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PubMed2005

Pulmonary sarcoidosis: comparison of findings of inspiratory and expiratory high-resolution CT and pulmonary function tests between smokers and nonsmokers.

OBJECTIVE: The purpose of our study was to compare the high-resolution CT and pulmonary function test findings of smokers and nonsmokers with pulmonary sarcoidosis. MATERIALS AND METHODS: Full inspiratory and expiratory high-resolution CT of the thorax and pulmonary function tests were performed in 46 patients (23 smokers and 23 lifelong nonsmokers) with histologically proven sarcoidosis. The median interval between high-resolution CT and pulmonary function tests was 8 days (range, 0-27 days). High-resolution CT findings were categorized into six patterns, and the overall extent of each pattern was scored independently (high-resolution CT score). Correlation between each high-resolution CT score with each pulmonary functional parameter was performed using Spearman's rank correlation and stepwise multiple regression analysis. RESULTS: Air trapping on expiration (45/46 patients, 98%) and small nodules on inspiration (all 46 patients, 100%) were the most common findings. Smokers had a greater extent of emphysema than nonsmokers (p = 0.002). No significant difference was seen in the extent of air trapping, consolidation, ground-glass attenuation, reticular opacities, or small nodules between smokers and nonsmokers. On Spearman's rank correlation, the extent of air trapping negatively correlated with forced vital capacity in smokers (p < 0.05) but not in nonsmokers. The extent of small nodules negatively correlated with forced vital capacity and positively correlated with the ratio of forced expiratory volume in 1 sec to forced vital capacity in nonsmokers (p < 0.05, both) but not in smokers, respectively. On stepwise multiple regression analysis, the extent of air trapping on CT was independently associated with decreased forced vital capacity (p < 0.05), and cigarette smoking was the main determinant of decrease in maximum midexpiratory flow and forced expiratory flow at 50% of vital capacity (p < 0.01). CONCLUSION: Cigarette smoking confounds the correlation between the CT and pulmonary function test findings in patients with sarcoidosis. Therefore, smoking history must be taken into account when correlating the extent of parenchymal sarcoidosis on CT with functional impairment.

Adult↗

PubMed1979

Effect of different workloads varying in intensity and duration on resolution acuity.

An experiment was conducted to determine the effect of participation in physical activity on resolution acuity. In the experiment, 21 undergraduate males participated in exercise sessions with work loads of 300, 700, and 1100 kmp for durations of 3 and 6 min. and a non-exercise control session. Resolution acuity was then determined by finding thresholds of a 20-cpd sinusoid-wave grating using the method of adjustment. A repeated-measures analysis of variance compared the effects of different workloads, intensities, and durations of workloads, and the interaction of intensity and duration on resolution acuity. Significant improvement of resolution acuity was found for all workloads relative to the non-exercise control session, for all other workloads relative to the 300 kpm/3 min. workload, and for the 1100 kpm/6 min. workload relative to the 300 kpm/6 min. and the 700/3 min. workloads. Increases in duration or intensity of exercise significantly improved resolution acuity. There was no significant interaction of the variables of intensity and duration of work on resolution acuity.

Humans↗

PubMed1995

Effect of temporal frequency and contrast on peripheral grating resolution.

We measured resolution at 10 degrees in the inferior temporal retina using horizontal and vertical gratings of different contrasts which modulated in time at temporal frequencies from 0 to 40 Hz. Since peripheral grating resolution is directly related to the sampling density of retinal ganglion cells this allowed us to observe changes in responding ganglion cell density as the stimulus properties changed to selectively stimulate magnocellular pathway cells (M cells) instead of parvocellular pathway cells (P cells). At all contrasts there was no decline in resolution performance up to 10 Hz, after which resolution deteriorated significantly, this effect being greater at lower contrasts. The predicted psychophysical resolution limit for M cells calculated from the anatomical data of Dacey indicates that resolution for high temporal frequency (30 Hz) or low contrast (5%) stimuli is too good to be mediated by M cells alone and there is still significant P cell stimulation by these stimuli.

Contrast Sensitivity↗

PubMed1993

High resolution pinhole SPECT for tumor imaging.

