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Human anatomy in wax during Florentine enlightenment.

The high mortality rate of mothers and children during delivery was not taken into consideration by science before the end of the XVII Century; gynaecology became an official discipline in the Schools of Medicine at the beginning of the next century. The knowledge of anatomy was fundamental for doctors but human cadavers were still difficult to obtain; thus the need of models for the teaching. Anatomical models were obtained by injection of salts and alcohol on bodies or part of bodies: the procedure was difficult and the preparation did not last for a long time. Models in wax proved to be scientifically reliable, and everlasting. Schools of anatomical wax modelling were established in Italy: first in Bologna and later in Florence at the Museum "La Specola", a laboratory which soon became famous all through Europe. Description follows of the technique and the material used for the construction of the models; the scientists and the workers in the laboratory. Short notes on Felice Fontana, Paolo Mascagni, Giuseppe Galletti, Clemente Susini, Luigi Calamai, Egisto Tortori. A last chapter is devoted to the XVII Century Sicilian wax modeller Gaetano Giulio Zumbo, mainly renouned for the "Plague waxes" and some anatomical heads: most of his works are exhibited in the Museum La Specola in Florence.

Anatomy↗

RF currents induced in an anatomically-based model of a human for plane-wave exposures (20-100 MHz).

The three-dimensional finite-difference time-domain (FDTD) method has been used to calculate local, layer-averaged and whole-body averaged specific absorption rates (SARs) and internal radiofrequency (RF) currents in a 5628-cell, anatomically-based model of a human for plane-wave exposures from 20-100 MHz. The conditions of exposure of the human considered are: 1) isolated from ground, and 2) feet in contact with ground. Also considered are various separations of the model from ground and the use of insulating, rubber-soled footwear close to the grounded resonance frequency of 45 MHz. The calculated results are in agreement with the experimental data of Hill and others. While the existence of large foot currents has been known previously, substantial RF currents (600-800 mA) induced over much of the body are obtained for E-polarized fields suggested in the 1982 ANSI RF safety guideline.

Electric Conductivity↗

[Zygomatic implants anchorage for the rehabilitation of maxillary defects].

PURPOSE: Prosthetic reconstruction of the upper jaw in patients with extensive bone and soft tissue defects is still a significant challenge. This study evaluated the functional results of zygomatic implants and vascularized bone graft reconstruction of the maxillary defects in 4 patients. METHODS: Complex resections of the maxilla produced a three-dimensional defect in 4 patients. On the basis of an axial spiral CT data, anatomical models of natural size by CAD/CAM system was manufactured to enable preoperative measurements of relevant parameters. After tumor resection, reconstruction using the fibula or iliac osteocutaneous flap with titanium osseointegrated implants was performed. Maxillary and zygomatic measurements were also used to obtain information for installing 6 zygomatic implants and 7 dental implants. RESULTS: The bone from the fibula or iliac osteocutaneous flap was contoured to recreate the maxillary arch in 4 patients. The anatomical model and surgical palate was used for preoperative planning and intraoperative control of the insertion of 6 zygomatic fixtures after subtotal maxillectomy. The implants could be positioned precisely as preoperatively planned. CONCLUSIONS: The use of zygomatic fixtures after ablative tumor surgery with resection of the maxillary bone is valuable in providing new zygomatic buttresses that play a key role in the form of the midface. Maxillary rehabilitation can be further improved by using the vascularized bone graft and zygomatic implants. Reconstitutions of the buttresses system ensure a stable base for occlusion, which is essential to optimal functional and esthetic maxillary rehabilitation. Supported by Research Fund (No. 2004BA720A27) of National Tenth Five-Year Project.

Bone Transplantation↗

[The installation of zygomatic implants and drilling guide].

