Differential evolution and cost-maps for needle path planning in Baker's cyst aspiration.

PURPOSE: The Baker's cysts appear within the popliteal fossa along with the progression of degenerative changes. Removal of its contents through aspiration is often a necessary complement to treatment at various stages of the development of gonarthritis. METHODS: The paper presented a procedure for needle automatic needle path planning in cyst aspiration in transverse plane. The method was based on optimization and used a custom objective function, which utilized cost maps obtained from preprocessed, segmented images of the knee. The optimization was carried out with Differential Evolution. Furthermore, a preliminary sensitivity analysis was carried out. The obtained paths were compared to the reference paths proposed by an experienced surgeon. RESULTS: The procedure was tested on 165 numerical simulations. In all of the obtained paths, the needle successfully avoided crucial objects, such as veins, arteries and nerves. Furthermore, the overall travel distance in the joint was also minimized. When compared to the reference from the surgeon, 90% of the paths were almost the same or only slightly different. Furthermore, the remaining 10% of the generated paths were viable but different. CONCLUSION: Based on the obtained results, the proposed solution could be a viable solution for planning the aspiration of Baker's cyst.

Selected aspects of the application of the hybrid circulatory system in the analysis of heart insufficiency.

PURPOSE: There are many causes of heart failure, one of them being valvular heart disease. In this case, the stage and type of the disease can significantly affect the hemodynamic parameters of the left ventricle of the heart. In turn, these parameters can significantly influence the mode, type and strategy of clinical treatment. The aim of the study was to analyze and map the hydrodynamic conditions of the heart using a hybrid-digital model of the circulatory system. METHODS: The tests performed using the circulatory system model allowed for the simulation of the failure of both heart's left ventricle and a set of arteries in the systemic circulation. Furthermore, the changes in hemodynamic parameters for valvular anomalies at various heartbeats were obtained. RESULTS: The results suggested that a higher heartbeat should be sustained in such cases of complex mitral-aortic anomalies in the clinical practice. When observing low aortic pressures, heartbeat should be increased to compensate for the valvular insufficiencies. CONCLUSIONS: Extending the already conducted research could result in constituting a wide database for clinicians who are treating the insufficiency of the left ventricle of the heart. Moreover, the information included in this paper may be used for a comparison of the clinical anomalies, which facilitates a correct diagnosis. The test-stand used in the research can be applied to predict the anomalies of the circulation system for a quick and precise analysis of a clinical anomaly of a patient without physical presence.

Effect of Fiber Posts on Stress Distribution of Endodontically Treated Upper Premolars: Finite Element Analysis.

By means of a finite element method (FEM), the present study evaluated the effect of fiber post (FP) placement on the stress distribution occurring in endodontically treated upper first premolars (UFPs) with mesial-occlusal-distal (MOD) nanohybrid composite restorations under subcritical static load. FEM models were created to simulate four different clinical situations involving endodontically treated UFPs with MOD cavities restored with one of the following: composite resin; composite and one FP in the palatal root; composite and one FP in the buccal root; or composite and two FPs. As control, the model of an intact UFP was included. A simulated load of 150 N was applied. Stress distribution was observed on each model surface, on the mid buccal-palatal plane, and on two horizontal planes (at cervical and root-furcation levels); the maximum Von Mises stress values were calculated. All analyses were replicated three times, using the mechanical parameters from three different nanohybrid resin composite restorative materials. In the presence of FPs, the maximum stress values recorded on dentin (in cervical and root-furcation areas) appeared slightly reduced, compared to the endodontically treated tooth restored with no post; in the same areas, the overall Von Mises maps revealed more favorable stress distributions. FPs in maxillary premolars with MOD cavities can lead to a positive redistribution of potentially dangerous stress concentrations away from the cervical and the root-furcation dentin.

Structural and Material Optimization for Automatic Synthesis of Spine-Segment Mechanisms for Humanoid Robots with Custom Stiffness Profiles.

Typical artificial joints for humanoid robots use actual human body joints only as an inspiration. The load responses of these structures rarely match those of the corresponding joints, which is important when applying the robots in environments tailored to humans. In this study, we proposed a novel, automated method for designing substitutes for a human intervertebral joint. The substitutes were considered as two platforms, connected by a set of flexible links. Their structural and material parameters were obtained through optimization with a structured Genetic Algorithm, based on the reference angular stiffnesses. The proposed approach was tested in three numerical scenarios. In the first test, a mechanism with angular stiffnesses corresponded to the actual L4-L5 intervertebral joint. Scenarios 2 and 3 featured mechanisms with geometry and structure comparable to the joint, but with custom stiffness profiles. The obtained results proved the effectiveness of the proposed method. It could be employed in the design of artificial joints for humanoid robots and orthotic structures for the human spine. As the approach is general, it could also be extended to different body joints.

