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PubMed1995

Performance evaluation of a prototype high resolution digital radiographic/near real-time fluoroscopic computerized tomographic system for radiotherapy simulation.

PURPOSE: A new prototype digital radiographic/near real-time fluoroscopic and computerized tomographic (CT) imaging system has been developed and its performance is evaluated for future implementation in a radiotherapy simulator. METHODS AND MATERIALS: The new imaging modality uses a slow scan cooled charge-coupled device (CCD) camera with 2 k x 2 k x 12 bit image resolution. X-ray images formed by a Gd2O2S:Tb flat screen are directly viewed by the CCD camera via a 45 degrees angled mirror and a high speed objective lens. For CT image reconstruction, digital data from a slit image on the CCD array obtained from time-controlled x-ray scans around the object are transferred to a second tomographic computer for processing and display. RESULTS: In the digital radiographic mode, and for a 43.2 x 43.2 cm field size at the phosphor plane, the spatial resolution of the system is 2.3 +/- 0.1 lp/mm (1 sigma) as measured at the 4% level of the modulation transfer function (MTF), whereas the contrast resolution has a value of 0.5%. In the fluoroscopic mode, the system may be operated at a maximum rate of eight frames/s at a relatively lower spatial and contrast resolution. For CT scans, although the potential intrinsic spatial resolution at the isocenter is 0.35 mm, display-limited spatial resolutions of 1.2 and 1.6 mm were obtained for 30 and 40 cm reconstruction circle diameters, respectively. A contrast resolution of 1% at 0.015 Gy entrance dose was achieved, and CT reconstruction circles of up to 51 cm were attainable. CONCLUSION: The new CCD-based imaging system is capable of delivering high-quality digital radiographic and CT images for radiotherapy simulation, whereas the near real-time fluoroscopic mode yields acceptable flicker-free lower quality images at object speeds typical of simulation motions.

Fluoroscopy↗

PubMed1994

Persistence of ventricular arrhythmia after resolution of occult myocarditis in children and young adults.

OBJECTIVES: We sought to examine whether resolution of occult myocarditis in children with associated ventricular arrhythmia correlated with the presence of arrhythmia at late follow-up. BACKGROUND: Complex ventricular arrhythmias have been documented in children with myocarditis. Therapy is aimed at controlling the arrhythmia and any associated ventricular dysfunction. However, no reported studies have documented whether resolution of myocarditis in children is associated with resolution of the associated arrhythmias. METHODS: We performed a retrospective analysis of 12 patients (mean age 12 years) with myocarditis. Ambulatory electrocardiographic (Holter) monitors were reviewed for ventricular arrhythmias at presentation and follow-up. Patients were assigned to Group I if they received corticosteroids in addition to any antiarrhythmic agents and to Group II if they did not receive steroids. Follow-up endomyocardial biopsy was performed in some patients, and results were analyzed in relation to the presence of arrhythmias at follow-up. RESULTS: Eleven patients had ventricular tachycardia, and one had multiform couplets. Corticosteroids were given to seven patients (Group I). Follow-up biopsy was performed in seven patients (six received steroids), with resolution of inflammation in all; four of the seven still had ventricular arrhythmias but with improved control. Of the five patients without follow-up biopsy, three had persistent arrhythmia. Absence of inflammation at follow-up biopsy did not correlate with loss of ventricular arrhythmias, and there was no difference between Group I and II patients with respect to resolution of arrhythmia (Fisher exact test, p = 0.70, power 11%). CONCLUSIONS: Complex ventricular arrhythmias persist after apparent resolution of occult myocarditis in children. Although these arrhythmias are easier to control after such resolution, the patients may require long-term antiarrhythmic therapy.

Adolescent↗

PubMed2005

Familial predictors of sibling and romantic-partner conflict resolution: comparing late adolescents from intact and divorced families.

