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At least 127 records · Page 7Linked to original sources
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↗
PubMedDate not supplied

A rare hernia of intra-abdominal fat in the thorax under an intact diaphragm: multidetector computed tomography.

Neither abdominal wall hernia nor diaphragmatic hernia is an unusual disease. But some may have difficulty diagnosing the presence of intra-abdominal fat in the thorax under an intact diaphragm. We report a case with an external compression of the right lower lung from intra-abdominal fat owing to a hernia through the right lateral abdominal wall and secondary through the ninth intercostal space of the chest wall to the right lower thorax without traumatic history. Multiple images, including multidetector row computed tomography, are reviewed.

Aged↗
PubMed2005

Normal anatomical imaging of the thorax in three dogs: computed tomography and macroscopic cross sections with vascular injection.

The purpose of this study was to provide a new reference for interpretation of the normal anatomy of the canine thorax as imaged using computed tomography (CT). Three mature dogs, all mixed breed males, were used for this study. The dogs were sedated, anaesthetized and maintained in sternal recumbency. CT study from the first to the thirteen thoracic vertebra was performed with a TOSHIBA 600 HQ scanner (third generation equipment). Dogs were killed and vascular-injection technique was performed: red latex and blue latex filled vascular system. Injected dogs were frozen and sectioned with an electric bandsaw, the cuts matched as closely as possible to the CT images. The CT images from this study are intended as a reference for clinical CT imaging studies of the thoracic cavity of the dog and for interpreting lesions of the thorax and associated structures.

Animals↗
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↗
PubMed2005

Fungus-infected fluid collections in thorax or abdomen: effectiveness of percutaneous catheter drainage.

PURPOSE: To retrospectively evaluate the effectiveness of percutaneous catheter drainage in the treatment of fungus-infected fluid collections in the thorax or abdomen and to identify any factor that may be predictive of a poor clinical outcome. MATERIALS AND METHODS: Approval for this study was obtained from the hospital ethics subcommittee on human studies. Because the study was retrospective, patient informed consent was not required. This study was compliant with the Health Insurance Portability and Accountability Act. Retrospective analysis was performed of cases of fungus-infected fluid collections in the thorax or abdomen treated by using percutaneous catheter drainage in 60 patients (36 male and 24 female patients; mean age, 57 years; range, 2 months to 91 years) during 5 years. The patient medical records were reviewed to identify recognized factors for predisposition to fungal infection. The details of percutaneous catheter drainage and microbiologic findings were recorded. The technical success (ability of catheters placed to drain collections treated) and the clinical success (ability of patients to recover fully without surgery) of percutaneous catheter drainage were determined. A multifactor logistic regression analysis was performed to identify any clinical or microbiologic factor predictive of a poor clinical outcome. RESULTS: Seventy-three fungus-infected fluid collections were drained in 60 patients. The collections originated from the pleura (n = 6), mediastinum (n = 2), liver (n = 3), pancreas (n = 5), obstructed biliary or urinary tract (n = 9), gallbladder (n = 1), and abdominopelvic area (n = 47). The technical success rate for catheter drainage was 79% (41 of 52 patients); the clinical success rate, 57% (34 of 60 patients). Twenty (33%) patients died from all causes during hospital admission. Multifactor logistic regression analysis was used to identify predictors of a poor clinical outcome; complexity of collection, history of malignancy, and admission to intensive care unit were significant (P < .03) and independent predictors. CONCLUSION: Despite a moderately high technical success rate with percutaneous catheter drainage of fungus-infected fluid collections, clinical success rate was much lower. Both imaging appearance (complexity of collection) and clinical factors (history of malignancy, admission to intensive care unit) influenced prognosis.

Abdomen↗
PubMed1991

Three-dimensional time-of-flight MR angiography: applications in the abdomen and thorax.

The application of three-dimensional (3D) time-of-flight (TOF) magnetic resonance (MR) angiographic techniques to the vasculature of the abdomen and thorax has not, to the authors' knowledge, been previously reported; this is possibly due to the large amount of physiologic motion in these regions along with the anticipated sensitivity of the 3D acquisition scheme to image degradation caused by motion artifact. The authors describe an asymmetric short-echo velocity-compensated 3D TOF technique that minimized the effects of physiologic motion on image quality and provided rapid high-resolution 3D MR arteriograms of the abdomen and thorax. Contiguous 3D volumes were often combined to provide sufficient anatomic coverage. Benefits include high spatial resolution and minimization of signal loss; limitations include sensitivity to motion artifact and progressive spin saturation.

