Study on the influence of ROI size for SNR measurement during the test of MR quality control / 中国医学装备

Objective:To explore the influence of region of interest(ROI)size on signal-to-noise ratio(SNR)measurement during the test of magnetic resonance(MR)quality control(QC),so as to provide references for selecting ROI in conducting SNR measurement during MR QC test.Methods:According to the national health industry standard"Specification of image quality test and evaluation for medical magnetic resonance imaging(MRI)equipment"(WS/T 263-2006),this study utilized Magphan SMR170 performance test phantom(abbreviation:SMR170 phantom)to perform QC test on MR equipment after conducted three times tests.The slices of SNR measurement were selected on the obtained QC images,and 41 circular ROIs,which were incremental from 200mm2 to 4200mm2 as 100mm2,were sequentially chosen in the central region of the images on the SNR slices.The SNR was calculated according to formula,and then,the SNR curve that changed with the increasing of ROI size was formed.Finally,the influence of ROI size on SNR was obtained.Results:In conducting the QC test for MRI equipment by SMR170 phantom,the influence of the selected ROI size of central region of image on SNR was significant.The SNR fluctuation could not be really reflected when ROI>1000mm2 because the basically stable SNR leaded to the SNR change could not be timely found.When ROI<1000mm2,the signal means slowly increased with the increasing of ROI size,and the increase amplitude of noise was larger,and the SNR faster decreased and was smaller and smaller with ROI increase,and it tended towards stability at finally.Conclusion:When SMR170 phantom is used to conduct QC test for MR equipment and SNR is measured,it is recommended to select≤1000 mm2 of ROI size of the central region of the images,and to choose the same ROI for each measurement,which can really reflect the SNR change and ensure the result of each measurement has comparability.

A compact-sized surface EMG sensor for myoelectric hand prosthesis

Myoelectric prosthesis requires a sensor that can reliably capture surface electromyography (sEMG) signal from amputees for its controlled operation. The main problems with the presently available EMG devices are their extremely high cost, large response time, noise susceptibility, less amplitude sensitivity, and larger size. This paper proposes a compact and affordable EMG sensor for the prosthetic application. The sensor consists of an electrode interface, signal conditioning unit, and power supply unit all encased in a single package. The performance of dry electrodes employed in the skin interface was compared with the conventional Ag/AgCl electrodes, and the results were found satisfactory. The envelope detection technique in the sensor based on the tuned RC parameters enables the generation of smooth, faster, and repeatable EMG envelope irrespective of signal strength and subject variability. The output performance of the developed sensor was compared with commercial EMG sensor regarding signal-to-noise ratio, sensitivity, and response time. To perform this, EMG data with both devices were recorded for 10 subjects (3 amputees and 7 healthy subjects). The results showed 1.4 times greater SNR values and 45% higher sensitivity of the developed sensor than the commercial EMG sensor. Also, the proposed sensor was 57% faster than the commercial sensor in producing the output response. The sEMG sensor was further tested on amputees to control the operation of a self-designed 3D printed prosthetic hand. With proportional control scheme, the myoelectric hand setup was able to provide quicker and delicate grasping of objects as per the strength of the EMG signal.

Assessment of Osteoporosis Based on Changes in SNR and ADC Values on MR Diffusion Weighted Images / 의학물리

This study tested how S/N (Signal to Noise Ratio) ratios and ADC (apparent diffusion coefficient) values vary with different T-scores in a group of patients with osteoporosis. Based on DEXA (Dual Energy X-ray Absorptiometry) T-scores for L1?L4 for two groups of subjects consisting of 30 healthy people without osteoporosis and 30 patients who came for treatment of waist (lumbar or low back) pain and were suspected to have osteoporosis as judged from the simple X-ray findings, this study classified every spine into two groups of osteoporosis and osteopenia. Signal intensity measurements were made in the four regions of L1 to L4 on diffusion-weighted MR images obtained using 1.5T MR scanner, while ADC measurements were obtained from ADC map images. As an approach for quantitative analysis, the comparison of the variances in S/N ratios and ADC values for varying T-scores in the selected regions of interest was carried out based on averaged T-scores, S/N ratios, and ADC values. Also, the variances in S/N ratios and ADC values for each of the groups of osteoporosis and osteopenia, which were classified into by T-scores, were compared. For qualitative analysis, a careful naked eye examination of signal intensity differences in the area of L4 was made on T1-weighted sagittal images for each of the healthy (normal), osteopenia, and osteoporosis groups. In the qualitative analysis, it was found that for both the osteopenia group and the osteoporosis group, as T-scores deceased, the S/N ratios on diffusion-weighted MR images also decreased, with the greatest decrease in the S/N ratio found in the osteoporosis group. Additionally, among the three groups, the lowest S/N ratio was found in the osteoporosis group. With respect to ADC map, it was found that for both the osteopenia group and the osteoporosis group, as T-scores deceased, the ADC values on diffusion-weighted MR images also decreased, with the greatest decrease in the ADC values found in the osteoporosis group. Additionally, among the three groups, the lowest ADC value was found in the osteoporosis group. On the other hand, in the qualitative analysis, the osteoporosis group showed the highest signal intensity. Additionally, among the three groups, the lowest signal intensity was found in the healthy (normal) group. It was found that as osteoporosis progressed, S/N ratio and ADC decreased, whereas signal intensity increased on T1-weighted images. Also, in diagnosing osteoporosis, MRI tests turned out to be (more) effective.

SNR and ADC Changes at Increasing b Values among Patients with Lumbar Vertebral Compression Fracture on 1.5T MR Diffusion Weighted Images / 의학물리

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.

Comparison of Speech Perception Performance of BTE Hearing Aids With Different Directional Microphones / 听力学及言语疾病杂志

Objective To compare the speech perception performance of BTE hearing aids with different directional microphones. Methods 20 adults with sensorineural hearing loss participated in the research. Two digital hearing aids were programmed for adaptive directional, fixed directional, and omni-directional microphone patterns. The multi-talker noise was presented in three conditions: 180?,?90?, and 360?. Each subject was tested in nine listening conditions (three microphone patterns and three noise presentations) by using modified Hearing In Noise Test. SNR was obtained in each testing condition. Results Under each noise presentation, the sequence of microphone patterns that obtained SNR from low to high was: adaptive directional, fixed directional, and omni-directional. Conclusion Adaptive directional microphone worked best when the noise source was changing or the noise was coming not only from behind but also from other directions; fixed directional microphone could be employed when the noise came from the rear; omni-directional microphone was suitable for hearing in quiet.