The present study examined whether predictors of romantic-partner conflict may vary as a function of family structure. Using a cross-sectional design, we tested a mediation model of conflict resolution behaviours among late adolescents from intact (n=185) and divorced (n=87) families. Adolescents rated conflict resolution behaviours in five dyadic relationships: interparental, mother-adolescent, father-adolescent, sibling, and romantic partner. Mother-adolescent and father-adolescent conflict resolution behaviours mediated the relationship between interparental and sibling conflict resolution. Moreover, both mother-adolescent and sibling conflict resolution behaviours mediated the relationship between interparental and romantic-partner conflict resolution behaviours. This model was supported for both positive and negative behaviours, and it applied equally well to adolescents from intact and divorced families. Results are discussed in the context of social learning theories and support conflict resolution behaviours within the family spilling over into romantic relationships for adolescents from both intact and divorced families.

Adolescent↗

PubMed2005

ST resolution in a single electrocardiographic lead: a simple and accurate predictor of cardiac mortality in patients with fibrinolytic therapy for acute ST-elevation myocardial infarction.

BACKGROUND: The extent of ST-segment resolution in the 12-lead electrocardiograph (ECG) obtained early after reperfusion therapy in patients with ST-elevation myocardial infarction (MI) has been shown to predict short- and long-term mortalities. To improve the ease of this method in clinical practice, we sought to evaluate the optimal cutoffs and the prognostic value of ST resolution (STR) measured in a single ECG lead. METHODS: In conjunction with the Intravenous nPA for the Treatment of Infarcting Myocardium Early (InTIME)-2 study, in which patients with an ST-elevation MI of <6 hours' duration were treated with alteplase or lanoteplase, 12-lead ECGs were obtained at baseline and 90 minutes after the start of fibrinolytic therapy in 3030 patients. RESULTS: There was a close correlation between the extent of the sum STR and single-lead ST-elevation resolution ( r = 0.94). The optimal cutoffs for definition of single-lead complete, partial, and no-STR groups were 70% and 50% for anterior infarcts and 70% and 20% for inferior infarcts. The cardiac 30-day mortality rates for the 2 sets of risk groups by sum or single-lead STR were as follows: no resolution, 9.5% vs 10.3%; partial resolution, 5.0% vs 3.6%; complete resolution, 2.0% vs 1.2%. The predictive power was significantly better for single-lead STR. CONCLUSIONS: ST resolution obtained in a single lead is an easy and accurate prognosticator of cardiac 30-day mortality in patients with ST-elevation MI. It is therefore useful for early identification of low- and high-risk subgroups after fibrinolysis and as a surrogate end point in clinical trials.

Aged↗

PubMed2005

Perfusion and diffusion imaging in acute focal cerebral ischemia: temporal vs. spatial resolution.

High-resolution diffusion- (DWI) and perfusion-weighted (PWI) imaging may provide substantial benefits in accurate delineation of normal, ischemic, and at-risk tissue. We compared the capability of low (400 x 400 microm(2)) and high (200 x 200 microm(2)) spatial resolution imaging in characterizing the spatiotemporal evolution of the ischemic lesion in a permanent middle artery occlusion (MCAO) model in rats. Serial measurements of cerebral blood flow (CBF) and the apparent diffusion coefficient (ADC) were performed. Lesion volumes were calculated by using viability thresholds or by visual inspection, and correlated with infarct volume defined by TTC staining at 24 h after MCAO. At the very early phase of ischemia, high-resolution resulted in a significantly larger ADC-derived lesion volume and a smaller PWI/DWI mismatch. At 3 h after MCAO, ADC and CBF lesions showed similar robust correlations with TTC-defined infarct volumes for both groups using previously established thresholds. When lesions were determined visually, low-resolution resulted in a substantial overestimation of TTC-defined infarct volume and a lower inter-observer reliability (r = 0.75), whereas high-resolution produced an excellent correlation with TTC-defined infarct volume and inter-observer reliability (r = 0.96). In conclusion, high-resolution MRI resulted in substantial temporal averaging of the ischemic lesion during the early phase, but was clearly superior in visual determination of final infarct size. Low-resolution reasonably evaluated the temporal and spatial evolution of ischemia when thresholds were used.

Acute Disease↗

PubMed2004

Effect of chromatographic conditions on resolution in high-performance ion-exchange chromatography of proteins on macroporous anion-exchange resin.

