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Biomedical subjects

R J Yang

Publications and source records attributed to R J Yang.

13 recordsLinked to original sources
PubMed2002

Electrokinetic injection techniques in microfluidic chips.

The separation efficiency of a microfluidic chip is influenced to a significant degree by the flow field conditions within the injection microchannel. Therefore, an understanding of the physics of the flow within this channel is beneficial in the design and operation of such a system. The configuration of an injection system is determined by the volume of the sample plug that is to be delivered to the separation process. Accordingly, this paper addresses the design and testing of injection systems with a variety of configurations, including a simple cross, a double-T, and a triple-T configuration. This paper also presents the design of a unique multi-T injection configuration. Each injection system cycles through a predetermined series of steps, in which the electric field magnitude and distribution within the various channels is strictly manipulated, to effectuate a virtual valve. The uniquemulti-T configuration injection system presented within this paper has the ability to simulate the functions of the cross, double-T, and triple-T systems through appropriate manipulations of the electric field within its various channels. In other words, the proposed design successfully combines several conventional injection systems within a single microfluidic chip.

Journal Article↗
PubMed2001

Treatment of malignant digestive tract obstruction by combined intraluminal stent installation and intra-arterial drug infusion.

AIM: To study the palliative treatment of malignant obstruction of digestive tract with placement of intraluminal stent combined with intra-arterial infusion of chemotherapeutic drugs. METHODS: A total of 281 cases of digestive tract malignant obstruction were given per oral (esophagus, stomach, duodenum and jejunum), per anal (colon and rectum) and percutaneous transhepatic (biliary) installation of metallic stent. Among them, 203 cases received drug infusion by cannulation of tumor supplying artery with Seldinger's technique. RESULTS: Altogether 350 stents were installed in 281 cases, obstructive symptoms were relieved or ameliorated after installation. Occurrence of restenotic obstruction was 8-43 weeks among those with intra-arterial drug infusion, which was later than 4-26 weeks in the group with only stent installation. The average survival time of the former group was 43 (3-105) weeks, which was significantly longer than 13 (3-24) weeks of the latter group. CONCLUSION: Intraluminal placement of stent combined with intra-arterial infusion chemotherapy is one of the effective palliative therapies for malignant obstruction of the digestive tract with symptomatic as well as etiological treatment.

Adult↗
PubMed1993

Self-expandable metallic stent therapy for superior vena cava syndrome: clinical observations.

PURPOSE: To study clinical and physiologic aspects of Z-stent therapy for superior vena cava (SVC) syndrome secondary to malignant disease. MATERIALS AND METHODS: Signs and symptoms of SVC syndrome were classified, graded, and scored in 11 cases. Six patients with caval pressure higher than 22 mm Hg peripheral to the stenosis underwent stent therapy. RESULTS: Immediately after Z-stent implantation into the stenotic lesion, the diameter of the constriction increased from 3.3 mm +/- 2.0 (mean +/- standard deviation) to 14.0 mm +/- 3.2, the mean caval pressure peripheral to the stenosis decreased from 26.6 mm Hg +/- 2.5 to 8.9 mm Hg +/- 0.7, and the symptom score decreased from 6.7 +/- 1.8 to 1.3 +/- 1.4. The caval pressure, lesion diameter, and symptom score correlated highly with each other. One complication--transient pulmonary edema attributable to volume overload caused by reperfusion--was observed. Mean survival exceeded 7.1 months. CONCLUSION: Stent placement could be a useful treatment for refractory SVC syndrome.

Aged↗
PubMed1992

[Expandable metallic stent therapy for SVC syndrome--effects on local venous pressure, vascular diameter, symptoms, and these correlations].

To evaluate the efficacy of Z-stent therapy for SVC syndrome, we studied changes in the pressure, the diameter of stenotic lumen and the symptoms in the cases of SVC syndrome with higher pressure than 30 cmH2O at distal to the stenosis. The symptoms were classified and graded to be scored up. Immediately after the Z-stent placement into the stenotic lesions, the venous pressure distal to the stenosis decreased from 36.0 +/- 3.4 cmH2O to 12.0 +/- 12.0 cmH2O (p < 0.001), the diameter of stenotic lumen increased from 3.3 +/- 3.4 mm to 14.0 +/- 3.4 mm (p < 0.01). According to the remarkable symptomatic improvements the averaged score decreased from 6.7 to 1.3 (p < 0.01). The pressure, the diameter and the symptom scores were highly correlated each other (magnitude of gamma not equal to 0.9). Among two cases with the right atrial pressure increase by 2 cmH2O after the placement one suffered transient cardiac in compensation due to overload by reperfusion. Conclusively, the Z-stent therapy was very effective on the SVC syndrome in reducing abnormally elevated venous pressure due to the stenosis, and relieving the symptoms, while the pressure monitor was necessary.

