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At least 451 records · Page 25Linked to original sources
PubMed2004

Gated myocardial perfusion SPECT: basic principles, technical aspects, and clinical applications.

Electrocardiographically gated myocardial perfusion SPECT (GSPECT) is a state-of-the-art technique for the combined evaluation of myocardial perfusion and left ventricular function within a single study. It is currently one of the most commonly performed cardiology procedures in a nuclear medicine department. Automation of the image processing and quantification has made this technique highly reproducible, practical, and user friendly in the clinical setting. In patients with coronary artery disease, gating enhances the diagnostic and prognostic capability of myocardial perfusion imaging, provides incremental information over the perfusion data, and has shown potentials for myocardial viability assessment and sequential follow-up after therapy. After reading this article, the readers will understand (a) the general principles of GSPECT and quantitation, (b) the methods of the image acquisition and analysis, (c) validation of GSPECT with other cardiac imaging modalities, and (d) application of the GSPECT-derived functional parameters in the clinical practice.

Coronary Disease↗
PubMed2003

Spiral magnetic resonance coronary angiography with rapid real-time localization.

A spiral high-resolution coronary artery imaging sequence (SH) interfaced with real-time localization system (RT) has been developed. A clinical study of 40 patients suspected of coronary artery disease (CAD) was conducted. Segmented k-space acquisition techniques have dominated magnetic resonance coronary angiography (MRCA) over the last decade. Although a recent multicenter trial using this technique demonstrated encouraging results, the technique was hampered by low specificity. Spiral k-space acquisition had demonstrated several advantages for MRCA. Therefore, a first clinical trial implementing spiral high-resolution coronary imaging sequence with real-time localization (SH-RT) was performed.A clinical study of 40 patients suspected of CAD undergoing X-ray angiography was conducted to analyze the clinical reliability of this novel imaging system. The SH-RT had been designed to exploit the unique capability of two imaging sequences. The RT allowed a rapid localization of the coronary arteries. Then SH achieved multislice acquisition during a short breath-hold with submillimeter resolution. The MRCA data were analyzed for scan time, anatomic coverage, image quality, and accuracy in detecting CAD. In 40 subjects, SH achieved 0.7 to 0.9 mm resolution with 14-heartbeat breath-holds. Excellent or good image quality was achieved in 78% (263/337) of the coronary segments. Blinded consensus reading among three observers generated sensitivity of 76% and specificity of 91% in the detection of CAD compared with X-ray angiography. The MRCA imaging sequence implementing a novel spiral k-space acquisition technique enabled rapid and reliable imaging of the CAD in submillimeter resolution with short breath-holds.

Adult↗
PubMed1982

Acquisition of proviral DNA of mouse mammary tumor virus in thymic leukemia cells from GR mice.

Male mice of strain GR develop T-cell leukemia at a low frequency late in life. These leukemia cells contain large amounts of mouse mammary tumor virus (MMTV) RNA and MMTV proteins in a precursor form (Nusse et al., J. Virol. 32:251-258, 1979). We used restriction enzyme analysis and molecular hybridization to identify MMTV proviruses in the DNA of these leukemia cells. GR leukemia cells contained additional integrated MMTV proviruses at various sites in the genome. This amplification of MMTV proviruses in GR leukemia cells is not restricted to one particular endogenous MMTV provirus of strain GR. The number and location of the extra MMTV proviruses present in transplants of GR leukemia cells did not change upon serial transplantation of the leukemia cells. Acquisition of MMTV proviruses was also found in a similar leukemia, L1210 of the DBA/2 mouse strain, but not in three other leukemias, SL2 of DBA/2, BW5147 of AKR, and a spontaneous thymoma of BALB/c. The two main classes of MMTV RNA, 35S and 24S, were present in the cytoplasmic RNA of GR leukemia cells, indicating that the aberrant processing of MMTV precursor proteins is not due to anomolously sized RNAs. We could not detect extra RNAs in GR leukemia cells which would represent read-through transcripts of cellular genes adjacent to the extra MMTV proviruses, initiated by a promoter signal in the right MMTV long terminal repeat sequence. These data suggest that acquisition of MMTV proviruses may coincide with the onset of leukemogenesis in GR male mice.

