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Results for “Models, Anatomic”

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PubMed1999

[Theoretical bases of semiology in pediatric psychiatry. I. Theoretical models].

This paper is the first part of a study on the theoretic concepts used in child psychiatry and their functioning during the first consultations with a child and his family. These models have different origins (medicine, psychology, education) and contribute to the true specificity of child psychiatry, which must take into account both the developmental aspect as in pediatrics, and the peculiarity of the human psyche. This gives a special stamp to child psychopathology and some usual ways of thinking (like normality, comparability) are quickly inoperative. The five main theoretic models available in child psychiatry are recalled: the model of the medical semiology which describes symptoms and gives them value, the clinical-anatomical model which tries to set up relationships between structure and function, the developmental and cognitive model which emphasizes the psychomotor and intellectual abilities of the child, the affective model (psychoanalysis and attachment) which studies his/her emotional development, and the environmental model which set the child in his/her conditions of growth. These models only support the thoughts of the consultant who must keep in mind the psychic development as a whole and try to aggregate all his findings in the various fields to extract the main features underlying the child's difficulties.

Affect↗

PubMed2005

Models of brain function in neuroimaging.

Inferences about brain function, using neuroimaging data, rest on models of how the data were caused. These models can be quite diverse, ranging from conceptual models of functional anatomy to nonlinear mathematical models of hemodynamics. However, they all have to be internally consistent because they model the same thing. This consistency encompasses many levels of description and places constraints on the statistical models, adopted for data analysis, and the experimental designs they embody. The aim of this review is to introduce the key models used in imaging neuroscience and how they relate to each other. We start with anatomical models of functional brain architectures, which motivate some of the fundaments of neuroimaging. We then turn to basic statistical models (e.g., the general linear model) used for making classical and Bayesian inferences about where neuronal responses are expressed. By incorporating biophysical constraints, these basic models can be finessed and, in a dynamic setting, rendered causal. This allows us to infer how interactions among brain regions are mediated.

Biophysical Phenomena↗

PubMed2004

Sensitivity of the results produced by the inverse dynamic analysis of a human stride to perturbed input data.

The results of the inverse dynamic procedures used in gait analysis are known to be highly dependent on the quality of the kinematic and dynamic input data and on the biomechanical model anatomical data. In this paper the sensitivities of the system response to imprecision in the input data and biomechanical model were calculated. It was shown that the gait analysis results were very sensitive to the identification of the point of application of the external forces. The quality of the results was less sensitive to errors made during motion reconstruction and to uncertainties in the biomechanical anatomical data. In this study it is also shown that the adopted inverse dynamic analysis method, based on natural coordinates, effectively shielded any error made on a particular kinematic chain from propagation to other branches of the biomechanical model.

Biomechanical Phenomena↗

PubMed2004

Numerical evaluation of heating of the human head due to magnetic resonance imaging.

In this paper, we present a numerical model for evaluating tissue heating during magnetic resonance imaging (MRI). Our method, which included a detailed anatomical model of a human head, calculated both the electromagnetic power deposition and the associated temperature elevations during an MRI head examination. Numerical studies were conducted using a realistic birdcage coil excited at frequencies ranging from 63 to 500 MHz. The model was validated both experimentally and analytically. The experimental validation was performed at the MR test facility located at the Food and Drug Administration's Center for Devices and Radiological Health.

Body Burden↗

PubMed1998

Psychoneuroendocrinology of anxiety disorders.

This article focuses on neuroendocrine measures in anxiety disorders and their relationships to neurotransmitter and neuroendocrine function. In particular, the hypothalamic-pituitary-somatotropin and the hypothalamic-pituitary-adrenal (HPA) axes are emphasized, and a role for extrahypothalamic corticotropin releasing factor is proposed. Additional neuroactive hormones are also considered. A nonhuman primate model of anxiety is discussed in terms of its neuroendocrine relevance. And, throughout, a hypothetical functional-anatomic model for anxiety and panic is proposed using the findings of cognitive neuroscience fear research. Finally, an effort is made to synthesize existing psychoneuroendocrinologic data into a current conceptualization of the pathophysiology of anxiety disorders.

Adrenal Cortex Hormones↗

PubMedDate not supplied

[Radiopharmacokinetic and gammagraphic studies for calculating personalized dosimetry].

