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61.
Li An PhD Jan Willem van der Veen PhD Shizhe Li PhD David M. Thomasson PhD Jun Shen PhD 《Journal of magnetic resonance imaging : JMRI》2013,37(6):1445-1450
Purpose:
To propose using the generalized least square (GLS) algorithm for combining multichannel single‐voxel magnetic resonance spectroscopy (MRS) signals.Materials and Methods:
Phantom and in vivo brain MRS experiments on a 7 T scanner equipped with a 32‐channel receiver coil, as well as Monte Carlo simulations, were performed to compare the coefficient of variation (CV) of the GLS method with those of two recently reported spectral combination methods.Results:
Compared to the two existing methods, the GLS method significantly reduced CV values for the simulation, phantom, and in vivo experiments.Conclusion:
The GLS method can lead to improved precision of peak quantification. J. Magn. Reson. Imaging 2013;37:1445–1450. © 2012 Wiley Periodicals, Inc. 相似文献62.
Curtis J. Billings Garnett P. McMillan Tina M. Penman Sun Mi Gille 《Journal of the Association for Research in Otolaryngology》2013,14(6):891-903
Speech perception in background noise is a common challenge across individuals and health conditions (e.g., hearing impairment, aging, etc.). Both behavioral and physiological measures have been used to understand the important factors that contribute to perception-in-noise abilities. The addition of a physiological measure provides additional information about signal-in-noise encoding in the auditory system and may be useful in clarifying some of the variability in perception-in-noise abilities across individuals. Fifteen young normal-hearing individuals were tested using both electrophysiology and behavioral methods as a means to determine (1) the effects of signal-to-noise ratio (SNR) and signal level and (2) how well cortical auditory evoked potentials (CAEPs) can predict perception in noise. Three correlation/regression approaches were used to determine how well CAEPs predicted behavior. Main effects of SNR were found for both electrophysiology and speech perception measures, while signal level effects were found generally only for speech testing. These results demonstrate that when signals are presented in noise, sensitivity to SNR cues obscures any encoding of signal level cues. Electrophysiology and behavioral measures were strongly correlated. The best physiological predictors (e.g., latency, amplitude, and area of CAEP waves) of behavior (SNR at which 50 % of the sentence is understood) were N1 latency and N1 amplitude measures. In addition, behavior was best predicted by the 70-dB signal/5-dB SNR CAEP condition. It will be important in future studies to determine the relationship of electrophysiology and behavior in populations who experience difficulty understanding speech in noise such as those with hearing impairment or age-related deficits. 相似文献
63.
Claire Zores André Dufour Claire Langlet Benoît Escande Dominique Astruc Pierre Kuhn 《Early human development》2013
Introduction
Infant crying is a major expression of distress and can occur without any exogenous stimulation. Little is known, however, about the effects of crying on physiological homeostasis in very preterm infants (VPIs).Methods
Environmental, behavioral (video and audio recording) and physiologic (heart rate [HR], respiratory rate [RR], and systemic [SaO2] and regional cerebral oxygenation [rSO2]) parameters were prospectively evaluated over 10 h in 18 VPIs (median gestational age, 28 [27–31] weeks). Only episodes of “spontaneous” and isolated cries were analyzed. Changes in parameters were compared over 5-second periods between baselines and 40 s following the onset of crying. Two periods were distinguished: 0–20 s (a) and 20–40 s (b). Minimal and/or maximal values in these periods were also compared to the baseline.Results
Of the 18 VPIs initially studied, 13 (72%) presented crying episodes (CE). They experienced 210 “spontaneous” and isolated CE, with a median of 9 [range, 1–63] CEs per child. Physiological values varied significantly from the baseline with mainly a mean decrease in HR of − 4.8 ± 5.3 beats/min (b) after an initial mean increase of + 2.6 ± 2.0 beats/min (a); a mean decrease in RR of − 3.8 ± 4.8 cycles/min (a), followed by a mean increase of + 5.6 ± 7.3 cycles/min (b) and mean unidirectional decreases in SaO2 and rSO2 (minimal values) of − 1.8 ± 2.3% and − 2.5 ± 3.0%, respectively.Conclusion
Spontaneous cries can alter the homeostasis of VPIs. Their possible adverse consequences and high occurrence emphasize the need for better prevention and response to them. 相似文献64.
Florian Schmid Carsten Höltke David Parker Cornelius Faber 《Magnetic resonance in medicine》2013,69(4):1056-1062
19F MRI offers high specificity but usually low sensitivity. Here, paramagnetic relaxation enhancement is assessed as a method to improve SNR efficiency in 19F MRI. Compounds with short relaxation times are used that combine fluorine and a paramagnetic ion within the same molecule. Different molecular designs provide T1 values in the range of 1.4–15 ms and /T1 ratios from 0.3 to 1. Gradient echo, as well as ultrafast radial MR sequences, is optimized to achieve highest SNR efficiency. Compared to nonparamagnetic compounds, ultrafast sequences can yield a gain of up to a factor 27 in sensitivity, whereas the gain with gradient echo is only factor 11. Comparison among the paramagnetic compounds shows that /T1 close to unity is a prerequisite for highest SNR efficiency gain and that best results are obtained for compounds with T1 in the range of 1–5 ms. Magn Reson Med 69:1056–1062, 2013. © 2012 Wiley Periodicals, Inc. 相似文献
65.
