PURPOSE: To investigate the effect of coating material in RF coil, which is one of main parts in MRI machine, on the Q-factor and SNR(signal-to-noise ratio) in MR images. MATERIALS AND METHODS: RF coils with inner diameter of 1.7 mm were made by using copper wires coated with polyester, polyurethane, polyimide, polyamideimide, and polyester-imide, and by using copper wires in which coating materials had been removed. Q-factors of the RF coils were measured by network analyzer, and SNR values in the spin-echo MR images obtained by 600 MHz (14.1 T, Bruker DMX600) micro-imaging system for the coated and uncoated cases. RESULTS: The measured SNRs were almost same for the RF coils with coat-removed copper wires, however SNRs and Q-factors were different for the coated cases depending on the coating material. They were maximized in the polyurethane-coated case in which the SNR was >30% greater than polyester-coated case. CONCLUSION: We made solenoid-type RF coils which were easily used for MR micro-imaging in Bruker MRI probe. There was a significant coating-material dependence in the measured Q values and SNRs for the home-made RF coils. The study demonstrated that the choice of coating material of RF coil may be a critical factor in the MRI sensitivity based on SNR value.
Copper ; Polyesters ; Polyurethanes ; Signal-To-Noise Ratio

A joint time–frequency localized three-band biorthogonal wavelet filter bank to compress Electrocardiogram signals is proposed in this work. Further, the use of adaptive thresholding and modified run-length encoding resulted in maximum data volume reduction while guaranteeing reconstructing quality. Using signal-to-noise ratio, compression ratio (C(R)), maximum absolute error (E(MA)), quality score (Q(s)), root mean square error, compression time (C(T)) and percentage root mean square difference the validity of the proposed approach is studied. The experimental results deduced that the performance of the proposed approach is better when compared to the two-band wavelet filter bank. The proposed compression method enables loss-less data transmission of medical signals to remote locations for therapeutic usage.
Electrocardiography ; Joints ; Methods ; Signal-To-Noise Ratio

To examine among patients with vertebral compression fracture the extent to which signal-to-noise ratio (SNR) and Apparent Diffusion Coefficient (ADC) values at the lumbar vertebral compression fracture site vary on diffusion-weighted MR images according to varying b values on the 1.5T MR device. Diffusion-weighted MR images of 30 patients with compression fracture due to chronic osteoporosis who underwent vertebral MRI from Jan. 2008 to Nov. 2009 were respectively obtained using a 1.5-T MR scanner with the b values increased from 400, 600, 800, 1,000 to 1,200 s/mm2. For diffusion-weighted MR images with different b values, the signal-to-noise ratio (SNR) was assessed at three sites: the site of compression fracture of the lumbar vertebral body at L1 to L5, and both the upper and lower discs of the said fracture site, while for ADC map images with different b values, the SNR and ADC were respectively assessed at those three sites. As a quantitative analysis, diffusion-weighted MR images and ADC map images with b value of 400 s/mm2 (the base b values) were respectively compared with the corresponding images with each different b value. As far as qualitative analysis is concerned, for both diffusion-weighted MR and ADC map images with b value of 400 s/mm2, the extent to which signal intensity values obtained at the site of compression fracture of the lumbar vertebral body at L1 to L5 vary according to the increasing b values were examined. The quantitative analysis found that for both diffusion-weighted MR and ADC map images, as the b values increased, the SNR were relatively lowered at all the three sites, compared to the base b value. Also, it was found that as the b values increased, ADC values were relatively lowered at all the three sites on ADC map images. On the other hand, the qualitative analysis found that as the b values increased to more than 400 s/mm2, the signal intensity gradually decreased at all the sites, while at the levels of more than 1,000 s/mm2, severe image noises appeared at all of the three sites. In addition, higher signal intensity was found at the site of compression fracture of the lumbar vertebral body than at the discs. Findings showed that with the b value being increased, both the signal-to-noise ratio (SNR) and Apparent Diffusion Coefficient (ADC) values gradually decreased at all the sites of the lumbar vertebral compression fracture and both the upper and lower discs of the fracture site, suggesting that there is a possibility of a wider range of applications to assessment of various vertebral pathologies by utilizing multi b values in the diffusion-weighted MRI examination.
Diffusion ; Fractures, Compression ; Hand ; Humans ; Noise ; Osteoporosis ; Signal-To-Noise Ratio