In nuclear medicine radiation absorbed doses are important in the patient's risk/benefit evaluation and are estimated by means of biological and complex mathematical models. The biological model includes radiopharmacokinetic data obtained through blood and urine samples taken at given intervals. A useful mathematical model is the MIRD model and with the value for the time of residence tau the MIRDOSE3 computer program uses several anatomic models and calculates radiation absorbed dose for 25 organs. At the Radiopharmacy Unit of the Nuclear Medicine Department at INCMNSZ two new bone seeking radiopharmaceuticals, 99mTc-ABP and 188Re-ABP, have been designed, characterized and animal-tested. Radiopharmaceutical parameters and sequential scanning were obtained for diagnostic 99mTc-ABP in 10 normal subjects and the aim was to use % 24 hour urine elimination and % bone uptake to calculate radiation absorbed dose and extrapolate the values to 188Re-ABP as the basis for a therapeutic treatment. 99mTc-ABP was eliminated in women's urine 63.2 +/- 7.3%/activity and 70 +/- 11%/activity in men. In women 36.8 +/- 7.3% of the radiopharmaceutical remains on the bone surface and in men 30 +/- 11%. ROIs were drawn on the images and the time-integrated renal cpm/pixel/ROI gave a residence time tau = 0.52 h. Cumulative bone activity A calculated with A = 1.443 (T1/2) A0 was 2358 +/- 469 MBq h for women and 1923 +/- 707 MBq h for men. Residence time tau was 3.19 +/- 0.63 h in women and 2.6 +/- 0.95 h in men. Radiation absorbed dose for the whole body was 0.0020 +/- 0.0004 mGy/MBq for women and 0.0013 +/- 0.0005 mGy/MBq for men. For women's bone marrow it was 0.0063 +/- 0.0013 mGy/MBq and for men 0.0041 +/- 0.0015 mGy/MBq. 188Re-ABP behaves as 99mTc-ABP therefore, the effective dose given by 188Re, a beta emitter, would be for women 0.0936 mSv/MBq and for men 0.0608 mSv/MBq. These characteristics and the radionuclidic characteristics of 188Re indicate that 188Re-ABP might be a good bone metastases pain palliation radiopharmaceutical.

Adult↗

PubMedDate not supplied

Mapping between MR brain images and a voxel model.

This paper describes an approach to establish the correspondence between a magnetic resonance (MR) image of the brain and a slice through a 3D anatomical model. The model is of voxel structure that symbolically labels primary tissue types such as grey matter, white matter, CSF, etc. In this approach a slice is first searched for in the model to achieve the best general match with the brain MR image in question. The operation involves a minimization of parameters such as position, rotation, slant, tilt and enlargement. Having thus found a globally good registration between the image and the model, local matches that link every pixel in the image through to the model slice are then searched for. This pixel-by-pixel match is expressed within a pair of maps, one for the vertical deformation and the other for the horizontal one. The matching algorithm consists of a series of octave separated blurring convolutions combined with exhaustive grey-valued correlation. Because every pixel in the model slice is labelled in terms of its tissue type, and because every pixel in the image has been matched directly to the model, every pixel in the image is now classified. This classification is used directly to perform segmentation which serves as a basis for the computation of medically relevant indices.

Algorithms↗

PubMed1995

Opioid-receptor mRNA expression in the rat CNS: anatomical and functional implications.

The cloning of the opioid receptors has profoundly affected our understanding of opioid-receptor expression, regulation and function. This review focuses on the impact that cloning has had on our understanding of opioid-receptor anatomy, and provides broad anatomical maps of the three opioid-receptor mRNAs in relation to their binding sites. In addition, three model anatomical systems, the nigrostriatal and mesolimbic dopamine systems, the hypothalamic neuroendocrine axes, and the ascending and descending pain pathways, have been highlighted to discuss issues of receptor transport, trafficking and pre- versus postsynaptic localization.

Animals↗

PubMed1999

Ultrasound power deposition model for the chest wall.

