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At least 55 records · Page 3Linked to original sources
PubMed1991

The use of CT-based 3-D anatomical modeling in the design of customized perineal templates for interstitial gynecologic implants.

A system for preplanning interstitial treatment of gynecologic malignancies with a CT-based 3-dimensional planning system is presented. The preplan produces a custom template design that optimizes catheter placement. The procedure begins with a CT scan with a vaginal cylinder and blank template in place. Contours of the anatomic structures of interest, cylinder, and template are entered into the system, and 3-D surfaces are generated. The first view evaluated is oriented in a "cylinder's-eye view," which shows the path of the catheters placed parallel to the cylinder. In most cases this path to the tumor is obstructed by the pubic bones and bladder. By rotating the view posteriorly, the catheters can travel under the symphysis and bladder to the tumor. Once the optimum angle for visualization of the tumor has been determined, an array of catheters is designed to optimize the dose to the tumor. This array includes the special distribution in the oblique plane as well as the depth of insertion for each catheter. The design is then used in drilling the appropriate guide holes in the template. Orthogonal film dosimetry as well as CT verification of source placement will be compared to the preplan distribution.

Brachytherapy↗
PubMed1995

The N-methyl-D-aspartate antagonists phencyclidine, ketamine and dizocilpine as both behavioral and anatomical models of the dementias.

Phencyclidine (PCP) and ketamine can induce a model psychosis in drug addicts and exacerbate the symptoms of chronic schizophrenics. The model psychoses these drugs induce mimic a variety of schizophrenic symptoms, including flattened affect, dissociative thought disorder, depersonalization and catatonic states. These symptoms can persist for prolonged periods and chronic PCP and ketamine addicts have persisting memory deficits. Dizocilpine (MK-801) is a simpler drug than PCP or ketamine in its actions, but it shares with both the property of blocking in a non-competitive manner the N-methyl-D-aspartate (NMDA) ion-channel. Behavioral observations and drug-discrimination studies in animals indicate that PCP and dizocilpine are similar in their effects and they both have a neurotoxic effect on neurons in posterior cingulate cortex. Recent studies have indicated that both of these drugs, when given continuously for several days, further induce neuronal degeneration in other limbic structures. These include brain regions of rats related to olfaction, associated limbic structures such as piriform cortex and posterior regions of entorhinal cortex and in it's projections, through the perforant pathway, to dentate gyrus and other cells in ventral hippocampus. These degenerative consequences may be excitatory neurotoxic effects, for these compounds also induce an elevation in glucose metabolism maximal in just those structures where degeneration is observed and the degeneration involves entire cells, with all of their processes. It has been suggested these non-competitive NMDA antagonists induce an increase in firing rate in a limbic circuit which includes the perforant pathway. At least some competitive NMDA antagonists induce the same pattern of degeneration and altered glucose utilization. There is anatomical and functional evidence that alterations in these same limbic structures are present in the dementia syndrome manifested by some schizophrenics and most Alzheimer's patients. This suggests that these non-competitive NMDA antagonists may provide a more complete model of psychoses and memory disturbances than previously recognized, in that they can mimic both persisting symptomatology and neuroanatomical abnormalities. While the neurochemical underpinnings of this effect remain elusive, it appears to be both age and sex dependent. Further studies of the mechanisms by which NMDA antagonists induce increased glucose utilization and neurotoxicity in these limbic structures may clarify these alterations in this simplified Papez-like circuit.

Animals↗
PubMed1993

A three-dimensional anatomical model of the human patello-femoral joint, for the determination of patello-femoral motions and contact characteristics.