PURPOSE: The purpose of this study was to analyze the flow signal chracteristics of 3 dimensional time of flight MR angiography (3D TOF MRA) by using a flow phantom model. MATERIALS AND METHODS: Nonpulsatile flow phantom and tap water were used in this experiment. We performed FISP 3D TOF MRA with various values of parameters (repetition time ; 34-100 msec, flip angle ; 10degrees-50degrees, flow velocity ; 14.7-73.6 cm/sec, Gd-DTPA concentration ; 0.6-3.6 mmol/liter). The values of flow signal intensity (SI), signal to noise ratio (SNR) and contrast to noise ratio (CNR) were measured from base images of each MRA. The measured values were displayed graphically and analyzed statistically in relation to various parameters. RESULTS: A prolongation of repetition time resulted in a decrease of CNR of flow. As flip angles increased, SNR and CNR of flow also increased but larger flip angles of more than 40degrees rapidly saturated exit flow. As the flow velocities increased in a range of 14.7-73.6 cm/sec, SNR and CNR of flow decreased. This may be related to the phase dispersion effect of laminar flow, more dominat than the TOF effect. The addition of Gd-DTPA to water increased SNR and CNR of exit flow. There were however, no significant differences of SI, SNR or CNR of flow among the various concentrations of Gd-DTPA. CONCLUSION: An experimental MRA study using a flow phantom model was useful in understanding the flow signal characteristics of 3D TOF MRA within various MRA parameters. Our preliminary results can be used as basic data for refined flow experiments.
Angiography* ; Gadolinium DTPA ; Noise ; Signal-To-Noise Ratio ; Water

BACKGROUND AND OBJECTIVES: The present study aimed to investigate the effect of active listening and listening effort on the contralateral suppression of transient evoked otoacoustic emissions (CSTEOAEs). SUBJECTS AND METHODS: Twenty eight young adults participated in the study. Transient evoked otoacoustic emissions (TEOAEs) were recorded using ‘linear’ clicks at 60 dB peSPL, in three contralateral noise conditions. In condition 1, TEOAEs were obtained in the presence of white noise in the contralateral ear. While, in condition 2, speech was embedded into white noise at +3, −3, and −9 dB signal-to-noise ratio (SNR) and delivered to the contralateral ear. The SNR was varied to investigate the effect of listening effort on the CSTEOAE. In condition 3, speech was played backwards and embedded into white noise at −3 dB SNR. The conditions 1 and 3 served as passive listening condition and the condition 2 served as active listening condition. In active listening condition, the participants categorized the words in to two groups (e.g., animal and vehicle). RESULTS: CSTEOAE was found to be largest in the presence of white noise, and the amount of CSTEOAE was not significantly different between active and passive listening conditions (condition 2 and 3). Listening effort had an effect on the CSTEOAE, the amount of suppression increased with listening effort, when SNR was decreased from +3 dB to −3 dB. However, when the SNR was further reduced to −9 dB, there was no further increase in the amount of CSTEOAE, instead there was a reduction in the amount of suppression. CONCLUSIONS: The findings of the present study show that listening effort might affect CSTEOAE.
Animals ; Ear ; Humans ; Noise ; Signal-To-Noise Ratio ; Young Adult

OBJECTIVE: To compare quantitative and qualitative image quality parameters in pediatric abdominopelvic dual-energy CT (DECT) using noise-optimized virtual monoenergetic image (VMI) and conventional VMI at different kiloelectron volt (keV) levels. MATERIALS AND METHODS: Thirty-six consecutive abdominopelvic DECT scans were retrospectively included. Noise-optimized VMI and conventional VMI were reconstructed at seven energy levels, from 40 keV to 100 keV at 10 keV intervals. The contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) of the liver, pancreas, and aorta were objectively measured and compared. Image quality was evaluated subjectively regarding image noise, image blurring of solid organ, bowel image quality and severity of beam-hardening artifacts. Optimal monoenergetic levels in keV for both algorithms were determined based on overall image quality score. RESULTS: The maximal CNR and SNR values for all investigated organs were observed at 40 keV in noise-optimized VMI (CNR and SNR of liver, pancreas, aorta in order [CNR; 20.93, 17.34, 46.75: SNR; 37.39, 33.80, 63.21]), at 60–70 keV and at 70 keV in conventional VMI (CNR; 8.12, 5.67, 15.97: SNR; 19.57, 16.66, 26.65). In qualitative image analysis, noise-optimized VMI and conventional VMI showed the best overall image quality scores at 60 keV and at 70 keV, respectively. Noise-optimized VMI at 60 keV showed superior CNRs, SNRs, and overall image quality scores compared to conventional VMI at 70 keV (p < 0.001). CONCLUSION: Optimal energy levels for noise-optimized VMI and conventional VMI were 60 keV and at 70 keV, respectively. Noise-optimized VMI shows superior CNRs, SNRs and subjective image quality over conventional VMI, at the optimal energy level.
Aorta ; Artifacts ; Liver ; Noise ; Pancreas ; Retrospective Studies ; Signal-To-Noise Ratio