Olubunmi V. Akinpelu Emilia Peleva W. Robert J. Funnell Sam J. Daniel 《International journal of pediatric otorhinolaryngology》2014
Background and objectives
Otoacoustic emission (OAE) tests are currently used to screen newborns for congenital hearing loss in many Universal Newborn Hearing Screening programs. However, there are concerns about high referral and false-positive rates. Various protocols have been used to address this problem. The main objective of this review is to determine the effects of different screening protocols on the referral rates and positive predictive values (PPV) of the OAE newborn screening test.Methods
Eligible studies published in English from January 1990 until August 2012 were identified through searches of MEDLINE, Medline In-Process, Embase, PubMed (NCBI), ISI Web of Science, and the Cochrane Central Register of clinical controlled trials. Two reviewers independently screened the data sources, using pre-defined inclusion criteria to generate a list of eligible articles. Data extracted included the number of newborns screened, age at screening, OAE pass criteria, frequencies screened, number of retests, referral rates, and the number of newborns identified with permanent congenital hearing loss.Results
Ten articles met the inclusion criteria, with a total of 119,714 newborn participants. The pooled referral rate was 5.5%. Individual referral rates ranged from 1.3% to 39%; the PPV from 2 to 40%. Increasing the age at initial screening and performing retests reduced the referral rate. Likewise, screenings involving higher frequencies had lower referral rates.Conclusion
Delaying newborn hearing screening improves test results but may not be practical in all contexts. The use of higher frequencies and more sophisticated OAE devices may be useful approaches to ensure better performance of the OAE test in newborn hearing screening. 相似文献66.
Mahmoud Abdel Latif Galal El HawaryAdel El Badrawy Hatem El Alfy 《The Egyptian Journal of Radiology and Nuclear Medicine》2014
Aim
To determine if focal liver masses could be differentiated as benign or malignant by DWI and ADC maps.Methods and materials
Sixty focal liver lesions were scanned using 1.5 T MRI. DWI was performed with b 0, b 500 and b 1000 gradients with ADC measurements. Comparison of mean ADC values between each benign and malignant lesion was done. Reference standard of diagnosis was obtained by correlating DWI with histopathologic findings and imaging follow-up. The accuracies of DWI and ADC values were assessed with the Student’s t test, and cut-off values were determined with receiver operating characteristic curve analysis.Results
When ADC value of 1.0 × 10−3 mm2/s was used as a threshold value for differentiation of malignant tumors from benign lesions, sensitivity was 90.3%, specificity 78.57% and accuracy 86.7%. The best result was obtained with the use of ADC cut off value (at b 500) of 1.5 × 10−3 mm2/s and ADC cut off value (at b 1000) of 1.0 × 10−3 mm2/s, with 90.3% sensitivity, 92.86% specificity, 91.1% accuracy, 96.6% positive predictive value and 81.3% negative predictive value.Conclusion
DWI and ADC map is a useful tool in differential diagnosis of malignant from benign liver lesions. 相似文献67.
Philipp Franke Michael Markl Sonja Heinzelmann Peter Vaith Jonas Bürk Mathias Langer J. Geiger 《European journal of radiology》2014
The aim of this study was to evaluate the diagnostic value of a 32-channel head coil for the characterization of mural inflammation patterns in the superficial cranial arteries in patients with giant cell arteritis (GCA) compared to a standard 12-channel coil at 3 T MRI. 相似文献
68.
69.
Melanie A. Zokoll Dilek Fidan Didem Türkyılmaz Sabine Hochmuth İclâl Ergenç Gonca Sennaroğlu 《International journal of audiology》2015,54(4):51-61
Objectives: The Turkish matrix sentence test, TURMatrix, was developed for precise, internationally comparable speech intelligibility testing. Design: The TURMatrix comprises a base matrix of ten well-known Turkish names, numbers, adjectives, objects, verbs, from which syntactically fixed sentences were randomly composed. Test conduction may be in an open-set (standard), or closed-set response format. Homogeneity in intelligibility of the test material was optimized by applying level adaptations (maximal ± 3 dB) based on word-specific speech reception thresholds (SRTs). Test list equivalence was verified and reference values were determined. Study sample: Thirty-eight native listeners of Turkish with normal hearing. Results: After training, mean SRT and slope of the final test lists were ? 8.3 ± 0.2 dB SNR and 14.1 ± 1.0%/dB, respectively (fixed SNR measurements; inter-list variability). For adaptive measurements, average across listeners was ? 7.2 ± 0.7 dB SNR in the open-set and ? 7.9 ± 0.7 dB SNR in the closed-set response format. Mean SRT for adaptive measurements in the open-set response format in quiet was 20.3 ± 4.1 dB. Individual SRTs in quiet correlated more closely with audiograms than with SRTs in noise. Conclusions: The TURMatrix was developed according to European standards and provides reliable speech intelligibility measurements in noise and quiet. 相似文献
70.
Jan S. Bauer MD Roberto Monetti PhD Roland Krug PhD Maiko Matsuura MS Dirk Mueller MD Felix Eckstein MD Ernst J. Rummeny MD Eva‐Maria Lochmueller MD Christoph W. Raeth PhD Thomas M. Link MD 《Journal of magnetic resonance imaging : JMRI》2009,29(1):132-140