A novel planning solution for semi-autonomous aspiration of Baker's cysts.

BACKGROUND: A Baker's cyst is a pathological structure located near a kneepit, which causes discomfort and reduces mobility of the knee. It is commonly treated with aspiration, which often requires MRI scanning and US guidance. The aim of this study was to propose a novel planning solution for semi-autonomous aspiration of the Baker's cyst using only MRI imaging. METHODS: The proposed method requires minimal user input and offers automatic cyst segmentation with collision-free path planning for the assumed robotic structure with four degrees of freedom. RESULTS: The prepared software was tested on four image sets obtained from patients eligible for cyst aspiration. It was possible to accurately segment the cyst in the considered cases. The collision-free path planning method was investigated in numerical scenarios. CONCLUSIONS: The simulations verified the proposed software solution. Future work will be devoted to experimental verification of the path planning procedure.

Path planning for minimally-invasive knee surgery using a hybrid optimization procedure.

The aim of this study was to develop a procedure for medical tool path planning in minimally-invasive knee surgery. The collision-free paths for the tool were obtained using the control locations method with a hybrid optimization strategy. The tool and knee elements were described with surface meshes. The knee model allowed for bones displacement and variable incision size and location. The proposed procedure was proven to be effective in path planning for minimally-invasive surgery. It can serve as a valuable aid in surgery planning and may also be used in systems for autonomous or semi-autonomous knee surgery.

A novel kinematic model for a functional spinal unit and a lumbar spine.

PURPOSE: The aim of this paper is to present the novel model for the functional spinal unit and spine designed as a rigid mechanism and solve it with methods commonly used in robotics. METHOD: The structure of the intervertebral joint is analyzed with special attention paid to elements defining the displacements in the joint. The obtained mechanism is then numerically solved using a constraint equations method. RESULTS: The input data set for the simulation is prepared using the 3D scan of the lumbar spine. The simulation results show that the intervertebral joint mechanism can satisfy the ranges of flexion, lateral bending and axial rotation as compared with literature data. It is also possible to study complex, coupled displacements of the lumbar spine segment. CONCLUSIONS: Structural analysis of the functional spinal unit with methods common in robotics can eventually lead to better understanding of stabilizing and guiding mechanisms. The proposed mechanism can be used as a reference in the study of spine guidance. It can reproduce the angular displacements of the actual functional spine unit. It is also possible to expand the model to facilitate the analysis of a lumbar spine segment.

Experimental strength analysis of orthodontic extrusion of human anterior teeth.

The paper presents the strength tests, in terms of in vitro examinations, of restored mesial incisor crowns after endodontic treatment with modelled orthodontic extrusion procedure. The strength tests were carried out for 25 teeth randomly divided into groups with various degree of root reduction. The analysis was done for the following quantities: the force to fracture, the work to fracture, the energy of the first micro-crackings and breaking, the total displacement. Statistical analysis with the use of the Kruskal-Wallis test was done in order to assess the significance level in four tooth groups. Numerical simulations of periodontal ligament effort due to the orthodontic extrusion have also been carried out.

Numerical analysis of displacements of mandible bone parts using various elements for fixation of subcondylar fractures.

The paper presents an analysis of the distribution of dislocations in the case of fixation of a mandible low subcondylar fracture. Three types of elements have been used for fixation: NiTi shape-memory staples, miniaturized titanium plates and the Synthes compression plate, also called the Synthes zygomatic plate. The analysis was conducted using the finite element method. The degree of the mobility of the fractures was analysed as well as the tendency towards their separation on the basis of value analysis and the distribution of dislocation areas. The results obtained allowed a preliminary assessment of predicted healing effects and the possibility of being able to predict developing complications after osteosynthesis with the use of the elements analysed.

Experimental and numerical approach to chosen types of mandibular fractures cured by means of miniplate osteosynthesis.

The paper presents experimental and numerical analyses of two cases of mandibular corpus fractures cured by means of miniplate implantation. In the laboratory tests, strain gauges and electronic speckle pattern interferometry methods were used, while in the numerical simulations finite element analyses were applied. The aim of such a combined approach was to verify a correctness of the numerical model applied with regard to the assumptions and simplifications which had been done when creating FEM for human mandible: healthy, broken and stabilized with miniplate implants.