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At least 559 records · Page 31Linked to original sources
PubMed1982

The design and construction of a realistic thorax phantom for in vivo measurements of low-energy photon emitters.

Calibration of detector systems for the in vivo measurement of transuranic radionuclides is notoriously difficult due to the low energies and intensities of the photon emissions and their severe attenuation within the tissues of the body. A realistic chest phantom has been designed and constructed to provide calibration data to relate detector responses to lung contents of radionuclides; the phantom incorporates a human thoracic cage and tissue substitutes that have been carefully selected to reproduce the scattering and absorption coefficients of muscle and lung tissue. The measured attenuation coefficients of the substitutes are compared with values calculated for the tissues of interest. Preliminary calibration data obtained from this phantom are presented and the uses and limitations of this calibration procedure are discussed.

Calibration↗
PubMed1995

Measured and expected Cole parameters from electrical impedance tomographic spectroscopy images of the human thorax.

Electrical impedance tomographic spectroscopy (EITS) images have been recorded from a group of 12 normal subjects using frequencies from 9.6 kHz to 1.2 MHz. The impedance changes with frequency have been modelled on a pixel by pixel basis to produce parametric images as a means of characterizing tissue. The modelling was based on the Cole equation. The lungs are seen as areas of high characteristic frequency and low time constants SC and RS. The R/S images are much less uniform over the region of the lungs. Values characterizing the lung and cardiac regions are given. The results appear to be consistent with a model for the lungs whereby the model parameters can be related to alveolar structure and composition.

Adult↗
PubMed2001

Realistic 2D human thorax modelling for EIT.

Electrical impedance tomography is a technique that permits estimation of resistivity within a subject by reconstructing from boundary measurements. Due to the ill conditioning of the problem, images are greatly affected by boundary errors. Reconstruction algorithms account for boundary shape and electrode position by using a forward solver. In this paper is presented the realization of a 2D realistic thoracic model as a better approach compared to circular meshing. Several meshes with different discretizations are compared in terms of accuracy with a complete electrode model forward solver. By comparing the different discretizations it is possible to choose an appropriate mesh density for the 2D EIT problem.

Algorithms↗
PubMed1996

Histological abnormalities of muscle from limb, thorax and diaphragm in chronic heart failure.

The aim of the study was to compare histological findings in limb and respiratory muscles from control subjects and patients with heart failure of two different aetiologies. Biopsies of the quadriceps femoris, strap, diaphragm and pectoralis major muscles were taken from each group. The control subjects all had normal left ventricular function, and comprised seven undergoing surgical ablation of electrical pathways and 10 undergoing coronary artery surgery. The heart failure group had severely impaired left ventricular function, and were undergoing cardiac transplantation in all except one case. Ten patients with idiopathic dilated cardiomyopathy and seven with heart failure of ischaemic origin were studied. Conventional histochemical techniques and specific anti-myosin immunofluorescent stains were used. There were no consistent differences in fibre type prevalence or diameter between the groups. There were no important histological abnormalities in the two control groups. There were minor/major changes in four of seven patients with ischaemic heart failure but no major abnormality, whilst in the dilated cardiomyopathy group there were five of 10 patients with minor/major changes and three of 10 with major abnormalities (P < 0.001 vs controls). A variety of changes were seen in both groups of heart failure subjects. These were more marked in the dilated cardiomyopathy than ischaemic group, and suggest the presence of fibre type regeneration and/or transformation. Amongst the findings were tubular aggregates, internalization of nuclei, bizzare staining of myosin and staining of neonatal myosin (seven of 14) and the presence of cores (five of 14). Such changes were more prominent in the diaphragm than in the other muscles. In conclusion, histological abnormalities are present in the limb and respiratory muscles from subjects with heart failure. The changes are most marked in subjects with idiopathic dilated cardiomyopathy, suggesting that there may be a generalized cardiac and skeletal myopathy in these subjects. The presence of histological abnormalities in the respiratory muscles may contribute to the pathogenesis of dyspnoea in heart failure.

Adolescent↗
PubMed1986

Magnetic resonance microscopy of the rat thorax and abdomen.

With magnetic resonance (MR) microscopy, high-resolution volumetric imaging (3DFT) of small animals is possible. Although these techniques are suitable for imaging the head and other small stationary objects, breathing and cardiac motion degrade the quality of body images. Scan synchronous ventilation and cardiac gating methods have been developed that permit acquisition of high-resolution images from anywhere in the body of small animals (150 to 400 g). Anesthetized rats were ventilated in synchrony with three-dimensional Fourier spin warp (3DFT) sequence (TR = 400 to 1000 ms, TE = 20 ms). Eight or 16 slices (1.2 or 2.5 mm thick) were acquired simultaneously. Effective pixel size was 200 X 200 mu. Imaging was performed in a 1.5 T, 1-m bore research system using a 28-cm diameter high field gradient coil and a 6-cm diameter radio frequency coil. For thoracic imaging, acquisitions were gated to the QRS of the ECG. Scan synchronous ventilation eliminated breathing motion artifacts and permitted visualization of peripheral vascular structures in the lung and liver. In images that were also cardiac gated, cardiac chambers and major thoracic vessels, including the coronary arteries, were well demonstrated. Thus, thoroughly characterized rodent models can now be studied with MR not only to explore noninvasively the intricacies of mammalian pathomorphology, but also to test the capabilities of MR and aid in interpreting MR data.

Abdomen↗
PubMedDate not supplied

MR "microscopy" of the rat thorax.

High resolution images can be obtained from anywhere in the body of small animals with magnetic resonance combined with cardiac gating and scan synchronous ventilation. We used these methods to examine the intrathoracic anatomy of the rat. Anesthetized rats were intubated and ventilated in synchrony with imaging acquisition. Images were obtained in a 1 m bore, 1.5 T system fitted with a 28 cm diameter high field gradient coil and a 5 cm radio-frequency coil. We used cardiac gated, three-dimensional spin warp acquisitions. Eight contiguous slices (2.5 mm thick) were obtained simultaneously. In addition to visualizing major vessels and cardiac chambers, cardiac valves and papillary muscles were clearly demonstrated. Major pulmonary vessels and peripheral parenchyma were also seen. These results demonstrate MR "microscopy" can be used to image all major cardiopulmonary structures in the rat with respect to selected times of the cardiac cycle. This capability for noninvasive "microscopy" opens new avenues for cardiopulmonary research using well characterized rodent models.

Animals↗
PubMed1993

Air-to-surface missile wound of the thorax reconstructed with a polytetrafluoroethylene patch: case report.

A method of reconstructing a chest wall defect following non-guided air-to-surface missile injury is described. The wall defect was simply closed with a polytetrafluoroethylene patch. The high risk of infection following use of the described method is well recognized. No infection occurred in this case. It could be stated that under the exigencies of the moment the use of prosthetic material to reconstruct the chest is not invariably followed by infection. However, when the patient is stable this latter problem can then be addressed by a variety of standard methods. It is concluded that the described method is particularly suitable in war circumstances, when it is usually necessary to attend to a large number of patients in a short period of time.

Adult↗
PubMed1989

Magnetic resonance imaging of the thorax.

The role of magnetic resonance imaging (MRI) in the evaluation of thoracic disease is emerging amidst much debate and study. Recent technical advances have led to new applications of this modality, and a reappraisal of previous conclusions seems warranted. This article reviews our 5 1/2 years' experience with thoracic MRI.

Contrast Media↗