Abdomen↗
PubMed1987

Comparison of volume changes in the upper airway and thorax.

To describe the mechanical cycles of the upper and lower portions of the respiratory system, we measured volume change in and out of the isolated upper airway in 13 anesthetized dogs and compared volume changes in the upper airway with tidal volume change during spontaneous respiratory efforts. During inspiration the onset and peak increase in volume into the upper airway preceded the onset and peak of inspiratory tidal volume by 84 +/- 8 and 638 +/- 47 ms, respectively. The volume cycle of the upper airway was nearly complete by the end of inspiratory airflow into the thorax. With progressive hypercapnia there was an increase in the change in both upper airway volume and tidal volume but the temporal sequence was preserved. End-expiratory tracheal occlusion increased the volume change in the isolated upper airway at any level of CO2; however, the effect was disproportionately greater at low rather than at high levels of CO2. Following hyperventilation-induced apnea, a change in volume in the upper airway and thorax occurred on the first inspiratory effort. In most animals at lower levels of CO2, the percent change in upper airway volume with inspiration was relatively less than tidal volume, but the reverse was true at higher levels of CO2. These differences represent dissimilarities in the mechanical forces occurring as the result of upper airway and chest wall muscle contraction during inspiration.

Animals↗
PubMed1992

Structural change of the thorax in chronic obstructive pulmonary disease.

This study examines structural changes of the thorax in hyperinflated subjects with chronic obstructive pulmonary disease (COPD). Age-matched normal subjects were used for comparison. Thoracic dimensions were determined using anteroposterior and lateral chest radiographs performed at total lung capacity, functional residual capacity, and residual volume. Rib cage dimensions (lateral diameter, rib angle, anteroposterior diameter) and diaphragm position were determined at each lung volume. There were no significant differences in rib cage dimension between the COPD and normal subjects for all lung volumes. In contrast, the diaphragm was significantly lower in the COPD subjects. The change of rib cage dimensions in the COPD subjects (for a similar volume change) was not different from that in normal subjects, whereas the change of diaphragm position in the COPD subjects (for a similar volume change) was reduced. In conclusion, the primary structural change of the thorax in COPD with chronic hyperinflation is confined to the diaphragm, with no appreciable structural change in the rib cage.

Aged↗
PubMed1976

Regional difference of respiratory changes in pleural pressure between left and right thoraxes in dogs.

Respiratory changes in pleural pressure were recorded simultaneously from the left and right pleural spaces in 6 anesthetized closed-chest dogs in the supine, prone, left lateral and right lateral positions. Saline-filled radiopaque catheters connected to strain-gauge manometers were inserted percutaneously in the left and right pleural spaces by an air tight technique and their tips were placed in the mid-thoracic plane. The esophageal pressure was also recorded with the saline-filled system. The value of respiratory pressure amplitude (deltap, the difference between end-expiratory and minimal inspiratory pressures) in the pleural spaces was significantly greater in the left thorax than in the right in the supine, prone and right lateral positions. In 4 body positions, deltap in pleural pressure was significantly greater than in esophageal pressure. It is concluded that respiratory variations in pleural pressure of the left and right thorax are not the same and that postural change does not produce significant regional difference of the respiratory variations.

Animals↗
PubMedDate not supplied

Magnetic susceptibility mapping of the human thorax using a SQUID biomagnetometer.

Biomagnetism is essentially the study of the weak magnetic fields generated by biological organisms, in particular the human body. The human thorax is composed of a variety of tissues and organs of slightly different magnetic susceptibility. In an applied magnetic field (of the order of milliTeslas) these small differences in susceptibility lead to measurable field variations (of the order of nanoTeslas) at the body surface which may be of diagnostic value. Physiological processes such as cardiac activity, cardiac output, blood flow and respiratory related lung volume changes also contribute to the observed signal. In this study susceptibility 'maps' were obtained by measuring the magnetic field at several hundred points over the thorax. Results indicate that magnetic susceptibility mapping produces low-resolution images of internal body structures from which is should be possible to detect pathologies that cause alterations in tissue susceptibility.

Biomedical Engineering↗