不同指向传声器技术对助听后噪声下言语理解力的影响

目的 比较不同的助听器指向传声器技术对助听后噪声下的言语理解力的影响。方法 20名感音神经性聋患者双耳配戴编程为自适应指向传声器、固定指向传声器和全指向传声器模式的全数码助听器,分别在3种言语噪声给声条件下进行改良的噪声下的听力测试（hearing in nose test,HINT)法,记录信噪比。结果 在3种噪声环境下,信噪比由低到高的传声器模式依次为自适应指向传声器,固定指向传声器,全指向传声器。结论 自适应指向传声器适宜于环境噪声不仅来自身后或／和主要噪声源在变换方向的听环境;固定指向传声器适宜于噪声仅来自身后的听环境;全指向传声器适宜于安静环境下使用。     

The effect of a hearing aid noise reduction algorithm on the acquisition of novel speech contrasts

Audiologists are reluctant to prescribe digital hearing aids with active digital noise reduction (DNR) to pre-verbal children due to their potential for an adverse effect on the acquisition of language. The present study investigated the relation between DNR and language acquisition by modeling pre-verbal language acquisition using adult listeners presented with a non-native speech contrast. Two groups of normal-hearing, monolingual Anglophone subjects were trained over four testing sessions to discriminate novel, difficult to discriminate, non-native Hindi speech contrasts in continuous noise, where one group listened to both speech items and noise processed with DNR, and where the other group listened to unprocessed speech in noise. Results did not reveal a significant difference in performance between groups across testing sessions. A significant learning effect was noted for both groups between the first and second testing sessions only. Overall, DNR does not appear to enhance or impair the acquisition of novel speech contrasts by adult listeners.     

In vitro and in vivo comparison of wrist MR imaging at 3.0 and 7.0 tesla using a gradient echo sequence and identical eight-channel coil array designs

Purpose

To evaluate in vivo MR imaging of the wrist at 3.0 Tesla (T) and 7.0T quantitatively and qualitatively.

Materials and Methods

To enable unbiased signal‐to‐noise ratio (SNR) comparisons, geometrically identical eight‐channel receiver arrays were used at both field strengths. First, in vitro images of a phantom bottle were acquired at 3.0T and 7.0T to obtain an estimate of the maximum SNR gain that can be expected. MR images of the dominant wrist of 10 healthy volunteers were acquired at both field strengths. All measurements were done using the same sequence parameters. Quantitative SNR maps were calculated on a pixel‐by‐pixel basis and analyzed in several regions‐of‐interest. Furthermore, the images were qualitatively evaluated by two independent radiologists.

Results

The quantitative analysis showed SNR increases of up to 100% at 7.0T compared with 3.0T, with considerable variation between different anatomical structures. The qualitative analysis revealed no significant difference in the visualization of anatomical structures comparing 3.0T and 7.0T MR images (P>0.05).

Conclusion

The presented results establish the SNR benefits of the transition from 3.0T to 7.0T for wrist imaging without bias by different array designs and based on exact, algebraic SNR quantification. The observed SNR increase nearly reaches expected values but varies greatly between different tissues. It does not necessarily improve the visibility of anatomic structures but adds valuable latitude for sequence optimization. J. Magn. Reson. Imaging 2011;33:661–667. © 2011 Wiley‐Liss, Inc.     

In vivo quantification of intracerebral GABA by single-voxel H-MRS—How reproducible are the results?

Gamma aminobutyric acid (GABA) is the major inhibitory neurotransmitter in the human brain. It plays a decisive role in a variety of nervous system disorders, such as anxiety disorders, epilepsy, schizophrenia, insomnia, and many others. The reproducibility of GABA quantification results obtained with a single-voxel spectroscopy J-difference editing sequence with Point Resolved Spectroscopy localization (MEGA-PRESS) was determined on a 3.0 Tesla MR scanner in healthy adults. Eleven volunteers were measured in long- and short-term intervals. Intra- and inter-subject reproducibility were evaluated. Internal referencing of GABA+ to total creatine (tCr) and water (H₂O), as well as two different post-processing methods for the evaluation (signal integration and time-domain fitting) were compared. In all subjects lower coefficient of variation and therefore higher reproducibility can be observed for fitting compared to integration. The GABA+/tCr ratio performs better than the GABA+/H₂O ratio or GABA+ without internal referencing for both fitting and integration (GABA+/tCr: 13.3% and 17.0%; GABA+/H₂O: 15.0% and 17.8%; GABA+: 19.2% and 21.7%). Four-day measurements on three subjects showed higher intra- than inter-subject reproducibility (GABA+/tCr ∼10-12%). With a coefficient of variation of about 13% for inter-subject and 10-12% for intra-subject variability of GABA+/tCr, this technique seems to be a precise tool that can detect GABA confidently. The results of this study show the reproducibility limitations of GABA quantification in vivo, which are necessary for further clinical studies.     

