Balloon venoplasty of acute subclavian vein thrombosis.

Two patients with subclavian vein thrombosis are presented in which a balloon venoplasty led to recanalization of the subclavian vein and complete remission of clinical symptoms. In patients with extreme symptoms and unsuccessful initial catheter-directed local thrombolysis, this non-operative approach can be considered despite known favourable spontaneous outcome of subclavian vein thrombosis.

Optimisation strategies and justification: an example in uterine artery embolisation for fibroids.

Radiation risk has to be justified and optimised. This study discusses the radiation risk of uterine artery embolisation (UAE) for the treatment of fibroids. A total of 70 consecutive UAE dosimetry parameters were assessed. Using Monte Carlo simulation, organ and effective doses and dose conversion coefficients (DCCs) (mSv Gy cm(-2)) were calculated. During UAE optimisation, avoidance of oblique views and use of last-image-hold (LIH) documentation instead of digital subtraction angiography (DSA) were investigated. Mean dose-area product (DAP) was 37.1 Gy cm2 (median 23.7 Gy cm2) and mean fluoroscopy time was 18.4 min (median 16.6 min). Dose values decreased as the study progressed: mean DAP for patients 1-21, 68.5 Gy cm2; patients 22-43, 35.7 Gy cm2; and patients 44-69, 13.0 Gy cm2. Average DCC for DSA image procedures was 0.572, yielding a mean effective dose of 29.6 mSv (median 17.1 mSv). For LIH-only procedures, an average DCC of 0.813 was estimated [using mean effective dose: 10.6 mSv (median 8.1 mSv)].

Communicating hydrocephalus. Cisternographic and neuropathologic studies.

Chronic communicating hydrocephalus was produced in adult dogs by injection of silastic into the subarachnoid space. Electron microscopy was used to verify the sequence of pathologic changes in the ventricular wall. The pathologic findings were correlated with cisternographic images and measurements of cerebrospinal fluid (CSF) pressure. Early in hydrocephalus, the CSF pressure was increased and cisternograms showed ventricular entry and clearing; the ependyma was stretched and fluid accumulated in subependymal regions. In animals with chronic hydrocephalus, the CSF pressure was normal and cisternograms disclosed radioactivity persisting in the ventricles. At this time the ependyma was severely damaged, the subependymal white matter showed enlargement of the extracellular space, and degenerative changes were present in axons and myelin sheaths.

Angiomorphometry in malignant tumors and inflammatory disease.

Angiographic differentiation of malignant and inflammatory lesions is occasionally impossible, since certain criteria for malignancy also apply to benign lesions. The authors analyzed samples of microangiographic specimens of kidneys with inflammation, tumor, and normal control organs to define mathematically the frequency of such angiographic parameters as caliber fluctuation, vascular avulsion, change of direction and diameter, and change in predominant vascular structure. The described method is transferred to clinical angiograms, and results of both groups are compared. In this preliminary analysis, caliber fluctuation appears to be the single most important criterion for differentiation of malignant and benign angiographic alterations.

Pathophysiology of chronic communicating hydrocephalus in dogs (Canis familiaris). Experimental studies.

A model designed to produce chronic communicating hydrocephalus in dogs has been developed in our laboratory. The animals tolerate the procedure well and the yield of animals with communicating hydrocephalus is high. Serial cisternograms show ventricular entry first with "clearing" and later with "stasis". CSF pressures are initially increased, but when the ventricles become enlarged the pressure falls into the normal range. Grossly there is generalized ventricular enlargement and, on histological studies, the ependyma is flattened and denuded. Periventricular edema occurs in the white matter. Autoradiographs show transependymal movement of protein. CSF production appears to be normal despite obstruction to flow of CSF to areas where resorption is greatest. Diversionary shunting probably produces relief of many of the neurological symptoms by providing an efficient pathway for the removal of CSF and thus by lessening edema and ventricular enlargement. A more appropriate treatment would appear to be a noninvasive method of decreasing CSF production. Only when the basic pathophysiological alterations of CSF production and absorption are understood will this be possible. We believe that this animal model affords us the opportunity of studying these mechanisms.