Animals↗
PubMed2006

[Language and behavioral difficulties at age 3 and half and reading delay in grade 2].

BACKGROUND: Early detection of specific language impairment and dyslexia in children is an important public health problem. Longitudinal studies are needed for the distinction of real impairments from simple transitory delays. METHODS: Teachers filled a 29-item questionnaire on language and behavior for 695 children aged 3.5 years. Four years later (at second grade of primary school) the same children were evaluated for reading and writing. Statistical analysis focused on the relationships between teacher's early observations and reading delay 4 years later. Associated factors were age, sex, educational level and bilinguism of the parents, and area of the school. RESULTS: The delay in written language acquisition (8.5% of the children) was significantly associated with low educational level (but not bilinguism) of the parents and to the area of the school. In univariate analysis, most of the teacher's early negative assessments were significantly related to reading/writing delay, with the exception of some behavioral problems. However, when the effect of associated factors was taken into account only a few items, mainly concerning language expression, remained significantly associated with later reading/writing delay. CONCLUSION: These data show a major role of associated factors (educational level of the parents, area of the school) in reading delay, and help to select specific teacher's observations for an early prediction of this delay.

Age Factors↗
PubMed2001

Quiet imaging with interleaved spiral read-out.

The acoustic noise generated during an MRI sequence can be effectively reduced with the help of soft gradient pulses using sinusoidal ramps. The long slope duration, however, leads to long acquisition times. The use of interleaved spiral trajectories, calculated with long gradient slopes, is proposed to reduce the acquisition time while maintaining low acoustic noise levels. The practicality of this approach is demonstrated on phantom and volunteer images.

Acoustics↗
PubMed2006

Causal connections in the acquisition of an orthographic rule: a test of Uta Frith's developmental hypothesis.

BACKGROUND: In a longitudinal study we tested Frith's causal hypothesis that children first gain orthographic knowledge through reading and then later, as a consequence, through spelling. METHOD: Children from Years 2 and 3 were tested three times over two years on their reading and spelling of pseudo-words which conformed to the conditional orthographic rule, the 'final -e' or 'split-digraph' rule. RESULTS: Cross-lagged panel correlation analyses suggested that the children's success in reading split-digraph words was a causal determinant of their learning to use split-digraphs in spelling, in the 7- to 8-year period and, with one year-group but not with the other, in the 8- to 9-year period. In the 9- to 10-year period children's success in reading no longer seemed to affect their spelling. CONCLUSIONS: These results strongly support Frith's causal hypothesis about the development of orthographic knowledge.

Age Factors↗
PubMed2005

[Written language and intellectual disability].

AIMS: Following the diagnosis of intellectual disability, a prognosis can be offered concerning the degree of autonomy the child will be able to achieve based on prior experience, but which depends on the aetiology of the disability. It is still difficult to give a prospective answer regarding the capacity to reach an operative level of written language. The goal of being able to offer an experience-based prognosis involves prior analysis of how learning dysfunctions are approached in the disabled population. DEVELOPMENT: Although we have an increasingly deeper understanding of the neurocognitive foundations of specific learning difficulties and the careful neuropsychological management of children with disorders affecting the acquisition of written language with a typical intellectual level, those with intellectual disability continue to be treated using a simplistic approach in which their intelligence quotient is still taken as the most relevant feature. Little attention is paid to neuropsychological aspects, the pedagogical and social environment or comorbid aspects that may affect the acquisition of the function. Yet, these are aspects that are submitted to thorough evaluation in children who are not disabled. CONCLUSIONS: The current concept of intellectual disability has gone beyond the definition based on the intelligence quotient. The wide variability in the reading function in children with intellectual disability cannot be explained only according to a psychometric assessment. A more complete neuropsychological approach, as carried out in the population with no disability, will enable us to detect cognitive, pedagogical, social and pathological dysfunctions that interfere with the acquisition of written language.

Learning Disabilities↗
PubMed1986

The utilization of two frequency-shifted sinc pulses for performing volume-selected in vivo NMR spectroscopy.

