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Biomedical subjects

K H Barth

Publications and source records attributed to K H Barth.

At least 19 recordsLinked to original sources
PubMed1995

Radiological intervention in upper and lower gastrointestinal bleeding.

The role of angiography in acute upper GI tract bleeding is less a diagnostic than a therapeutic one because it provides a guide to selective embolization of either the left gastric artery, or the gastroduodenal artery and its two principal branches, the pancreaticoduodenal and the right gastroepiploic artery. Angiographic catheter techniques may also provide substantial diagnostic and therapeutic support for the management of acute lower GI bleeding from a variety of bleeding sources. The advantages are minimal invasion and relatively low risk. The intermittent nature of GI bleeding often interferes with the ability of angiography to demonstrate the source of bleeding. However, at times angiographic techniques provide the only reasonable means of localizing and controlling bleeding.

Adult↗
PubMed1992

Injection characteristics and downstream contrast material distribution of flush aortography catheters: in vitro study.

Performance of 11 commercially available 4- and 5-F aortic flush catheters was evaluated with respect to the extent of upstream injection, catheter motion, and downstream homogeneity of a 10-, 15-, and 20-mL/sec bolus of 76% meglumine sodium diatrizoate at room temperature. Tests were made in a pulsatile aortic flow model containing circulating fluid isoviscous to blood. The injection process was recorded on videotape. Homogeneity of the contrast material bolus was determined spectrophotometrically from samples collected from the center and each of the four quadrants of the vessel lumen. Upstream contrast material injection between 1.5 and 7 cm in length emerged from all catheters; it was lowest with one of the "tennis racket" designs from one and a new spiral end-loop design (Halo) from another manufacturer. All catheters, except the most rigid and largest-caliber catheter (5.8 F) showed considerable shaft motion at the higher injection rates. Downstream contrast material mixing homogeneity was always best at the highest injection rate but altogether was better for the Halo catheter than for any other catheter tested. It is concluded that all tested 4- and 5-F aortic flush catheters show some undesirable features, but certain design modifications improve performance and comparative testing is helpful to distinguish such features.

Aortography↗
PubMed1992

Gadolinium-enhanced magnitude contrast MR angiography of popliteal and tibial arteries.

To evaluate the efficacy of gadopentetate dimeglumine in MR angiography of the lower extremities, a flow phantom, seven healthy volunteers, and seven patients with peripheral vascular disease were studied with a magnitude contrast (MC) technique. The combination of an MC rephase-dephase gradient-refocused-echo pulse sequence, a 40-cm-long transmit-receive coil, and intravenous administration of a bolus of gadopentetate dimeglumine improved MR angiographic quality in the phantom, volunteers, and patients. Gadolinium enhancement decreased deleterious saturation effects and improved images of the popliteal and tibioperoneal arteries in the volunteers and patients. However, in some cases, venous overlap, imaging artifacts, and suboptimal visualization of subtle lesions limited interpretation. The authors conclude that gadolinium enhancement combined with an MC subtraction pulse sequence appreciably improves MR angiography of lower extremity arteries.

Arterial Occlusive Diseases↗
PubMed1990

Autoantigens in human neuroblastoma cells.

Neuroblastoma cells are frequently used as targets in studies of autoimmune diseases of the nervous system. We examined the human neuroblastoma cell line, LAN-5, for the presence of autoantigens that react with naturally occurring autoantibodies in human sera. Antibodies to the HNK-1 and Gal(beta 1-3)GalNAc epitopes, which have been implicated in human autoimmune neuropathy and motor neuron disease, respectively, immunostained the surface of the neuroblastoma cells, and antibodies to the 200 kDa high molecular weight neurofilament protein (NFH) immunostained the cytoplasm and cell processes. The NHK-1 and Gal(beta 1-3)GalNAc epitopes were associated with several glycoprotein bands in Western blots of the neuroblastoma cells, and the HNK-1 epitope was also shared by a glycolipid which co-migrated with 3-sulfoglucuronyl paragloboside (SGPG) from peripheral nerve, indicating that SGPG is synthesized in neuronal cells. Northern blot analysis revealed a single RNA band of 4800 bp for NFH in normal brain but two RNA species of 4800 and 3800 bp in both neuroblastoma and adrenal cells, confirming their common origin. The neuroblastoma cells appear to contain antigens that bind to naturally occurring autoantibodies in human serum and might therefore be useful for detecting and investigating the effects of anti-neuronal antibodies. The antibody populations being investigated, however, should be distinguished from other autoantibodies which might be present in the patients' serum.

Antibodies, Monoclonal↗
PubMed1990

Optimization of gradient-echo imaging parameters for intracaval filters and trapped thromboemboli.

Flow-phantom magnetic resonance (MR) gradient-echo (GRE) imaging at 1.5 T was performed on a titanium Greenfield filter containing trapped blood clots with a high concentration of either deoxyhemoglobin (DHb) or methemoglobin (MHb), simulating acute and older thromboemboli, respectively. Flip angle, repetition time (TR), and echo time (TE) were varied, and a contrast-to-noise ratio between trapped clots and flowing fluid (clot-flow contrast) was determined for each set of imaging parameters. Use of very low flip angles (less than or equal to 10 degrees) rendered MHb clots indistinguishable from flowing fluid. In general, DHb clots displayed greater clot-flow contrast than MHb clots regardless of flip angle. With increasing TE values, T2* effect was observed with MHb clots, and magnetic susceptibility artifacts increased. Overall, optimum clot-flow contrast for imaging of both DHb and MHb clots was achieved with a flip angle of 45 degrees-60 degrees, a TR of 50 msec, and the shortest TE possible. Using GRE parameters similar to the optimum parameters determined in vitro, the authors imaged four patients with nickel-titanium Simon filters and one dog with a titanium Greenfield filter. MR imaging was successful in demonstrating filter location, caval patency, and the presence and extent of intraluminal thrombus.