An ultrasound power deposition model for the chest wall was developed based on secondary-source and plane-wave theories. The anatomic model consisted of a muscle-ribs-lung volume, accounted for wave reflection and refraction at muscle-rib and muscle-lung interfaces, and computed power deposition due to the propagation of both reflected and transmitted waves. Lung tissue was assumed to be air-equivalent. The parts of the theory and numerical program dealing with reflection were experimentally evaluated by comparing simulations with acoustic field measurements using several pertinent reflecting materials. Satisfactory agreement was found. A series of simulations were performed to study the influence of angle of incidence of the beam, frequency, and thickness of muscle tissue overlying the ribs on power deposition distributions that may be expected during superficial ultrasound (US) hyperthermia of chest wall recurrences. Both reflection at major interfaces and attenuation in bone were the determining factors affecting power deposition, the dominance of one vs. the other depending on the angle of incidence of the beam. Sufficient energy is reflected by these interfaces to suggest that improvements in thermal doses to overlying tissues are possible with adequate manipulation of the sound field (advances in ultrasonic heating devices) and prospective treatment planning.

Computer Simulation↗

PubMed2004

3-D anatomically based dynamic modeling of the human knee to include tibio-femoral and patello-femoral joints.

An anatomical dynamic model consisting of three body segments, femur, tibia and patella, has been developed in order to determine the three-dimensional dynamic response of the human knee. Deformable contact was allowed at all articular surfaces, which were mathematically represented using Coons' bicubic surface patches. Nonlinear elastic springs were used to model all ligamentous structures. Two joint coordinate systems were employed to describe the six-degrees-of-freedom tibio-femoral (TF) and patello-femoral (PF) joint motions using twelve kinematic parameters. Two versions of the model were developed to account for wrapping and nonwrapping of the quadriceps tendon around the femur. Model equations consist of twelve nonlinear second-order ordinary differential equations coupled with nonlinear algebraic constraint equations resulting in a Differential-Algebraic Equations (DAE) system that was solved using the Differential/Algebraic System Solver (DASSL) developed at Lawrence Livermore National Laboratory. Model calculations were performed to simulate the knee extension exercise by applying non-linear forcing functions to the quadriceps tendon. Under the conditions tested, both "screw home mechanism" and patellar flexion lagging were predicted. Throughout the entire range of motion, the medial component of the TF contact force was found to be larger than the lateral one while the lateral component of the PF contact force was found to be larger than the medial one. The anterior and posterior fibers of both anterior and posterior cruciate ligaments, ACL and PCL, respectively, had opposite force patterns: the posterior fibers were most taut at full extension while the anterior fibers were most taut near 90 degrees of flexion. The ACL was found to carry a larger total force than the PCL at full extension, while the PCL carried a larger total force than the ACL in the range of 75 degrees to 90 degrees of flexion.

Computer Simulation↗

PubMed2005

Biologic mechanical advantages of 3 different cranial bone grafting techniques for implant reconstruction of the atrophic maxilla.

PURPOSE: The purpose of this study was to test the mechanical capacities of 3 different bone grafting techniques in the atrophic maxilla when co-stabilized with dental implants. Reconstruction of the atrophic maxilla is a difficult clinical challenge and implants cannot be placed without adequate bone. METHODS: The biomechanical performance of 3 different grafting techniques was evaluated in vitro using a maxillary model, cadaveric cranial bone blocks, and dental implants. A maxillary model fabricated from polyurethane (sawbone) was selected as a substrate for this study because of consistency in shape, size, and mechanical properties. This anatomic model was more consistent than different cadaveric maxilla, where significant variation was found to exist among atrophic specimens. Cadaveric cranial bone graft blocks were secured to the model maxilla (sandwich, ridge only, and sinus inlay) with a dental implant. The strength of the implant/bone graft complex was tested to failure in an Instron machine (Instron Inc, Canton, MA). RESULTS: The 3 bone grafting methods showed significantly different deformation and strength characteristics. The sandwich technique enhanced resistance to deformation under higher imposed loads. The location of the graft influenced the overall mechanical performance (eg, the ridge onlay) and showed a significantly higher resistance to compressive loads applied toward the alveolar ridge (mastication force). CONCLUSION: The ridge onlay grafting procedures created a higher biomechanical tolerance to imposed load than the sinus grafting (sinus inlay). Sinus grafting, although successful, was not the most ideal location for immediate mechanical loading resistance when compared with ridge augmentation in this in vitro model.

Alveolar Bone Loss↗

PubMed2002

On the metrics and euler-lagrange equations of computational anatomy.