High-resolution, non-invasive, 3D-imaging techniques would greatly benefit the investigation of the localization properties of tumor-specific radiopharmaceuticals in laboratory animals. The present study reports how pinhole SPECT can be applied to tumor localization studies in small laboratory animals to provide high resolution SPECT images in vivo. Pinhole SPECT was performed using a rotating scintillation camera, equipped with a pinhole collimator. The sensitivity of a 2 mm diameter collimator at 45 mm from the source is 90 cps/MBq for 99mTc. The planar spatial resolution at a 45 mm distance is 2.2 mm. The transaxial spatial resolution, with a distance of 45 mm between the collimator aperture and the axis of rotation, is 3.1 mm. For SPECT imaging, spatial linearity is preserved across the usable field-of-view. The major advantage of the high resolution properties of pinhole tomography is demonstrated by the enhanced lesion-to-normal-brain uptake ratio achieved on tomographic slices as compared to planar images. For example, 201Tl tumor-to-normal-brain uptake ratios of 1.1 to 1.3 observed on planar images, corresponded to ratios ranging from 3.2 to 3.7 on the SPECT slices. Examples of the activity distributions of two radiopharmaceuticals in tumor and in normal brain for sagittal and coronal images are given. In all cases, tumors are clearly delineated on the pinhole SPECT slices. The present study shows that pinhole SPECT performed with standard SPECT instrumentation can give high spatial resolution images, with a FWHM approximately 3 mm and a sensitivity approximately 100 cps/MBq for 99mTc.

Animals↗

PubMed1982

Frequency resolution and hearing loss.

Future scientific and diagnostic interest in frequency resolution requires an evaluation of the different methods that are available to measure it. We compared three methods: (1) pure-tone thresholds in broadband noise, (2) pure-tone thresholds in the presence of a fixed pure-tone masker and (3) psychoacoustical tuning curves. We additionally obtained estimates of temporal integration and of speech intelligibility in noise. Three subject groups were tested: 10 normals, 13 subjects with a noise-induced hearing loss and 18 subjects with a cochlear hearing loss but no history of noise exposure. Generally the three measures of frequency resolution show moderate agreement with each other. Poor frequency resolution is invariably associated with a pure-tone threshold loss. Temporal integration appears unrelated either to the pure-tone threshold loss or frequency resolution. Some of the measures of frequency resolution display significant correlation with speech intelligibility in noise. However, since both variables are correlated with pure-tone threshold loss the exact relationship between frequency resolution and speech intelligibility cannot be clearly established.

Adolescent↗

PubMed1999

Squinting with the mind's eye: effects of stimulus resolution on imaginal and perceptual comparisons.

Subjects either viewed or visualized arrays that were divided into four quadrants, with each quadrant containing a set of stripes. In two experiments, one array contained only relatively narrow (high-resolution) stripes, and one contained only relatively thick (low-resolution) stripes. The subjects compared sets of stripes in different quadrants according to their length, spacing, orientation, or width. When the subjects visualized the arrays, they required much more time to compare high-resolution patterns than low-resolution patterns; when the subjects saw the arrays, they evaluated both types of arrays equally easily. In addition, the results from the third experiment provide strong evidence that people use imagery in this task; in one condition, the subjects evaluated oblique sets of stripes, and in another condition, they evaluated vertical and horizontal stripes. In both imagery and perception, the subjects made more errors when evaluating oblique stimuli; in imagery, they also required more time to evaluate oblique stimuli. The results suggest that additional effort is required in imagery to represent visual patterns with high resolution. This finding demonstrates that, although imagery and perception may activate common brain regions, it is more difficult to represent high-resolution information in imagery than in perception.

Adult↗

PubMed2006

[Performance evaluation of computed tomography with equivalent resolution images].

A method of evaluating the performance of computed tomography (CT) with equivalent resolution images was investigated. Generally, in performance evaluations of CT, the resolution property is measured by the wire method, and the noise property is measured from noise images of a cylindrical water phantom. The signal-to-noise ratio (SNR) is then calculated for the integrated evaluation. Our proposed method enabled perceptual integrated evaluation by using equivalent resolution images created with frequency processing. The frequency-processing factor was calculated from the ratio of the modulation transfer factors of two models of CT, and the image of one of the two was processed by the factor. Because these processed images have resolution equivalent to images of the other CT, the perceptual evaluation with noise images becomes effective. In this investigation, images of a water phantom and a middle contrast resolution phantom were employed. Perceptual comparison of the amount of noise with equivalent resolution images could be performed easily, and effective performance evaluation was achieved. Therefore, our proposed method is useful for noise property and performance evaluation of CT.

Evaluation Studies as Topic↗

PubMed2000

PET with a dual-head coincidence camera: spatial resolution, scatter fraction, and sensitivity.

