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PubMed1985

Quantification of lumbar function. Part 3: Preliminary data on isokinetic torso rotation testing with myoelectric spectral analysis in normal and low-back pain subjects.

A prototype isokinetic torso rotation unit and an EMG signal processing system were utilized to obtain preliminary information on torso rotation. In Study 1, range-of-motion was found to be surprisingly uniform between low-back pain patients and normal subjects, although there was a significant strength variation between them at all isokinetic speeds tested. Both female patients and normal females showed approximately 70%-75% of the strength (torque/body weight) levels relative to their male counterparts. The decrement in trunk strength at high speeds was proportional for both patients and controls and was not nearly as dramatic as the decrement seen in the sagittal plane. In Studies 2 and 3, anatomic relationships evaluated by EMG testing of obliques and erector spinae showed that the contralateral abdominal obliques were the most consistent muscles providing a significant torsional moment to the spine.

Adult↗
PubMed1983

Sternum length, torso length, and internipple distance in newborn infants.

In order to define standards for sternal length, torso length, and internipple distance in the newborn infant, 198 term and preterm infants (27 to 41 gestational weeks) were examined. In every case, the gestational age was determined chronologically and clinically. Sternal and torso length and internipple distance were measured by two observers using standard measurement techniques. Normal values are presented by plotting the mean +/-2 SD for each gestational week v the gestational age.

Anthropometry↗
PubMed1995

Pulmonary failure following lower torso ischemia: clinical evidence for a remote effect of reperfusion injury.

Acute lung injury as a remote sequela of severe lower torso ischemia-reperfusion has been demonstrated experimentally, in a process involving leukosequestration and generation of the arachidonate derivatives thromboxane and leukotriene B4. However, contemporary clinical reports have been limited to development of transient, subclinical "reperfusion pulmonary edema" several hours after declamping in patients undergoing elective abdominal aortic aneurysm repair. This report refocuses attention on the clinical syndrome of severe, acute deterioration in pulmonary function occurring several hours after restoration of perfusion to an ischemic lower torso in two patients. The lung injury is characterized by progressive hypoxemia, pulmonary hypertension, decreased lung compliance, and non-hydrostatic pulmonary edema, consistent with adult respiratory distress syndrome (ARDS). This report reinforces the concept that humoral mediators generated at reflow may induce end-organ injury at a site remote from the focus of ischemia-reperfusion, and that the lung is a target organ.

Aged↗
PubMed1977

Penetrating torso injuries: the role of paracentesis and lavage.

Controversy still exists regarding the proper approach to patients with penetrating torso injuries. Mandatory immediate celiotomy and selective observation both have associated risks. Paracentesis with lavage is a rapid, easily performed and readily available technique which can, with a high degree of accuracy, differentiate on initial evaluation those patients with penetrating visceral injuries from those without such injuries. Complications are minimal. The use of these two procedures in evaluating penetrating torso injuries has led to improved patient care and produced major lowering of medical and socioeconomic costs.

Abdominal Injuries↗
PubMed1997

Evaluation of right and left ventricular volume and ejection fraction using a mathematical cardiac torso phantom.

