Diagnosis with spiral CT imaging before gastric carcinoma surgery.

This study was carried out to study multi-slice spiral CT imaging for patients with gastric carcinoma and explore the values of multi-slice spiral CT imaging in staging prior to gastric carcinoma (GC) surgery. Forty-eight patients with GC underwent multi-slice spiral CT, and the scanning results were compared with the pathological results. The similarity of the results was observed, and the accuracy was calculated. Of 48 patients, 8 did not undergo surgery because of metastasis. In the diagnosis of the remaining 40 patients, the sensitivity of multi-slice spiral CT in the diagnosis of staging of invasive depth of GC was 77.5%; κ = 0.642 in the analysis of consistency; there was no significant difference with the pathological results (p >0.05). The overall accuracy of diagnosis for stage N was 80%. The accuracy of multi-slice CT in detecting distant metastasis of GC was 87.5%. Multi-slice spiral CT can determine and evaluate various metastases of GC. The diagnostic results obtained using multi-slice spiral CT was probably consistent with the pathological results.

Detection of c-reactive protein based on a magnetic immunoassay by using functional magnetic and fluorescent nanoparticles in microplates.

We report the preparation and application of biofunctional nanoparticles to detect C-reactive protein (CRP) in magnetic microplates. A CRP model biomarker was used to test the proposed detection method. Biofunctional magnetic nanoparticles, CRP, and biofunctional fluorescent nanoparticles were used in a sandwich nanoparticle immunoassay. The CRP concentrations in the samples were deduced from the reference plot, using the fluorescence intensity of the sandwich nanoparticle immunoassay. When biofunctional nanoparticles were used to detect CRP, the detection limit was 1.0 ng ml(-1) and the linear range was between 1.18 ng ml(-1) and 11.8 µg ml(-1). The results revealed that the method involving biofunctional nanoparticles exhibited a lower detection limit and a wider linear range than those of the enzyme-linked immunosorbent assay (ELISA) and most other methods. For CRP measurements of serum samples, the differences between this method and ELISA in CRP measurements of serum samples were less than 13%. The proposed method can reduce the analysis time to one-third that of ELISA. This method demonstrates the potential to replace ELISA for rapidly detecting biomarkers with a low detection limit and a wide dynamic range.

Multifocal multiphoton microscopy based on a spatial light modulator.

We present a new multifocal multiphoton microscope that employs a programmable spatial light modulator to generate dynamic multifocus arrays which can be rapidly scanned by changing the incident angle of the laser beam using a pair of galvo scanners. Using this microscope, we can rapidly select the number and the spatial density of focal points in a multifocus array, as well as the locations and shapes of arrays according to the features of the areas of interest in the field of view without any change to the hardware.

Biochip∕laser cell deposition system to assess polarized axonal growth from single neurons and neuron∕glia pairs in microchannels with novel asymmetrical geometries.

Axon path-finding plays an important role in normal and pathogenic brain development as well as in neurological regenerative medicine. In both scenarios, axonal growth is influenced by the microenvironment including the soluble molecules and contact-mediated signaling from guiding cells and cellular matrix. Microfluidic devices are a powerful tool for creating a microenvironment at the single cell level. In this paper, an asymmetrical-channel-based biochip, which can be later incorporated into microfluidic devices for neuronal network study, was developed to investigate geometric as well as supporting cell control of polarized axonal growth in forming a defined neuronal circuitry. A laser cell deposition system was used to place single cells, including neuron-glia pairs, into specific microwells of the device, enabling axonal growth without the influence of cytophilic∕phobic surface patterns. Phase microscopy showed that a novel "snag" channel structure influenced axonal growth in the intended direction 4:1 over the opposite direction. In heterotypic experiments, glial cell influence over the axonal growth path was observed with time-lapse microscopy. Thus, it is shown that single cell and heterotypic neuronal path-finding models can be developed in laser patterned biochips.

Hydrodynamics of a long-body bileaflet mechanical heart valve.

A new bileaflet substitute mechanical heart valve (MHV) that incorporates an optimal length-to-annulus ratio for improved hydrodynamic efficiency was recently introduced. Efforts have been made on this new prosthesis to use the current advances in carbon materials and design technology to achieve higher net forward flow with minimal energy loss for the smaller aortic valves, while reducing regurgitant closure volume for the larger size valves by an elongated orifice. Benchtop experiments performed in a pulsatile flow loop, under simulated physiologic conditions, substantiated these improvements as claimed.