Evaluation of the central canal of the spinal cord in experimentally induced hydrocephalus.

The central canal of the spinal cord has been proposed as a significant compensatory alternative pathway of cerebrospinal fluid (CSF) flow in hydrocephalus. Ten dogs were made hydrocephalic by a relatively atraumatic experimental model that simulates the human circumstance of chronic communicating hydrocephalus. The central canal was studied by histopathology and compared with 10 normal control dogs. In both groups the central canal of the spinal cord was normal in size, configuration, and histological appearance. In this experimental model dilatation of the canal and increased movement of CSF does not appear to be a compensatory alternative pathway.

Current status of the Strecker stent.

Knitted flexible tantalum stents proved to be a valuable adjunct to percutaneous transluminal angiplasty (PTA) in the case of insufficient PTA results, and their use was established in the distal aorta, the iliac, the femoro-popliteal, the renal, and the coronary arteries. Recently, long arterial occlusions were defined as new indications for primary stenting; stent indications were further extended to the subclavian, the carotid, and the splanchnic arteries. Due to higher incidence of acute and late complications after stent treatment of small diameter arteries, patients have to be selected thoroughly. Newly designed drug-releasing stents tested in animal experiments promised to be suitable to diminish the incidence of late restenosis due to intinal hyperplasia, thus providing better long-term patency.

NMR tomography for the visualization of the diffusion of Gd-DTPA in agar-gel and in brain tissue--in vitro studies.

Serial magnetic resonance images of a diffusion model and of brain specimens have been performed to study the diffusion behavior of a paramagnetic complex (Gd-DTPA). The model consisted of solidified agar gel with layered Gd-DTPA solution on top of the gel. Corresponding studies have been performed with the brain specimen to visualize the penetration of the marker through the extracellular space into the brain tissue. Diffusion coefficients for the agar gel and the brain tissue model have been calculated. Magnetic resonance tomography proves to be a promising method for the study of complicated diffusion processes of paramagnetic complexes in biological tissue.

Influence of NMR measuring sequences and gradient variation on signals from flowing systems. Magnetic resonance tomography on experimental models.

The influence of flow on MR tomography images and signal intensities has been studied using experimental model tubes and an aqueous NiCl2 solution having the same relaxation time as human blood. We applied the inversion recovery (IR) and the spin-echo (SE) sequence on a .15T MR tomography system. The influence of RF pulse distance (tau) in the IR and SE experiment as well as the influence of magnetic z-gradient strength on the flow images has been investigated. IR images revealed that signals from flowing systems recover more rapidly due to influx of non-inverted longitudinal magnetization into the scan slice. SE images in presence of flow are characterized by signal intensity loss with increasing time caused by the outflow and dephasing of transverse magnetization. With increasing strength of the z-gradient, the MR signals of flowing fluids decrease drastically. Thus for detection of flow, all the above mentioned parameters are of importance.

[The effect of selective autoperfusion through an extracorporeal circulation on the formation of arterial collaterals. Animal experimental results (author's transl)]. / Die Wirkung der selektiven Autoperfusion mittels eines extrakorporalen Kreislaufes auf die arterielle Kollateralenausbildung. Tierexperimentelle Untersuchungen.

In 11 mongrel dogs (10-15 kg) with ligated superficial femoral arteries the formation of collaterals induced by increased arterial pressure with an extracorporal circulation was studied. In general anesthesia a teflon tube was inserted into one deep femoral artery. The other end of this tube war introduced through the right carotid artery into the thoracic aorta and arterial blood was drawn by a peristaltic tube pump from the aorta to the femoral artery. Different arterial pressures created by the pump were used to perfuse this hind limb. After 40 minutes perfusion time with 200 mmHG pressure, there was marked increase of collateralization by the deep femoral artery. At the contralateral non treated side, only minimal development of collaterals was visualized. These angiograms demonstrate that collaterals are opened by increased pressure within a short time interval The experimental model might have clinical implisations and accelerate collateral formation in non-surgical treatment of arterial occlusive disease.