Background Balanced steady-state free precession MR angiography （b-SSFP MRA） has shown great promise in diagnosing renal artery stenosis （RAS） as a non-contrast MR angiography （NC-MRA） method. However, results f...Background Balanced steady-state free precession MR angiography （b-SSFP MRA） has shown great promise in diagnosing renal artery stenosis （RAS） as a non-contrast MR angiography （NC-MRA） method. However, results from related studies are inconsistent. The purpose of this meta-analysis was to assess the accuracy of b-SSFP MIRA compared to contrast-enhanced MR angiography （CE-MRA） in diagnosing RAS. Methods English and Chinese studies that were published prior to September 4, 2013 and that assessed b-SSFP MRA diagnostic performance in RAS patients were reviewed. Quality of the literature was assessed independently by two observers. The statistical analysis was adopted by the software of Meta-Disc version 1.4. Using the heterogeneity test, a statistical effect model was chosen to calculate different pooled weighted values. The receiver operator characteristic （ROC） space and Spearman correlation coefficient were to explore threshold effect. Sensitivity analysis and the publication bias were performed to demonstrate if the pooled estimates were stable and reliable. We produced forest plots to calculate the pooled values and corresponding 95% confidence interval （Cl） of sensitivity, specificity, positive likelihood ratio （PLR）, negative likelihood ratio （NLR）, diagnostic odds ratio （DOR）, and constructed a summary receiver operating characteristic curve （SROC） to calculate the area under the curve （AUC）. Results A total of 10 high quality articles were used in this meta-analysis. The studies showed a high degree of heterogeneity. The ＂shoulder-arm＂ shape in the ROC plot and the Spearman correlation coefficient between the log（SEN） and Iog（1-SPE） suggested that there was a threshold effect. Sensitivity analysis demonstrated that the actual combined effect size was equal to the theoretical combined effect size. The publication bias was low after quality evaluation of the literature and the construction of a funnel plot. The pooled sensitivity was 0.88 （95% CI, 0.83-0.91） and pooled specificity was 0.94 （95% CI, 0.93-0.95）; pooled PLR was 14.57 （95% CI, 9.78-21.71]） and pooled NLR was 0.15 （95% CI, 0.11- 0.20）. The AUC was 0.964 3. Conclusion In contrast to CE-MRA, the b-SSFP MIRA is more accurate in diagnosing RAS, and may be able to replace other diagnostic methods in patients with renal insufficiency.展开更多
Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short ...Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction.展开更多
A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the...A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the ferrite,the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field,and the hysteresis loss disappears in the ferrites.Both theoretical and experimental results indicate that the permeability and magnetic loss in the ferrite can be controlled by adjusting the transverse magnetic field.A higher Q value with relatively low permeability can be achieved by increasing the transverse field,which ensures that the ferrite can be operated at high frequencies,with magnetic loss being very low.展开更多
目的探讨三维稳态自由进动成像技术在先天心脏病Fontan术后随访中的价值和技术要点。方法 3D SSFP技术应用于30例(7.87±2.52岁)先天性心脏病Fontan术后随访中,同时进行对比剂血管增强造影序列扫描,然后对两者图像质量进行比较分析...目的探讨三维稳态自由进动成像技术在先天心脏病Fontan术后随访中的价值和技术要点。方法 3D SSFP技术应用于30例(7.87±2.52岁)先天性心脏病Fontan术后随访中,同时进行对比剂血管增强造影序列扫描,然后对两者图像质量进行比较分析。结果 21例收缩末期采集图像,心电触发延迟时205~245 ms,平均(226.57±12.50)ms,采集窗宽48~65 ms;9例舒张中晚期采集图像,心电触发延迟时间565~680 ms,平均(646.11±34.17)ms,采集窗宽85~120 ms。膈肌导航窗宽4~8 mm。上腔静脉与肺动脉吻合口清晰度3D SSFP(4.83±0.38)高于CE-MRA(3.93±0.58),差异有统计学意义(P<0.001)。下腔静脉与肺动脉吻合口清晰度3D SSFP(4.93±0.25)优于CE-MRA(3.77±0.57),差异有统计学意义(P<0.001)。结论 3D SSFP在Fontan术后随访中,可以减少造影剂的应用,清晰显示腔静脉与肺动脉吻合口、肺动脉发育情况,是Fontan术后很好的随访手段。展开更多