OBJECTIVE: To discuss the technique of installation of zygomatic implants in severely resorbed edentulous maxillae, and maxillary defect. METHODS: Five patients received 8 zygoma implants and 11 dental implants. On the basis of an axial spiral CT data, anatomical models of natural size were manufactured using CAD/CAM system and before operation preoperative measurements of relevant parameters (length, areas, and volumes) carried out. Theses maxillary and zygomatic measurements obtained were referred for installing zygomatic implants. RESULTS: The ideal direction and position of installation of the 8 zygomatic fixtures were obtained in 5 patients. The anatomical model and surgical plate were used for preoperative planning and intraoperative control of the insertion of zygomatic fixtures. The implants could be positioned precisely as preoperatively planned. The length of the zygomatic implants was between 40 mm and 50 mm. CONCLUSIONS: The use of surgical drilling guides should be encouraged for zygomatic implant placement. 3-D image data and anatomical models improves preoperative planning and facilitates clinical procedure.

Adult↗

A time dependent anatomically detailed model of cardiac conduction.

In order to understand the determinants of transitions in cardiac electrical activity from normal patterns to dysrhythmias such as ventricular fibrillation, we are constructing an anatomically and physiologically detailed finite element simulation of myocardial electrical propagation. A healthy human heart embedded in paraffin was sectioned to provide a detailed anatomical substrate for model calculations. The simulation of propagation includes anisotropy in conduction velocity due to fiber orientation as well as gradients in conduction velocities, absolute and relative refractory periods, action potential duration and electrotonic influence of nearest neighbors. The model also includes changes in the behaviour of myocardial tissue as a function of the past local activity. With this model, we can examine the significance of fiber orientation and time dependence of local propagation parameters on dysrhythmogenesis.

Action Potentials↗

Objective structured assessment of technical skills for episiotomy repair.

OBJECTIVE: This study was undertaken to estimate the reliability and validity of an objective structured assessment of technical skills (OSATS) for midline episiotomy repair using a lifelike anatomic model. STUDY DESIGN: Eighteen residents were administered an episiotomy OSATS. Two evaluators independently completed an objective score sheet assessing six key components of the repair, seven global surgical skills, and a pass/fail score for each resident. Residents also completed an anonymous self-assessment. RESULTS: Reliability indices were 0.95 for the checklist and global surgical skills rating. Construct validity found significant differences on the checklist, global surgical skills, and pass/fail score sheets by residency level. Residents more often assessed their own global surgical skills performance lower than the independent evaluators. Surprisingly, 61% (11/18) of the residents failed the assessment, including all postgraduate year 1 and postgraduate year 2 residents. CONCLUSION: Episiotomy OSATS that used task-specific and global checklists provide a reliable and valid method of assessing resident skills in this anatomic model, and performance correlates with resident year level of training.

Clinical Competence↗

Magnetic resonance angiography: from anatomical knowledge modeling to vessel segmentation.

Magnetic resonance angiography (MRA) has become a common way to study cerebral vascular structures. Indeed, it enables to obtain information on flowing blood in a totally non-invasive and non-irradiant fashion. MRA exams are generally performed for three main applications: detection of vascular pathologies, neurosurgery planning, and vascular landmark detection for brain functional analysis. This large field of applications justifies the necessity to provide efficient vessel segmentation tools. Several methods have been proposed during the last fifteen years. However, the obtained results are still not fully satisfying. A solution to improve brain vessel segmentation from MRA data could consist in integrating high-level a priori knowledge in the segmentation process. A preliminary attempt to integrate such knowledge is proposed here. It is composed of two methods devoted to phase contrast MRA (PC MRA) data. The first method is a cerebral vascular atlas creation process, composed of three steps: knowledge extraction, registration, and data fusion. Knowledge extraction is performed using a vessel size determination algorithm based on skeletonization, while a topology preserving non-rigid registration method is used to fuse the information into the atlas. The second method is a segmentation process involving adaptive sets of gray-level hit-or-miss operators. It uses anatomical knowledge modeled by the cerebral vascular atlas to adapt the parameters of these operators (number, size, and orientation) to the searched vascular structures. These two methods have been tested by creating an atlas from a 18 MRA database, and by using it to segment 30 MRA images, comparing the results to those obtained from a region-growing segmentation method.

