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Biomedical subjects

K C Wright

Publications and source records attributed to K C Wright.

87 records · Page 5Linked to original sources
PubMedDate not supplied

New retrievable coil anchors: preliminary in vivo experiences in swine.

PURPOSE: To design and test retrievable coil anchors to improve the safety and efficacy of coil embolization. METHODS: Fifty-two 0.038-inch homemade retrievable stainless steel coils were equipped with one of four different pre-shaped nitinol anchors and tested in 38 pigs. All coils with the anchor were completely retrieved and redeployed 3-18 times (median 7 times) prior to release. Types 1 and 2 anchored coils were acutely deployed in the external iliac arteries (n = 10 each), and chronically tested (1 week) in the common carotid arteries (n = 6 each). Larger type 1 (n = 4), type 3 (n = 6), and type 4 (n = 4) anchored coils were acutely deployed in the abdominal aorta. The largest type 1 anchors (n = 6) were acutely tested in the inferior vena cava. RESULTS: All anchored coils were successfully retrieved and repositioned several times. All but two coils formed a compact plug and there was no coil migration except with two mechanically defective type 3 anchors. CONCLUSION: The use of retrievable anchors allowed the coils to be retrieved and repositioned, prevented coil migration, and enabled compact coil configuration.

Alloys↗
PubMedDate not supplied

Preliminary experimental evaluation of temporary segmental hepatic venous occlusion: angiographic, pathologic, and scintigraphic findings.

PURPOSE: Pigs were used to evaluate temporary segmental hepatic venous occlusion as a means of improving the selective delivery of therapeutic agents within the liver. MATERIALS AND METHODS: Hepatic angiography and scintigraphy were performed alone and in combination with hepatic venous occlusion. RESULTS: Arteriograms obtained during venous obstruction demonstrated a greater number of peripheral arterial branches in the occluded area compared with the nonoccluded areas. A prolonged hepatogram showing hepatofugal opacification of the portal branches was observed in the occluded area. Microscopically, mild congestion of the sinusoids and central veins was seen immediately after 60-minute occlusion, but these changes were not evident 2 hours after balloon deflation. Severe congestion and focal hemorrhage were found in the occluded segment of the liver 2 hours after 90-minute venous occlusion. When the right or left hepatic vein was occluded during hepatic arterial infusion of technetium-99m macroaggregated albumin, there was a significant (P < or = .05) increase in the amount of radioactivity measured in the obstructed segment and a significant (P < or = .05) decrease in that found in the nonoccluded regions. CONCLUSION: These results indicate that temporary segmental hepatic vein occlusion is safe for up to 60 minutes and may be clinically applicable as a means of improving the therapeutic index of agents within the liver when they are administered via concomitant hepatic arterial infusion.

Angiography↗
PubMedDate not supplied

Placement of covered self-expanding metallic stents in the common bile duct: a feasibility study.

PURPOSE: Gianturco self-expanding metallic stents have been useful in cases of benign biliary stenoses; however, the stents have not worked well in the presence of intraluminal tumor because of tumor growth between the wire struts. Stents were covered with polymeric membranes, which may prevent tumor ingrowth, and the feasibility of using these covered stents in the common bile duct was studied in healthy adult dogs. MATERIALS AND METHODS: Initially, stents (10 x 6 mm) covered with polycaprolactone (PCL), segmented polyether polyurethane (SPP), and silicone were placed in the common bile duct of dogs and were followed up for 3-12 months. Subsequently, four types of modified silicone-covered stents were evaluated. Rough-surface, small-diameter (3-mm), half-covered, and tapered stents were placed and followed up for 3 months. RESULTS: In the initial study, the SPP and silicone membranes remained intact, but the PCL covering broke in all dogs. In all but two dogs, luminal narrowing caused by varying degrees of papillary mucosal hyperplasia at both ends of the stent was observed. In the subsequent study, mucosal hyperplasia was considerably reduced by using half-covered stents and was virtually eliminated with tapered stents. All small-diameter stents migrated into the bowel. CONCLUSION: These studies suggest that tapered Gianturco self-expanding stents covered with silicone may be useful in the biliary tract in cases of intraluminal tumor.

Animals↗
PubMedDate not supplied

Working with laboratory animals: general principles and practical considerations.

Laboratory animals play an indispensable role in research discovery and technological advances, and they will continue to yield basic, exciting, and prodigious information that can enrich the future of people and other animals. For both ethical and scientific reasons, all-individuals whose work requires the use of laboratory animals must take the time to conduct a thorough review of the literature to determine what animal models are available and which are the most relevant, and they must learn and understand the uniqueness of the selected species, breed, and strain. Scientists have the privilege, but not the right, to use animals as experimental subjects. This privilege must not be abused. Therefore, it is imperative that before working with any laboratory animal, you know your "subject."

Analgesia↗
PubMedDate not supplied

Experimental evaluation of a new device for percutaneous transrenal ureteral occlusion.