We explored chromatographic conditions to obtain high resolution in protein separations by ion-exchange chromatography (IEC) on a macroporous anion-exchange resin of 10 microm in particle diameter. We studied effects of flow-rate, gradient time (steepness of salt concentration gradient) and column length on resolution in wide ranges. It was found that very high resolutions are attainable at long gradient times with long columns. The resolution continuously became higher as the gradient time and the column length became longer except in some special cases. The dependence of resolution on gradient time was particularly great when the column was long and the gradient time for the change of 0-0.5 M NaCl was longer than 2 h. On the other hand, the effect of flow-rate on resolution was very small. Although the separations at long gradient times with long columns have not been popular in high-performance IEC and it takes several hours for one separation, such separations should be advantageous when very high resolutions are required like in proteomics research.

Anion Exchange Resins↗

PubMed2006

The variation of intrinsic spatial resolution across the UFOV of scintillation cameras.

The aim of the present study was to investigate in detail the variation of the intrinsic spatial resolution across the useful field of view (UFOV) of gamma-cameras and to explore whether this variation could lead to observable effects in clinical images. Two gamma-cameras were used, without their collimators, to acquire 560 (99m)Tc point source images at different points across their UFOVs, in order to measure the intrinsic spatial resolution at each point. Possible clinical effects of the resolution variation were examined on images of a thyroid phantom using a LEHR collimator, acquired at different locations on the UFOV and at various distances from the collimator. The gamma-camera intrinsic resolution varied significantly across the UFOV, being generally lower at the central region and deteriorating at the edges. Pronounced local maxima and minima were found at points corresponding to the centers of the photomultiplier tubes (PMTs) and halfway in between. Maximum differences of more than 50% were observed between the points presenting the best and worst intrinsic resolution. Differences between neighboring points reached 17%. The effects of resolution variation were clearly observable on the thyroid phantom images. It was concluded that an appropriate correction algorithm might be necessary in order to correct for the variation of the intrinsic spatial resolution across the UFOV of gamma-cameras.

Gamma Cameras↗

PubMed2004

Admission Troponin T and measurement of ST-segment resolution at 60 min improve early risk stratification in ST-elevation myocardial infarction.

AIMS: The prognostic value of admission troponin T (tnT) levels and the resolution of the ST-segment elevation in ST-elevation myocardial infarction (STEMI) is well established. However, the combination of these two early available markers for predicting risk has not been evaluated. METHODS AND RESULTS: We evaluated 516 patients with fibrinolytic treated STEMI from the ASSENT-2 and ASSENT-PLUS studies, which had both admission tnT and ST-monitoring available. We used a prospectively defined cut-off value of tnT of 0.1microg/l. For ST-segment resolution, a cut-off of 50% measured after 60min was used. Both a tnT >/=0.1microg/l (n=116) and ST-segment resolution <50% (n=301) were related to higher one-year mortality, 13% vs 4% (P<0.001) and 8.4% vs 2.8% (P=0.009), respectively. In a multivariate analysis ST-segment resolution was and tnT showed a strong trend to be independently related to mortality. The combination of both further improved risk stratification. The one-year mortality in the group with elevation of tnT and without ST-segment resolution compared to the group without tnT elevation and with ST-segment resolution was 18.2% vs 2.8% (P<0.001). CONCLUSIONS: Both tnT on admission and ST-segment resolution after 60min are strong predictors of one-year mortality. The combination of both gives additive early information about prognosis and further improves risk stratification.

Arrhythmias, Cardiac↗

PubMed2005

Rippled-spectrum resolution dependence on masker-to-probe ratio.

Resolution of rippled sound spectrum (probe) in the presence of additional noise band (masker) was studied as a function of masker-to-probe ratio and sound level in normal listeners. The probe bands were 0.5-oct wide (ERB) centered at 2 kHz; the masker band either coincided with the probe (on-frequency masker), or was 3/4 octaves below (low-frequency masker), or 3/4 octaves above the probe (high-frequency masker). Ripple-density resolution in the probe band was measured by finding the highest ripple density at which an interchange of ripple peaks and valleys was detectable (the phase-reversal test). (i) The effect of the low-frequency masker increased (resolution decreased) when masker-to-probe ratio changed from -25 dB to +20 dB; the effect increased (resolution decreased) with sound level increase. (ii) The effect of the on-frequency masker steeply increased (resolution abruptly decreased) when masker-to-probe ratio exceeded 0 dB; the effect was little dependent on sound level. (iii) The high-frequency masker was little effective unless the masker-to-probe ratio reached 30-40 dB; the effect increased (resolution decreased) with sound level decrease. Thus, different position of the masker band relative to the probe resulted in qualitatively different kinds of spectrum-pattern resolution dependence on both the masker-to-probe ratio and sound level.

