BACKGROUND Iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification sequence(IDEAL-IQ)is based on chemical shift-based water and fat separation technique to get proton d...BACKGROUND Iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification sequence(IDEAL-IQ)is based on chemical shift-based water and fat separation technique to get proton density fat fraction.Multiple studies have shown that using IDEAL-IQ to test the stability and repeatability of liver fat is acceptable and has high accuracy.AIM To explore whether Gadoxetate Disodium(Gd-EOB-DTPA)interferes with the measurement of the hepatic fat content quantified with the IDEAL-IQ and to evaluate the robustness of this technique.METHODS IDEAL-IQ was used to quantify the liver fat content at 3.0T in 65 patients injected with Gd-EOB-DTPA contrast.After injection,IDEAL-IQ was estimated four times,and the fat fraction(FF)and R2* were measured at the following time points:Precontrast,between the portal phase(70 s)and the late phase(180 s),the delayed phase(5 min)and the hepatobiliary phase(20 min).One-way repeated-measures analysis was conducted to evaluate the difference in the FFs between the four time points.Bland-Altman plots were adopted to assess the FF changes before and after injection of the contrast agent.P<0.05 was considered statistically significant.RESULTS The assessment of the FF at the four time points in the liver,spleen and spine showed no significant differences,and the measurements of hepatic FF yielded good consistency between T1 and T2[95%confidence interval:-0.6768%,0.6658%],T1 and T3(-0.3900%,0.3178%),and T1 and T4(-0.3750%,0.2825%).R2* of the liver,spleen and spine increased significantly after injection(P<0.0001).CONCLUSION Using the IDEAL-IQ sequence to measure the FF,we can obtain results that will not be affected by Gd-EOB-DTPA.The high reproducibility of the IDEAL-IQ sequence makes it available in the scanning interval to save time during multiphase examinations.展开更多
Purpose: Commonly used diffusion weighted (DW) imaging such as DW spin echo (SE) type echo planar imaging (DW-SE-EPI) is known to be a snapshot-like acquisition and to have a relatively high signal-to-noise ratio. Spi...Purpose: Commonly used diffusion weighted (DW) imaging such as DW spin echo (SE) type echo planar imaging (DW-SE-EPI) is known to be a snapshot-like acquisition and to have a relatively high signal-to-noise ratio. Spiral MRI sequence (SPIRAL) has characteristics similar to these of EPI, but it has rarely been used for diffusion-weighted imaging (DWI). In vivo DW-SPIRAL of the rat brain has almost never been reported. Our purpose in this study was to examine the potential of SE-type two-dimensional (2D) multi-shot spiral acquisition MRI for apparent diffusion coefficient (ADC) mapping of the rat brain in vivo. Materials and Methods: We made an SE-type DW-2D-spiral MRI sequence (DW-SPIRAL) which was prepared on a 2.0-T animal-experiment MR scanner. Comparing the phantom experimental result of DW-SPIRAL with the phantom experimental result of DW SE-type echo-planar imaging (DW-SE-EPI) and conventional DW spin echo imaging (DW-SE), we estimated the characteristics of DW-SPIRAL and assessed the clinical application of DW-SPIRAL in an animal experiment on the rat brain. Results: There was not much difference between the calculated water/glycerol phantom diffusion coefficient of DW-SPIRAL and the calculated diffusion coefficient of DW-SE. This result shows that the DW-SPIRAL sequence is appropriate for use in diffusion weighted imaging. There were fewer phantom image distortions and ghosting artifacts with DW-SPIRAL than with DW-SE-EPI, and this tendency was similar in the animal experiment on the rat brain. Conclusion: The DW-SPIRAL sequence had been successfully tested in phantom experiments and rat brain experiments. It has been demonstrated that the DW-SPIRAL sequence is capable of producing in vivo rat brain DWI.展开更多
