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PubMed1992

Anatomically derived attenuation coefficients for use in quantitative single photon emission tomography studies of the thorax.

Elimination of errors due to poor attenuation correction is an essential part of any quantitative single photon emission tomography (SPET) technique. Attenuation coefficients (mu Tc) for use in attenuation correction of SPET data were determined using technetium 99m and cobalt 57 flood sources and using topographical information obtained from computed tomography (CT) scans and magnetic resonance (MR) images. In patients with carcinoma of the bronchus, the mean attenuation coefficient for 99mTc was 0.096 cm-1 when determined across a transverse section of the thorax at the level of the tumour by means of a 57Co flood source (13 patients) and 0.093 and 0.074 cm-1 as determined from CT scans for points in the centre of the tumour and contralateral normal lung, respectively (21 patients). In 18 patients with breast tumours, the mean attenuation coefficient for 99mTc was 0.110 and 0.076 cm-1 when determined from MRI cross-sections for points in the centre of the tumour and normal contralateral lung, respectively. This indicates significant overcorrection for attenuation when the conventional value of 0.12 cm-1 is used. A value in the range 0.08-0.09 cm-1 would be more appropriate for SPET studies of the thorax. An alternative approach to quantitative region of interest (ROI) analysis is to perform attenuation correction appropriate to the centre of each ROI (using topographical information derived from CT or MRI) on non-attenuation-corrected reconstructions.

Breast Neoplasms↗
PubMedDate not supplied

Impedance tomography: computational analysis based on finite element models of a cylinder and a human thorax.

A direct image reconstruction method of electrical impedance tomography (EIT) is evaluated using three-dimensional (3-D) finite element models of cylindrical and torso-shaped volume conductors. The cylindrical model is used to examine the effect of electrode configurations and the sensitivity to off-plane objects and to noise in the measured data. It is also used to validate the modeling procedures by comparison with experimental data acquired from a similar cylindrical tank filled with saline. Simulation results show only minor differences in performance between the various electrode configurations. In the second part, a realistic human thorax model constructed from CT images is used to evaluate monitoring of pulmonary edema by EIT. The conductivity, volume, and vertical position of an abnormal region in the lungs are varied to simulate the progress of edema. Dynamic EIT images are reconstructed from data computed for the inhomogeneous thorax (heart and lungs) as the reference set and a realistic amount of noise is added to reproduce the conditions in which the technique would be used in practice. Simulation results show that a 10 ml edema region with a conductivity equal to that of blood can be detected at a 40 dB signal-to-noise ratio (SNR). Detection of a smaller volume, in the order of 2 ml, should be possible by improving either the instrumentation to achieve 60 dB SNR or the performance of reconstruction algorithms.

Cardiography, Impedance↗
PubMed1992

A computer model for the study of electrical current flow in the human thorax.

Electrocardiography has played an important role in the detection and characterization of heart function, both in normal and abnormal states. In this paper we present an inhomogeneous, anisotropic computer model of the human thorax for use in electrocardiography with emphasis on the calculation of transthoracic potential and current distributions. Knowledge of the current pathways in the thorax has many applications in electrocardiography and has direct utility in studies pertaining to cardiac defibrillation, forward and inverse problems, impedance tomography, and electrode placement in electrocardiography.

Computer Simulation↗
PubMed1989

Rotational and translational movement features of the pelvis and thorax during adult human locomotion.

The kinematics of the pelvis and thorax are important in gait studies since their movement patterns are closely related to gait efficiency and 'smoothness' of locomotion. The purpose of this study was to identify features of normal gait patterns for later comparisons with pathological and developmental gait patterns. A two camera SELSPOT system interfaced with an HP1000 minicomputer was used to obtain three-dimensional kinematic/temporal data for the pelvis and thorax. Data from treadmill walking of eight adults were used for within subject (at different speeds) analyses. The analyses revealed a very complex pattern with a set of breakpoints which was consistent over all subjects. Some features were invariant over a range of walking speeds although the total range of motion changed considerably.

Adult↗
PubMed2001

Imaging of beta-adrenoceptors in the human thorax using (S)-[(11)C]CGP12388 and positron emission tomography.