UNLABELLED: Scintillation cameras with options for detecting positron annihilation quanta in the coincidence acquisition mode may be the most innovative diagnostic devices introduced in nuclear medicine during the last few years. Besides conventional low-energy imaging in the collimated single-photon mode, these options offer a relatively inexpensive opportunity to perform uncollimated PET by switching into the coincidence acquisition mode. Instead of collimators, scatter frames (with 2 optional configurations: axial or open scatter frame) can be mounted to reduce the amount of quanta reaching the detectors from parts of the patient's body outside the field of view. This study investigates the coincidence imaging properties of the scintillation camera by measuring spatial resolution, scatter fraction, sensitivity, and count-rate response for 18F. METHODS: A needle in air and a plastic tube in water, each filled with 18F, were oriented axially and transversally to measure the transverse and axial spatial resolutions, respectively. Using either the axial or the open scatter frame, a standard cylinder filled homogeneously with activity was studied over several half-life periods to deduce the respective scatter and random fractions of the system by means of a sinogram technique. The activity of the cylinder was kept low to determine the sensitivity to coincidence events for both scatter frames. RESULTS: Depending on the distance between the line source and the axis of rotation and on the choice of the axial acceptance angle used to reconstruct the coincidence events (single-slice rebinning algorithm), the axial resolution was found to be between 6 and 10 mm (full width at half maximum) with the axial scatter frame mounted. The transversal resolution was 6-6.5 mm on the axis of rotation, independent of the scatter frame used. The scatter fraction amounted to roughly 25% for the axial and 38% for the open scatter frames. The sensitivity when measuring true coincidence pairs ran to nearly 650 Hz/kBq/mL, when acquisition was performed with the axial scatter frame using a 30%-wide photopeak energy window. When acquiring with the open scatter frame, the sensitivity increased to nearly 3000 Hz/kBq/mL. Using the axial scatter frame, the homogeneously filled cylinder could be scanned with a maximum true coincidence rate of 2000 Hz for an activity of 55-60 MBq. Although this maximum true coincidence counting rate did not change significantly when the acquisition was performed with the open scatter frame, the respective activity in the standard cylinder was decreased to 10-15 MBq. CONCLUSION: The spatial resolution of the scintillation camera is sufficient for high-resolution coincidence imaging. Compared with a dedicated PET scanner, the scatter fraction is relatively high and should therefore be corrected adequately. The relatively low sensitivity and the rather low maximum true coincidence counting rate are considerably inferior compared with a conventional PET scanner. However, these drawbacks can be partially compensated for, facilitating its clinical use.

Gamma Cameras↗

PubMed2000

[Study of helical CT low-contrast resolution and its influencing factors].

This paper studies the helical CT low-contrast resolution and its influencing factors by experimental analysis. The CT low-contrast resolution increased with mA, kV, slice thickness, scan time and FOV, and decreased with matrix, pitch and thickness of the scanned objective. The reconstruction algorithm of high resolution results lower low-contrast resolution. Mostly helical image low-contrast resolution is slightly lower than axial image. It's very important for us to understand CT low-contrast resolution and its influencing factors for the correct evaluation of the performance of CT scanner.

Algorithms↗

PubMed1991

Spatial resolution in SPECT: influence of measurement set-up and reconstruction parameters.

The ability of a tomographic system to detect small lesions and to assess them quantitatively is affected by several performance parameters, among them spatial resolution in the transverse slice and in the axial direction. This study was done to determine reconstructed resolution under clinical conditions for various parameters, i.e. radius of rotation, radial position within the transverse field of view, and amount of smoothing in the reconstruction process (various reconstruction filters and a Metz prefilter). The axial resolution is independent of the reconstruction filter but depends on the prefilter, the radius of rotation (ROR), and the source position. The transaxial resolution is dependent on the reconstruction filter, the prefilter, the ROR, and the source position. The reconstructed resolution and the system resolution were compared and differences between both are discussed.

Humans↗

PubMed1989

[Comparison of high resolution computed tomography and pulmonary function tests in diagnosis of mild emphysema].

To assess the ability of high resolution CT scan and pulmonary function tests in detecting and grading mild emphysema, we correlated the high resolution CT scan and pulmonary function tests with the pathologic grade of emphysema and the destructive index of lung specimens from 42 patients undergoing thoracotomy for solitary pulmonary nodules. Using the high resolution CT scan, we could identify the pathologic grade of mild and moderate emphysema. By measuring diffusing capacity per unit alveolar gas volume (DLco/VA), it seemed to be possible to detect the mildest degree of alveolar destruction assessed by the destructive index, which was not detected by high resolution CT scan. The reason for these results seemed to be that we assessed the severity of emphysema by detecting the air space enlargement on high resolution CT scan images caused by the destruction of alveolar walls, which were detectable by measuring DLco/VA. We conclude that it is possible to detect mild emphysema using the combination of high resolution CT scan and pulmonary function tests.

