AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was ...AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was performed on Pub Med, MEDLINE and EMBASE up to August 2014. Nine studies(10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time(TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-Di Sc and Stata 11.0.RESULTS: The pooled sensitivity and specificity of singleshot EPI DWI were 0.83(95%CI: 0.79-0.87) and 0.77(95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09(95%CI: 2.19-11.84) and 0.23(95%CI: 0.15-0.36), respectively. The P value for the χ2 heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present(t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity(all P > 0.05). CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.展开更多
The mobile communication (radio, mobile, satellite telephony…) insert band filters which are required to comply with stringent pass-band characteristics concerning the selectivity, the group delay, the insertion loss...The mobile communication (radio, mobile, satellite telephony…) insert band filters which are required to comply with stringent pass-band characteristics concerning the selectivity, the group delay, the insertion losses and the mass and volume. The mass and volume of payload electronic equipment is a significant contributor to the overall cost of space systems. Within this framework, many improvements were made in the design of filters and multiplexers which represent a considerable portion of the overall satellite payload. The High Temperature Superconducting (HTS) planar technology permits to realize compact size filtering devices. Moreover, it could also provide a superior performance not attainable by any other technology. However, not controllable parameters in the manufacturing processes (indistinctness of the engraving, the not uniformity of substratum thickness) do not allow to obtain a precision on the echo’s frequency and to keep a high quality factor. So, it is necessary to use method to tune the center frequency of filters after the fabrication or to study new resonator topologies which present lower sensitivity to LAIO3 substrate thickness. This last point is the object of this article.展开更多
Ghost artifacts occur in magnetic resonance imaging （MRI） reconstruction because odd and even echoes have different phase offsets. A method based on the projection in hybrid-space is described to remove ghost artifa...Ghost artifacts occur in magnetic resonance imaging （MRI） reconstruction because odd and even echoes have different phase offsets. A method based on the projection in hybrid-space is described to remove ghost artifacts. First, the projection of the even and odd lines along phase-encoding direction in hybrid-space was used to estimate the phase difference between odd and even echoes. Secondly, we fit the phase difference and used it to correct the phase of even or odd echoes. Finally, the corrected image was obtained by performing the inverse Fourier transform along phase-encoding direction in hybrid-space. The experimental results show that linear and nonlinear differences can be corrected and the intensity of ghost artifacts is significantly reduced. The effectiveness of the proposed method is demonstrated in ghost artifact removal.展开更多
基金Supported by Key Program of Scientific Research of Fujian Medical University,FMU 09ZD014
文摘AIM: To investigate the diagnostic ability of single-shot echo-planar imaging(EPI) diffusion-weighted imaging (DWI) to differentiate between malignant and benign pancreatic lesions. METHODS: A computerized search was performed on Pub Med, MEDLINE and EMBASE up to August 2014. Nine studies(10 sets of data) with a total of 304 malignant pancreatic lesions and 188 benign pancreatic lesions were included. The characteristics of each study included the study name, year of publication, magnetic resonance modalities used, patient population, strength of field, pulse time, repetition time, echo time(TE), maximum b factor, mean age, mean body weight, fat suppression, number of benign and malignant lesions, and true positive, true negative, false positive and false negative results. All analyses were performed using Meta-Di Sc and Stata 11.0.RESULTS: The pooled sensitivity and specificity of singleshot EPI DWI were 0.83(95%CI: 0.79-0.87) and 0.77(95%CI: 0.70-0.83), respectively. The positive likelihood ratio and negative likelihood ratio were 5.09(95%CI: 2.19-11.84) and 0.23(95%CI: 0.15-0.36), respectively. The P value for the χ2 heterogeneity for all pooled estimates was < 0.05. From the fitted summary receiver operating characteristic curve, the area under the curve and Q* index were 0.89 and 0.82, respectively. Publication bias was not present(t = 0.58, P = 0.58). Meta-regression analysis indicated that fat suppression, mean age, TE, and maximum b factor were not sources of heterogeneity(all P > 0.05). CONCLUSION: Single-shot EPI DWI is useful to differentiate between malignant and benign pancreatic lesions. Lesion size ≥ 2 cm is the limit for the diagnosis of early lesions.
文摘The mobile communication (radio, mobile, satellite telephony…) insert band filters which are required to comply with stringent pass-band characteristics concerning the selectivity, the group delay, the insertion losses and the mass and volume. The mass and volume of payload electronic equipment is a significant contributor to the overall cost of space systems. Within this framework, many improvements were made in the design of filters and multiplexers which represent a considerable portion of the overall satellite payload. The High Temperature Superconducting (HTS) planar technology permits to realize compact size filtering devices. Moreover, it could also provide a superior performance not attainable by any other technology. However, not controllable parameters in the manufacturing processes (indistinctness of the engraving, the not uniformity of substratum thickness) do not allow to obtain a precision on the echo’s frequency and to keep a high quality factor. So, it is necessary to use method to tune the center frequency of filters after the fabrication or to study new resonator topologies which present lower sensitivity to LAIO3 substrate thickness. This last point is the object of this article.
文摘目的探讨基于联合压缩感知(Compressed Sensing,CS)平面回波成像(Echo Planer Imaging,EPI)的动脉自旋标记(Arterial Spin Labeling,ASL)技术,即EPICS-ASL序列在脑灌注成像中的应用价值,并与传统EPI-ASL序列进行比较。方法前瞻性收集30例志愿者行EPICS-ASL和传统EPI-ASL序列扫描。在ASL原始图上选取基底节、灰质、白质、脑干和小脑作为感兴趣区(Region of Interest,ROI),测量并计算各ROI的信噪比(Signal to Noise Ratio,SNR)和灰质/白质对比噪声比(Contrast to Noise Ratio,CNR灰质/白质);2名医师独立双盲采用4分法主观评估两组图像质量。采用配对t检验比较两组图像的SNR和CNR灰质/白质,采用秩和检验比较两组图像主观评分结果。结果客观评价,EPICS-ASL组各ROI的SNR和CNR灰质/白质均优于EPI-ASL组各ROI的SNR和CNR灰质/白质(均P<0.001);主观评价,EPICS-ASL组的图像质量评分也优于EPI-ASL组(均P<0.001)。结论EPICS-ASL序列显著优于传统EPI-ASL序列的图像SNR和CNR,图像质量更高,具有进一步临床应用的潜力。
文摘Ghost artifacts occur in magnetic resonance imaging （MRI） reconstruction because odd and even echoes have different phase offsets. A method based on the projection in hybrid-space is described to remove ghost artifacts. First, the projection of the even and odd lines along phase-encoding direction in hybrid-space was used to estimate the phase difference between odd and even echoes. Secondly, we fit the phase difference and used it to correct the phase of even or odd echoes. Finally, the corrected image was obtained by performing the inverse Fourier transform along phase-encoding direction in hybrid-space. The experimental results show that linear and nonlinear differences can be corrected and the intensity of ghost artifacts is significantly reduced. The effectiveness of the proposed method is demonstrated in ghost artifact removal.