The object of this study is to develop a three-dimensional mathematical model of the patello-femoral joint, which is modelled as two rigid bodies representing a moving patella and a fixed femur. Two-point contact was assumed between the femur and patella at the medial and lateral sides and in the analysis, the femoral and patellar articular surfaces were mathematically represented using Coons' bicubic surface patches. Model equations include six equilibrium equations and eleven constraints: six contact conditions, four geometric compatibility conditions, and the condition of a rigid patellar ligament; the model required the solution of a system of 17 nonlinear equations in 17 unknowns, its response describing the six-degrees-of-freedom patellar motions and the forces acting on the patella. Patellar motions are described by six motion parameters representing the translations and rotations of the patella with respect to the femur. The forces acting on the patella include the medial and lateral component of patello-femoral contact and the patellar ligament force, all of which were represented as ratios to the quadriceps tendon force. The model response also includes the locations of the medial and lateral contact points on the femur and the patella. A graphical display of its response was produced in order to visualize better the motion of the components of the extensor mechanism. Model calculations show good agreement with experimental results available from the literature. The patella was found to move distally and posteriorly on the femoral condyles as the knee was flexed from full extension. Results indicate that the relative orientation of the patellar ligament with respect to the patella remains unchanged during this motion. The model also predicts a patellar flexion which always lagged knee flexion. Our calculations show that as the angle of knee flexion increased, the lateral contact point moved distally on the femur without moving significantly either medially or laterally. The medial contact point also moved distally on the femur but moved medially from full extension to about 40 degrees of knee flexion, then laterally as the knee flexion angle increased. The lateral contact point on the patella did not change significantly in the medial and lateral direction as the knee was flexed; however, this point moved proximally toward the basis of the patella with knee flexion. The medial contact point also moved proximally on the patella with knee flexion, and in a similar manner the medial contact point on the patella moved distally with flexion from full extension to about 40 degrees of flexion.(ABSTRACT TRUNCATED AT 400 WORDS)

Biomechanical Phenomena↗
PubMed1997

Laparoscopic pelvic lymphadenectomy in an anatomical model: results of an experimental comparative trial.

OBJECTIVES: The aim of this paper was to compare the accuracy of laparoscopic versus open pelvic lymphadenectomy in an experimental trial. STUDY DESIGN: We performed unilateral laparoscopy pelvic lymphadenectomy (LPL) in 33 non-embalmed cadavers between the external iliac vein, the obliterated umbilical artery and the obturator nerve. Then a laparotomy was performed to inspect the LPL limits, look for laparoscopic complications and finally realize a controlateral lymphadenectomy. The LPL side was randomly decided. A pathologist counted the number of lymph nodes collected with both techniques. We compared the number of retrieved lymph nodes, the completeness of the dissection and the complication rate with those two procedures. Student's t-test, chi 2-test and non-parametric tests were used when appropriate. RESULTS: No dissection had to be aborted. One hundred and twelve nodes were removed laparoscopically (mean, 3.73; S.E., 2.9) and 84 at laparotomy (mean, 2.77; S.E., 2.06). There was no significant difference in the number of nodes retrieved with both procedures. Effectiveness of laparoscopy was not significantly different in the first ten procedures, in the second ten or in the last ten LPL. Residual tissue was observed after LPL in 13.3% of the procedures whereas all open lymphadenectomies were complete. LPL sensitivity reached at least 86% in this paper. Failures were more frequent at the beginning of the study (50% among the first ten dissections), in obese subjects or in subjects with prior history of laparotomy (but the difference was not significant). Two venous injuries occurred during LPL (6.7%). Complication rates for the two techniques were not significantly different. However, the LPL complication rate was higher at the beginning of the study and increased significantly in subjects with prior history of laparotomy (P < 0.05). CONCLUSIONS: This randomized study shows that LPL and laparotomy have similar effectiveness. Incomplete dissections and complications are more frequent in obese subjects or in case of prior history of laparotomy. Fifteen procedures seems necessary to learn the technique and provide constant and safe results in routine practice.

Aged↗
PubMed1994

Electrical coupling and impulse propagation in anatomically modeled ventricular tissue.