This paper reviews literature, current concepts and approaches in computational anatomy (CA). The model of CA is a Grenander deformable template, an orbit generated from a template under groups of diffeomorphisms. The metric space of all anatomical images is constructed from the geodesic connecting one anatomical structure to another in the orbit. The variational problems specifying these metrics are reviewed along with their associated Euler-Lagrange equations. The Euler equations of motion derived by Arnold for the geodesics in the group of divergence-free volume-preserving diffeomorphisms of incompressible fluids are generalized for the larger group of diffeomorphisms used in CA with nonconstant Jacobians. Metrics that accommodate photometric variation are described extending the anatomical model to incorporate the construction of neoplasm. Metrics on landmarked shapes are reviewed as well as Joshi's diffeomorphism metrics, Bookstein's thin-plate spline approximate-metrics, and Kendall's affine invariant metrics. We conclude by showing recent experimental results from the Toga & Thompson group in growth, the Van Essen group in macaque and human cortex mapping, and the Csernansky group in hippocampus mapping for neuropsychiatric studies in aging and schizophrenia.

Algorithms↗

PubMed1997

Virtual reality (VR) techniques in orthopaedic research and practice.

Modeling the musculoskeletal joint system using biomechanical analysis and computer graphics techniques allows us to visualize normal, diseased and reconstructed joint function. This model can be used to study the loading of bones and joints under theoretical and simulated activities. In this study, intact cadavers were imaged using MRI, CT scanning and cryo-sectioning techniques. Using sequential pixel information of bone and soft tissue boundaries collected from digital camera images, MRI and CT scans, the volumetric models of the musculoskeletal joint system are reconstructed. "Descriptive geometry" techniques which treat bones as rigid bodies and cartilage, ligament and muscles as deformable bodies were used to construct the model. Joint resultant forces and moments were determined using an inverse dynamics formulation, while ligament tension, joint contact pressure, and bone stresses are solved through a simplified Rigid Body Spring Modeling technique and the Finite Element Method. The results under static and dynamic loading activities can be visualized using interactive computer graphics. The advantages of such a model are the elimination of the need for large numbers of intact cadaveric specimens, and the unprecedented capability to study joint loading responses under normal, abnormal and surgically reconstructed states. Such a model and its analytical capability are ideal for pre-operative planning and computer-assisted orthopaedic surgery. This Visual, Interactive, Computational, and Anatomic Model(VICAM) and its associated analysis capability represent the next generation of technology which will have an enormous impact in orthopaedic research, education and patient care.

Biomechanical Phenomena↗

PubMed2000

Fear and anxiety: animal models and human cognitive psychophysiology.

The aim of this paper is to explicate what is special about emotional information processing, emphasizing the neural foundations that underlie the experience and expression of fear. A functional, anatomical model of defense behavior in animals is presented and applications are described in cognitive and physiological studies of human affect. It is proposed that unpleasant emotions depend on the activation of an evolutionarily primitive subcortical circuit, including the amygdala and the neural structures to which it projects. This motivational system mediates specific autonomic (e.g., heart rate change) and somatic reflexes (e.g., startle change) that originally promoted survival in dangerous conditions. These same response patterns are illustrated in humans, as they process objective, memorial, and media stimuli. Furthermore, it is shown how variations in the neural circuit and its outputs may separately characterize cue-specific fear (as in specific phobia) and more generalized anxiety. Finally, again emphasizing links between the animal and human data, we focus on special, attentional features of emotional processing: The automaticity of fear reactions, hyper-reactivity to minimal threat-cues, and evidence that the physiological responses in fear may be independent of slower, language-based appraisal processes.

Animals↗

PubMed2007

The use of a new 3D splint and double CT scan procedure to obtain an accurate anatomic virtual augmented model of the skull.

Three-dimensional (3D) virtual planning of orthognathic surgery requires detailed visualization of the interocclusal relationship. The purpose of this study was to introduce the modification of the double computed tomography (CT) scan procedure using a newly designed 3D splint in order to obtain a detailed anatomic 3D virtual augmented model of the skull. A total of 10 dry adult human cadaver skulls were used to evaluate the accuracy of the automatic rigid registration method for fusion of both CT datasets (Maxilim, version 1.3.0). The overall mean registration error was 0.1355+/-0.0323 mm (range 0.0760-0.1782 mm). Analysis of variance showed a registration method error of 0.0564 mm (P < 0.001; 95% confidence interval = 0.0491-0.0622). The combination of the newly designed 3D splint with the double CT scan procedure allowed accurate registration and the set-up of an accurate anatomic 3D virtual augmented model of the skull with detailed dental surface.

