RESUMO
An ultrasound reflection technique was designed and implemented to study the mechanical properties of bone material. The technique uses the fact that an ultrasound beam produced in water undergoes total internal reflection off a bone sample at a critical angle formally related to the velocity of a pressure wave in bone. When the plane of scattering is rotated around the normal to the sample surface, the critical angle varies with a periodic dependence dictated by the intrinsic symmetry of the bone structure at the point being examined. Most current measurements of sound velocity are made using transmission techniques. A double-blind intercomparison between this technique and a transmission technique, which was previously validated against tensile mechanical testing, was performed for samples of isotropic materials and of human cortical bone. Strong correlations were found for both sets of samples. For the isotropic materials the velocities were approximately equal, but for bone they were on average 11% higher in reflection than in transmission. This was the result both of the higher frequency employed in reflection (3.5 rather than 2.25 MHz) and of the different effects of sample imperfections on the two measurements. In particular, the reflection technique used in this work studied the surface of the sample, but the ultrasound beam in the transmission method propagated through its interior. In assessing the mechanical properties of bone specimens by ultrasound, the reflection technique samples a discrete bone surface element and the transmission method analyzes the entire volume of the specimen. Thus the reflection technique may yield a measure of the mechanical property of bone trabeculae that is largely unaffected by the mass of the entire specimen, but mass and the structural density of the specimen affect the transmission method.
Assuntos
Osso e Ossos/diagnóstico por imagem , Osso e Ossos/fisiologia , Fenômenos Biomecânicos , Humanos , Técnicas In Vitro , Modelos Biológicos , Ultrassonografia/métodosRESUMO
The initial radiographic features of 188 patients with pulmonary infections due to Mycobacterium tuberculosis were compared to 184 patients with M kansasii and 100 patients with M intracellularis infections. The patients were all from the University of Texas Health Center at Tyler, all had at least two positive sputum cultures and no other potential pathogen, and none had a past medical history of any type of tuberculosis. The comparison showed that all three organisms have a strong tendency to produce cavitary infiltrates in the posterior portions of the upper lobes. No distinctive or pathognomonic feature could be found. The atypical organisms were more likely to produce thin-walled cavities and far advanced unilateral disease, but both of these patterns also occurred with M tuberculosis. Endobronchial spread and volume loss were common in all three diseases. The only definite difference seems to be the absence of a primary or juvenile form of atypical tuberculosis and a much greater incidence of empyema and postprimary pleural effusions with M tuberculosis. In an individual case, the roentgenographic manifestations of the three diseases are indistinguishable.
Assuntos
Tuberculose Pulmonar/fisiopatologia , Idoso , Empiema Tuberculoso/etiologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Mycobacterium tuberculosis , Micobactérias não Tuberculosas , Derrame Pleural/microbiologia , Radiografia , Estudos Retrospectivos , Escarro/análise , Escarro/microbiologia , Tuberculose Pulmonar/complicações , Tuberculose Pulmonar/diagnóstico por imagemRESUMO
A partial chest phantom was constructed to compare two commonly employed radiographic techniques, 70 kVp without a grid and 120 kVp with a grid, for the detection of pulmonary nodules. The phantom consisted of human ribs embedded in paraffin, the lungs of a dog injected with silicone rubber, a tissue equivalent wax heart and beeswax nodules. The nodules ranged in size from 3-7 mm. A series of 120 films was exposed, half with each technique, and the films were interpreted by three senior residents and seven staff radiologists. More nodules of all sizes except 3 mm were detected with the 120 kVp technique. The 3 mm nodules were rarely detected with either technique. The disadvantages of the 120 kVp technique were an approximate 50 percent increase in patient exposures and almost twice as many false-positive nodule detections.
Assuntos
Radiografia Torácica/métodos , Modelos Estruturais , Tecnologia RadiológicaRESUMO
Digital tomosynthesis represents a new technique for digital manipulation of data acquired during a single tomographic sweep. With the aid of a computer, data can be processed to yield images in any parallel plane of the body. This technique allows rapid tomographic studies requiring a much lower radiation dose to the patient. Dynamic studies such as angiotomography are feasible, and application to digital subtraction intravenous angiography is also possible with this technique. Early experience with clinical application in patient studies is presented.