Computer simulations were used to study the role of resistive couplings on flat-wave action potential propagation through a thin sheet of ventricular tissue. Unlike simulations using continuous or periodic structures, this unique electrical model includes random size cells with random spaced longitudinal and lateral connections to simulate the physiologic structure of the tissue. The resolution of the electrical model is ten microns, thus providing a simulated view at the subcellular level. Flat-wave longitudinal propagation was evaluated with an electrical circuit of over 140,000 circuit elements, modeling a 0.25 mm by 5.0 mm sheet of tissue. An electrical circuit of over 84,000 circuit elements, modeling a 0.5 mm by 1.5 mm sheet was used to study flat-wave transverse propagation. Under normal cellular coupling conditions, at the macrostructure level, electrical conduction through the simulated sheets appeared continuous and directional differences in conduction velocity, action potential amplitude and Vmax were observed. However, at the subcellular level (10 microns) unequal action potential delays were measured at the longitudinal and lateral gap junctions and irregular wave-shapes were observed in the propagating signal. Furthermore, when the modeled tissue was homogeneously uncoupled at the gap junctions conduction velocities decreased as the action potential delay between modeled cells increased. The variability in the measured action potential was most significant in areas with fewer lateral gap junctions, i.e., lateral gap junctions between fibers were separated by a distance of 100 microns or more.

Action Potentials↗
PubMed1992

Transmaxillary-transnasal approach to the anterior clivus: a microsurgical anatomical model.

Numerous procedures to expose the anterior clival region have been described, including the transoral, transcervical, transseptal-transsphenoidal, transantral, transnasal, bilateral Le Fort I maxillotomy, transbasal, transpalatal, and modifications of the Caldwell-Luc approach. Despite the large number of surgical options available, it may be necessary to have wider access to the midline skull base than these approaches provide. We have developed a microsurgical transmaxillary-transnasal approach to the anterior clivus that has been studied in both dry skull and cadaveric preparations and used clinically. The surgical technique has four stages: 1) antromaxillary; 2) nasal; 3) sphenoidal; and 4) clival. The wider access of this approach is achieved mainly by an osteotomy of the frontal process of the maxilla, which transforms the nasal cavity and the antrum into a single cavity while preserving the functional anatomy of the nose. Cosmesis is preserved by replacement of the cartilaginous nasal septum and the frontal process at the end of the procedure. The technique provides the good cosmetic results of the sublabial approaches and prevents vascular and neural injury in the same way that other anterior approaches do. This transmaxillary-transnasal technique may be used in combination with other approaches for extensive tumors.

Adolescent↗
PubMed1992

The three-dimensional architecture of the myosalpinx in mammals: an anatomical model for a functional hypothesis.

Direct visualization of the three-dimensional architecture of the tubal musculature (myosalpinx) was made possible by a technique involving chemical digestion of interstitial connective tissue, followed by ultrasonic microdissection and final observations under the scanning electron microscope. The isthmic myosalpinx in the guinea pig, rabbit and in humans consists of muscular bundles that tend to lie longitudinally, circularly or oblique. The muscular bundles along the tubal wall change direction, branch and intermingle with one another, giving rise to an irregular network in which distinct layers are not readily distinguishable. In the ampulla, the muscle bundles form a very irregular three-dimensional network of fibres that follow different orientations. The authors suggest a primary role for such a structure in the random pendular transport of the gametes as well as in the denudation of the egg by deformation of the myotubal wall.

Animals↗
PubMedDate not supplied

[Total cranio-facial anatomical model of plio-pleistocene hominids].

For a correct assessment of the fossil specimens are analysed ten characters or structural complexes of neuro - and splancno - cranium. Not individual characters but a total pattern, according to Le Gros Clark's original concept, provide a positive identification of hominid single taxon. Following items are examined: 1) facial prognathism; 2) mid-facial architecture; 3) nasal bone, fronto-nasal and fronto-maxillary suture; 4) frontal region morphology; 5) temporal lines and cranial cresting; 6) occipital and nuchal plane; 7) steepness of nuchal plane, foramen magnum position; 8) skull base diagrams; 9) mastoid process and neighbouring regions; 10) size and form of mandibular fossa. To conclude: it is possible a taxonomic classification of plio-pleistocenic hominid specimens on the basis of an analysis of the "total morphological pattern".

Animals↗