Adult↗

PubMed1999

Anatomical characteristics and three-dimensional model of the dog dorsal lateral geniculate body.

The morphological and laminar characteristics of the dorsal lateral geniculate nucleus (LGN) and medial interlaminar nucleus (MIN) of the domestic dog (Canis familiaris) were studied by three-dimensional computer reconstruction of labeled retinal afferents following intraocular HRP injections. As previously reported, the dog LGN consisted of layers A, A1, C, C1, C2, and C3. Layers A, C, and C2 receive contralateral-eye inputs, and layers A1 and C1 ipsilateral inputs. The dog MIN was found to have four orderly interdigitating layers; layers 1, 2, 3, and 4, medial to lateral. MIN layers 1 and 3 received contralateral inputs, and layers 2 and 4 ipsilateral inputs. Layer 1 had the largest soma of all LGN/MIN layers. LGN layer A was partially separated into medial and lateral subdivisions by a cleft free of somata. The overall three-dimensional shape of the lateral geniculate body was like the letter C, with the convex part of the C directed posteriorly. The relative volume of the MIN was smaller than in the cat; the canine MIN comprised 8.3% of the combined volume of layers A, A1 and the MIN, while that of the cat comprised 14.2% as estimated from Sanderson's map. The volume of all contralateral-eye layers, combining both LGN and MIN, was 31.2 mm(3) (78%), and that for ipsilateral layers was 8.6 mm(3) (22%). The ratio of ipsilateral to contralateral laminar volumes is much lower in the dog than in the cat.

Animals↗

PubMed2003

Laparoscopic ureterocalicostomy: a feasibility study.

PURPOSE: Ureterocalicostomy is occasionally indicated for reconstruction of recurrent, recalcitrant ureteropelvic junction obstruction associated with postoperative fibrosis and a relatively inaccessible renal pelvis. We investigated the feasibility of performing laparoscopic ureterocalicostomy in a survival porcine model. Anatomical, histological and chronic functional outcomes were evaluated. MATERIALS AND METHODS: Laparoscopic ureterocalicostomy was performed in 10 survival female swine. A ureteropelvic junction obstruction model was created by laparoscopic ligation of a 2 to 3 cm. segment of upper ureter. After an interval of complete ureteropelvic junction obstruction laparoscopic ureterocalicostomy was performed in a manner duplicating the steps of conventional open surgery. After transverse amputation of the lower renal pole end-to-end anastomosis of the proximal ureter to the inferior calix was formed by laparoscopic freehand suturing and knot-tying techniques. RESULTS: Mean ureter stricture length was 2.2 cm. (range 1.7 to 3.1). Mean duration of obstruction before laparoscopic ureterocalicostomy was 6.3 days (range 2 to 18). Mean operative time for laparoscopic ureterocalicostomy was 165.3 minutes (range 105 to 240). Mean estimated blood loss was 145 cc (range 25 to 400). Mean stent duration in 6 pigs was 8.7 days (range 7 to 11). Excretory urograms demonstrated immediate function with symmetrical and unobstructed drainage in all operated renal units. At 4 to 8 weeks of followup no urine leaks were noted and histological examination documented complete urothelial healing without fibrosis or scar formation. CONCLUSIONS: Laparoscopic ureterocalicostomy is technically feasible in the porcine model and it effectively duplicates the established principles of open surgery. Our technique further extends the application of laparoscopic surgery for difficult ureteropelvic junction obstruction.

Anastomosis, Surgical↗

PubMed1998

Spiral breakup as a model of ventricular fibrillation.

The phenomenon of spiral breakup in a 2D and a 3D excitable medium is described. Differences between breakup in two dimensions and in three dimensions are discussed. Spiral breakup in an anatomical model of the ventricles of the heart is also studied. The patterns of excitation in the heart are presented at different wavelengths together with their electrocardiograms. Finally it is suggested that the phenomenon of spiral breakup is a possible mechanism of the ventricular fibrillation (VF). (c) 1998 American Institute of Physics.

Journal Article↗