Algorithms↗

Web-based viewer for systematic combination of anatomy and nomenclature.

Integrating anatomic nomenclature with geometric anatomic data via a web interface and providing illustration and visualization tools presents numerous challenges. We have developed a library of anatomic models and methods for navigating anatomic nomenclature. Based on the library and tools, we have developed a simple, yet powerful, open web-based tool that uses tree navigation and selection for assembling and downloading self-documenting anatomic scenes in Virtual Reality Modeling Language.

Computer Simulation↗

Can synthetic bone models approximate the mechanical properties of cadaveric first metatarsal bone?

The authors evaluated the value of plastic foam models for approximating the mechanical properties of cadaveric bone. Three mechanical tests (3-point bending, cantilevered load to failure, screw push-out) were performed to evaluate the performance of fresh (nonpreserved) human metatarsals, plastic solid foam anatomic models, and modified anatomic models. The test results indicate that plastic models may simulate the mechanical properties of natural bone in tests in which only elastic deformation is achieved. However, under circumstances where load is applied until material failure, the mechanical properties vary dramatically. These tests indicate that specific goals should be established with these results in mind, when planning mechanical testing studies with either plastic or cadaveric models.

Biomechanical Phenomena↗

Prediction of the range of hand positions available to a patient with movement restrictions at the joints of the upper limb--a mathematical model.

A mathematical model has been constructed to predict the workspaces available to patients with reduced ranges of motion at the joints of the upper limb. The model uses the inverse kinematic method of Benati et al. (1982) together with simplified anatomical data. Comparisons with experimental data (Dempster, 1955) show significant discrepancies which are believe to be due to differences in scapular constraint and to simplified anatomical modelling. It is intended to improve the anatomical model by the use of the published data of Eyclesheimer and Shoemaker (1911). Despite the discrepancies, the model already detects significant differences between normal workspaces and those of patients with restriction at the joints of the upper limb. It is believed that this model could, when incorporated with empirical data, form the basis of an "expert" system to assist the therapist and clinician in the planning of rehabilitation of the upper limb.

Activities of Daily Living↗

Preformed acrylic cranial implants using fused deposition modeling: a clinical report.

Fabrication of acrylic cranial implants by conventional methods of moulage and mold formation may be difficult when the margin of the defect cannot be accurately detected. Three-dimensional anatomic models built by fused deposition modeling can serve as templates for the fabrication of custom acrylic implants for large or complicated cranial defects. Virtual mirror imaging of the contralateral nondefect side can facilitate the restoration of symmetry in appearance-sensitive areas. This clinical report presents a method for the fabrication of cranial implants for 2 patients using anatomic modeling technology.

Acrylic Resins↗

Three-dimensional surface model analysis in the gastrointestinal tract.

The biomechanical changes during functional loading and unloading of the human gastrointestinal (GI) tract are not fully understood. GI function is usually studied by introducing probes in the GI lumen. Computer modeling offers a promising alternative approach in this regard, with the additional ability to predict regional stresses and strains in inaccessible locations. The tension and stress distributions in the GI tract are related to distensibility (tension-strain relationship) and smooth muscle tone. More knowledge on the tension and stress on the GI tract are needed to improve diagnosis of patients with gastrointestinal disorders. A modeling framework that can be used to integrate the physiological, anatomical and medical knowledge of the GI system has recently been developed. The 3-D anatomical model was constructed from digital images using ultrasonography, computer tomography (CT) or magnetic resonance imaging (MRI). Different mathematical algorithms were developed for surface analysis based on thin-walled structure and the finite element method was applied for the mucosa-folded three layered esophageal model analysis. The tools may be useful for studying the geometry and biomechanical properties of these organs in health and disease. These studies will serve to test the structure-function hypothesis of geometrically complex organs.

Algorithms↗

Computational analysis of subthalamic nucleus and lenticular fasciculus activation during therapeutic deep brain stimulation.