We report positron emission tomography studies of beta-adrenoceptors in the human thorax with (S)-[(11)C]CGP12388 (4-(3-(2'-[(11)C]-isopropylamino)-2-hydroxypropoxy)-2H-benzimidazol-2-one). Beta-adrenoceptors have previously been quantified using (S)-[(11)C]CGP12177 (4-(3-tert-butylamino-2-hydroxypropoxy)-2H-benzimidazol-2[(11)C]-one), but (S)-[(11)C]CGP12388 is more easily prepared and therefore more suitable in a clinical setting. (S)-[(11)C]CGP12388 was administered to five healthy volunteers on two separate days (control and pindolol block study). Arterial plasma samples were used to determine clearance, metabolites, and protein binding of the radioligand. Heart, lung and spleen showed high uptake of radioactivity, which was strongly suppressed (68-77%) by pindolol. Plasma clearance of (S)-[(11)C]CGP12388 was rapid, binding to plasma proteins was low (53+/-4%), and the radioligand was slowly metabolized. (S)-[(11)C]CGP12388 produces high-quality images of the human thorax. Uptake of (S)-[(11)C]CGP12388 in heart, lung and spleen represents binding to beta-adrenoceptors. (S)-[(11)C]-CGP12388 seems useful for imaging of beta-adrenoceptors in a clinical setting.

Adult↗
PubMed1998

Ultrasonography of the thorax (excluding the heart).

Until recently, ultrasonography has had a subordinate role in the evaluation of the thorax in both small animals and humans, most likely due to the inability of sound to penetrate air-filled lung. When pathologic processes such as pleural effusion and lung consolidation provide an acoustic window to the thorax, however, thoracic ultrasonography becomes feasible. As this article illustrates, ultrasonography may be effectively employed in the diagnosis and management of various thoracic wall, pleural, mediastinal, pulmonary, and diaphragmatic diseases by providing valuable information not obtainable with routine radiography and enabling percutaneous aspiration or tissue core biopsy of lesions.

Animals↗
PubMed2004

Combination of finite element modeling and optimization for the study of lumbar spine biomechanics considering the 3D thorax-pelvis orientation.

A model of the lumbar spine capable of taking into account realistic loads derived from human activity would be of great benefit in studying its normal biomechanical functioning as well as its in vivo behavior in injured and surgically altered states. This paper proposes a method to analyze the mechanical response of the lumbar spine subjected to loads derived from human activity, combining a non-linear finite element model (FEM) and an optimization-based force predicting algorithm. Loads borne by the lumbar spine at the T12-L1 level (joint loads) are first predicted with the optimization algorithm and then applied to the FEM, while a boundary condition prescribing the relative L1-sacrum rotation is imposed onto the FEM to account for three-dimensional physiological thorax-pelvis orientation. The prescribed rotation is achieved through the application of moments on L1. To account for the effect of these moments on lumbar joint loads, an iteration between the optimization technique and the FEM computation has been carried out. This method provides two main benefits over previous studies: first, it allows for the application of any 3D loading condition while considering the real 3D rotation measured between the thorax and the pelvis, and second, it makes it possible to estimate the moments that must be applied on L1 in order to maintain this rotation, taking them into account when predicting joint loads. As an example application of the method, results are presented for the lumbar spine mechanical response at the time of peak T12-L1 joint force during walking.

Algorithms↗
PubMed1982

Genes controlling segmental specification in the Drosophila thorax.

The roles of three homeotic genes, Ubx+, Scr+, and Antp+, in the Drosophila thorax have been studied by determining the cellular phenotypes of mutations resulting in loss of gene function. The principal results are: (i) The Scr+ and Ubx+ genes are required in the prothorax and metathorax, respectively; in the absence of these genes, both segments develop like the mesothorax. (ii) The Antp+ gene is required in all three thoracic segments: in its absence, parts of the mesothorax are transformed into corresponding parts of the antenna, and similar transformations to antenna are found in the prothorax and metathorax if the Scr+ and Ubx+ genes also are absent. (iii) Loss of the Ubx+ gene early in embryogenesis, but not later, leads to the inappropriate activity of the Scr+ gene in the meso- and metathorax. Results i and ii argue strongly that segmental determination is specified in a combinatorial fashion in the head and thorax by the selective activities of the Scr+, Ubx+, Antp+, and putative head-determining genes. Result iii suggests that a product of the Ubx+ gene also plays an early, regulatory role in ensuring the correct spatial expression of the Scr+ gene during subsequent development.

Animals↗
PubMed2001

Intensity modulated irradiation of a thorax phantom: comparisons between measurements, Monte Carlo calculations and pencil beam calculations.

The present study investigates the application of compensators for the intensity modulated irradiation of a thorax phantom. Measurements are compared with Monte Carlo and standard pencil beam algorithm dose calculations. Compensators were manufactured to produce the intensity profiles that were generated from the scientific version of the KonRad IMRT treatment-planning system for a given treatment plan. The comparison of dose distributions calculated with a pencil beam algorithm, with the Monte Carlo code EGS4 and with measurements is presented. By measurements in a water phantom it is demonstrated that the method used to manufacture the compensators reproduces the intensity profiles in a suitable manner. Monte Carlo simulations in a water phantom show that the accelerator head model used for simulations is sufficient. No significant overestimations of dose values inside the target volume by the pencil beam algorithm are found in the thorax phantom. An overestimation of dose values in lung by the pencil beam algorithm is also not found. Expected dose calculation errors of the pencil beam algorithm are suppressed, because the dose to the low density region lung is reduced by the use of a non-coplanar beam arrangement and by intensity modulation.

