2009, 24(6):395-400. DOI: 10.3871/j.1004-7220.2009.6.400.
Abstract:Hemodynamics-simulation-based cardiovascular surgical planning, which is the patient-specific surgical hemodynamics optimization based on medical image, is the further development of clinical-application-oriented computational hemodynamics, it is very helpful for cardiovascular surgical decision-making. The art-in-work of hemodynamics-simulation-based cardiovascular surgical planning in both domestic and overseas research was reviewed, the key problems and solutions involved were analyzed, and the further developing objectives were presented.
2009, 24(6):401-407. DOI: 10.3871/j.1004-7220.2009.06.407.
Abstract:The mechanism of thrombus formation in living vessel wall is complex and involves a combination of blood and vessel wall properties and local flow conditions. The significance, theory and experimental techniques of thrombus formation in vivo were comprehensively reviewed. Particularly, the important role of signaling pathway and hemodynamic in thrombus formation in vivo was pointed out. The difficulty in in vivo animal models was analyzed. Some recent new phenomena as well as new approaches and directions worthy of investigation also were summarized.
2009, 24(6):408-413. DOI: 10.3871/j.1004-7220.2009.6.413.
Abstract:Objective Children’s heart valves by DS CT images were enhanced and segmented in order to reconstruct 3D construction of heart valves and do motion analysis according to this model. Methods Adaptive seed-filling algorithm is proposed in this paper to segment region of interest of heart based on DS CT images. Contourlet transform is used to enhance and segment heart valve based on the part-segmented image. Results With these methods, DS CT images were successfully processed and segmented in Matlab7.0 and clear images of mitral valves were got. Conclusion The adaptive seed-filling algorithm proposed in this paper and Contourlet transform are very useful for segmentation in different situation. The conclusion in this paper provides useful reference for doctors to do research on the motion of mitral valves and plan on surgical operation of mitral valves.
2009, 24(6):414-417. DOI: 10.3871/j.1004-7220.2009.06.417.
Abstract:Objective To study the method of internal boundary parameters identification of middle ear. Methods The numerical model is created using CT technology. Based on Matlab tools, the neural network for identifying internal boundary is proposed. Results The uniform pressure of 105 dB is applied at the outside of the tympanic membrane, and the harmonic analysis is calculated on the model to take the training samples. The internal condition parameters are identified using the good neural network. Conclusion The investigation shows that the inverse method reveals a fast convergence and a high degree of accuracy.
2009, 24(6):418-426. DOI: 10.3871/j.1004-7220.2009.6.426.
Abstract:Objective Simulate the blood flow numerically in patient-specific cerebral aneurysms and help assessing the risks of rupture and reoccurrence of cerebral aneurysms in clinic. Methods Geometrical models were constructed from three-dimensional rotational angiography data, Herschel-Bulkley non-Newtonian fluid model was chosen for the blood, and the commercial CFD software was employed to simulate the blood flow in the two patient-specific computational models. Results The streamlines, the velocity fields in important cross sections, the wall shear stress distribution and total pressure distribution on the aneurysmal wall were obtained. Furthermore, the graphs of wall shear stress and total pressure, at 20 points of the neck and top of each aneurysm respectively, at systolic time, were plotted. Conclusion Hemodynamic factors play important roles in the growth and rupture of cerebral aneurysms and patient-specific CFD simulation of blood flow in cerebral aneurysm can make a contribution in studying the hemodynamics in cerebral aneurysms. Distribution of wall shear stress is different from that of unsteady index of wall shear stress at the neck of the aneurysm, and the relationship between the oscillation of wall shear stress and the risks of rupture and reoccurrence of the aneurysm should be studied.
2009, 24(6):427-423. DOI: 10.3871/j.1004-7220.2009.06.423.
Abstract:Objective Impedance control plays an important role in stability. This paper intends to explore such mechanism through modeling human reaching movement. Method Implemented with revised model, we apply optimal control theory to neuro-muscle-skeleton model to calculate the stiffness ellipses. Result Compared with the original model and experimental figures, the model we proposed could overcome the shortage of monotonous changing of the original one and fit the data better. Conclusions So that this paper concludes that co-contraction contributes to impedance control even during free upper limb planar movement.
2009, 24(6):434-438. DOI: 10.3871/j.1004-7220.2009.06.438.
Abstract:Objectives To explore the isometricity of grafts in PCL（posterior cruciate ligament）double-bundle reconstruction under femoral tunnel shifting condition . Methods Knee specimens from ten fresh frozen cadavers were used. PCL were divided into anterolateral bundles (ALB) and posteromedial bundles (PMB) to the insertion footprint .The anterior , posterior , proximal , distal and central points of the two bundles’ femoral attachment site were respectively anchored to the middle of the PCL’s tibial attachment site by the trial wires. Changes in length of the intra-articular part of the wires were recorded while the knee was flexed from 0°to 120°. Results The length changes in every points were compared. All of the maximal length changes of ALB’s proximal, posterior points and PMB’s proximal points were not greater than 2mm. No significant difference between the length changes of ALB’s proximal point and posterior (P=0.864＞0.05) . Conclusions The femoral tunnel for the PCL double-bundle reconstruction should be located as follows: ALB should be at the middle point of upper edge of femoral attachment site (proximal point), while PMB at the middle point of femoral attachment site (proximal point).
2009, 24(6):439-443. DOI: 10.3871/j.1004-7220.2009.06.443.