Assuntos
Vértebras Cervicais/lesões , Aneurisma Intracraniano/diagnóstico por imagem , Luxações Articulares/diagnóstico por imagem , Hemorragia Subaracnóidea/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Adulto , Artérias Carótidas/diagnóstico por imagem , Angiografia Cerebral/métodos , Diagnóstico Diferencial , Feminino , Humanos , Pessoa de Meia-Idade , Osteofitose Vertebral/diagnóstico por imagem , Técnica de SubtraçãoRESUMO
To investigate the quality of gamma camera images obtained with moving collimators, a group of collimators was constructed which could be rotated or sinusoidally oscillated in two dimensions. The date indicate a broadening effect on images in the direction of collimator motion. Moving the collimator during imaging will reduce septal aberrations but will not increase resolution.
Assuntos
Cintilografia/instrumentação , Cintilografia/métodosRESUMO
A technique is described for obtaining tomographic images through retrospective reconstruction of digital data. The apparatus used for this technique, called digital tomosynthesis consists of a linear tomographic x-ray machine that has been modified by the addition of a fluoroscope and TV system, a video disk recorder, an analog-to-digital converter, and a small computer for data processing and manipulation. Video frames are collected and stored during a single tomographic sweep. The stored data are then digitized and retrospectively processed in the computer for reconstruction of any desired tomographic plane within the body. The major advantages of DTS include short patient study time, low radiation dose compared with conventional tomography, the ability to enhance the digitized image through manipulation of window and level display, and the applicability of this technique to dynamic studies such as angiotomography. Phantom studies show good diagnostic quality of the resulting images, and preliminary vascular studies in dogs indicate the clinical potential of this technique for use in digital subtraction angiotomography.
Assuntos
Técnica de Subtração , Tomografia Computadorizada por Raios X/métodos , Animais , Angiografia Cerebral , Cães , Eletrônica Médica , Modelos Estruturais , Tecnologia RadiológicaRESUMO
Fourteen rested and fatigued residents read a set of 25 test radiographs on two separate occasions approximately one month apart. The radiographs were made with partial chest phantom using pulmonary nodules as test objects. Seven rested and 7 fatigued residents read the radiographs, and a month later the order of fatigue was reversed. Fatigued residents had worked a minimum of 15 consecutive hours before their interpretations. Performance did not deteriorate with fatigue, and the nodule detection rate was almost identical on both occasions.
Assuntos
Erros de Diagnóstico , Internato e Residência , Fadiga Mental , Radiografia , HumanosRESUMO
A partial chest phantom was constructed to examine the effect of kilovoltage on the detectability of pulmonary nodules. Four different energies were studied: 100, 150, 200, and 300 kVp. Nodule detectability improved with increasing energies up to 200 kVp, but improvement was relatively small and was accompanied by an almost equal rise in the number of false positive readings. Patient exposures were least at 200 kVp. There seems to be no advantage in a 300 kVp technique, since nodule detectability decreased and patient exposures increased at this energy.
Assuntos
Modelos Estruturais , Doses de Radiação , Nódulo Pulmonar Solitário/diagnóstico por imagem , Tórax , Humanos , RadiografiaRESUMO
The radiographic characteristics of 187 pristine cases of pulmonary Mycobacterium kansasii infection are reviewed. The cases were selected from a total of 309 patients with two positive sputum cultures. All but three of the 187 patients had pulmonary disease. The progenitive focus of disease almost always involved the upper lobes, the right side (72%) more often than the left (50%). Upper lobe disease began posterior to the trachea in every case. Only one patient had disease that originated in an atypical location, that is, in the superior segment of the right lower lobe. The most frequent radiographic abnormality was cavitation (96% of diseased patients). The classical description of a thin walled cavity (or cavities) occurred in 33% of patients. A cicatricial reaction was common (two-thirds of cases). About 63% of patients had endobronchial spread. The likelihood of endobronchial disease decreased as the distance from the progenitive focus increased. Pleural effusions and adenopathy were rare. In an individual case, it is not possible to differentiate between pulmonary M. tuberculosis and M. kansasii infections.
