An estimation of mechanical stress on alveolar walls during repetitive alveolar reopening and closure.

Alveolar overdistension and mechanical stresses generated by repetitive opening and closing of small airways and alveoli have been widely recognized as two primary mechanistic factors that may contribute to the development of ventilator-induced lung injury. A long-duration exposure of alveolar epithelial cells to even small, shear stresses could lead to the changes in cytoskeleton and the production of inflammatory mediators. In this paper, we have made an attempt to estimate in situ the magnitudes of mechanical stresses exerted on the alveolar walls during repetitive alveolar reopening by using a tape-peeling model of McEwan and Taylor (35). To this end, we first speculate the possible ranges of capillary number (Ca) ≡ µU/γ (a dimensionless combination of surface tension γ, fluid viscosity µ, and alveolar opening velocity U) during in vivo alveolar opening. Subsequent calculations show that increasing respiratory rate or inflation rate serves to increase the values of mechanical stresses. For a normal lung, the predicted maximum shear stresses are <15 dyn/cm(2) at all respiratory rates, whereas for a lung with elevated surface tension or viscosity, the maximum shear stress will notably increase, even at a slow respiratory rate. Similarly, the increased pressure gradients in the case of elevated surface or viscosity may lead to a pressure drop >300 dyn/cm(2) across a cell, possibly inducing epithelial hydraulic cracks. In addition, we have conceived of a geometrical model of alveolar opening to make a prediction of the positive end-expiratory pressure (PEEP) required to splint open a collapsed alveolus, which as shown by our results, covers a wide range of pressures, from several centimeters to dozens of centimeters of water, strongly depending on the underlying pulmonary conditions. The establishment of adequate regional ventilation-to-perfusion ratios may prevent recruited alveoli from reabsorption atelectasis and accordingly, reduce the required levels of PEEP. The present study and several recent animal experiments likewise suggest that a lung-protective ventilation strategy should not only include small tidal volume and plateau pressure limitations but also consider such cofactors as ventilation frequency and inflation rate.

A micromechanical model for estimating alveolar wall strain in mechanically ventilated edematous lungs.

To elucidate the micromechanics of pulmonary edema has been a significant medical concern, which is beneficial to better guide ventilator settings in clinical practice. In this paper, we present an adjoining two-alveoli model to quantitatively estimate strain and stress of alveolar walls in mechanically ventilated edematous lungs. The model takes into account the geometry of the alveolus, the effect of surface tension, the length-tension properties of parenchyma tissue, and the change in thickness of the alveolar wall. On the one hand, our model supports experimental findings (Perlman CE, Lederer DJ, Bhattacharya J. Am J Respir Cell Mol Biol 44: 34-39, 2011) that the presence of a liquid-filled alveolus protrudes into the neighboring air-filled alveolus with the shared septal strain amounting to a maximum value of 1.374 (corresponding to the maximum stress of 5.12 kPa) even at functional residual capacity; on the other hand, it further shows that the pattern of alveolar expansion appears heterogeneous or homogeneous, strongly depending on differences in air-liquid interface tension on alveolar segments. The proposed model is a preliminary step toward picturing a global topographical distribution of stress and strain on the scale of the lung as a whole to prevent ventilator-induced lung injury.

Contributions of non-spherical hip joint cartilage surface to hip joint contact stress.