万东i-open磁共振信噪比的测试

目的:通过对MRI设备信噪比的检测,及时发现设备存在的问题并加以解决。方法:利用两种测试方法(国家标准方法、包尚联教授的方法)分别测试万东i-open磁共振设备头线圈、颈线圈和体线圈的信噪比,比较不同线圈在两种测试方法下的信噪比并分析结果。结果:测试计算出的信噪比均低于标准值,证实了测试设备的信噪比偏低且不同线圈的信噪比存在差异。结论:所测试MRI设备的信噪比低于标准值,可能与磁屏蔽不良有关。     

Improved myocardial tagging contrast in cine balanced SSFP images

PURPOSE: To improve the tag persistence throughout the whole cardiac cycle by providing a constant tag-contrast throughout all the cardiac phases when using balanced steady-state free precession (bSSFP) imaging. MATERIALS AND METHODS: The flip angles of the imaging radiofrequency pulses were optimized to compensate for the tagging contrast-to-noise ratio (Tag-CNR) fading at later cardiac phases in bSSFP imaging. Complementary spatial modulation of magnetization (CSPAMM) tagging was implemented to improve the Tag-CNR. Numerical simulations were performed to examine the behavior of the Tag-CNR with the proposed method, and to compare the resulting Tag-CNR with that obtained from the more commonly used spoiled gradient echo (SPGR) imaging. A gel phantom, as well as five healthy human volunteers, were scanned on a 1.5T scanner using bSSFP imaging with and without the proposed technique. The phantom was also scanned with SPGR imaging. RESULTS: With the proposed technique, the Tag-CNR remained almost constant during the whole cardiac cycle. Using bSSFP imaging, the Tag-CNR was about double that of SPGR. CONCLUSION: The tag persistence was significantly improved when the proposed method was applied, with better Tag-CNR during the diastolic cardiac phase. The improved Tag-CNR will support automated tagging analysis and quantification methods.     

The simplified French Matrix. A tool for evaluation of speech intelligibility in noise

IntroductionIn audiology, the usual tests of speech perception in silence are non-predictive of intelligibility in noise. The French Matrix was developed to assess intelligibility in noise in adults with normal cognitive capacity. A simplified adaptive version, FRA-SIMAT, was derived for use with children and elderly persons with diminished memory span. The aim of the present study was to apply this adaptive procedure to determine signal-to-noise ratio (SNR) according to percentage intelligibility.MethodsTwenty normal-hearing adults and 60 normal-hearing children aged 5–6 years (G1), 7–8 years (G2) and 9–10 years (G3) were included. FRA-SIMAT uses groups of 3 words, to limit memory demand.ResultsIn adults, SNR for 50% (SNR-50) and 80% intelligibility (SNR-80) was respectively −7.1 ± 1.4 dB and −3.7 ± 1.6 dB. In children, SNR-50 was −4.2 ± 1.3 dB in G1, −4.6 ± 1.2 dB in G2, and −5.5 ± 1.5 dB in G3.ConclusionThe FRA-SIMAT test of speech perception in noise was validated in adults and children of different ages, and can be implemented as a diagnostic and rehabilitation tool in clinical practice.     

Knee MRI under varying flexion angles utilizing a flexible flat cable antenna

The aim of this study is to fabricate and test a novel flexible flat cable antenna (FFCA) for MRI of the knee at different flexion angles. The FFCA was made of a flat cable, a tuning/matching circuit and a signal transmission line. To test its feasibility and validity, in vitro and in vivo experiments were carried out on a 3.0 T MR scanner. The in vitro experiment suggested that the proposed FFCA could achieve a high signal‐to‐noise ratio (SNR) of 336, while the SNR of an eight‐channel knee coil was 291, and phantom images from the FFCA are homogeneously distributed. In the in vivo experiment, the FFCA had a higher SNR of 169 in the region of interest and more than 48.5 cm of longitudinal coverage, while the corresponding values for the commercial coil were 153 and 22.5 cm. Finally, five sagittal knee images at different flexion angles were acquired. The FFCA could acquire satisfactory knee images at different flexion angles, with the advantages of simplicity, low cost, large field of view and high SNR. It may therefore be further used to improve MR image quality of the knee joint. Copyright © 2015 John Wiley & Sons, Ltd.