Dose-Response Relationship, Radiation↗
PubMed2003

Evaluation of an EIT reconstruction algorithm using finite difference human thorax models as phantoms.

A finite difference model of the human thorax with 113,400 control volumes (nodes) based on ECG gated MRI images was used to evaluate the Sheffield DAS-01P EIT system. Sixteen simulated electrode positions equally spaced around the thorax model at approximately the fourth intercostals space level were selected. Pairs of adjacent positions were excited sequentially by injecting current in a manner similar to that used by the Sheffield DAS-01P EIT system. The resulting voltages on the non-excited electrode positions were calculated and used to reconstruct the image using the Sheffield filtered back projection algorithm. By changing the resistivities of the lungs, the ventricles and the atria over a range of 1% to 40%, the resulting changes in the images were quantified by measuring the average resistivity change over a region defined automatically by two thresholds, 40% or 80% of the average of the first four pixels with the largest change. The results show that the changes observed in the images are consistently less than the changes in the model, but changed in a nearly linear manner as a function of resistivity in the model. For 40% resistivity changes in the model for right lung, right ventricle and right atrium, the observed resistivity changes in the region of interest (ROI, defined by the 80% threshold) of the images are 32% for the right lung, 11% for the right ventricle and 5.5% for the right atrium, which suggests strong volume dependence of EIT imaging. The effect of structural (size) change between end diastole and end systole was also studied, which showed large resistivity changes caused in the heart region of the constructed image. The study demonstrates that the Sheffield DAS-01P EIT reconstruction algorithm tracks the change occurring in the lungs most closely and with proper scaling may be used to observe physiological changes.

Algorithms↗
PubMed1973

The effects of disruptive and stabilizing selection on body size in Drosophila melanogaster. II. Analysis of responses in the thorax selection lines.

An analysis was made of changes in mean and variance in some thorax selection lines. The decrease of mean thorax length in the stabilizing selection lines (S) was a consequence of a directional selection component, caused by the skewness of the frequency distributions. The slight or temporary increase of the phenotypic variance and the large increase of the mean value in the disruptive selection lines with random mating (D(R)) could be attributed to differences in reproduction between small and large flies (egg production and mating success). Phenotypic variability was high in two disruptive selection lines with compulsory mating of opposite extremes (D(-)). The mechanism of the change in variability was different in these replicate lines. In D(-)-1 the change was obtained by an increase of the environmental and the nonadditive genetic components of the variance. In D(-)-2 almost exclusively an increase of additive genetic variance occurred.

Analysis of Variance↗
PubMed1988

Identification of calcium binding proteins in two-dimensional gel electrophoretic pattern of Drosophila thorax and their distribution in two types of muscles.

Ten Drosophila thorax proteins (six myosin light chains and four proteins called a, b, c, d) were found to have high affinities with Ca2+. This was proved after subjecting the total Drosophila thorax proteins to two-dimensional (2D) transblot, followed by 45Ca2+ autoradiography. Three proteins (a, c, d) showed Ca2+ dependent electrophoretic mobility changes. To know their tissue-specific localization, fibrillar and tubular type muscle fibers were individually dissected from freeze-dried flies and separately subjected to 2D gel electrophoresis. Fibrillar type muscle had protein b and a small amount of protein a. Tubular type muscle had proteins c, d and a very large amount of protein a. Protein d was characterized to be calmodulin.

Animals↗
PubMed1986

Common congenital skeletal anomalies of the thorax.

Bony anomalies of the thorax may occur as isolated problems, but are also seen in conjunction with other skeletal or organ anomalies. Among the most common thoracic osseous anomalies are pectus excavatum, pectus carinatum, sternal ossification abnormalities, and deformity of the spine, ribs, clavicle, or scapula. The presence of any of these anomalies should increase the index of suspicion for associated problems. Review of the history and physical examination, combined with a knowledge of commonly associated malformations, will allow appropriate additional imaging studies to be selected. Many osseous anomalies of the thorax do not require treatment; in some instances, however, problems with function, progressive deformity, or cosmetic considerations may necessitate surgical treatment.

Adult↗
PubMed1997

Simulated internal defibrillation in humans using an anatomically realistic three-dimensional finite element model of the thorax.