Assuntos
Infecções por Mycobacterium não Tuberculosas/diagnóstico por imagem , Infecções por Mycobacterium/diagnóstico por imagem , Tuberculose Pulmonar/diagnóstico por imagem , Adolescente , Adulto , Idoso , Feminino , Humanos , Pneumopatias Obstrutivas/complicações , Pneumopatias Obstrutivas/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Doenças Pleurais/diagnóstico por imagem , Radiografia , Estudos RetrospectivosRESUMO
A group of 100 carefully selected chest radiographs was read by ten observers, five experienced and five inexperienced. The radiographs were chosen to present the readers with a disproportionately large number of both subtle abnormalities and nonpulmonary lesions. Each reader was allowed to search the radiographs for as long as appropriate, up to a maximum of four minutes. The length of time taken for each observation was recorded to the nearest second. The time-perception data were plotted on both linear and semilogarithmic graphs. The results showed that experienced readers concluded their visual search while positive detection rate was higher than the rate for false-positives. For lesions in the central phasic, with both a rapid and a slow component of perception. If these data are plotted on a semilogarithmic scale, each of the two components plots as a straight line. For lesions in the periphery of the radiograph (chest wall and upper abdomen), the time-perception curve is monophasic, showing only a slow component.
Assuntos
Radiografia Torácica , Radiologia , Percepção Visual , Reações Falso-Negativas , Coração/diagnóstico por imagem , Humanos , Internato e Residência , Pulmão/diagnóstico por imagem , Mediastino/diagnóstico por imagem , Pleura/diagnóstico por imagem , Radiografia Abdominal , Fatores de TempoRESUMO
Digital tomosynthesis studies (DTS) using a linear tomographic motion can provide good quality clinical images when combined with subtraction angiotomography. By modifying our hardware system and the computer software algorithms, we were able to reconstruct tomosynthesis images using an isocentric rotation (IR) motion. Since this is the motion used by C-arm and U-arm angiographic units, these modifications allow for the use of DTS studies in most modern angiographic suites at a reasonable cost. Applying a combination of linear tomographic and IR techniques in clinical cases, we performed DTS studies in six patients, five with aneurysms and one with a hypervascular tumor. The results showed detailed definitions of the pathologic entities and the regional neurovascular anatomy. Based on this early experience, DTS would seem to be a useful technique for the preoperative surgical planning of vascular abnormalities.
Assuntos
Angiografia Cerebral/métodos , Tomografia por Raios X/métodos , Neoplasias Encefálicas/irrigação sanguínea , Neoplasias Encefálicas/diagnóstico por imagem , Angiografia Cerebral/instrumentação , Humanos , Aneurisma Intracraniano/diagnóstico por imagem , Rotação , Técnica de Subtração , Televisão/instrumentação , Tomografia por Raios X/instrumentação , Gravação de Videodisco/instrumentaçãoRESUMO
Pulmonary manifestations in 114 patients with at least two sputum cultures positive for M. intracellularis, no history of any kind of tuberculosis, and not other potential pathogen are described. Even with these stringent diagnostic criteria, seven patients had normal chest radiographs and another seven had reticulonodular-appearing disease without a definite focus of infection. In the other 100 patients, 92% had infiltrates in the apical and/or posterior segments of the upper lobes, and 88% had cavitary disease. The cavities were usually multiple and frequently measured over 4 cm. Scarring and volume loss were common, occurring to some degree in 70% of upper lobe foci. Pleural effusions were uncommon (5%) and usually small. Adenopathy was less common (4%) and usually occurred with upper lobe disease in younger patients. Most patients had some degree of endobronchial spread (81%). The radiographic characteristics of Mycobacterium intracellularis are not believed distinctive enought to differentiate it from Mycobacterium tuberculosis.