BACKGROUND AND OBJECTIVES: In auditory tests, several kinds of background noises have been used ; multitalker babble noise, speech noise and white noise, etc. The aim of the present study was to evaluate the effects of different types of background noises on speech intelligibility. SUBJECTS AND METHOD: Sixty volunteers having pure-tone thresholds less than 25 dB HL participated in this study. Their ages ranged from teens to sixties with ten subjects in each age group (mean age=40+/-15.4 years, m=25, f= 35) We used three types of background noises used in this study ; multitalker babble noise using the voices of Korean speakers, speech noise using English sentences and white noise. Fifty percent recognition of signal to noise ratios (SNRs) and word recognition scores (WRSs) at -10, -5, 0 dB SNR conditions were measured at 70 dB HL of noise intensity. RESULTS: Fifty percent recognition of SNRs on multitalker babble, speech and white noise were -12.4+/-1.4 dB, -13.7+/-1.0 dB and -15.8 +/-1.0 dB, respectively and they were significantly different each other (p< 0.05). Multitalker babble noise generated the lowest WRSs followed by speech noise and then white noise (p< 0.05). CONCLUSION: These results support that multitalker babble noise using the voices of Korean speakers influence on normal listener's speech intelligibility more than speech noise from English sentences or white noise
Adolescent ; Hearing ; Humans ; Noise ; Signal-To-Noise Ratio ; Speech Intelligibility ; Voice

In this paper, an adaptive artefact canceller is designed using the bounded range artificial bee colony (BR-ABC) optimization technique. The results of proposed method are compared with recursive least square and other evolutionary algorithms. The performance of these algorithms is evaluated in terms of signal-to-noise ratio (SNR), mean square error (MSE), maximum error (ME) mean, standard deviation (SD) and correlation factor (r). The noise attenuation capability is tested on EMG signal contaminated with power line and ECG noise at different SNR levels. A comparative study of various techniques reveals that the performance of BR-ABC algorithm is better in noisy environment. Our simulation results show that the ANC filter using BR-ABC technique provides 15 dB improvement in output average SNR, 63 and 83% reduction in MSE and ME, respectively as compared to ANC filter based on PSO technique. Further, the ANC filter designed using BR-ABC technique enhances the correlation between output and pure EMG signal.
Artifacts ; Bees* ; Electrocardiography ; Methods* ; Noise ; Signal-To-Noise Ratio

This letter presents an automated obstructive sleep apnoea (OSA) detection method with high accuracy, based on a deep learning framework employing convolutional neural network. The proposed work develops a system that takes single lead electrocardiography signals from patients for analysis and detects the OSA condition of the patient. The results show that the proposed method has some advantages in solving such problems and it outperforms the existing methods significantly. The present scheme eliminates the requirement of separate feature extraction and classification algorithms for the detection of OSA. The proposed network performs both feature learning and classifies the features in a supervised manner. The scheme is computation-intensive, but can achieve very high degree of accuracy—on an average a margin of more than 9% compared to other published literature till date. The method also has a good immunity to the contamination of the signals by noise. Even with pessimistic signal to noise ratio values considered here, the methods already reported are not able to outshine the present method. The software for the algorithm reported here can be a good contender to constitute a module that can be integrated with a portable medical diagnostic system.
Classification ; Electrocardiography ; Humans ; Learning ; Methods ; Noise ; Signal-To-Noise Ratio

This paper analyzes the shortcomings of the existing pure tone audiometers, and proposes a system to realize pure tone audiometry and speech audiometry with a new DSP processor. The pure tone test signal produced by the system has accurate frequency, high signal-to-noise ratio, and small harmonic distortion. The noise generator that comes with DSP adds a band-pass filter to realize the generation of narrow-band noise. At the same time, due to the modular structure of software design, the system has good ease of use and scalability. The test results show that the hearing test system has excellent performance and can be better used in hearing medical diagnosis.
Audiometry, Pure-Tone/methods* ; Hearing ; Noise ; Signal-To-Noise Ratio