UNLABELLED: The availability of gated SPECT has increased the interest in the determination of volume and ejection fraction of the left ventricle (LV) for clinical diagnosis. However, the same indices for the right ventricle (RV) have been neglected. The objective of this investigation was to use a mathematical model of the anatomical distribution of activity in gated blood-pool imaging to evaluate the accuracy of two ventricular volume and ejection fraction determination methods. In this investigation, measurements from the RV were emphasized. METHODS: The mathematical cardiac torso phantom, developed to study LV myocardium perfusion, was modified to simulate the radioactivity distribution of a 99mTc-gated blood-pool study. Twenty mathematical cardiac torso phantom models of the normal heart with different LV volumes (122.3 +/- 11.0 ml), RV volumes (174.6 +/- 22.3 ml) and stroke volumes (75.7 +/- 3.3 ml) were randomly generated to simulate variations among patients. An analytical three-dimensional projector with attenuation and system response was used to generate SPECT projection sets, after which noise was added. The projections were simulated for 128 equidistant views in a 360 degrees rotation mode. RESULTS: The radius of rotation was varied between 24 and 28 cm to mimic such variation in patient acquisitions. The 180 degrees and 360 degrees projection sets were reconstructed using the filtered backprojection reconstruction algorithm with Butter-worth filtering. Comparison was made with and without application of the iterative Chang attenuation correction algorithm. Volumes were calculated using a modified threshold and edge detection method (hybrid threshold), as well as a count-based method. A simple background correction procedure was used with both methods. CONCLUSION: Results indicate that cardiac functional parameters can be measured with reasonable accuracy using both methods. However, the count-based method had a larger bias than the hybrid threshold method when RV parameters were determined for 180 degrees reconstruction without attenuation correction. This bias improved after attenuation correction. The count-based method also tended to overestimate the end systolic volume slightly. An improved background correction could possibly alleviate this bias.

Female↗
PubMed1999

Membrane polarization induced in the myocardium by defibrillation fields: an idealized 3-D finite element bidomain/monodomain torso model.

This study develops a three-dimensional finite element torso model with bidomain myocardium to simulate the transmembrane potential (TMP) of the heart induced by defibrillation fields. The inhomogeneities of the torso are modeled as eccentric spherical volumes with both the curvature and the rotation features of cardiac fibers incorporated in the myocardial region. The numerical computation of the finite element bidomain myocardial model is validated by a semianalytic solution. The simulations show that rotation of fiber orientation through the depth of the myocardial wall changes the pattern of polarization and decreases the amount of cardiac tissue polarized compared to the idealized analytic model with no fiber rotation incorporated. The TMP induced by transthoracic and transvenous defibrillation fields are calculated and visualized. The TMP is quantified by a continuous measure of the percentage of myocardial mass above a potential gradient threshold. Using this measure, the root mean square differences in TMP distribution produced by reversing the electrode polarity for anterior-posterior and transvenous electrode configurations are 13.6 and 28.6%, respectively. These results support the claim that a bidomain model of the heart predicts a change of defibrillation threshold with reversed electrode polarity.

Computer Simulation↗
PubMed1990

Treatment of lower torso stages I and II Hodgkin's disease with radiation with or without adjuvant mechlorethamine, vincristine, procarbazine, and prednisone.

From 1956 to 1987, 60 patients with either lymphangiogram-staged or laparotomy-staged I-II lower torso presentations of Hodgkin's disease were treated with radiation with or without Mustargen (mechlorethamine), vincristine, procarbazine, and prednisone (MOPP). In 22 with inguinal/femoral or pelvic disease and 24 with abdominal disease, treatment consisted of radiation only. Fourteen other patients with abdominal disease received MOPP chemotherapy before radiotherapy. In 11, the chemotherapy was limited to two cycles. At 10 years, the determinate survival and freedom from progression rates for all patients were 82% and 72%, respectively. For patients with inguinal/femoral or pelvic disease who were treated with radiation only, the corresponding rates were 90% and 86%. For patients with abdominal disease who received radiation only, the determinate survival and the freedom from progression rates were only 66% and 50%, respectively. However, corresponding results for 14 patients with abdominal disease who were treated with MOPP and radiation were 100% and 92% (P = 0.033 and P = 0.009, respectively.

Abdominal Neoplasms↗
PubMed1991

A realistic torso model for magnetocardiography.

This paper contains the description of an inhomogeneous, multi-compartmental volume conductor model which is in use in our group. Although initially developed for the study of the ECG, it has been found to serve equally well for simulating the magnetocardiogram (MCG), the forward problem, and as a basis for source analysis of the MCG, the inverse problem. For both problems some illustrative examples are included demonstrating the necessity of using an inhomogeneous volume conductor model of the torso, having realistic--preferably tailored--geometry. A simple inverse procedure, based on correlation techniques, is included for the solution of the problem of source localization when an accurate description of the inhomogeneous volume conductor is available.