A new approach to volume-selected in vivo NMR spectroscopy uses two frequency-shifted sinc pulses, in conjunction with pulsed field gradients, to destroy the coherence of the unwanted signals. A hard pi/2 pulse can then be used to read the z magnetization in the region of interest. This method is independent of T2, provides complete volume selection in a single acquisition, and can be readily implemented on most high-field commercial imaging/spectroscopy systems.

Magnetic Resonance Spectroscopy↗
PubMed1998

Evaluation of a cold/flu self-care public education campaign.

The purpose of the study was to evaluate an Ontario Ministry of Health (MOH) cold/flu self-care public education campaign to reduce unnecessary patient visits to doctors. The MOH campaign consisted of an information booklet delivered to every household in an Ontario city, newspaper ads and radio spots. The program ran during January-March 1994. The evaluation consisted of: (1) 2x2 telephone survey in London (experimental area) and Windsor (comparison area), before and during the campaign; and (2) a telephone survey of London family practitioners during the campaign. In addition, data on the incidence of cold/flu visits to three hospital emergency departments and a sample of family physicians' offices were gathered. The data suggest that program rationale may have been questionable because the majority of the surveyed public were knowledgeable and self-reported appropriate doctor visits for cold/flu. Campaign evaluation showed limited impact. Message penetration was low; only one-third of London residents knew of the campaign or read the booklet. Only two of 10 questions showed increases in knowledge in London and no changes were found for beliefs, attitudes, acquisition of new health practices or self-reported visits to the doctor. The physician survey, emergency room and family physician office visit data were consistent with the public survey findings.

Adult↗
PubMed1991

Color mammography. Image generation and receiver operating characteristic evaluation.

Color mammography is a technique whereby dual-energy mammographic image data are used to calculate a calcium image; the calcium image is colorized and overlaid onto the conventional (lower energy) gray scale mammogram for radiologist viewing. This technique is presented as a practical way to use the increased calcium sensitivity of dual-energy mammography without requiring an increase in the number of images that the radiologist must read, and without subjecting the radiologist to the unfamiliar appearance of the dual-energy subtracted images. Using straightforward imaging theory, the acquisition techniques for both conventional and dual-energy mammography were optimized, and the optimal technique factors were used to generate a series of computer-simulated mammographic images that were used in a receiver operating characteristic (ROC) comparative study. Ideal observer ROC experiments indicate that (dual-energy) calcium images yield consistently higher sensitivity and specificity to the presence of calcifications, regardless of the amount of tissue "clutter," whereas conventional mammography results show degraded detectability performance as tissue contrast increases. Using human observers viewing simulated images, color mammography delivered greater calcification detectability than conventional mammography.

Breast Diseases↗
PubMed2006

Plasmid-mediated quinolone resistance determinant qnrS in Enterobacter cloacae.

PCR was used to investigate the occurrence of the plasmid-encoded quinolone resistance determinants qnrA and qnrS among diarrhoeagenic enterobacterial isolates recovered from Hanoi, Vietnam, during the period March 2001 to April 2002. In total, 162 Escherichia coli isolates, 28 Shigella isolates and three Enterobacter cloacae isolates were negative for qnrA, while a single Ent. cloacae isolate harboured a 50-kb qnrS-positive conjugative plasmid. Cloning and sequencing identified a qnrS gene bracketed by open reading frames identical to those surrounding the qnrS gene of a Shigella flexneri isolate from Japan, thereby suggesting a common mechanism of acquisition.

Bacterial Proteins↗
PubMed2003

Evaluation of rapid dose map acquisition of a scanning liquid-filled ionization chamber electronic portal imaging device.