Bileaflet mechanical heart valves at low cardiac output.

Several earlier studies have indicated that bileaflet mechanical heart valves behave irregularly at low cardiac output and low pulse rate conditions, and that their hydrodynamic performances are generally inadequate. The authors conducted in vitro experiments in a pulsatile mock circulatory loop to compare the performance of the St. Jude Medical (SJM) valve and a long body bileaflet prosthesis recently introduced by Medical Carbon Research Institute (MCRI) (Austin, TX). The new MCRI mechanical heart valve model was designed with emphasis on improved hydrodynamic efficacy by introducing a long body with parallel leaflets and by leaflets increasing the flow area. Experimental studies were conducted on five test valves (MCRI 19 mm, MCRI 25 mm, SJM 19 mm, SJM 23 mm, and SJM 29 mm) with cardiac outputs of 2.0, 2.5, 3.0, and 3.5 L/min at a pulse rate of 40 beats/min, and 3.5, 4.0, 4.5, and 5.0 L/min at a pulse rate of 70 beats/min. Transvalvular pressure drop and closure volume were assessed by measuring the instantaneous ventricular and aortic pressures and aortic flow. The leaflet motions of the tested valves were observed by direct video recording using a charge coupled device camera while the flow measurements were being conducted. Testing under simulated physiologic ventricular and aortic pressure waveforms, the results of this study show that the MCRI bileaflets remained fully open during the entire ejection phase, even at very low cardiac output conditions (2.0 L/min). The closure volume (defined as percentage of forward flow volume) increased with decreasing cardiac output, as reported earlier by others. Comparative results also indicate that the MCRI design has nearly a two size pressure drop advantage over the SJM, with significantly smaller closure volume.

Transient pressure at closing of a monoleaflet mechanical heart valve prosthesis: mounting compliance effect.

An in vitro experimental study was performed to investigate the mounting compliance effect on the occluder closing dynamics and the transient pressure at the closing of the mitral Medtronic Hall (MH) mechanical heart valve (MHV). The closing velocity and the transient pressure were simultaneously measured at heart rates of 70, 90, 120, and 140 beats/minute with cardiac outputs of 5.0, 6.0, 7.5, and 8.5 liters/minute, respectively. The experiment was conducted under simulated physiologic ventricular and aortic pressures in a pulsatile mock flow loop. The characteristics of the transient pressure were investigated by detailed mapping of the transient pressure field in the atrial chamber using high frequency pressure transducers. Simultaneous measurements of the occluder closing velocity and the transient pressure around the seat stop of the MH showed that the transient pressure generated on the inflow side dropped below the vapor pressure of liquid during the occluder's sudden deceleration at closing. The amplitude of the transient pressure reduction (TR) was proportional to the occluder approaching velocity. The development of the transient pressure in the rigid and flexible mountings were significantly different. In the rigid mounting (RM), the pressure was reduced below the liquid's vapor pressure and maintained below -350 mmHg for approximately 180 microseconds. Strong signals of high frequency pressure oscillations (HPO) were recorded in the transient pressure traces. The timing of the HPO was found to be consistent with that of the cavitation bubble collapse as observed by others. In the flexible mounting (FM), TR also occurred, but recovered quickly and was followed immediately by a positive pressure spike. Relatively weak HPO appeared in the transient pressure trace. The mapping of the transient pressure field showed that both the transient pressure reduction (on the major orifice side) or rise (on the minor orifice side) as well as the HPO were locally generated near the valve occluder surface. The transient pressure attenuated with distance away from the occluder surface. The HPO were detectable as far as 40 mm away from the occluder surface. The rigid mounting pressure signals showed characteristically two occurrences of high frequency pressure oscillations. The HPO with smaller amplitude occurred first after the initiation of the TR, followed by a burst of strong HPO at about 450 microseconds. It is believed that they were the result of the collapse of cavitation bubbles. The strong HPO did not appear in the flexible mounting signals. The study indicated that the mounting compliance played a significant role in the MHV cavitation inception and the subsequent bubble growth. It also suggested the possibility of detecting the cavitation by using a high frequency pressure transducer positioned in the atrial chamber.