Adult↗
PubMed1990

Self-contained, coaxial delivery system for intraarterial infusion of thrombolytic agents.

To facilitate continued direct intrathrombus infusion of a thrombolytic agent and yet minimize catheter exchanges and manipulations, the authors developed a simple, self-contained delivery system. It involves the use of supplies available in most angiographic suites. The system has been used in 44 patients; there have been no infectious complications, and it has been well tolerated by the patients.

Fibrinolytic Agents↗
PubMed1990

Flexible tantalum stents implanted in aortas and iliac arteries: effects in normal canines.

Vascular endoprostheses made of knitted tantalum wire and expanded over angioplasty balloons were placed into aortas or iliac arteries of 14 normal dogs. Twelve stents were placed into the infrarenal abdominal aorta and two stents in the left common iliac arteries by the left carotid artery approach. To firmly expand the stent against the vascular wall, nominal stent sizes 0.5-1.0 mm larger than the measured arterial diameter were required. Arteriography performed at specified follow-up intervals showed no evidence of thrombi or emboli; all side branches (lumbar arteries) covered by the stents remained patent. Vascular diameter decreased minimally at 8 and 26 weeks, associated with histopathologic evidence of neointimal buildup. This buildup was highest at 8 weeks (mean, 313 microns) and was slightly less at 26 weeks (mean, 223 microns). Almost complete coverage by endothelium was seen as early as 3 weeks. It is concluded that the flexible tantalum wire stents are well tolerated by the arterial wall and become quickly endothelialized. No excessive neointimal buildup was observed during the 6-month study.

Animals↗
PubMed1990

Expandable tubular stents for treatment of arterial occlusive diseases: experimental and clinical results. Work in progress.

The balloon-expandable vascular prosthesis consists of a flexible, knitted tantalum wire mesh tube. To demonstrate its pliability, this prosthesis was tested experimentally in 10 mongrel dogs by implanting it into the proximal femoral arteries. The maximum follow-up time was 1 year. On the basis of the experimental results, in which there was no relevant stenosis, occlusion, or migration of the vascular prosthesis, nine patients were treated: one with iliac artery occlusive disease and eight with superficial femoral artery (SFA) occlusive disease (four reocclusions after angioplasty and four unsatisfactory primary angioplasty results). One SFA lesion was treated with the crossover method from the contralateral side. All implants remained patent without hemodynamically significant stenoses, with the longest observation time being 6 months. Flexible, expandable vascular prostheses are promising adjuncts to angioplasty.

Aged↗
PubMed1990

Percutaneous biliary drainage for high obstruction.

PBD is the preferred route of palliative drainage for patients with high biliary obstruction. The frequency of bifurcational obstruction in this setting requires familiarity with drainages from both the right and the left transhepatic approach. The preferred right transhepatic approach is fluoroscopically guided; on the left, ultrasonography is the guidance of choice. Large caliber drainage catheters are required, and dilatation of the necessary transhepatic tracts is extremely painful unless adequate inhalation anesthesia or, preferably, epidural anesthesia, is provided. Long-term biliary drainage requires a choice between internal-external external drainage catheters and endoprostheses that is made by considering the patient's life expectancy and his or her adjustment to a stent extending to the outside. The feasibility of corrective procedures if an internal-external drainage catheter or an endoprosthesis becomes blocked needs to be considered before definitive placement. The interventional radiologist becomes intimately involved in the follow-up care of patients and frequently has to direct appropriate patient evaluation. Familiarity with antibiotic regimens is important.

Cholangiography↗
PubMed1989

Tantalum vascular stents: in vivo evaluation with MR imaging.

Magnetic resonance (MR) imaging at 1.5 T was performed on tantalum vascular stents placed in the aortas of six dogs. The stents produced no significant artifact and allowed for clear depiction of the aortic lumina as flow-void zones with spin-echo imaging and as high-signal areas with gradient-echo imaging. The MR findings correlated with the angiographic studies of the stented vessels. These results demonstrate the feasibility of MR imaging as a noninvasive means of evaluating vessel patency in the presence of tantalum vascular stents.

Animals↗
PubMed1989

Hepatic artery model for evaluating the distribution of intraarterial chemotherapy infusion: nonpulsed versus pulsed infusions.

The effect of a commercially available pulsatile slow-infusion system on the degree of infusate mixing and distribution was assessed in a life-size glass model of the hepatic arterial system. The authors determined, both visually and quantitatively, the mixing homogeneity of a low-flow infusion (1.4 mL/min) of red dye through a side-hole catheter (2.5 F outer diameter) into pulsatile flow (300 mL/min) of a fluid with the same viscosity as blood. When comparing nonpulsed versus pulsed infusion techniques, the authors found that the pulsatile infusion system did not significantly improve the inhomogeneity of dye distribution in the 16 hepatic arterial branches. The results of this in vitro study suggest that a pulsatile infusion system that uses low pulse velocities without regard for cardiac cycle is less than optimal and does not significantly improve drug mixing at the standard slow infusion rates. Moreover, as potential new intraarterial delivery systems are developed to improve drug mixing, in vitro models may be the most useful means of initially evaluating their efficacy.

Hepatic Artery↗