文摘Background Balanced steady-state free precession MR angiography （b-SSFP MRA） has shown great promise in diagnosing renal artery stenosis （RAS） as a non-contrast MR angiography （NC-MRA） method. However, results from related studies are inconsistent. The purpose of this meta-analysis was to assess the accuracy of b-SSFP MIRA compared to contrast-enhanced MR angiography （CE-MRA） in diagnosing RAS. Methods English and Chinese studies that were published prior to September 4, 2013 and that assessed b-SSFP MRA diagnostic performance in RAS patients were reviewed. Quality of the literature was assessed independently by two observers. The statistical analysis was adopted by the software of Meta-Disc version 1.4. Using the heterogeneity test, a statistical effect model was chosen to calculate different pooled weighted values. The receiver operator characteristic （ROC） space and Spearman correlation coefficient were to explore threshold effect. Sensitivity analysis and the publication bias were performed to demonstrate if the pooled estimates were stable and reliable. We produced forest plots to calculate the pooled values and corresponding 95% confidence interval （Cl） of sensitivity, specificity, positive likelihood ratio （PLR）, negative likelihood ratio （NLR）, diagnostic odds ratio （DOR）, and constructed a summary receiver operating characteristic curve （SROC） to calculate the area under the curve （AUC）. Results A total of 10 high quality articles were used in this meta-analysis. The studies showed a high degree of heterogeneity. The ＂shoulder-arm＂ shape in the ROC plot and the Spearman correlation coefficient between the log（SEN） and Iog（1-SPE） suggested that there was a threshold effect. Sensitivity analysis demonstrated that the actual combined effect size was equal to the theoretical combined effect size. The publication bias was low after quality evaluation of the literature and the construction of a funnel plot. The pooled sensitivity was 0.88 （95% CI, 0.83-0.91） and pooled specificity was 0.94 （95% CI, 0.93-0.95）; pooled PLR was 14.57 （95% CI, 9.78-21.71]） and pooled NLR was 0.15 （95% CI, 0.11- 0.20）. The AUC was 0.964 3. Conclusion In contrast to CE-MRA, the b-SSFP MIRA is more accurate in diagnosing RAS, and may be able to replace other diagnostic methods in patients with renal insufficiency.
基金Project partially supported by the National Natural Science Foundation of China (Grant Nos 10527003 and 60672104)the State Key Development Program for Basic Research of China (Grant No 2006CB705700-05)+1 种基金Joint Research Foundation of Beijing Education Committee (Grant No SYS100010401)Beijing Natural Science Foundation (Grant No 3073019)
文摘Robust and fast fat suppression is a challenge in balanced steady-state free precession （SSFP） magnetic resonance imaging. Although single-acquisition phase-sensitive SSFP can provide fat-suppressed images in short scan time, phase errors, especially spatially-dependent phase shift, caused by a variety of factors may result in misplacement of fat and water voxels. In this paper, a novel phase correction algorithm was used to calibrate those phase errors during image reconstruction. This algorithm corrects phase by region growing, employing both the magnitude and the phase information of image pixels. Phantom and in vivo imagings were performed to validate the technique. As a result, excellent fat-suppressed images were acquired by using single-acquisition phase-sensitive SSFP with phase correction.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFB3504800 and 2021YFB3502400)the Key Research and Development Plan of Anhui Province,China(Grant No.202003c08020012)the Key Program of Education Department of Anhui Province,China(Grant No.KJ2019ZD03)。
文摘A big enough transverse magnetic field applied to soft magnetic ferrite toroid can magnetize the ferrite to a saturation level in transverse direction and almost completely suppresses magnetic domain structures in the ferrite,the response to the longitudinal alternating electromagnetic field changes from the original domain wall displacements and spin rotations to the precession of magnetization around the transverse field,and the hysteresis loss disappears in the ferrites.Both theoretical and experimental results indicate that the permeability and magnetic loss in the ferrite can be controlled by adjusting the transverse magnetic field.A higher Q value with relatively low permeability can be achieved by increasing the transverse field,which ensures that the ferrite can be operated at high frequencies,with magnetic loss being very low.