Adult↗

PubMed1979

[Time resolution of scintigraphically determined left ventricular volume curves (author's transl)].

In 25 patients with angiographically proven coronary heart disease and in 15 patients without heart disease, gated cardiac blood pool scintigraphy was done with 15 mCi 99mTc-HSA in LAO projection. Scintigraphic data were collected in list mode by means of a gamma camera connected to a computer system (Siemens 330). A cumulative scintigram scintigram sequence with a time resolution of 100, 50 and 25 frames/sec was constructed using several hundred heart cycles of equal duration. After background correction volume curves of the left ventricle with a time resolution of 25, 50 and 100 Hz were obtained and the following parameters of these curves were compaired: ejection fraction, maximum ejection rate and maximum filling rate. It could be demonstrated that smoothing by sliding average requires a time resolution of at least 50 Hz, whereas in volume curves smoothed by Fourier-Analysis a time resolution of only 25 Hz is necessary. However, using a time resolution of 25 Hz, the course of the volume curve can not always be clearly demonstrated, so that time resolution of 50 Hz combined with Fourier-Analysis for the gated cardiac blood pool scintigraphy is preferred.

Cardiac Volume↗

PubMed1993

[High-resolution electrocardiography in arrhythmogenic right ventricular disease].

PURPOSE: To determine the value of the high-resolution ECG for the differential diagnosis of arrhythmogenic right ventricular disease. METHODS: A group of 33 patients were studied, 16 males, mean age 34 +/- 16 years. All patients presented non-sustained or sustained or repetitive monomorphic ventricular tachycardias, with left bundle branch block morphology. The anatomic and functional evaluation of the right ventricle was made by a previous echocardiogram. No patient presented left ventricular or septal pathology. High-resolution ECG were obtained from a Corazonix-Predictor II program. In the filtered QRS was analyzed root mean square of the last 40ms QRS, the final lasting of the low amplitude signals < 40 microV and filtered QRS duration. Ten patients underwent to electrophysiological study with right ventricular mapping. RESULTS: The ventricular tachycardias was non-sustained in 18 patients, sustained in 8 and repetitive monomorphic in 7 patients. The echocardiogram was normal in 23 patients, and all these also presented normal high resolution ECG. Among the 10 patients with altered echocardiogram, 9 presented abnormal high-resolution ECG (sensibility 90%; specificity 100%; positive predictive value 100%; negative predictive value 96%; efficacy of the method to define the presence of manifested right ventricular pathology was 96%). Among the 10 patients with altered echocardiogram, 8 underwent to electrophysiological study. In all was detected an abnormal ventricular mapping and abnormal high-resolution ECG. CONCLUSION: The high-resolution ECG is an useful method to define a right ventricular manifested pathology in presence of arrhythmogenic disease of this cavity.

Adolescent↗

PubMed1996

Resolution dependency of microstructural properties of cancellous bone based on three-dimensional mu-tomography.

Micro-computed tomography (microCT) is an emerging technique for the non-destructive assessment and analysis of the three-dimensional cancellous bone architecture. However, the procedures the procedures and applications used to quantify bone structures are not yet standardized. The aim of this study was to provide more insight in the resolution-dependency of microstructural properties of three-dimensional trabecular bone. Ten iliac crest bone biopsies were measured using a newly devised microCT system providing a nominal isotropic resolution of 14 microns. To study the resolution dependency the measured data were reconstructed on reduced image arrays with reduction factors ranging from 2 to 20. To assess the structural properties, morphometric parameters were computed based on a truly three-dimensional approach. The results showed a strong resolution dependency of the structural properties and that, if very precise results are needed, only the highest resolution will predict the correct values. Nevertheless, since the properties either decrease or increase monotonously up to a nominal resolution of about 175 microns, the values appear to be restorable using a suitable calibration procedure.

Bone Matrix↗

PubMed1996

Value of high-resolution computed tomography in routine evaluation of lung transplantation recipients during development of bronchiolitis obliterans syndrome.