Adult↗
PubMed2005

Rapid construction of a patient-specific torso model from 3D ultrasound for non-invasive imaging of cardiac electrophysiology.

One of the main limitations in using inverse methods for non-invasively imaging cardiac electrical activity in a clinical setting is the difficulty in readily obtaining high-quality data sets to reconstruct accurately a patient-specific geometric model of the heart and torso. This issue was addressed by investigation into the feasibility of using a pseudo-3D ultrasound system and a hand-held laser scanner to reconstruct such a model. This information was collected in under 20 min prior to a catheter ablation or pacemaker study in the electrophysiology laboratory. Using the models created from these data, different activation field maps were computed using several different inverse methods. These were independently validated by comparison of the earliest site of activation with the physical location of the pacing electrodes, as determined from orthogonal fluoroscopy images. With an estimated average geometric error of approximately 8 mm, it was also possible to reconstruct the site of initial activation to within 17.3 mm and obtain a quantitatively realistic activation sequence. The study demonstrates that it is possible rapidly to construct a geometric model that can then be used non-invasively to reconstruct an activation field map of the heart.

Cardiac Pacing, Artificial↗
PubMed1994

Forward problem of electrocardiography: construction of human torso models and field calculations using finite element method.

Finite element models of the human torso were constructed using anatomical data measured by serial computerised tomography scans in a subject. A first set of three models with a mesh resolution of 5517 nodes and 29810 elements included an homogeneous conductivity, lungs inhomogeneity, and heart, lungs and spinal region inhomogeneities. A second set comprised similar models with a mesh resolution of 12084 nodes and 67045 elements. A cylindrically shaped volume conductor was also constructed to evaluate the convergency and accuracy of the finite element solutions by comparison with the analytical solution. Forward simulations were performed using different excitation sites on the cardiac surface. The inclusion of conductivity inhomogeneities altered the maximum and minimum values of the body surface potentials, but did not substantially modify the pattern of the potential distributions. The greatest effect was due to the inclusion of the lungs. Increasing the mesh resolution from 5517 to 12084 nodes did not change noticeably the shape or amplitude of the simulated body surface potential maps. These models can readily be used for other bioelectromagnetic problems.

Electrocardiography↗
PubMed2005

Vortex shaped current sources in a physical torso phantom.

Recent studies reported differential information in human magnetocardiogram and in electrocardiogram. Vortex currents have been discussed as a possible source of this divergence. With the help of physical phantom experiments, we quantified the influence of active vortex currents on the strength of electric and magnetic signals, and we tested the ability of standard source localization algorithms to reconstruct vortex currents. The active vortex currents were modeled by a set of twelve single current dipoles arranged in a circle and mounted inside a phantom that resembles a human torso. Magnetic and electric data were recorded simultaneously while the dipoles were switched on stepwise one after the other. The magnetic signal strength increased continuously for an increasing number of dipoles switched on. The electric signal strength increased up to a semicircle and decreased thereafter. Source reconstruction with unconstrained focal source models performed well for a single dipole only (less than 3-mm localization error). Minimum norm source reconstruction yielded reasonable results only for a few of the dipole configurations. In conclusion active vortex currents might explain, at least in part, the difference between magnetically and electrically acquired data, but improved source models are required for their reconstruction.

Action Potentials↗
PubMed1990

Analysis of cytoplasmic activity dependent on the Drosophila terminal pattern gene torso.

Cytoplasm from wildtype Drosophila embryos was transplanted into torso (tor) mutant embryos to determine the distribution of terminal rescuing activity at the cleavage stage. Although posterior and lateral wildtype cytoplasm contained rescuing activity that restored posterior terminal (telson) structures Klingler et al. (1988, Nature (London) 335, 275-277) this rescuing activity was not found in anterior cytoplasm. Similarly, transplantation of anterior and lateral wildtype cytoplasm into the anterior of tor embryos rescued anterior terminal (acron) structures, whereas posterior cytoplasm did not. This failure of reciprocal rescue is due to the presence of the products of the anterior and posterior classes of genes, because anterior cytoplasm from bicoid mutant embryos restored the telson in the posterior as well as the acron in the anterior of tor embryos, and because posterior cytoplasm from nanos embryos rescued the acron in the anterior as well as the telson in the posterior of tor embryos. Therefore terminal rescuing activity is evenly distributed throughout the cleavage stage embryo as anticipated from molecular studies.