Abstract:Objective To study the stability of micro-implant orthodontic anchorage (MIA) with different pitch in the case of immediate loading. Method Employing 3d finite element analysis method, the stress and displacement distribution on the bone interface of MIA with different pitch (0.3mm、0.5mm、0.7mm and 1.0mm, respectively) , which was 1.47N loaded vertically in the major axis direction, were analyzed. Result The pitch affected the stress distribution significantly, because the maximum stress increased with pitch increasing and the impact of pitch on stress distribution on the neck and the central location of MIA were different; to decrease the pitch could reduce the max displacement of the jaw,but the impact of pitch on displacement distribution of MIA was not significant. Conclusion In the case of immediate loading,MIA with pitch 0.5mm-0.7mm should be selected as orthodontic anchorage in the clinic.
2009, 24(6):444-447. DOI: 10.3871/j.1004-7220.2009.06.447.
Abstract:Objective To adopt a three-dimensional limited element analytic method to research into the cause and mechanism of the complications taking place after resection of head radius. Method To adopt a three-dimensional limited element analytic method to research into the stress transmission action of the head radius and the distribution alteration of the stress transmission after resection of head radius impacting on the stability of elbow and wrist. Results In normal cases, the stress value transmitted via head of radius takes 58% of the stress placed, 36.85% via humeroulnar joint. The head of radius places a leading role in the stress transmission of the elbow joint. After resection of the head of radius, the lateral of humeroulnar joint bears about 43% of the stress placed while the medial part bears about 21.6% of the stress. To compare with that before the resection of the head of radius the stress on the lateral is obviously increased more than the medial part. Conclusion The head of radius places a leading role in the stress transmission of the elbow joint. The resection of the head radius breaks the normal distribution of the stress on the elbow joint and produces great effect on the stability of the elbow joint and wrist joint. Therefore, in clinics we should pay great attention to the indication of resection of the head of radius.
2009, 24(6):448-451. DOI: 10.3871/j.1004-7220.2009.06.451.
Abstract:Objective To study the compression properties of articular cartilage and polyvinyl alcohol hydrogel (PVA-H) as artificial cartilage. Methods Unconfined compression tests were conducted on articular cartilage and PVA-H, including stress-strain tests, creep tests and stress relaxation tests. The stress-strain relationship of articular cartilage and PVA-H were measured. Results The compression modulus of articular cartilage was higher than that of PVA hydrogel.The average compression modulus of articular cartilage and PVA hydrogel was (3.6492±0.6199) Mpa and (1.5951±0.1469) Mpa, respectively.
2009, 24(6):452-457. DOI: 10.3871/j.1004-7220.2009.06.457.
Abstract:Objective To investigate and evaluate the biomechanical property of the skin in pig’s back in order to provide the essential theoretical basis for clinical and skin products. Methods Based on the monotonic tensile tests at various loading rates and the cyclic tension-tension tests at different load levels about the skin of pig’s back, the influence of loading rate and direction on the skin’s deformation and its creep deformation were discussed, the emphasis is addressed on the cyclical accumulation phenomenon of axial strain (i.e., ratcheting) of the skin and its dependence upon the applied stress level. Results The capacity of resisting tensile, creep and cyclic deformation of pig’s skin in the direction along the Langer’s line is more stronger than that perpendicular to the Langer’s line. The creep curve of pig’s skin is load-dependent and consisted of three phases about deceleration phase, stabilization phase and destruction stage. Pig’s skin exhibits apparent ratcheting under asymmetry stress cycle. Ratcheting deformation displays significant mean stress, stress amplitude and loading speed dependence.
2009, 24(6):458-461. DOI: 10.3871/j.1004-7220.2009.06.461.
Abstract:Objective To research the mechanical style (compressive or tensile force) of the key site of brain tissue in brain deceleration impact. Methods A transparent physical brain model with air bubbles was built and loaded on an upright brain deceler ation impacting experimental platform. Then, the moveable platform was made to free fall from a height of 400mm and impacted on a fixed platform, and the whole deceleration impacting process was recorded by a high-speed video camera. Using the serial pictures analyzing software, the length change of the long axis (vertical to the impacting direction) and the short axis (in the impacting direction) of the air bubbles were analyzed and calculated. Results The length change of the long axis was smaller than the absolute value of the length change of the short axis in the coup site air bubble; the length change of the long axis was bigger than the absolute value of the length change of the short axis in the contrecoup site air bubble. Conclusion The results showed that the air bubble in the coup site mainly suffered from the tensile force vertical to the impacting direction and the air bubble in the contrecoup site mainly suffered from the compressive force in the impacting direction. Since the property of tensile resistance of the brain tissue is inferior to the property of compressive resistance of the brain tissue, the injury is often easier to occur in the contrecoup site than in coup site. The results were of significance to the research of biomechanical mechanism, diagnosis and prevention of the brain deceleration impacting injury.
2009, 24(6):462-467. DOI: 10.3871/j.1004-7220.2009.06.467.
Abstract:There are many physical factors affecting the development of cartilage tissue. Particularly, mechanical condition is an important aspect to culture cartilage tissue. The mechanical conditions in engineering cartilage tissue, such as compressive and shear force, fluid flow, hydrostatic pressure and tissue deformation or them partly combined, were reviewed. From the standpoint of bionics, the mechanical environments applied on tissue engineering should work in three aspects: providing adequately mechanical stimuli to the cells seeded in 3-D scaffold; ensuring the efficient mass-transport of the nutrients and waste products of the cells; promoting the development of functionally extracellular matrix in 3-D scaffold. The mechanical environments currently used only represent the part of mechanical conditions of in vivo articular cartilage. We concluded that rolling depression load may achieve the cultivation of functional cartilage constructs in vitro.