adenoma with a focal dose of 10340R. An organic psychosyndrome of many years preceded the recurrence. The immunocytologic examination of the recurrent tumor showed a prolactinoma. As radiogenic fibroses without primary parenchyma necrosis, massive angiofibroses within tumor, hypothalamus, and neostriatum and less massive angiofibroses in the cerebrum and cortex of cerebrum are opposed to the classical late radiation damage with plasmatic infiltration necrosis.

Adult↗

PubMedDate not supplied

Use of MR angiography for stereotactic planning.

With the introduction of MR angiography (MRA) into clinical routine MR protocols, it has become possible now to image flowing as well as stationary tissue with excellent contrast using a single modality. This has opened up new perspectives for planning stereotactic approaches, which are characterized by high risks for damaging intracerebral vessels or vital brain structures. In this article we present an MRA based planning method for the treatment of arteriovenous malformations by stereotactic radiosurgery. It includes flow compensated gradient echo pulse sequences for the acquisition of angiographic MR datasets, a stereotactic MR marker system, an algorithm for the correction of geometric distortion of MR image data, and a three-dimensional workstation system for the creation and evaluation of treatment plans. The latter is based on the concept of simultaneously displaying both MR slice and angiographic projection images. This allows the evaluation of intracerebral vasculature together with brain anatomy. The MRA guided planning approach was tested and compared to a conventional X-ray angiographic technique in a clinical study. Our satisfactory results suggest that MRA is a technique that can be used advantageously for stereotactic planning.

Brain↗

PubMedDate not supplied

3D TOF MR angiography of cerebral arteriovenous malformations after radiosurgery.

To investigate the potential of three-dimensional time-of-flight MR angiography (MRA) to complement SE imaging, 18 patients with intracerebral arteriovenous malformations were prospectively followed after undergoing radiosurgery. Vessel occlusion after stereotaxic single high dose radiotherapy develops slowly. The MRA detected signs of nidus obliteration earlier and with a higher sensitivity than did SE imaging. Six months after radiosurgery, MRA showed a reduction of the nidus flow signals in nine patients and after 1 year it showed reduction in 15 of the 18 patients. As shown by MRA, the loss of flow signals was related to a reduction of the nidus size in 4 patients after 6 months and in 11 after 1 year. The SE imaging revealed a reduction of the nidus size in only two patients after 6 months and in eight after 1 year. The signal intensity of the feeding arteries was reduced in nine patients and that of the draining veins was reduced in six. The T2-weighted images exhibited white matter lesions in eight patients after 1 year. For complete follow-up, SE imaging should be performed together with MRA.

Adolescent↗