Acoustic Stimulation↗

PubMed2004

The effect of the season on otitis media with effusion resolution rates in the New York Metropolitan area.

OBJECTIVE: To study the relationship between season and resolution rates of otitis media with effusion (OME) in the New York Metropolitan area, in order to provide objective data useful to the practicing otolaryngologist in determining if seasonal factors should be considered in OME management decisions. METHODS: This was a prospective study of children referred to a tertiary medical center. Children with OME (confirmed by pneumatoscopy and tympanometry) were followed by an otologist at an academic medical center over a 3 years period. They returned approximately every 6 weeks until the end points of resolution of the effusions or ventilating tube placement. Each period between visits is termed an "interval." RESULTS: 127 patients with 231 effusions were followed for a total of 354 intervals. Effusions at intervals beginning in autumn were least likely to resolve by the next visit (24.29%) while intervals ending in the summer had the greatest rate of resolution (44.32%). Analyzed by month, the lowest rates of resolution were seen in intervals beginning in September, November, February, and March (16.67, 21.05, 20.51, and 19.15%, respectively). Intervals beginning in May had the greatest chance of resolution (51.72%). There was a positive correlation between resolution rates and average daily temperatures as reported by month. CONCLUSIONS: The season and month of the year are relevant factors in the clinical course of OME in the New York Metropolitan area. Based on the observed rates of resolution, one could reasonably consider taking a more conservative approach to OME management in May through August, and a more aggressive approach in the fall and winter months.

Acoustic Impedance Tests↗

PubMed2005

Intraocular lens-capsular bag imaging with ultrahigh-resolution optical coherence tomography Pseudophakic human autopsy eyes.

PURPOSE: To compare in vitro ultrahigh-resolution optical coherence tomography (UHR OCT) cross-sectional images of the pseudophakic human autopsy eye with histology to evaluate the potential of this imaging technique for enhanced visualization of the anterior segment, especially the capsular bag, intraocular lens (IOL), and posterior capsule opacification (PCO) formation after cataract surgery. SETTING: Department of Medical Physics and Department of Ophthalmology, University of Vienna, Vienna, Austria, and Department of Oral and Maxillofacial Surgery Institute of Dentistry, University of Turku, Turku, Finland. METHODS: Ultrahigh-resolution OCT images were acquired from 7 pseudophakic human autopsy eyes using 1.4 microm axial x 3.0 microm transverse resolution. The axial resolution with UHR OCT is 1.4 microm compared to 10.0 microm with the commercially available OCT. Plastic-embedded histologic sections were obtained in precise alignment with the OCT tomograms. RESULTS: Ultrahigh-resolution OCT cross-sectional tomograms corresponded to the histologic sections. With the wavelength used (800 nm), the anterior and posterior capsules, area of lens epithelial cell growth and extracellular matrix proliferation, and IOL could be clearly visualized. The extent of capsular bag adhesion to the IOL could be detected, as well as the amount of PCO formation. CONCLUSIONS: The improved resolution makes UHR OCT a powerful tool in anterior segment imaging and evaluation of the capacity of IOL materials and models to induce capsular bag adhesion. Ultrahigh-resolution OCT may also help in determining the area of origin of PCO after cataract surgery.

Autopsy↗

PubMed2005

Effect of temporal resolution on the estimation of left ventricular function by cardiac MR imaging.