The natural non-spherical incongruent hip joint cartilage surface is normally assumed as spherical in shape, which has been extensively applied in orthopedic clinic, hip joint simulation studies and hip joint prosthesis design. The aim of the study was to investigate the contributions of non-spherical incongruent hip joint cartilage surface to the hip joint contact stress, and to assess the effect of simplified spherical assumption on the predicted contact stress. Based on our previous anatomic studies that the acetabular cartilage surface was demonstrated as rotational ellipsoid in shape, three finite element (FE) models involving the natural hip joint cartilage shape, the hip joint cartilage shape replaced by the rotational ellipsoid and the sphere, respectively, were developed using the computed tomography (CT) image data of healthy volunteers. The FE predictions of contact stress on the replaced hip joint cartilage surface were compared with that on the natural hip joint cartilage surface. The result showed that the non-spherical hip joint cartilage surface contributed to the optimal contact stress magnitude and distribution. The replaced fitting spherical surface led to the increased contact stress of hip joint and the uneven distributed patterns of contact stress, whereas the replaced fitting rotational ellipsoid surface was comparatively more consistent with the natural results than the sphere one. The surface fitting error of the replaced rotational ellipsoid was fewer than that of the replaced sphere. These results indicate that the simplified spherical assumption will lead to misestimating the contact mechanics of hip joint, and the rotational ellipsoid model rather than the sphere model may represent the hip joint contact surface applied in the hip joint simulation study and the hip joint prosthesis design.

The shape of the acetabular cartilage surface and its role in hip joint contact stress.

The acetabular cartilage is normally represented as a spherical shape in orthopedic clinic and related researches. The aim of the study was to present a new mathematic representation with better fit to the acetabular cartilage surface and to investigate the role of its shape on the hip joint contact stress.

High-intensity focused ultrasound with large scale spherical phased array for the ablation of deep tumors.

Under some circumstances surgical resection is feasible in a low percentage for the treatment of deep tumors. Nevertheless, high-intensity focused ultrasound (HIFU) is beginning to offer a potential noninvasive alternative to conventional therapies for the treatment of deep tumors. In our previous study, a large scale spherical HIFU-phased array was developed to ablate deep tumors. In the current study, taking into account the required focal depth and maximum acoustic power output, 90 identical circular PZT-8 elements (diameter =1.4 cm and frequency=1 MHz) were mounted on a spherical shell with a radius of curvature of 18 cm and a diameter of 21 cm. With the developed array, computer simulations and ex vivo experiments were carried out. The simulation results theoretically demonstrate the ability of the array to focus and steer in the specified volume (a 2 cmx2 cmx3 cm volume) at the focal depth of 15 to 18 cm. Ex vivo experiment results also verify the capability of the developed array to ablate deep target tissue by either moving single focal point or generating multiple foci simultaneously.

Computer-assisted orthopedic diagnosis and preoperative planning system based on the integrated electronic patient record.

Computer-assisted orthopedic diagnosis and preoperative planning have been recognized as efficient tools to improve the accuracy of clinic diagnosis and surgical procedure. In orthopedic clinic, such practices are heavily relied on the patient-specific medical image data.

[Experimental study on ultrasound heating affecting the sensitivity of oral carcinoma to chemotherapy drugs].

OBJECTIVE: To explore the influence of chemosensitivity of Tca8113 cells by modified MTT assay after the animal model of Tca8113 were treated by the ultrasound hyperthermia. METHODS: The MTT assay of the BALB/C nu/nu mice model of Tca8113 cells treated by the ultrasound hyperthermia in vivo was performed. RESULTS: The chemosensitivity to the 9 kinds of drugs demonstrated no significant differences between the Tca8113 cells in the control group, the 39 degrees C-treated group and the groups treated from 41 degrees C to 44 degrees C. But significant differences between the 40 degrees C-treated group and the 41 degrees C or 42 degrees C-treated group existed. In the heating-time grades test, there were no significant differences in the chemosensitivity to the 9 kinds of drugs between these three pairs of group (the control group and the 15 min-treated group, the 30 min-treated and the 45 min-treated group, the 60 min-treated and the 75 min-treated group). But there were significant differences between the 30 min-treated or the 45 min-treated group and the 60 min-treated or the 75 min-treated group. CONCLUSION: Ultrasound hyperthermia performed in 42 degrees C for 30-45 min can improve the chemosensitivity of Tca8113 cells to some drugs significantly, which confirms the rationality of synchronous combination of hyperthermia and chemotherapy in the chemosensitivity point of view for the first time.

SVM for density estimation and application to medical image segmentation.

