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PubMed1990

Auditory frequency resolution in human infancy.

Frequency resolution is a fundamental capacity of the auditory system that underlies the perception of all complex sounds. The development of this capacity has not been well characterized in humans. This investigation used a nonsimultaneous pulsation threshold technique to examine the development of infant frequency resolution. Psychophysical tuning curves were obtained for 3- and 6-month-olds and for adults at either 500, 1,000, or 4,000 Hz. Both the sensation level and the sound pressure level of the stimulus were varied for adults to determine the contribution of stimulus intensity to age differences in frequency resolution. At 500 and 1,000 Hz, 3- and 6-month-olds' tuning curve widths were equivalent to adults'. At 4,000 Hz, the 3-month-olds' tuning curves were broader than those of 6-month-olds and adults, even when absolute sound pressure level was equivalent. The maturation of psychophysical frequency resolution in infants is discussed in terms of the general development of the auditory system and of nonsensory factors that might contribute to age differences in performance.

Attention↗

PubMed1989

Why is high resolution computerized tomography scanning used in evaluating the lungs?

High resolution computerized tomography scans have been used for medical and legal purposes to evaluate patients with a history of exposure to asbestos. Some investigators argue that high resolution scanning provides a better image of the lungs than routine computerized tomography. A review of the literature shows that although high resolution scanning displays the lymphatics in the lung, it offers no new useful diagnostic information. The authors conclude that no real advantage is attained with high resolution scanning of the lung and that pathology of disease can be determined decisively only by histology.

Evaluation Studies as Topic↗

PubMed1989

Ultrahigh resolution scanning electron microscopy of biological materials.

In recent years, several ultrahigh resolution scanning electron microscopes (SEM) were successively developed. They were all equipped with a field emission electron gun and an objective lens with a short focal length, and showed a resolution better than 1 nm. With such instrument, not only intracellular structures but also virus, bacteriophages, and biological macromolecules were clearly observed. With improvement of the instrumental resolution, some unexpected problems came to the fore in the area of specimen preparation. The first is the metal coating of the specimen, because coated metal particles are plainly seen as rounded "pebbles" at very high magnifications. For observations at the high magnifications, therefore, uncoated and not conductively stained specimens were used. The second problem is contamination by the electron beam. This problem is complicated and remains unsolved. Although the ultra-high resolution scanning electron microscopy has just begun, it will surely open new research fields in biomedicine.

Animals↗

PubMed1986

Evaluation of high resolution digital subtraction angiography in neuroradiology.

A digital subtraction angiography (DSA) system has been modified for capabilities of a 1024 x 1024 matrix with 10 bit depth. Spatial resolution was increased with expansion of the matrix, but contrast resolution was not increased as determined by phantom experiments. Smaller focal spots and magnification factors were also important for improvement of spatial resolution. Clinical evaluation using carotid, vertebral, and cervical DSA with intra-arterial contrast injections demonstrated that there was slight improvement in the image quality, but the final diagnosis and management of patients were not changed with the use of high resolution DSA. Further improvements in image quality of DSA will be accomplished by improvements of image intensifiers and use of smaller focal spots.

Angiography, Digital Subtraction↗

PubMed1988

[High resolution computerized tomography in the study of traumatic pathology of the temporal bone].

Thirty-five patients with temporal bone fractures were examined; the fractures were sometimes associated with dislocation of the ossicular chain caused by road fatalities. Computed Tomography (CT) was performed either because of the presence of clinical symptoms associated with trauma of the temporal bone, or because of a hemotympanum discovered during a CT scan of the brain. Thirty-three fractures were detected: 19 longitudinal, 6 transverse, and 8 complex. An incudostapedial dislocation was also detected, together with a displacement of a stapedial prosthesis from the lenticular process of incus, and 3 incus-malleus dislocations associated with fractures. High resolution CT allows the precise definition of the course of the fractures, of the associated dislocation of the ossicular chain, and of facial nerve lesion, thus allowing a more accurate surgical intervention. In the examination of the temporal bone, high resolution CT is preferable to pluridirectional tomography because it is easier and faster to perform. Moreover, high resolution CT helps reduce the radiation dose, and yields higher-quality images with more accurate diagnostic information. High resolution CT also allows the brain and the temporal bone to be studied at the same time.