PURPOSE: We evaluated the performance of a new dosimetry module in the LC250 scanning liquid-filled ionization chamber (SLIC) electronic portal imaging device (EPID) for intensity-modulated radiotherapy (IMRT) verification. This module permits one to convert EPID readings to two-dimensional (2D) maps of IMRT dose rate in real time, and to integrate them over time to produce a profile of accumulated dose for treatment verification. METHODS AND MATERIALS: The EPID was calibrated using an iterative procedure, from which a lookup table for dose integration was generated and transferred to the image-acquisition hardware. To evaluate the EPID's integration capability, we investigated the linearity of imaging time (vs. monitor unit [MU]) and integrated dose (vs. planned dose) for static and IMRT fields, in both standard ( approximately 2.7 s/image) and fast ( approximately 1 s/image) synchronous acquisition modes (S- and F-modes). We also compared the EPID-measured profiles with that measured using film and ionization chamber, or calculated from the treatment planning system. For the EPID's patient dose verification capability, we compared the integrated central-axis (CAX) dose with the planned dose for 25 prostate IMRT fields. We also compared the measured relative profiles with the planned ones using a linear regression model, which returns an index sigma (root mean squared error) for the goodness of fit. We identified errors that are either associated with the timing of the EPID-start delay and end truncation, or with the integration process-detector memory effects (decrease in detector's sensitivity with time during the fast continuous acquisition) and beam hold-off effects (the withholding of linac beam pulses when multileaf collimator leaves are not in the correct positions). The CAX doses of static fields were corrected using the ratio of the irradiation time to the imaging time. A linear decay model was proposed to correct the detector memory effect. To investigate the beam hold-off effect, we verified the relative profiles of a five-field prostate IMRT plan for five different MU settings, and correlated the goodness of fit with the percent of beam hold-off. RESULTS: The imaging time is linearly proportional to the given MU with a slope of 0.250 MU/s (ideal slope is 0.250 MU/s) and a R(2) = 1.0. Although the R(2) of the linearity for the measured vs. planned dose is 1.0 for both modes, only the slopes for the S-mode are within 3% of unity. The slopes for the F-mode deviate from unity due to detector memory effects, and are accurately corrected using the linear decay model. The EPID measured profiles agree well (within 2.0%) with the planned dose and profiles for both modes. For the CAX dose of the 25 IMRT fields, the S-mode is within 2% of the planned dose, whereas the F-mode is off significantly (>3%) if not corrected for detector memory effects. For the relative profile verification, lower MU always produces higher sigma for the same mode. The F-mode is more accurate than the S-mode for the same MU; however, the improvement is not proportional to the difference in imaging speed. Analysis of the correlation of the goodness of fit with the percent of beam hold-off indicates that the accuracy of profile verification for the F-mode is predominantly determined by the beam hold-off effect for lower MU. CONCLUSION: The S-mode of LC250 combined with a large MU can be used for the pretreatment verification of IMRT beam delivery with a significant reduction of processing time and computer resources in comparison to off-line processing. Real-time verification during treatment requires the F-mode. Although the detector memory effects encountered in the F-mode can be compensated using the proposed linear decay model, sufficient accuracy for real-time verification requires a resolution of the beam hold-off problem.

Equipment Design↗
PubMed1998

Rhs elements comprise three subfamilies which diverged prior to acquisition by Escherichia coli.

The Rhs elements are complex genetic composites widely spread among Escherichia coli isolates. One of their components, a 3.7-kb, GC-rich core, maintains a single open reading frame that extends the full length of the core and then 400 to 600 bp beyond into an AT-rich region. Whereas Rhs cores are homologous, core extensions from different elements are dissimilar. Two new Rhs elements from strains of the ECOR reference collection have been characterized. RhsG (from strain ECOR-11) maps to min 5.3, and RhsH (from strain ECOR-45) maps to min 32.8, where it lies in tandem with RhsE. Comparison of strain K-12 to ECOR-11 indicates that RhsG was once present in but has been largely deleted from an ancestor of K-12. Phylogenetic analysis shows that the cores from eight known elements fall into three subfamilies, RhsA-B-C-F, RhsD-E, and RhsG-H. Cores from different subfamilies diverge 22 to 29%. Analysis of substitutions that distinguish between subfamilies shows that the origin of the ancestral core as well as the process of subfamily separation occurred in a GC-rich background. Furthermore, each subfamily independently passed from the GC-rich background to a less GC-rich background such as E. coli. A new example of core-extension shuffling provides the first example of exchange between cores of different subfamilies. A novel component of RhsE and RhsG, vgr, encodes a large protein distinguished by 18 to 19 repetitions of a Val-Gly dipeptide occurring with a eight-residue periodicity.

Amino Acid Sequence↗
PubMed2000

The blocking effect of pictorial prompts on sight-word reading.