Aged↗
PubMed1992

[A stent therapy for portal tumor thrombi. Use of Dacron sheet covered self expandable metallic stent].

We developed a method of intraportal placement of a covered stent against portal tumor thrombi. Half around a z-stent was covered with a Dacron mesh sheet. In one case with portal tumor thrombi protruding into the main portal branch, the stent was placed percutaneously-transhepatically, through a coaxial introducer. Immediately after the placement, portal vein was dilated and, which was still patent after six months. No complication has been observed.

Carcinoma, Hepatocellular↗
PubMed1992

[Direct injection chemotherapy combined with arterial embolization in the treatment of liver cancers].

Direct injection chemotherapy in combination with transcatheter arterial embolization (TAE) was carried out in primary and secondary liver cancers. In this treatment, the anticancer agents dissolved in contrast media were directly injected into the tumor tissue with the echo-guided puncture needle after TAE. The dynamics of the injected drugs marked with non-ionic and water-soluble contrast media was followed up by the sequential CT studies, on which the contrast media was observed only in the tumor area in 18 out of 30 nodules from 2 to 8 weeks after the injection. The procedure is considered an effective drug delivery system to achieve a targeting chemotherapy in the liver cancers.

Antineoplastic Agents↗
PubMed1991

[A study of new retrievable expandable metallic stent].

The authors improved retrievable expandable metallic stent (REMS), instead of the nylon suture, the REMS was connected with the stainless steel thread. Under fluoroscopy the stainless steel thread of the shrinking body could be observed and was strong enough to retract the placed stent, then the stent could be removed by the stainless steel hook. We placed the REMS in the I.V.C. of canine, and removed them after one week placement, we could not remove them after two weeks placement. This study suggested that the REMS was considered to be useful and safe for clinical application.

Animals↗
PubMed1984

Design sensitivity analysis: a new method for implant design and a comparison with parametric finite element analysis.

A unified theory of structural design sensitivity is proposed to be used in conjunction with the parametric design variation method traditionally used in finite element analyses applied to biomechanics problems. Bone cement strain energy density dependence on cement and stem modulii of elasticity as analyzed with the theory of structural design sensitivity analysis is compared parametrically varied finite element results. Two-dimensional, eight-noded isoparametric and interface finite elements with optimal stresses at Gauss points are employed. Design sensitivity for strain energy density compares well with perturbation of design and reanalysis by finite element techniques.

Hip Prosthesis↗
PubMedDate not supplied

Dependency of tissue necrosis on gelatin sponge particle size after canine hepatic artery embolization.

PURPOSE: To determine the optimal size of gelatin sponge particles (GSPs) to produce maximum tumor necrosis with minimum side effects after canine hepatic artery embolization (HAE). METHODS: GSPs were separated into four size ranges: A, up to 200 microns (mean 152) as Gelfoam powder; B, 200-500 microns (mean 336) as Gelfoam powder; C, 500-1000 microns (mean 649) as Spongel; and D, 1000-2000 microns (mean 1382) as Spongel. Three mongrel dogs were assigned randomly to HAE with each particle size. On day 7 after HAE, the livers were removed and subjected to pathological examination. RESULTS: The mean volume of liver necrosis was 11% after embolization, with particle size A, 36.3% with B, 0% with C, and 1% with D. Coagulation necrosis was found in all livers with particles of sizes A and B, and in 1 of 6 with sizes C and D. Bile duct injury was found in five of six dogs with sizes A and B and in none with sizes C and D. Gallbladder necrosis was found in one dog with size B and pancreas necrosis in one with size A. CONCLUSION: GSPs of 500 microns are considered optimally effective for tissue necrosis according to this model.

Animals↗