PURPOSE: To develop a device for percutaneous transrenal ureteral occlusion. MATERIALS AND METHODS: The device was a double-body Gianturco-Rösch biliary stent constrained at the junction of the two stents to create an hourglass shape. One stent was coated with silicone. One device was percutaneously placed in each of nine pigs through a 9-F Teflon sheath. Urographic and hematologic follow-up was performed for up to 12 weeks. RESULTS: Seven pigs showed immediate, complete ureteral occlusion, and two pigs exhibited persistent incomplete high-grade obstruction. All animals exhibited varying degrees of hydronephrosis and hydroureter. No device migration was noted. Minor complications were encountered during device placement in three pigs. Mucosal folds and villus-like projections that arose from the lamina propria protruded into the lumen of the ureter at the cranial end of the covered stent and around the wire of the caudal stent. Varying degrees of mural inflammation and edema were noted. CONCLUSION: Transrenal ureteral occlusion with the described device appears to be a viable method for treating urinary fistulas.

Animals↗
PubMedDate not supplied

Anchoring coil embolization in a high-flow arterial model: a pilot study.

PURPOSE: To devise and test an occluding coil anchoring system to improve the safety of coil embolization. MATERIALS AND METHODS: The anchoring system was attached to Gianturco embolization coils and investigated in 15 pigs. In the short-term studies, one 0.035-inch anchored coil (15-18 cm in length and 7-10 mm in diameter) was placed in the infrarenal portion of the abdominal aorta in each of 12 pigs with use of an 8-F catheter from the carotid approach. Aortography was performed before and up to 4 hours after coil placement. In the long-term studies, 0.028-inch anchored coils (8 cm in length and 5 mm in diameter) were placed in the left femoral and the right carotid arteries in each of three pigs with use of a 6-F catheter positioned from the right femoral approach. One week later, the animals were evaluated angiographically for coil migration and vascular occlusion. RESULTS: Radiographically, the coils created a compact conglomerate on placement in all but one of the animals. No coil migration was noted during follow-up. Necropsy confirmed compact arrangement of the coils within the vessels and revealed effective anchoring of the device in all cases. CONCLUSIONS: The anchoring coil has proved effective in making coil embolization safer, especially in a high-flow arterial model.

Animals↗
PubMedDate not supplied

Alteration in starch microsphere degradation following contrast angiography in the dog kidney.

Six adult mongrel dogs received bilateral sequential renal arterial injections of degradable starch microspheres following preadministration arteriograms. Renal arterial flow was measured using electromagnetic flow probes, and microspheres were administered until flow was blocked completely. One kidney in each dog was subjected to immediate postembolization arteriography, while the contralateral kidney served as a control. In the control kidneys, arterial flow returned to 90-95% of baseline within 30 minutes of embolization, and angiography at this time revealed a normal nephrogram. Blood flow in the kidneys that received postembolization arteriography returned to only 60-65% of baseline, even when followed up to 1 hour. Angiography at this time revealed persistent defects in the nephrogram. The effect of heparin, Renografin-60, and distilled deionized water on amylase activity was evaluated in vitro. No change in enzyme activity was noted.

Angiography↗
PubMedDate not supplied

Vascular gene therapy.

Gene therapy is an exciting frontier in medicine today. Radiologists will be involved in tracking the effects of these new therapies through imaging. Vascular and interventional radiology techniques also are ideally suited for minimally invasive, readily monitored gene delivery. Gene therapy is accomplished through gene augmentation or gene blocking. The latter is accomplished through antisense oligonucleotides or transcription factor decoys. Vectors are agents that facilitate gene delivery and expression and can be viral or nonviral. The vascular wall is an ideal target for gene therapy because of its central role in many biologic processes and its ready accessibility. Recombinant genes can be delivered ex vivo and in vivo, with the latter approaches involving open surgical, percutaneous injection, and endovascular catheter-based methods. Perforated, hydrogel-coated, and double balloon catheters have been used with varying success. Optimal catheter systems for gene transfer will enable delivery of the vector to the precise anatomic location with transfection limited to the cells of interest and will minimize shedding of the vector to distal sites, systemic effects of the therapeutic agent, and morbidity from the delivery method. Radiologists must become familiar with the basic rationale, strategies, and mechanisms of gene therapy and involved in its clinical trials to ensure an active role in this field.

Coronary Disease↗
PubMedDate not supplied

Microcapsules for arterial chemoembolization: appearance and in vitro drug release characteristics.

Microcapsules made of eight different capsular materials and containing floxuridine (FUDR) were formulated and evaluated with regard to physical properties (size and structure) and in vitro drug release characteristics. Capsules averaged 100, 150 and 200 micron in diameter and appeared as either round or 'crystalline' particles. The degree and pattern of drug release was dependent on the capsular material used. Alteration in the molecular architecture of a specific material produced changes in the percentage of total encapsulated drug released per unit of time, but not in the pattern of release. Changing capsular size or amount of drug contained within the capsules failed to alter either the pattern of drug release or the percentage of encapsulated drug released per unit of time. However, changes in either parameter did affect the total amount of drug released per unit of time.

Capsules↗
PubMedDate not supplied

Afterloading intracavitary irradiation and expanding stent for malignant biliary obstruction.

A double lumen catheter was developed as an applicator for the remote afterloading (RALS) of 60Co source for the intracavitary irradiation of an obstructed common bile duct caused by carcinoma of the gallbladder. This was followed by the placement of nylon-covered expandable metallic stents to maintain patency. This combination effectively provided palliation.

Brachytherapy↗