The aim of this study was to investigate the effect of temporal resolution on the estimation of left ventricular (LV) function by cardiac magnetic resonance (MR) imaging using a steady-state free precession (SSFP) sequence. Left ventricular function was assessed by cine MR imaging using a segmented SSFP sequence in 10 healthy volunteers. Views per segment (VPS) were set at 8 and 20, resulting in high and low true temporal resolution, respectively. Irrespective of VPS, images were reconstructed at 40 cardiac phases, providing high apparent temporal resolution. Data were analyzed using 40, 20 and 10 phases to simulate different apparent temporal resolutions. Increasing the cardiac phases used for analysis slightly decreased mean end-systolic volume (ESV) and slightly increased mean ejection fraction (EF). No substantial difference in estimates of end-diastolic volume (EDV) was found between VPSs of 8 and 20. Imaging with a VPS of 20 yielded a larger ESV and smaller EF than imaging with a VPS of 8 when 40 phases were used. In conclusion, low true temporal resolution causes overestimation of ESV and underestimation of EF. Improvement of apparent temporal resolution mildly reduces but does not eliminate the errors caused by low true temporal resolution.

Adult↗

PubMed2005

Resolution for spatial segregation and spatial localization by motion signals.

We investigated two types of spatial resolution for perceiving motion-defined contours: grating acuity, the capacity to discriminate alternating stripes of opposed motion from transparent bi-directional motion; and alignment acuity, the capacity to localize the position of motion-defined edges with respect to stationary markers. For both tasks the stimuli were random noise patterns, low-pass filtered in the spatial dimension parallel to the motion. Both grating and alignment resolution varied systematically with spatial frequency cutoff and speed. Best performance for grating resolution was about 10 c/deg (for unfiltered patterns moving at 1-4 deg/s), corresponding to a stripe resolution of about 3'. Grating resolution corresponds well to estimates of smallest receptive field size of motion units under these conditions, suggesting that opposing signals from units with small receptive fields (probably located in V1) are contrasted efficiently to define edges. Alignment resolution was about 2' at best, under similar conditions. Whereas alignment judgment based on luminance-defined edges is typically 3-10 times better than resolution, alignment based on motion-defined edges is only 1.1-1.5 times better, suggesting motion contours are less effectively encoded than luminance contours.

Cues↗

PubMed2003

Does 24-hour ST-segment resolution postfibrinolysis add prognostic value to a Q wave? An ASSENT 2 electrocardiographic substudy.

BACKGROUND: Both ST resolution and Q-wave development postfibrinolysis provide important prognostic insights in patients with acute myocardial infarction (MI). However, the relative contributions of these 2 factors to risk assessment have not been examined prospectively. METHODS AND RESULTS: ST resolution and Q development were evaluated 24 to 36 hours (24-36 h) postfibrinolysis in ASSENT-2: 13,100 out of 16,949 patients who had both baseline and 24-36 h electrocardiograms free of confounders (left bundle branch block, ventricular rhythm, reinfarction before 24-36 h electrocardiograms) were included in this analysis. Q-wave MI evolved in 10,466 patients (79.9%) and 2634 patients (20.1%) had non-Q-wave MI at 24-36 h postfibrinolysis. Mortality rates at 1-year were 7.0% for patients with Q-wave MI and 5.8% for non-Q-wave MI patients, respectively (P =.046). Patients with Q-wave MI versus those without were less likely to have complete ST-segment resolution (49.1% vs 59.1%) and more likely to have partial (37.1% vs 27.8%) or no resolution (13.8% vs 13.1%) at 24 to 36 hours postfibrinolysis (P <.001). Mortality rates at 1 year for Q-wave MI with complete, partial, and no resolution were 5.2%, 8.1%, and 10.1%, respectively (P <.001), and for non-Q-wave MI with complete, partial, and no resolution were 4.5%, 7.6%, and 8.0% (P =.003). CONCLUSION: These results demonstrate the additional prognostic significance of ST-segment resolution to Q-wave development at 24 to 36 hours after fibrinolysis.

Aged↗

PubMed2000

ST-segment resolution and infarct-related artery patency and flow after thrombolytic therapy. Thrombolysis in Myocardial Infarction (TIMI) 14 investigators.