The subthalamic nucleus (STN) is the most common target for the treatment of Parkinson's disease (PD) with deep brain stimulation (DBS). DBS of the globus pallidus internus (GPi) is also effective in the treatment of PD. The output fibers of the GPi that form the lenticular fasciculus pass in close proximity to STN DBS electrodes. In turn, both STN projection neurons and GPi fibers of passage represent possible therapeutic targets of DBS in the STN region. We built a comprehensive computational model of STN DBS in parkinsonian macaques to study the effects of stimulation in a controlled environment. The model consisted of three fundamental components: 1) a three-dimensional (3D) anatomical model of the macaque basal ganglia, 2) a finite element model of the DBS electrode and electric field transmitted to the tissue medium, and 3) multicompartment biophysical models of STN projection neurons, GPi fibers of passage, and internal capsule fibers of passage. Populations of neurons were positioned within the 3D anatomical model. Neurons were stimulated with electrode positions and stimulation parameters defined as clinically effective in two parkinsonian monkeys. The model predicted axonal activation of STN neurons and GPi fibers during STN DBS. Model predictions regarding the degree of GPi fiber activation matched well with experimental recordings in both monkeys. Only axonal activation of the STN neurons showed a statistically significant increase in both monkeys when comparing clinically effective and ineffective stimulation. Nonetheless, both neural targets may play important roles in the therapeutic mechanisms of STN DBS.

Animals↗

A veterinary digital anatomical database.

This paper describes the Veterinary Digital Anatomical Database Project. The purpose of the project is to investigate the construction and use of digitally stored anatomical models. We will be discussing the overall project goals and the results to date. Digital anatomical models are 3 dimensional, solid model representations of normal anatomy. The digital representations are electronically stored and can be manipulated and displayed on a computer graphics workstation. A digital database of anatomical structures can be used in conjunction with gross dissection in teaching normal anatomy to first year students in the professional curriculum. The computer model gives students the opportunity to "discover" relationships between anatomical structures that may have been destroyed or may not be obvious in the gross dissection. By using a digital database, the student will have the ability to view and manipulate anatomical structures in ways that are not available through interactive video disk (IVD). IVD constrains the student to preselected views and sections stored on the disk.

Anatomy, Veterinary↗

Pulsed and color Doppler analysis of normal carotid bifurcation flow dynamics using an in-vitro model.

An anatomically accurate model of the human carotid bifurcation was studied by using color Doppler flow mapping and pulsed Doppler signal analysis. In concordance with dye injection studies, a zone of flow separation was clearly demonstrated at the origin of the internal carotid artery opposite the flow divider. This zone of flow reversal was detected when the ratio of external to common carotid flow rates was greater than 0.27 and became progressively larger as the ratio increased, finally evolving into a zone of heterogenous flow at a ratio greater than 0.5. The authors conclude that the zone of flow reversal seen in the human carotid artery is a geometric property of the bifurcation and that its size depends on the relative flow between both branches. Doppler color imaging can be used to noninvasively map out its extent.

Blood Flow Velocity↗

Quantitative evaluation of arterial pulsatile flow and pressure, applying impedance plethysmography to a human arterial model incorporating anatomical branching and scale.

This paper presents the theoretical basis of a new noninvasive method for obtaining arterial pulsatile flow and pressure. The proposed technique uses a model of the human arterial system based on the anatomical branching structure of the arterial tree. Arteries are divided into segments represented by uniform thin-walled elastic tubes with realistic arterial dimensions and wall properties. A simple mathematical model equivalent to electrical transmission lines is developed which is able to fit the electrical impedance plethysmograph waveform produced by the subjects throughout the complete cardiac cycle. Ensemble averaging is suggested as an option for processing of the impedance data. This technique provides artifact-free impedance data which enables the model to be used during exercise as well as quiet breathing. The proposed model provides an enhanced capability for measuring pulsatile blood flow and pressure in both clinical and research applications.

Arteries↗