A method of medical image segmentation based on support vector machine (SVM) for density estimation is presented. We used this estimator to construct a prior model of the image intensity and curvature profile of the structure from training images. When segmenting a novel image similar to the training images, the technique of narrow level set method is used. The higher dimensional surface evolution metric is defined by the prior model instead of by energy minimization function. This method offers several advantages. First, SVM for density estimation is consistent and its solution is sparse. Second, compared to the traditional level set methods, this method incorporates shape information on the object to be segmented into the segmentation process. Segmentation results are demonstrated on synthetic images, MR images and ultrasonic images.

[A study on the mechanism of inducing apoptosis of Tca8113 cells by means of ultrasound hyperthermia].

PURPOSE: To investigate the mechanism of apoptosis in Tca8113 cells induced by ultrasound hyperthermia by detecting changes in related index. METHODS: Tca8113 cells were treated in vitro by ultrasound hyperthermia in different heating temperatures (38 degrees C to 44 degrees C,10 minutes) and heating times (42 degrees C,10 to 60 minutes), and then the dynamic changes of early apoptosis and secondary necrosis treated by 42 degrees C for 10 minutes were assayed to detect deltapsim and Caspase-3 levels of different groups by flow cytometry (FCM). The means of each group were compared by ANOVA with SAS6.12 software package. RESULTS: After heated by ultrasound in 42 degrees C for 10 minutes, the early apoptosis of Tca8113 was detected. The apoptosis index reached its highest level at the 6th to 8th hour, then decreased rapidly and maintained in a lower level after 12 hours. The level of secondary necrosis increased with the level of early apoptosis, but kept in a higher level until the 10th hour, the level of secondary necrosis correlated with that of the early apoptosis (r = 0.7909, P = 0.0064). The fraction of cells with low mitochondria membrane potential and increased activity of Caspase-3 were detected either in the heating-temperature grads group or in the heating-time grads group, which showed significant relationship between thetwo apoptosis related index (r = 0.89189, P = 0.0029 in the heating-temperature grads group; r = 0.9679, P = 0.0003 in the heating-time grads group). CONCLUSIONS: Tca8113 cells developed apoptosis after heated by ultrasound hyperthermia along with deltapsim level decreasing and Caspase-3 activity increasing. Ultrasound hyperthermia induces apoptosis of Tca8113 cells by the mitochondrum-Caspase pathway.

[The software design of an ultrasonic hyperthermia instrument based on an ARM embedded system].

Development of an ultrasonic hyperthermia instrument's software based on ARM32 microprocessor is here introduced. The system integrates the embedded SOC system, memory system, PWM system, A/D system, JTAG debug system, UART communication system, I/O system and GUI system (include LCD, keyboard) in one PCB board. It effectively completes the control and constance of temperature through the improved PID algorithm, and the instrument miniaturization. Experiments have proved that the system accords with the design requirements.

Multi-modality medical image registration using support vector machines.

The registration of multi-modality medical images is an important tool in surgical application. We presented a method of computing different modality medical images registration of the same patient. It incorporates prior joint intensity distribution between the two imaging modalities based on registered training images. The prior joint intensity distribution is modeled by support vector machine. Results aligning CT/MR and Pet/MR scans demonstrate that it can attain sub-voxel registration accuracy. Furthermore, it is a fast registration method because support vector machine solution is sparse.

Investigation of a phenylalanine-biosensor system for phenylketonuria detection.

Detection and prevention of Phenylketonuria (PKU) is becoming more and more important. However, the current methods are either imprecise or time-consuming. We propose a biosensor system based on phenylalanine ammonia-lyase (PAL) immobilized on an ammonia electrode to measure blood phenylalanine for PKU prevention. The biosensor exhibits good linearity from 10-5000μM and the response time is only about 2 minutes. It remains stable for at least 5 days and less than 20% drop of the original activity after ten day storage at 4□, while the service life of the biosensor could be up to 30 days. We also develop an intelligent system to ensure optimal conditions for operation and preservation of the biosensor and to make detection more convenient and reliable. All of these advantages indicate that the newly developed method could be a better one for solving the problems of PKU detection.