Adolescent↗

PubMed1986

Effects of asymmetric photopeak windows on flood field uniformity and spatial resolution of scintillation cameras.

Pulse height analyzer windows that are set on the high side of the photopeak are known to improve spatial resolution and contrast when used for scintillation camera imaging. Asymmetric windows can be used with some scintillation cameras that have energy correction circuitry. In this study the improvement in spatial resolution and loss of field uniformity for 99mTc, 201Tl, and 131I were measured as a function of window asymmetry (up to 30%, defined relative to the loss of counts as compared to a symmetric window under intrinsic conditions). Flood field uniformity was inversely related to the degree of window asymmetry. With 10 cm of scatter the 99mTc integral uniformity deteriorated from 7.9% with a symmetric window to 11.5% for a 30% asymmetric window. The corresponding values for 201Tl were 9.9 and 10.9%. Even without additional scatter, the values for 131I were 23.0 and 26.5%. Spatial resolution, as measured by the full width at half maximum in 10 cm of scatter improved by only 5% for 99mTc and 7% for 201Tl. However, the full width at tenth maximum increased by as much as 20% for 99mTc and 201Tl. A large percentage of this improvement was attained with small degrees of asymmetry. This study demonstrates that 10% or less asymmetry can provide most of the benefit in spatial resolution and contrast that is to be gained without significant losses in field uniformity and count rate.

Image Enhancement↗

PubMedDate not supplied

High-resolution CT investigation of nonchromaffin paragangliomas of the temporal bone.

Twenty-six cases of surgically verified nonchromaffin paragangliomas (NCPs) of the temporal bone were investigated by contrast-enhanced, thin-section, multiplanar high-resolution computed tomography (CT). Based on the high-resolution CT findings the tumors were classified according to a recently introduced surgical classification of NCP into four main types (A, B, C1-C3, and D1-D3). With high-resolution CT tumors were correctly classified in all cases, as was shown with intraoperative correlation. On the basis of these findings, high-resolution CT should replace conventional tomography and should be regarded as complementary to selective angiography in the preoperative evaluation of NCP.

Ear Neoplasms↗

PubMed1984

[Feasibility of high resolution CT in the demonstration of the vestibular aqueduct (Ménière) and otospongiosis of the labyrinth].

Ever since the introduction of temporal bone imaging by means of high-resolution CT, it appears that the combination of high spatial resolution, high density resolution and the freedom of patient positioning for scanning of optimal otological planes may play a unique role in the diagnosis and follow-up of a number of otological disorders. Two examples are described here. The first is the possibility of determining whether the vestibular aqueduct in idiopathic Ménière's disease is obliterated or not, and if so, whether it is a bony or a fibrous obliteration. Although the results are preliminary, there are indications that all three cathegories occur and that the efficacy of drainage of the endolymphatic sac can be evaluated prior to surgery. The second example is the possibility of outlining and quantifying the bone mineral loss in cases of labyrinthine otospongiosis. Preliminary studies have outlined that there is a relationship between the degree of decalcification and the severity of sensorineural hearing loss. These examples show high-resolution, thin-section multiplanar CT to have great potential in the diagnosis and treatment of otological disorders. This will become evident as the techniques that were used here are worked out in more detail and become more widely known.

Hearing Loss, Sensorineural↗

PubMed1983

Standards for measuring spatial resolution in biological X-ray microanalysis.

Lateral resolution in biological X-ray microanalysis is usually severely limited by the necessity to obtain an adequate number of X-ray counts, which requires the use of a relatively large electron beam spot size. Resolution is further degraded by spreading of the beam within the specimen. Although it is possible to make theoretical calculations of resolution, no straightforward and general method of measuring lateral resolution in biological X-ray microanalysis appears to have been proposed hitherto. In this paper, standards are proposed consisting of distinctive protein-bound elements embedded in araldite, and their use is described.

Egg Proteins↗

PubMed1983

The rejection of noncellular artifacts in Papanicolaou-stained slide specimens by an automated high-resolution system. Identification of important cytometric features.