Animals↗
PubMed1989

Anatomic localization of a single electrical source within the boundary of the human torso.

A closed prolate ellipsoid was used to approximate the surface of the Rush torso model to permit recovery of the site and orientation of known dipoles in 15 cardiac locations. Localization was found to be reasonably close, usually within 2 cm. When body surface potential maps of 37 subjects with right ventricular pacemakers were similarly treated, the discrepancy between known pacemaker site and the site of earliest activation was relatively large (mean, greater than 4 cm) and rapidly increased within the ensuing millisecond. The discrepancy not only emphasizes the wide variation in body shape and tissue distribution in living subjects, but also points to probable physical separation between stimulus site and earliest detectable activation site because of ischemia, infarction, or myocardial response to variation in current strength of the stimulus.

Cardiac Pacing, Artificial↗
PubMed1989

Computational issues of importance to the inverse recovery of epicardial potentials in a realistic heart-torso geometry.

In vitro data from a realistic-geometry electrolytic tank were used to demonstrate the consequences of computational issues critical to the ill-posed inverse problem in electrocardiography. The boundary element method was used to discretize the relationship between the body surface potentials and epicardial cage potentials. Variants of Tikhonov regularization were used to stabilize the inversion of the body surface potentials in order to reconstruct the epicardial surface potentials. The computational issues investigated were (1) computation of the regularization parameter; (2) effects of inaccuracy in locating the position of the heart; and (3) incorporation of a priori information on the properties of epicardial potentials into the regularization methodology. Two methods were suggested by which a priori information could be incorporated into the regularization formulation: (1) use of an estimate of the epicardial potential distribution everywhere on the surface and (2) use of regional bounds on the excursion of the potential. Results indicate that the a posteriori technique called CRESO, developed by Colli Franzone and coworkers, most consistently derives the regularization parameter closest to the optimal parameter for this experimental situation. The sensitivity of the inverse computation in a realistic-geometry torso to inaccuracies in estimating heart position are consistent with results from the eccentric spheres model; errors of 1 cm are well tolerated, but errors of 2 cm or greater result in a loss of position and amplitude information. Finally, estimates and bounds based on accurate, known information successfully lower the relative error associated with the inverse and have the potential to significantly enhance the amplitude and feature position information obtainable from the inverse-reconstructed epicardial potential map.

Animals↗
PubMed1993

Down-regulation of the Drosophila morphogen bicoid by the torso receptor-mediated signal transduction cascade.

Anterior body pattern in Drosophila is specified by the graded distribution of the bicoid protein (bcd), which activates subordinate genes in distinct anterior domains. Subsequently, transcription of these target genes is repressed at the anterior pole owing to the activity of the receptor tyrosine kinase torso (tor). We show that both activation by bcd and repression by tor can be reproduced by a minimal promoter containing only bcd-binding sites upstream of a naive transcriptional start site. Repression requires the D-raf kinase and is associated with phosphorylation of bcd protein. Repression does not require either tailless or huckebein, which were previously thought to constitute the sole zygotic output of the tor signaling system. Finally, addition of a heterologous transcriptional activation domain to bcd renders the protein insensitive to tor-mediated repression. We propose that phosphorylation resulting from the activity of the tor signal transduction cascade down-regulates transcriptional activation by the bcd morphogen.

Animals↗
PubMed1996

Development and evaluation of a scalable and deformable geometric model of the human torso.