Segmentation of LSCM Images based on Multi-channel Information Fusion.

The two channels of LSCM, the fluorescent light channel and the visible light channel, provide us with different modality images that contain special information respectively. In this paper we propose a new and integrated approach to segment images in the fluorescent light channel of LSCM, which have rather low SNR and can not provide sufficiently high intensity gradient at the boundary. Our approach, rather than relying on information of the velocity field alone, also includes statistical information of images in the visible light channel which provide subtle information of vessel structures. Information is described by corresponding image force. The approach is tested on LSCM images and experimental results show that it can segment low SNR vasculature structures automatically. Comparison is made between C-V model and the new approach, we find that the latter has better performance and can provide vasculature delineation with higher quality since information of both channels is utilized.

Correlation dimension and the largest Lyapunov exponent characterization of RR interval.

OBJECTIVE: To search for evidence of deterministic chaos and to characterise it quantitatively in RR intervals of different subjects. METHOD: An improved Grassberger-Procaccia (GP) algorithm was proposed for computing the correlation dimensions (CD) of RR intervals in ten healthy young men, ten healthy old men, and ten atrial fibrillation (AF) patients. Analysis was also performed by calculating the largest Lyapunov exponents. RESULT: It was found that the cardiac systems of healthy young men are some 7-8 dimensional complex dynamic systems, while those of healthy old men are 6-6.5 dimensional, and those of AF patients had dimensions of about 4-4.5. The young men had the largest Lyapunov exponents of about 0.019-0.23, the largest Lyapunov exponents of old men was 0.12-0.16, and that of AF patients was 0.083-0.123. CONCLUSION: The above results demonstrated that the RR intervals could be chaotic. The decrease in the CDs and the largest Lyapunov exponents as we move from the young to the old and then to the AF patients reflects the loss of complexity as the heart becomes less healthy. Therefore, correlation dimension and the largest Lyapunov exponent could be used as some novel non-invasive analysis tools for clinical cardiology.

[Development of the combined tumor therapeutic equipment].

This paper describes the development of the combined tumor therapeutic equipment based on the theory of 1 + 1 = 3 or 1 + 1 > 3 tumor combined treatment synergism. It has become a promising and valuable method dealing with cancer tumors for its good adaptability, better effectiveness and convenience. The therapeutic equipment is combined with PC and MS windows operation system, and adopts intellectual temperature control device, which realizes homogeneous and smooth heating to intracavity tumor focus and automatic processing and statistical management of all case data. The equipment works stably and is of great value in clinical applications.

[The development of 3D US system for treating target localization in focused ultrasound surgery].

Focused Ultrasound Surgery (FUS) is a promising minimally invasive technique in tissue ablation. Because of the high intensity at the ultrasound focus, a precise 3D-localization system is required to determine the site of the treating target in order to increase the efficiency and security of FUS. This paper represents a three dimensional ultrasound (3D US) localization system developed and its workflow. The system is mainly composed of imaging and image processing system, movement device and its controlling circuits, and position feedback device. The system has a maximum scan range of +/- 30 degrees with a resolution of 8 levels from 0.54' to 0.36 degrees. For a spherical shape like target, in theory, the maximum diameter is 160 mm the system can treat. The system can be used to localize precisely the treatment targets with general sizes in the suitable parts of the body in FUS.

[Development of RF ablation therapeutic instrument based on improved PID algorithm].

The development of a RF ablation therapeutic instrument based on improved PID algorithm is introduced here. It is based on the theory of radio frequency local destruction. By adopting the improved PID temperature control algorithm, the problem of the temperature control precision reduction due to tumor tissue characteristic changing by heating has been solved, thus ensuring homogeneous and smooth radio frequency heating to tumor foci. Experiments demonstrate that the new algorithm has strong adaptability and anti-disturbance capability, the equipment works stably and reliably, and can control therapeutic temperature precisely (+/- 2 degrees C), which indicates a good clinical application value.