This study replicates and extends previous work showing that pictorial prompts can interfere with the learning of sight words by students with moderate mental retardation. Effects of training with 6 students were assessed during five conditions using an alternating treatments design. In four conditions, words were presented either alone or with a corresponding picture. In a fifth condition, pictures were used to provide feedback. The results showed that acquisition was achieved fastest during the word-alone conditions with 5 students.

Child↗
PubMed2004

Mannose-binding lectin enhances phagocytosis and killing of Neisseria meningitidis by human macrophages.

Deficiency of mannose-binding lectin (MBL) is probably the most common human immunodeficiency and is associated with an increased risk of mucosally acquired infections including meningococcal disease. Tissue macrophages are an important component of mucosal defense, and so we determined the effect of MBL on uptake of meningococci by human monocyte-derived macrophages. Opsonization with MBL significantly increased the capture and doubled the amount of internalization of Neisseria meningitidis. Inhibition of f-actin polymerization indicated that MBL exerted this effect by a dose-dependent acceleration of uptake into phagosomes, which was maximal within the normal physiological concentration of MBL (1.5 microg/ml) and was independent of scavenger receptors. MBL accelerated the acquisition and subsequent loss of the early endosome marker, early endosomal antigen-1, and enhanced the acquisition of the late endosomal marker, lysosome-associated membrane protein-1. MBL reduced the survival of meningococci within macrophages by more than half, despite the increased uptake of organisms, and significantly reduced the number of viable extracellular bacteria by 80%. We conclude that MBL is a dependent opsonin able to accelerate microbial uptake and killing. These results suggest that MBL could modify disease susceptibility by modulating macrophage interactions with mucosal organisms at the site of initial acquisition.

Cells, Cultured↗
PubMed1991

Hepatitis C in liver transplant recipients.

HCV infection is commonly found in patients with chronic liver disease undergoing liver transplantation. However, the presence of antibody to HCV does not appear to be associated with the development of hepatitis posttransplant. No other risk factors were identified that appear to predispose patients to development of hepatitis in the posttransplant period, including amount of blood product exposure. The role of immunosuppression in the acquisition and expression of liver disease caused by HCV remains to be determined.

Hepacivirus↗
PubMed2003

Using an adaptive semiautomated self-evaluated registration technique to analyze MRI data for myocardial perfusion assessment.

PURPOSE: To validate the adaptive semiautomated self-evaluated registration technique (ASSERT) followed by factor analysis of medical image sequence (FAMIS) for analyzing myocardial perfusion using magnetic resonance imaging (MRI) images. MATERIALS AND METHODS: Eleven patients having a significant stenosis of at least one coronary artery detected by coronarography were examined by thallium tomoscintigraphy and perfusion MRI (first-pass of Gd-DTPA-BMA) at rest and under pharmacologic stress. The MRI images were analyzed by ASSERT to correct for rigid motion in the acquisition plane and to reject those images that were severely deformed or acquired outside the slice plane. The images thus obtained were analyzed by FAMIS. The resulting factor images representing myocardial perfusion were read to identify the ischemic territories corresponding to left anterior descending coronary arteries and right coronary arteries. RESULTS: ASSERT allowed automatic correction for motion and the exclusion of images that could not be registered. The ischemic territories, identified from the factor images of the myocardium, agreed with those identified by coronarography and tomoscintigraphy for 20 of the 22 territories. CONCLUSION: The results demonstrate the feasibility of analyzing myocardial perfusion using MRI acquisition and treating the resulting images by ASSERT and FAMIS. Extending this method to multislice examinations will enable evaluation of the perfusion of the whole myocardium.

Aged↗
PubMed2003

Semantic effects in word naming: evidence from English and Japanese Kanji.

Three experiments investigated whether reading aloud is affected by a semantic variable, imageability. The first two experiments used English, and the third experiment used Japanese Kanji as a way of testing the generality of the findings across orthographies. The results replicated the earlier findings that readers were slower and more error prone in reading low-frequency exception words when they were low in imageability than when they were high in imageability (Strain, Patterson, & Seidenberg, 1995). This result held for both English and Kanji even when age of acquisition was taken into account as a possible confounding variable, and the imageability effect was stronger in Kanji compared to English.

Adult↗