Biomedical subjects

Bensheng Qiu

Publications and source records attributed to Bensheng Qiu.

8 recordsLinked to original sources

PubMed2006

Intravascular magnetic resonance/radiofrequency may enhance gene therapy for prevention of in-stent neointimal hyperplasia.

RATIONALE AND OBJECTIVES: We evaluated the potential of using intravascular magnetic resonance (MR)/radiofrequency (RF) to enhance vascular endothelial growth factor (VEGF) gene therapy of in-stent neointimal hyperplasia. MATERIALS AND METHODS: By using a catheter-based approach, VEGF/lentivirus was locally transferred into 10 (five paired) bilateral femoral-iliac arteries of five hypercholesterolemic pigs, whereas the right arteries were heated up to approximately 41 degrees C by using an intravascular MR/RF system. Then, identical stents were placed immediately into the bilateral VEGF-targeted arteries to create in-stent neointimal hyperplasia. At day 60 after gene/stent interventions, the targeted arteries were harvested for histological correlation. RESULTS: X-Ray angiography-detectable in-stent stenoses were found in three of the arteries treated with VEGF genes only, whereas there were no in-stent stenoses in arteries treated by using MR/RF-heated VEGF genes. Correlative histological examination confirmed a 138% reduction in average thickness of neointimal hyperplasia in VEGF/RF-treated arteries compared with VEGF-only-treated arteries (P < .01). CONCLUSION: We report a potential method of using an intravascular MR/RF heating technique to enhance gene therapy of in-stent restenosis.

Animals↗

PubMed2005

Radiofrequency-enhanced vascular gene transduction and expression for intravascular MR imaging-guided therapy: feasibility study in pigs.

PURPOSE: To evaluate the feasibility of radiofrequency (RF)-enhanced vascular gene transduction and expression by using a magnetic resonance (MR) imaging-heating guidewire as an intravascular heating vehicle during MR imaging-guided therapy. MATERIALS AND METHODS: The institutional committee for animal care and use approved the experimental protocol. The study included in vitro evaluation of the use of RF energy to enhance gene transduction and expression in vascular cells, as well as in vivo validation of the feasibility of intravascular MR imaging-guided RF-enhanced vascular gene transduction and expression in pig arteries. For in vitro experiments, approximately 10(4) vascular smooth muscle cells were seeded in each of four chambers of a cell culture plate. Next, 1 mL of a green fluorescent protein gene (gfp)-bearing lentivirus was added to each chamber. Chamber 4 was heated at approximately 41 degrees C for 15 minutes by using an MR imaging-heating guidewire connected to a custom RF generator. At day 6 after transduction, the four chambers were examined and compared at confocal microscopy to determine the efficiency of gfp transduction and expression. For the in vivo experiments, a lentivirus vector bearing a therapeutic gene, vascular endothelial growth factor 165 (VEGF-165), was transferred by using a gene delivery balloon catheter in 18 femoral-iliac arteries (nine artery pairs) in domestic pigs and Yucatan pigs with atherosclerosis. During gene infusion, one femoral-iliac artery in each pig was heated to approximately 41 degrees C with RF energy transferred via the intravascular MR imaging-heating guidewire, while the contralateral artery was not heated (control condition). At day 6, the 18 arteries were harvested for quantitative Western blot analysis to compare VEGF-165 transduction and expression efficiency between RF-heated and nonheated arterial groups. RESULTS: Confocal microscopy showed gfp expression in chamber 4 that was 293% the level of expression in chamber 1 (49.6% +/- 25.8 vs 16.8% +/- 8.0). Results of Western blot analysis showed VEGF-165 expression for normal arteries in the RF-heated group that was 300% the level of expression in the nonheated group (70.4 arbitrary units [au] +/- 107.1 vs 23.5 au +/- 29.8), and, for atherosclerotic arteries in the RF-heated group, 986% the level in the nonheated group (129.2 au +/- 100.3 vs 13.1 au +/- 4.9). CONCLUSION: Simultaneous monitoring and enhancement of vascular gene delivery and expression is feasible with the MR imaging-heating guidewire.

Animals↗

PubMed2005

Development of a 0.014-inch magnetic resonance imaging guidewire.

The purpose of this study was to develop a standard 0.014-inch intravascular magnetic resonance imaging guidewire (MRIG), a coaxial cable with an extension of the inner conductor, specifically designed for use in the small vessels. After a theoretical analysis, the 0.014-inch MRIG was built by plating/cladding highly electrically conductive materials, silver or gold, over the inside and outside of the coaxial conductors. The conductors were made of superelastic, nonmagnetic, biocompatible materials, Nitinol or MP35N. Then, in comparison with a previously designed 0.032-inch MRIG, the performance of the new 0.014-inch MRIG in vitro and in vivo was successfully evaluated. This study represents the initial work to confirm the critical role of highly conductive and superelastic materials in building such small-size MRIGs, which are expected to generate high-resolution MR imaging of vessel walls/plaques and guide endovascular interventional procedures in the small vessels, such as the coronary arteries.

Alloys↗

PubMed2005

MR imaging of biodegradable polymeric microparticles: a potential method of monitoring local drug delivery.

Gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA) was encapsulated into biodegradable, bioadhesive polymeric microparticles to enable noninvasive monitoring of their local intravesical delivery with MRI. The microparticles were characterized by contrast agent encapsulation and release kinetics, T(1) relaxation rates, and contrast enhancement in vivo. The level of Gd-DTPA loading into microparticles was 14.3 +/- 0.6 mug/mg polymer. The measured T(1) relaxation rates of the microparticles showed a direct dependence on Gd-DPTA content. Both 1.5T and 4.7T MR scanners were used to image murine bladders instilled intravesically with Gd-DTPA-loaded particles in vivo. MR images showed ring-shaped regions of enhancement inscribing the bladder wall, which were attributed to the microparticles that were preferentially adherent to the mucosa lining the urothelium. The images of controls exhibited no such enhancement. The normalized signal intensities measured from post-instillation images were significantly greater (P < 0.05) than those in the pre-instillation images. Contrast enhancement was observed for at least 5 days after the initial instillation, although the enhancement decreased due to microparticle degradation or mucosa renewal. The localized distribution of biodegradable, bioadhesive microparticles encapsulating Gd-DTPA was successfully visualized with MRI in vivo, allowing particle-mediated delivery to be temporally and spatially monitored noninvasively.

Animals↗

PubMed2005

Simultaneous radiofrequency (RF) heating and magnetic resonance (MR) thermal mapping using an intravascular MR imaging/RF heating system.

Previous studies have confirmed the possibility of using an intravascular MR imaging guidewire (MRIG) as a heating source to enhance vascular gene transfection/expression. This motivated us to develop a new intravascular system that can perform MR imaging, radiofrequncy (RF) heating, and MR temperature monitoring simultaneously in an MR scanner. To validate this concept, a series of mathematical simulations of RF power loss along a 0.032-inch MRIG and RF energy spatial distribution were performed to determine the optimum RF heating frequency. Then, an RF generator/amplifier and a filter box were built. The possibility for simultaneous RF heating and MR thermal mapping of the system was confirmed in vitro using a phantom, and the obtained thermal mapping profile was compared with the simulated RF power distribution. Subsequently, the feasibility of simultaneous RF heating and temperature monitoring was successfully validated in vivo in the aorta of living rabbits. This MR imaging/RF heating system offers a potential tool for intravascular MR-mediated, RF-enhanced vascular gene therapy.

Animals↗

PubMed2003

In vivo US monitoring of catheter-based vascular delivery of gene microspheres in pigs: feasibility.

In this study, the authors tested the feasibility of using ultrasonography (US) to monitor catheter-based vascular gene microsphere delivery. Polymeric biodegradable microspheres (mean diameter, 5 microm) were prepared by using a double-emulsion technique to encapsulate DNA-plasmid-encoding green fluorescent protein (GFP) genes. With use of gene-delivery catheters, GFP microspheres were locally delivered into the left femoral arterial walls of six pigs; the contralateral arteries were not infused with microspheres and thus served as negative control vessels. The delivery procedures were monitored with high-frequency (8-15-MHz) transducer US. The effectiveness of monitoring with US was compared with the effectiveness of monitoring with immunohistochemical anti-GFP staining. A highly echogenic "star burst" sign around the entire vessel wall was seen at US and correlated with immunohistochemical findings that showed the destination of the gene microspheres. Study results demonstrate the potential of US for monitoring catheter-based vascular gene microsphere delivery in vivo.

Animals↗

PubMed2002

Development of an intravascular heating source using an MR imaging guidewire.

PURPOSE: To develop a novel endovascular heating source using a magnetic resonance (MR) imaging guidewire (MRIG) to deliver controlled microwave energy into the target vessel for thermal enhancement of vascular gene transfection. MATERIALS AND METHODS: A 0.032-inch MRIG was connected to a 2.45-GHz microwave generator. We 1) calculated the microwave power loss along the MRIG, 2) simulated the power distribution around the MRIG, 3) measured the temperature increase vs. input power with the MRIG, and 4) evaluated the thermal effect on the balloon-compressed/microwave-heated aorta of six living rabbits. In addition, during balloon inflation, we also simultaneously generated high-resolution MR images of the aortic wall. RESULTS: The power loss was calculated to be 3.9 dB along the MRIG. The simulation-predicted power distribution pattern was cylindrically symmetric, analogous to the geometry of vessels. Under balloon compression, the vessel wall could be locally heated at 41 degrees C with no thermal damage apparent on histology. CONCLUSION: This study demonstrates the possibility of using the MRIG as a multifunctional device, not only as a receiver antenna to generate intravascular high-resolution MR images of atherosclerotic plaques and as a conventional guidewire to guide endovascular interventions during MR imaging, but also as a potential intravascular heating source to produce local heat for thermal enhancement of vascular gene transfection.

Animals↗

PubMed2002

Fast maximum intensity projection algorithm using shear warp factorization and reduced resampling.

Maximal intensity projection (MIP) is routinely used to view MRA and other volumetric angiographic data. The straightforward implementation of MIP is ray casting that traces a volumetric data set in a computationally expensive manner. This article reports a fast MIP algorithm using shear warp factorization and reduced resampling that drastically reduced the redundancy in the computations for projection, thereby speeding up MIP by more than 10 times.

Algorithms↗