INTRODUCTION: Determination of the optimal electrode configuration during implantable cardioverter defibrillator (ICD) implantation remains largely an empirical process. This study investigated the feasibility of using a finite element model of the thorax to predict clinical defibrillation metrics for internal defibrillation in humans. Computed defibrillation metrics from simulations of three common electrode configurations with a monophasic waveform were compared to pooled metrics for similar electrode and waveform configurations reported in humans. METHODS AND RESULTS: A three-dimensional finite element model was constructed from CT cross-sections of a human thorax. Myocardial current density distributions for three electrode configurations (epicardial patches, right ventricular [RV] coil/superior vena cava [SVC] coil, RV coil/SVC coil/subcutaneous patch) and a truncated monophasic pulse with a 65% tilt were simulated. Assuming an inexcitability threshold of 25 mA/cm2 (10 V/cm) and a 75% critical mass criterion for successful defibrillation, defibrillation metrics (interelectrode impedance, defibrillation threshold current, voltage, and energy) were calculated for each electrode simulation. Values of these metrics were within 1 SD of sample-size weighted means for the corresponding metrics determined for similar electrode configurations and waveforms reported in human clinical studies. Simulated myocardial current density distributions suggest that variations in current distribution and uniformity partially explain differences in defibrillation energy requirements between electrode configurations. CONCLUSION: Anatomically realistic three-dimensional finite element modeling can closely simulate internal defibrillation in humans. This may prove useful for characterizing patient-specific factors that influence clinically relevant properties of current density distributions and defibrillation energy requirements of various ICD electrode configurations.

Adult↗
PubMedDate not supplied

Normal cross-sectional anatomy of the feline thorax and abdomen: comparison of computed tomography and cadaver anatomy.

Computed tomographic images of two adult domestic short-haired cats were obtained with a whole body scanner. Images of the thorax and abdomen were compared with cross-sectional anatomy cadaver specimens from the same two cats. Anatomic structures were first identified on the cadaver specimens with the aid of numerous anatomy texts and references and were then identified and labeled on the computed tomographic images. Results from this project provide an atlas of normal cross-sectional gross and CT anatomy of the feline thorax and abdomen that can be used in the interpretation of any cross-sectional imaging modality.

Abdomen↗
PubMed2003

Use of computed tomography in the diseased feline thorax.

Computed tomography (CT) scanning of the thorax is gaining more attention in veterinary medicine as therapeutic possibilities increase. Plain and contrast-enhanced CT images of the thorax of five referred cats with signs of respiratory disease were evaluated using soft tissue (pleural) and lung windows. The common CT pattern in all cats was involvement of the lung lobes, either as a homogeneous or heterogeneous single lobe hyperdensity. It involved the main bronchus, invaded the cranial or caudal mediastinum, and crossed the border to the opposite lung. Right lung atelectasis and mediastinal shift caused left lung overinflation. Bronchial lymph node enlargement was found unilaterally or bilaterally. CT-guided percutaneous fine needle aspiration biopsy of the lobar lung lesion was performed in four cats; in three cases it revealed carcinoma and in one inflammation, although the cat with suspected inflammation was subsequently found to have a carcinoma on lung lobectomy. Histopathology confirmed lung metastasis in one case and bronchial adenocarcinoma in four cases. A protocol for systematic examination of thoracic CT images is proposed.

Adenocarcinoma↗
PubMed1979

The localization of honey bee thorax trehalase.

Differential and sucrose gradient centrifugation of honey bee thoraces, disrupted by gentle methods and using mannitol-triethanolamine-EDTA buffer at pH 6.5, showed that in the honey bee thorax 92-94.8% of the trehalase was mitochondrial. Since only 92-95% of the cytochrome c oxidase, a known mitochondrial enzyme, was found in the mitochondrial fraction by these methods, it was concluded that honey bee trehalase is totally mitochondrial. Significant amounts of 'microsomal' or 'soluble' trehalase were formed only by harsh methods of thorax disruption and similar 'microsomal' or 'soluble' trehalases were also formed by harsh treatment of purified whole mitochondria. They thus seem to be artifacts of the isolation procedure. Studies (using marker enzymes) with purified intact mitochondria which were dispersed by various chemical, enzymatic, and physical methods showed that the trehalase in the mitochondria was membrane bound and that it was bound to either the outside of the inner membrane or to one of the sides of the outer membrane.

Animals↗
PubMed1978

Computed tomography of the thorax.

Computed tomography (CT) provides a valuable new perspective in assessing abnormalities of the thorax. In the patient with a mediastinal mass or widening detected by plain chest radiography, a definitive diagnosis is sometimes possible which would not be obtainable by conventional noninvasive radiological techniques. In certain clinical situations, CT is a highly sensitive modality for examining the lungs. The proved and potential clinical uses of CT in solving diagnostic problems of the thorax are discussed.

Adult↗