Because patients who fail to achieve reperfusion after thrombolytic therapy remain at high risk for morbidity and mortality, noninvasive measures of infarct-related artery (IRA) patency are needed to identify candidates for rescue interventions. We prospectively studied 444 patients from the Thrombolysis In Myocardial Infarction (TIMI) 14 trial with interpretable baseline and 90 minute 12-lead electrocardiograms. The percent resolution of ST-segment deviation from baseline to 90 minutes was compared with 90-minute IRA TIMI flow grade, as determined in an angiographic core laboratory. Patients with complete (> or = 70%) ST resolution (n = 208; 47%) had a patency (TIMI 2 or 3 flow) rate of 94%, a TIMI 3 flow rate of 79%, and a 30-day mortality rate of 1.0%. Patients with partial (30% to 70%) or no (< or = 30%) ST resolution had significantly lower rates of patency (72% and 68%; p < 0.0001 vs complete ST resolution) and TIMI 3 flow (50% and 44%; p < 0.0001 vs complete ST resolution), and higher 30-day mortality (4.2% and 5.9%; p = 0.01 vs complete ST resolution). With use of electrocardiographic criteria alone, approximately 50% of patients can be classified as having a high (94%) probability of IRA patency and a very low risk for mortality. Angiography to determine patency of the IRA may be unnecessary in these patients. In patients without complete (> or = 70%) ST resolution, the IRA is still likely to be patent, and additional information from clinical variables or serum markers may help to identify candidates for coronary angiography. Patients with persistent ST elevation despite a patent IRA are at increased risk for mortality, likely due to extensive microvascular and tissue injury.

Abciximab↗

PubMed2000

Resolution optimisation in micellar electrokinetic chromatography using empirical models.

Theoretical and empirical models can be used to model the migration or separation characteristics in micellar electrokinetic chromatography in order to optimise the resolution. In this paper only empirical models were used, because it is easier and more straightforward to obtain these models. Several empirical approaches for the optimisation of the resolution were compared in order to determine which response should be modelled preferably. The use of models of the effective mobility in combination with average plate numbers proved to be the most suitable approach to optimisation of the resolution, because the relative prediction errors of the models of the effective mobility were a factor of 2-4 smaller than the relative prediction errors of the models of the apparent mobility. Moreover for the least separated peak pair the resolutions based on the models of the apparent and effective mobility showed relative prediction errors that were approximately a factor of 2 smaller than the relative prediction errors of the resolutions based on the models of the resolution and separation factor. The predictions of the separation factor based on the different models generally showed lower prediction errors than the predictions of the corresponding resolutions. Although the relative prediction errors were large, particularly for closely migrating compounds, the empirical approach will probably lead to the optimum separation buffer composition.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2002

What limits detection and resolution of short-wavelength sinusoidal gratings across the retina?

Peripheral resolution acuity for achromatic gratings is known to be limited by the density of the underlying ganglion cell sampling array. After confirming isolation of the short-wavelength sensitive (SWS) system using chromatic adaptation methods, we wished to determine if resolution is limited by blue/yellow ganglion cell sampling (evidenced by a superiority of detection over resolution acuity and the perception of aliasing) and thus directly related to SWS-driven ganglion cell density. We measured detection and resolution acuity between 0 degrees and 35 degrees, using blue sinusoidal gratings superimposed on a yellow adapting background which ranged in intensity from 2.5 to 4.7logTrolands. At all locations, a break could be observed in the acuity vs. illumination curves followed by a plateau. Detection and resolution acuity were the same for low background intensities, but resolution acuity was lower than detection at higher intensities, accompanied by observations of chromatic aliasing. SWS resolution is sampling-limited across the retina and agrees well with predicted performance based on anatomical estimates of small bistratified ganglion cell density.

Adolescent↗

PubMed1999

Foveal and peripheral thresholds for detection and resolution of vanishing optotype tumbling E's.

We measured detection and resolution acuity for vanishing optotype tumbling E stimuli in both the fovea and at 30 degrees in the periphery to determine if peripheral resolution is sampling limited for this stimulus. In the fovea, where acuity is optically limited, detection and resolution were the same. At 30 degrees, however, detection was markedly better than resolution indicating that peripheral resolution is sampling limited for this stimulus. Detection acuity was higher when contrast was 90% rather than 40%, but resolution did not change with contrast. The vanishing optotype is a legitimate perimetric stimulus to measure retinal ganglion cell density provided the task is resolution and not detection.

Contrast Sensitivity↗