The important cytodiagnostic features that permit discrimination of typical cell types by high-resolution image analysis and pattern recognition techniques have been previously studied in detail. An automated system for the diagnosis of Papanicolaou-stained specimens must also deal, however, with the "real world" of extraneous noncellular artifacts and debris found on every slide. Features that are ideal for the separation of typical normal and abnormal cells may not be adequate by themselves to reject these objects. A new set of discriminatory features must be found. In order to identify those features, a large set of images acquired using the TICAS high-resolution television rapid-scanning system was analyzed and studied. These images, from a variety of slide types, included normal cells, abnormal cells and noncellular artifacts identified by low-resolution preprocessing logic as suspicious enough to warrant high-resolution study. The results indicate that the more important features for such discrimination are not those traditionally important in distinguishing abnormal from normal cells but include color relations, shape measures, boundary properties and texture features.

Cell Separation↗

PubMed1982

Production of L-[1-11C]valine by HPLC resolution.

Based on a recently developed analytical technique, preparative high-performance liquid chromatographic (HPLC) resolution of DL-[1-11C]valine has been achieved. A conventional reverse-phase HPLC column and a chiral mobile phase (aqueous solution of L-proline, cupric acetate, and sodium acetate) were used. The copper can be removed from the L-valine fraction by precipitation as the sulfide, and final purification by cation-exchange chromatography yields L-[1-11C]valine in a form that is acceptable for clinical positron tomographic studies. This purification method does not remove the L-proline introduced in the resolution process, but added L-proline did not affect the tissue distribution of L-[1-14C]valine in rats. We have produced up to 60 mCi of L-[1-11C]valine in an overall synthesis and resolution time of 50 min. This procedure should be adaptable to the rapid resolution of other C-11-labeled amino acid racemates.

Carbon Radioisotopes↗

PubMed1982

Ocular defocus, spurious resolution and contrast reversal.

With the increasing popularity of periodic gratings in vision research, the effects of ocular defocus, such as spurious resolution and the presence of more than one maximum in the contrast - defocus level function, are very important. Optical transfer function theory is used to develop graphs and formulae that can be used to predict the presence of spurious resolution for given levels of defocus and spatial frequency in aberration-free optical system. Geometrical optical approximations are used extensively, as these lead to very simple formulae. These general equations, applying to any optical system, are extended to the particular case of ocular defocus. Formulae are presented that can be used to predict the presence of spurious resolution, in terms of such variables as pupil size and longitudinal focus error. Conditions for the observation of spuriously resolved gratings are also discussed. An example is presented for observing spurious resolution and contrast reversal and this example can be presented as a "pseudo" visual illusion.

Humans↗

PubMed1982

Resolution of gratings oriented along and across meridians in peripheral vision.

Grating resolution was measured at various locations of the visual field for four grating orientations. As an instance of the oblique effect, vertical and horizontal gratings produced the highest resolution values in the central area. At eccentricities larger than about 20 deg, the oblique effect was replaced by a meridional resolution effect, in which resolution was systematically best for meridionally oriented grating bars and worst for grating bars perpendicular to the visual-field meridians. The origin of the effect seems to be neural because it was not caused by peripheral refractive errors or optical distortion of the peripheral retinal image.

Humans↗

PubMed1982

[Time resolution ability of the ear in presbycusis and sensorineural hearing disorders].

In psychoacoustical and electrophysiological experiments the time resolution ability in monaural and binaural hearing was investigated for defined signal parameters. The binaural stimulation is characterized by signals of different structure (dichotic stimulation). With regard to different functional changes in the peripheral and central areas of the hearing organ caused by presbycusis, these investigations confirm that there are similar changes in time resolution processes which may influence speech discrimination in presbycusis to a high degree. In patients with sensorineural hearing loss time resolution ability was reduced only slightly. No defined correlation between lack of time resolution ability and type or degree of hearing loss could be established.

Adult↗

PubMed1982

The impact of employment impasse and its resolution in the allied health professions.

Although conflict within organizations is inevitable, any of its damaging consequences may be minimized or controlled if a consensual process for its rational resolution exists. Since collective bargaining is becoming an increasingly prevalent mechanism for governing the relationships between employees and employers in the allied health professions, knowledge about the various formal conflict resolution mechanisms available is vital. The concept of impasse and its resolution in negotiations and in administration of a labor contract are analyzed. The impact of impasse resolution is summarized, in order to emphasize the interdependent nature of the employment relationship.