A model is developed to provide a geometric representation of the human spine including thoracic and lumbar motion segments, lumbar muscles, ribs, sternum, sacrum, and pelvis. An existing model was modified in order to allow for scaling using standard anthropometric measures, deformation to specific 3-dimensional postures using surface markers, and incorporation of muscle length-tension and motion segment passive bending properties. Experiments were performed to evaluate the accuracy of model postural predictions. Analysis of surface marker displacements demonstrated that the thoracic spine deforms only minimally over a range of flexion, extension, and lateral bending torso postures, suggesting that it can be treated as essentially rigid during low-weight lifting over the range of passive flexibility. Locations of bony landmarks were accurately reproduced (mean errors 2.9-6.8 mm) as were several body dimensions (mean differences 2.6-15.4 mm). It is concluded that linear scaling to subject-specific anthropometry and the use of specific surface markers provides an accurate and direct technique for describing spinal geometry. Predicted passive spinal moments were found to be comparable to those required to support body weight in different extreme postures. It is recommended that data obtained from this type of model be incorporated in future investigations of spinal loading.

Journal Article↗
PubMed1992

Evaluation of the Lawrence Livermore National Laboratory (LLNL) torso phantom by bone densitometry and x-ray.

The recent Workshop on Standard Phantoms recommended that the LLNL torso phantom be adopted as a calibration standard for the quantitation of in vivo radioactivity. This phantom was designed for the calibration of systems for the detection of x-rays of less than 20 keV. The anthropomorphic characteristics and tissue substitute composition of the phantom were assessed with techniques using photons of higher energy. Dual photon absorptometry at 42 and 100 keV showed that the phantom was representative of in vivo tissue composition. Chest radiography showed that the phantom was representative of a human even though the stomach, GI tract and the scapulae were not present and air gaps were observed at organ boundaries.

Absorptiometry, Photon↗
PubMed2006

An evaluation of backpack harness systems in non-neutral torso postures.

Much of the research on backpack design has been focused on spinal loading/biomechanics while the wearer is in a neutral/upright trunk posture, such as those employed by outdoor enthusiasts and schoolchildren. This research has led to some important harness design improvements that reduce trunk muscle exertions, fatigue and improve overall comfort. There are number of occupations, however, wherein workers wear back-mounted packs/devices (e.g. air tanks) while working in non-neutral trunk postures. The objective of the current study was to evaluate the effects of these non-neutral postures on biomechanical loading and then reconsider the backpack system design recommendations. Fifteen participants were asked to support a 18.2 kg load on their back while assuming static forward flexed postures of the torso (15 degrees , 30 degrees , 45 degrees , and 60 degrees of sagittal bend). The mass on the back was attached to the participant through two different harness mechanisms: a basic harness design (as seen on college student backpacks) and a more advanced design containing lateral stiffness rods and a weight-bearing hip belt (as seen on backpacks for hikers). While performing these static, posture maintenance tasks, the activation levels of the bilateral trapezius, erector spinae, and rectus abdominis were collected. Participants also provided subjective ratings of comfort. The results showed that there was a significant interaction between harness type and forward flexion angle for the trapezius and the erector spinae muscles. The normalized EMG for the trapezius muscles showed a 14% and 11% reduction in muscle activity at 15 degrees and 30 degrees , respectively, with the advanced design but these positive effects of the advanced design were not found at the greater flexion angles. Likewise the erector spinae muscles showed a 24% and 14% reduction in muscle activity at 15 degrees and 30 degrees , respectively, with the advanced design harness but these effects of the advanced design were not found at the greater forward flexion angles. The level of forward flexion angle affected the rectus abdominis muscle activity, but neither the harness type main effect nor the interaction of harness type and forward flexion angle was significant. The subjective survey results agreed with the EMG results and showed the advanced design harness was generally more comfortable with respect to the shoulder and low back areas. Collectively, the subjective and objective results show a significant improvement with the advanced harness system but also note an interesting interaction with degree of sagittal flexion, indicating a diminished effectiveness of the design improvements at forward flexed postures. Design criteria for harness systems in these forward flexed postures are discussed.

Adult↗