BACKGROUND: Chronic rejection is a major long-term complication after lung transplantation. The purpose of our study was to evaluate the role of repeated high-resolution computed tomographic examinations in monitoring the development of bronchiolitis obliterans syndrome after lung transplantation. METHODS: A total of 126 high-resolution computed tomographic examination in 13 lung transplant recipients was analyzed. During a mean follow-up period of 23 months, bronchiolitis obliterans syndrome developed in eight of the patients. A scoring system from 0 to 10 based on the number of chronic changes on high-resolution computed tomography was developed, and the score of each patient was compared with decline in the forced expiratory volume in 1 second and maximal forced expiratory flow rate of 50% of the forced vital capacity. RESULTS: The score of chronic changes, measured at 1 year after transplantation, correlated inversely with the values of forced expiratory volume in 1 second and maximal forced expiratory flow rate at 50% of the forced vital capacity (p < 0.05). Stage I bronchiolitis obliterans syndrome was associated with scores of 4 to 6 (mean 5.0), stage 2 with scores of 6 to 9 (mean 7.0), and stage 3 with scores of 6 to 9 (mean 7.7). The sensitivity of high-resolution computed tomography was 93% and its specificity was 92% when five chronic changes were used as a cutoff level. CONCLUSIONS: The progress of chronic changes on high-resolution computed tomography occurs concurrently with the development of bronchiolitis obliterans syndrome. High-resolution computed tomography may provide additional morphologic information for noninvasive evaluation of chronic lung rejection.

Adult↗

PubMedDate not supplied

Time course of methacholine induced bronchoconstriction during drugs and spontaneous resolution.

We examined the resolution of the bronchial spasm induced by methacholine after administration of a dose sufficient to provoke PD20 to study, in patients with bronchial asthma, how spontaneous resolution (as opposed to bronchodilator-induced resolution) takes place. According to a randomization criterion, the patients were divided into four groups: 1) resolution induced by salbutamol (S), 2) by ipratropium bromide (I), 3) after placebo (P) and 4) spontaneous resolution (R). In brief, we observed that variations in FEV1 after methacholine PD20, reach statistically significant levels after 15 minutes in patients from groups (S) and (I), after 30 minutes in patients from groups (P) and (R) (p < 0.05). Comparing the phenomenon at various intervals in the four experimental situation, we found a pairing trend: groups (S) and (I) on the one hand, and groups (P) and (R) on the other. On the whole, this phenomenon shows that pharmacological treatment accelerates the process of spontaneous resolution of the bronchial spasm induced by methacholine which, in our experience, beings to show after 15 minutes, and that after 60 minutes, there are no statistically significant differences in the four groups. It is our opinion that closer examination of this phenomenon may provide greater knowledge of the mechanisms that come into play during the phase after stimulation of the muscarinic receptors and that reasonably involve the system to eliminate the muscarinic drug.

Adolescent↗

PubMed1997

Urodynamic correlates of resolution of reflux in meningomyelocele patients.

PURPOSE: Resolution of reflux in meningomyelocele patients is a reflection of improved bladder storage. We correlated resolution of reflux with changes observed in sequential urodynamic studies. MATERIALS AND METHODS: The study included 27 children with meningomyelocele born between 1975 and 1985 who presented with or developed vesicoureteral reflux. Resolution of reflux was observed during the 10-year followup period as they were treated with a regimen of clean intermittent catheterization and pharmaco-therapy. Urodynamic studies were performed when vesicoureteral reflux was present and subsequent to its resolution. The urodynamic parameters compared in the 2 studies included bladder capacity, pressure specific bladder volume, bladder compliance and leak point pressure. RESULTS: Significant increases in bladder capacity, pressure specific bladder volume and bladder compliance were noted. Leak point pressure appeared to be decreased subsequent to resolution of reflux. CONCLUSIONS: Resolution of reflux in meningomyelocele patients correlates with changes in parameters of bladder storage observed on sequential urodynamic studies.

Child↗

PubMed1997

Evaluation of GRAMM low-resolution docking methodology on the hemagglutinin-antibody complex.

A single protein-protein pair, the complex of the influenza virus hemagglutinin with an antibody (Fab BH151), was suggested for prediction at the second experiment on the Critical Assessment of Techniques for Protein Structure Prediction. To predict the structure of the complex, we applied our docking program GRAMM at a decreased resolution (to accommodate the conformational inaccuracies). The lowest-energy match showed a remarkable "low-resolution" surface complementarity between the molecular structures. After receiving the experimental structure of the complex we had a chance to verify our assumptions and results. The analysis of the hemagglutinin-antibody interface revealed several significant conformational changes in the side chains, which resulted in deep interpenetrations of the hemagglutinin and the antibody structures. This confirmed our initial assumption that the structural changes will be beyond the tolerance of high-resolution rigid-body docking. The comparison of the predicted low-resolution match, submitted as the solution, and the experimentally determined complex showed significant structural discrepancies in the orientation of the antibody, due to the low-resolution character of the docking. Because of the severe structural errors, no residue-residue contacts were predicted correctly. However, a significant part of the antigenic site was determined. This illustrates the practical value of the present methodology for the initial prediction of the binding site, as well as points out the problem of transition from the low-resolution predictions of protein-protein complexes to the accurate structure.

Antibodies, Viral↗