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Many industrial computer aided design (CAD) programs contain highly developed facilities that can be used to create and analyze three dimensional models of biological structures. In this paper we describe the use of one such program package for modeling the rat brain and a component thereof. Special features of the models of interest to morphologists are illustrated.
Physical fitness has been reported to be inversely related to coronary heart disease and other health related problems. One of the most valid means of assessing physical fitness is the test of aerobic capacity. Aerobic capacity is the greatest rate at which the body can consume oxygen and represents the most efficient integration of the various physiological processes which make up the oxygen transport system. However, direct measurement of aerobic capacity requires sophisticated laboratory equipment, and is adversive to subjects. Step tests are widely used to estimate aerobic capacity. Because the biomechanical efficiency and work rate is determined by step height, accommodation of step height to the subject's statute height should provide a better estimation of aerobic capacity. A hip angle of 73.3 degrees, when stepping, was found to give the best relationship of recovery heart rate of a step test to direct measurement of aerobic capacity. Using 73.3 degrees, the following equations were developed for determining the stepping height when using the step test: Hf = 0.189 Ih and Hf = 0.192 Ih for females and males respectively, where hf is the step height and Ih is the statute height of the subject. A correlation coefficient (r) of 0.93 was calculated between various hip angles and calculated foot height of 182 observations of 47 females while a correlation coefficient (r) of 0.96 was calculated from 208 observations of 53 males. Using these equations to determine step height, measurement of 30 females showed a mean hip angle of 73.3 degrees +/- 2.2 and measurement of 30 males showed a mean hip angle of 73.3 degrees +/- 2.1.(ABSTRACT TRUNCATED AT 250 WORDS)
PURPOSE: Development of a software for fully automated image analysis of lateral lumbar spine X-rays. MATERIAL AND METHOD: Using the concept of active shape models, we developed a software that produces a form model of the lumbar spine from lateral lumbar spine radiographs and runs an automated image segmentation. This model is able to detect lumbar vertebrae automatically after the filtering of digitized X-ray images. The model was trained with 20 lateral lumbar spine radiographs with no pathological findings before we evaluated the software with 30 further X-ray images which were sorted by image quality ranging from one (best) to three (worst). There were 10 images for each quality. RESULTS: Image recognition strongly depended on image quality. In group one 52 and in group two 51 out of 60 vertebral bodies including the sacrum were recognized, but in group three only 18 vertebral bodies were properly identified. CONCLUSION: Fully automated and reliable recognition of vertebral bodies from lateral spine radiographs using the concept of active shape models is possible. The precision of this technique is limited by the superposition of different structures. Further improvements are necessary. Therefore standardized image quality and enlargement of the training data set are required.
Time-domain potentials measured at 64 points on the surface of a large canine heart, considered comparable with those of a human heart, were used to calculate the electric fields and current densities within various organs of the human body. A heterogeneous volume conductor model of an adult male with a resolution of approximately 6 mm3 and 30 segmented tissue types was used along with the admittance method and successive over-relaxation to calculate the voltage distribution throughout the torso and head as a function of time. From this time-domain voltage description, values of [E(t)] and [J(t)] were obtained, allowing for maximum values to be found within the given tissues of interest. Frequency analysis was then used to solve for [E(f)] and [J(f)] in the various organs, so that average, minimum and maximum values within specific bandwidths (0-40, 40-70 and 70-100 Hz) could be analysed. A comparison was made between the computed results and measured data from both EKG waveforms and isopotential surface maps for validation, with good agreement in both amplitude and shape between the computed and measured results. These computed endogenous fields were then compared with exogenous fields induced in the body from a 60 Hz high-voltage power line and a 60 Hz uniform magnetic field of 1 mT directed from the front to the back of the body. The high-voltage power line EMFs and 1 mT magnetic field were used as 'bench' marks for comparison with several safety guidelines for power frequency (50/60 Hz) EMF exposures. The endogenous electric fields and current densities in most of the tissues (except for organs in close proximity to the heart, for example lungs, liver, etc) in the frequency band 40-70 Hz were found to be considerably smaller, between 5% and 10%, than those induced in the human body by the electric and magnetic fields generated by the 60 Hz sources described above.
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The objective of this study is to develop a two-dimensional dynamic model of the knee joint to simulate its response under sudden impact. The knee joint is modeled as two rigid bodies, representing a fixed femur and a moving tibia, connected by 10 nonlinear springs representing the different fibers of the anterior and posterior cruciate ligaments, the medial and lateral collateral ligaments, and the posterior part of the capsule. In the analysis, the joint profiles were represented by polynomials. Model equations include three nonlinear differential equations of motion and three nonlinear algebraic equations representing the geometric constraints. A single point contact was assumed to exist at all times. Numerical solutions were obtained by applying Newmark constant-average-acceleration scheme of differential approximation to transform the motion equations into a set of nonlinear simultaneous algebraic equations. The equations reduced thus to six nonlinear algebraic equations in six unknowns. The Newton-Raphson iteration technique was then used to obtain the solution. Knee response was determined under sudden rectangular pulsing posterior forces applied to the tibia and having different amplitudes and durations. The results indicate that increasing pulse amplitude and/or duration produced a decrease in the magnitude of the tibio-femoral contact force, indicating thus a reduction in the joint stiffness.(ABSTRACT TRUNCATED AT 250 WORDS)
Bones are a vital educational material in anatomy classes. However, it is not always easy to provide bones in sufficient quantity for a full class. In this article an easy method is presented for duplicating bones by using thermoplastic impression material and polymer cast material which can be used in anatomy laboratories with minimum cost. The method may be used to duplicate any bones, including rare anthropological bones or models made from materials like plaster or clay. Duplication of a mandible is described as an example.
Virtual reality offers the promise of highly interactive, natural control of the visualization process, greatly enhancing the scientific value of the data produced by medical imaging systems. Due to the computational and real time update requirements of virtual reality interfaces, however, the complexity of polygonal surfaces which can be displayed is limited. In this paper, we present a novel method for the production of a polygonal surface containing a pre-specified number of polygons from volumetric data. To preserve surface detail, we extract a set of curvature weights from the volumetric data and use these weights as the input vectors to a 2-D Kohonen network. The adaptation of the network to the input vectors results in a display surface that preserves useful detail relative to the number of polygons used.
Traditionally, finite element analysis or mass-spring systems are used to calculate deformations of geometric surfaces. Patient-specific geometric models can be comprised of tens of thousands, even hundreds of thousands of polygons, making finite element analysis and mass-spring systems computationally demanding. Simulations using deformable patient specific models at real time rates are prohibitive under such a computational burden. This paper presents a method for simulating deformable surfaces by deforming a skeletal representation of the surface, rather than the surface itself, yielding an efficient method for interactive simulation with models.
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In ten human hands the mesotendons of m. extensor digitorum longus and m. extensor indicis have been examined and described in detail. The various sources of their blood supplies have also been demonstrated and described.