Modeling of biological objects on the basis of computer and magnetic resonance imaging is a common practice today. DICOM source files (CT with contrast agent, heart without pathologies) were obtained at the Saratov cardiology center and correspond to diastole of cardiac cycle. The created geometric model consists of the internal volume of blood, ventricles, atria, heart valves and tendon chords. The resulting model can be studied using various computer systems, in particular, the finite element method.
The study developed criteria for the success of surgical reconstructive treatment of patients with diseases and injuries of the spine and hip joints. Based on the analysis of scientific literature, success criteria were divided into three groups: clinical, geometric and biomechanical. The clinical criteria for the success of surgical treatment include international scales assessing the patient's condition before and after surgery. The geometrical criteria for success include the parameters of the frontal and sagittal balances of the elements of the vertebral-pelvic complex. Biomechanical criteria for the success of surgical treatment allow one to analyze the results of biomechanical modeling in order to substantiate the choice of the most rational option of surgical treatment for a particular patient. The biomechanical criteria for the success of surgical reconstructive treatment include: assessment of displacement values (displacements) of adjacent elements of the pelvic-pelvic complex, estimation of range of motion, evaluation of the values of effective (equivalent) stresses.
Surgical methods form the basis of modern approach to forefoot deformities correction. Scientific and practical interest in this topic is based on the patients’ growing need for specialized care, which is required by 64% of women and 25% of men. In most cases, there is bilateral deformation of both feet. Some scientists are strongly against simultaneous surgery on both feet. It is obvious that the solution regarding acceptability of the load in the early postoperative period requires quantitative individual assessment. This assessment can be performed using biomechanics. This paper presents the technique for assessing the bone-screw system when performing corrective osteotomies of the first metatarsal bone based on biomechanical methods. This technique allows to perform comparative analysis of various osteotomy methods for a particular patient. In this study we examined Chevron and Scarf osteotomy with displacement of bone fragments by 1/3 and 2/3 with different fixation variants. To solve this problem, personalized geometric models of the first metatarsal bone were built on the basis of computed tomography data using 3D Slicer and SolidWorks systems. The implant models were built as well. Finite element analysis was carried out using Ansys Workbench software. The focus of the study was to analyse stresses that occur on the plantar surface of the first metatarsal bone head during walking. Assessment of the maximum allowable shift of bone fragments for normalization of the forefoot deformities was carried out. The developed technique allows to choose osteotomy variant and justify the possibility of simultaneous surgery on both feet for a particular patient.
Planning of surgical reconstructive treatment of diseases and injuries of the vertebral-pelvic complex is a very responsible and complex challenge. For the successful outcome of surgery, doctors can use a prognosis based on a biomechanical simulation as support. It is very important for such simulation to know the physical properties, such as the estimation of Young's modulus value of bony tissues. The estimations of Young's modulus are possible only in vivo according to computed tomography (CT) since all calculations must be completed before the surgery. So the methods of determining proposed the value of Young's modulus (E) by Hounsfield units (HU) are proposed. Hounsfield units characterize the intensity of the gray color of bones on the tomogram. Within this article, in order to estimate the values of Young's modulus using the CT data, we performed a series of measurements in two ways on the same bony tissue samples. For the same bone tissue samples, measurements of Hounsfield units by a computer tomography data were first performed, and then during the experiment on the test machine, the values of maximum stresses and strains were determined, stressstrain graphs were constructed, and the values of Young's modulus were calculated. According to the results of two series of experiments, a comparative analysis was carried out. Note that changes caused by a disease or injury lead to an increase in bone heterogeneity, which is numerically expressed on the results of CT scan by an increase in the variation of Hounsfield units. The increase of HU variation in turn, affects the results of averaging, and consequently, the result of the study as a whole.
Object of study: The investigation is focused on development of personalized medicine. The determination of mechanical properties of bone tissues based on in vivo data was considered. Methods: CT, MRI, natural experiments on versatile test machine Instron 5944, numerical experiments using Python programs. Results: The medical diagnostics methods, which allows determination of mechanical properties of bone tissues based on in vivo data. The series of experiments to define the values of mechanical parameters of bone tissues. For one and the same sample, computed tomography (CT), magnetic resonance imaging (MRI), ultrasonic investigations and mechanical experiments on single-column test machine Instron 5944 were carried out. The computer program for comparison of CT and MRI images was created. The grayscale values in the same points of the samples were determined on both CT and MRI images. The Haunsfield grayscale values were used to determine rigidity (Young module) and tensile strength of the samples. The obtained data was compared to natural experiments results for verification.
Object of study: The research is aimed at development of personalized medical treatment. Algorithm was developed for patient-specific surgical interventions of the cardiovascular system pathologies.
Methods: Geometrical models of the biological objects and initial and boundary conditions were realized by medical diagnostic data of the specific patient. Mechanical and histomorphological parameters were obtained with the help mechanical experiments on universal testing machine. Computer modeling of the studied processes was conducted with the help of the finite element method.
Results: Results of the numerical simulation allowed evaluating the physiological processes in the studied object in normal state, in presence of different pathologies and after different types of surgical procedures.
Object of study: A study of the biomechanical characteristics of the human heart ventricles was performed. 80 hearts were extracted during autopsy of 80 corpses of adults (40 women and 40 men) aged 31-70 years. The samples were investigated in compliance with the recommendations of the ethics committee.
Methods: Tension and compression tests were performed with help of the uniaxial testing machine Instron 5944. Cardiometry was also performed.
Results: In this work, techniques for human heart ventricle wall biomechanical properties estimation were developed. Regularities of age and gender variability in deformative and strength properties of the right and left ventricle walls were found. These properties were characterized by a smooth growth of myocardial tissue stiffness and resistivity at a relatively low strain against reduction in their strength and elasticity from 31-40 to 61-70 years. It was found that tissue of the left ventricle at 61-70 years had a lower stretchability and strength compared with tissues of the right ventricle and septum. These data expands understanding of the morphological organization of the heart ventricles, which is very important for the development of personalized medicine. Taking into account individual, age and gender differences of the heart ventricle tissue biomechanical characteristics allows to rationally choosing the type of patching materials during reconstructive operations on heart.
Object of study: Improvement of life quality of patients with high stroke risk ia the main goal for development of system for patient-specific modeling of cardiovascular system. This work is dedicated at increase of safety outcomes for surgical treatment of brain blood supply alterations. The objects of study are common carotid artery, internal and external carotid arteries and bulb. Methods: We estimated mechanical properties of carotid arteries tissues and patching materials utilized at angioplasty. We studied angioarchitecture features of arteries. We developed and clinically adapted computer biomechanical models, which are characterized by geometrical, physical and mechanical similarity with carotid artery in norm and with pathology (atherosclerosis, pathological tortuosity, and their combination). Results: Collaboration of practicing cardiovascular surgeons and specialists in the area of Mathematics and Mechanics allowed to successfully conduct finite-element modeling of surgical treatment taking into account various features of operation techniques and patching materials for a specific patient. Numerical experiment allowed to reveal factors leading to brain blood supply decrease and atherosclerosis development. Modeling of carotid artery reconstruction surgery for a specific patient on the basis of the constructed biomechanical model demonstrated the possibility of its application in clinical practice at approximation of numerical experiment to the real conditions.