Collective Bargaining↗

PubMed1995

Small letter contrast sensitivity: an alternative measure of visual resolution for aviation candidates.

Exceptional vision is needed to maintain high levels of aviation performance. Current standards for helicopter pilot training include superior visual acuity with minimal refractive error. Despite these demanding criteria, it is likely that visual ability varies among those who meet the standards for pilot training. A more complete knowledge of visual capabilities in these individuals will allow us to better correlate vision with performance and to develop more incisive criteria for selection. The purpose of this study was to investigate an alternative test of visual resolution for aviation candidates using small letter contrast sensitivity (SLCS). Computer-generated letter charts were used to measure visual acuity (VA) and SLCS in 16 candidates who had satisfied military vision standards for pilot training. The acuity and contrast charts varied, by line, in equal log steps such that the letter recognition task was comparable for the two types of measurement. VA and SLCS were highly correlated in these subjects, indicating that the two tests measure similar aspects of visual resolution. Scores were distributed across two lines on the acuity chart, but across four lines on the contrast chart, suggesting that SLCS offers a more discriminating test of resolution. This assumption was confirmed in that SLCS was more highly correlated with small amounts of refractive error in the candidates tested. SLCS offers a sensitive, adjunctive measure of visual resolution which may be useful for identifying the unique visual abilities required for aviation.

Analysis of Variance↗

PubMed1994

Assessment of emphysema using high resolution CT, CT expiratory density mask, and plain chest films.

Pulmonary function tests (diffusing capacity for carbon monoxide of the lungs) and radiological imaging (plain chest film, high resolution computed tomography (CT) and CT expiratory density mask) were compared in the assessment of 29 patients with suspected airways obstruction. Conventional roentgenogram showed a good agreement with the diffusing capacity of the lungs and proved to be useful in predicting the presence of severe emphysema, but the extension of the disease was more precisely assessed by computed tomography. A good agreement was found between high resolution CT and density mask CT, although the "subjective" high resolution identified more patients with mild emphysema than the "automated" density mask. In conclusion, although the plain chest film is useful in the diagnosis of severe emphysema, CT (especially when high resolution is used) is helpful in identifying cases of mild disease and in diagnosing the type of emphysema.

Adult↗

PubMedDate not supplied

The ECAT EXACT HR: performance of a new high resolution positron scanner.

OBJECTIVE: The ECAT EXACT HR is a newly designed CTI-Siemens PET scanner with high spatial resolution. Its physical performance with respect to resolution, count rate efficiency, and scatter was investigated and evaluated with phantom studies. MATERIALS AND METHODS: The new tomograph consists of three rings of 112 BGO block detectors (50 mm x 23 mm x 30 mm deep) each, covering an axial field of view of 15 cm with a patient port of 56 cm diameter. Each block is sawed into an 8 x 7 matrix giving 24 detector rings with 784 crystals each. RESULTS: Total sensitivity for a 20 cm cylinder phantom is 177 kcps/microCi/ml in two-dimensional (2D) mode and increases to 1.46 Mcps/microCi/ml in 3D mode. Count rate performance was investigated for different low energy discriminator thresholds. Smaller detector blocks improve noise equivalent counts by approximately 50% compared with the EXACT system both in 2D and in 3D mode. Scatter fractions vary in 2D from 0.09 to 0.13 for energy thresholds from 450 to 250 keV for line sources in a 20 cm diameter phantom. In 3D mode an increase of scatter by a factor of 3 is observed. Transaxial spatial resolution varies from 3.6 mm full width at half-maximal (FWHM) at the center to 4.5 mm FWHM tangentially and 7.4 mm FWHM radially at R = 20 cm. Average axial resolution changes from 4.0 mm FWHM at center to 6.7 mm FWHM at R = 20 cm. CONCLUSION: Due to its special properties, the EXACT HR can be equally applied to routine clinical brain and whole-body imaging and to noninvasive experimental studies of regional tracer concentrations in medium-sized animals.

Animals↗