The contrast agent concentration, the time of repetition (TR) and magnetic field strength are significant parameters that influence for the accurate signal intensity (SI) in quantitative Magnetic Resonance Imaging (MR...The contrast agent concentration, the time of repetition (TR) and magnetic field strength are significant parameters that influence for the accurate signal intensity (SI) in quantitative Magnetic Resonance Imaging (MRI). Therefore, this study was conducted to investigate and refine the dependence and the optimal effect of Time of Repetition (TR) on the relationship between signal intensity and Gd-DTPA (Gadolinium-diethylene-triaminepenta-acetic acid) concentration, after applying two-dimensional (2D) Spin Echo (SE) pulse sequence under low-field MRI. In addition to that, the optimal concentration of Gd-DTPA at given sequence parameters at low-field MRI was also evaluated. A water-filled phantom was constructed for a range of Gd-DTPA concentrations (0 - 6 mmol/L) and the mean signal intensities (SIs) were assessed in the defined region of interest on T1-weighted images with different TR values (40 - 2000 ms). The generated signal-concentration curves for Gd-DTPA revealed that increasing TR was associated with the increase of the overall SIs and the maximum relationship between SI to concentration. Moreover, the required Gd-DTPA concentration to produce the maximum SI was associated to decrease with the increase of TR. In addition to this, the application of beyond 100 ms TR values in this study with relatively higher concentrations (beyond 1 - 2 mmol/L) has resulted predominantly non-linear patterns in the signal-concentration curves and it appears the saturation or decay of the SIs due to T2 effect. From these results, it can be suggested that the selection of relatively lower Gd-DTPA concentration ( mmol/L) with less than 800 ms (<800 ms) TR values can produce a better linear relationship between the concertation and SIs in T1-weighted SE low field contrast-enhanced MRI. Furthermore, this study also outlined the significance and necessity of the optimization of TR in SE sequence in low field MRI prior to a particular examination.展开更多
Purpose: To increase the efficiency of densely encoded magnetization transfer imaging of the brain, we time-multiplex multiple slices within the same readout using simultaneous echo refocusing FLASH imaging with magne...Purpose: To increase the efficiency of densely encoded magnetization transfer imaging of the brain, we time-multiplex multiple slices within the same readout using simultaneous echo refocusing FLASH imaging with magnetization transfer (MT) preparation (MT-SER-FLASH). Materials and Methods: Inefficiency in total scan time results from the number of frequency samples needed for sufficient quality of quantitative parameter maps for a binary spin bath model. We present a highly efficient multiplexing method, simultaneous echo refocused magnetization transfer imaging (MT-SER-FLASH) for reducing the total scan time of MT imaging by one-third. The specific absorption rate (SAR) was also reduced by reducing the number of MT-pulses per volume. Results: 2D-MT-SER-FLASH is performed in 19 minutes rather than 1 hour, acceptable for routine clinical application. The SAR could be reduced to 69% instead of more than 100% with a standard 2D or 3D-FLASH with MT-preparation. Conclusion: The net reduction of scan time and SAR enables the use of quantitative model based magnetization transfer imaging within a clinical environment.展开更多
Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal t...Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal the fine structure of the spinal cord with precision. We used the readout segmentation of long variable echo-trains（RESOLVE） sequence in this cross-sectional study of 45 healthy volunteers aged 20 to 63 years. We found that the RESOLVE sequence significantly increased the resolution of the diffusion images and improved the median signal-to-noise ratio of the middle（C4–6） and lower（C7–T1） cervical segments to the level of the upper cervical segment. In addition, the values of fractional anisotropy and radial diffusivity were significantly higher in white matter than in gray matter. Our study verified that the RESOLVE sequence could improve resolution of diffusion tensor imaging in clinical applications and provide accurate baseline data for the diagnosis and treatment of cervical spinal cord diseases.展开更多
目的:采用3.0 T MRI非对称回波的最小二乘估算法迭代水脂分离(IDEAL-IQ)技术测量成人腮腺脂肪分数(FF)值,评估其与年龄的相关性。方法:回顾性分析行常规头颈部MRI检查的女性患者120例,分为4组:18~44岁为青年组,45~59岁为中年组,60~74岁...目的:采用3.0 T MRI非对称回波的最小二乘估算法迭代水脂分离(IDEAL-IQ)技术测量成人腮腺脂肪分数(FF)值,评估其与年龄的相关性。方法:回顾性分析行常规头颈部MRI检查的女性患者120例,分为4组:18~44岁为青年组,45~59岁为中年组,60~74岁为年轻老年组,75~89岁为高龄老年组,每组各30例。测量4组双侧腮腺FF值,比较各组左侧与右侧腮腺FF值的差异,以及各组间BMI、FF值的差异,并评估FF值与年龄及BMI的相关性。结果:4组左侧与右侧腮腺FF值差异均无统计学意义(均P>0.05)。4组双侧腮腺平均FF值两两比较,差异均有统计学意义(均P<0.001);BMI两两比较,差异均无统计学意义(均P>0.05)。腮腺FF值与年龄呈正相关(r=0.443,P<0.001)。结论:成人双侧腮腺脂肪含量不存在差异,腮腺脂肪含量与年龄增长显著相关,在研究干燥综合征时应综合考虑腮腺脂肪含量的增龄性变化。展开更多
目的:以MRI测定的全肝脏质子密度脂肪分数(PDFF)为标准,探讨MRI可变容积加速肝脏采集(LAVA-Flex)技术和非对称回波最小二乘估算法迭代水脂分离(IDEAL-IQ)技术测定的代谢相关脂肪性肝病(MAFLD)患者的水相、脂相图肝脏脂肪分数(FF)与PDFF...目的:以MRI测定的全肝脏质子密度脂肪分数(PDFF)为标准,探讨MRI可变容积加速肝脏采集(LAVA-Flex)技术和非对称回波最小二乘估算法迭代水脂分离(IDEAL-IQ)技术测定的代谢相关脂肪性肝病(MAFLD)患者的水相、脂相图肝脏脂肪分数(FF)与PDFF的一致性。探讨LAVA-Flex技术行全肝脏脂肪定量快速检测的可行性。方法:收集97例MAFLD患者及23例健康志愿者。在GE 1.5 T MRI扫描仪上行IDEAL-IQ和LAVA-Flex序列扫描,前者得出PDFF、R2*、水相、脂相、同相位、反相位图,后者得出水相、脂相、同相位、反相位图。使用3D Slicer软件对PDFF、水相、脂相图进行全肝勾画,计算全肝各水相、脂相图的脂肪信号分数(FF_(IQ))和(FF_(Flex))。根据PDFF将120例分成4组:正常组23例,PDFF<5%;轻度组15例,5%≤PDFF<10%;中度组48例,10%≤PDFF<25%;重度组34例,PDFF≥25%。使用Pearson相关性分析评估4组FF_(IQ)、FF_(Flex)与PDFF的一致性,并绘制相关性热图及Bland-Altman图。结果:总体FF_(Flex)与PDFF呈极强相关(r=0.959);正常组FF_(IQ)与PDFF呈极强的相关(r=0.991,P<0.01);轻度组FF_(IQ)与PDFF呈较强相关(r=0.848,P<0.01);中度组FF_(IQ)与PDFF呈极强相关(r=0.997,P<0.01),FF_(Flex)与PDFF呈较强相关(r=0.756,P<0.01);重度组FF_(IQ)、FF_(Flex)均与PDFF呈显著相关(r=0.779,0.793;均P<0.01)。Bland-Altman图显示,FF_(Flex)与FF_(IQ)大部分数据点均落在一致性限内,且中心线接近0,两者与PDFF均具有很好的一致性。结论:IDEAL-IQ和LAVA-Flex技术测定的全肝FF与PDFF呈高度一致性,尤其是在中、重度脂肪肝患者中表现更佳,LAVA-Flex技术以其快速成像的优势为临床肝脏脂肪含量的测定提供了重要工具。展开更多
基金Supported by National Natural Science Foundation of China,No.82272053.
文摘BACKGROUND Iterative decomposition of water and fat with echo asymmetry and least squares estimation quantification sequence(IDEAL-IQ)is based on chemical shift-based water and fat separation technique to get proton density fat fraction.Multiple studies have shown that using IDEAL-IQ to test the stability and repeatability of liver fat is acceptable and has high accuracy.AIM To explore whether Gadoxetate Disodium(Gd-EOB-DTPA)interferes with the measurement of the hepatic fat content quantified with the IDEAL-IQ and to evaluate the robustness of this technique.METHODS IDEAL-IQ was used to quantify the liver fat content at 3.0T in 65 patients injected with Gd-EOB-DTPA contrast.After injection,IDEAL-IQ was estimated four times,and the fat fraction(FF)and R2* were measured at the following time points:Precontrast,between the portal phase(70 s)and the late phase(180 s),the delayed phase(5 min)and the hepatobiliary phase(20 min).One-way repeated-measures analysis was conducted to evaluate the difference in the FFs between the four time points.Bland-Altman plots were adopted to assess the FF changes before and after injection of the contrast agent.P<0.05 was considered statistically significant.RESULTS The assessment of the FF at the four time points in the liver,spleen and spine showed no significant differences,and the measurements of hepatic FF yielded good consistency between T1 and T2[95%confidence interval:-0.6768%,0.6658%],T1 and T3(-0.3900%,0.3178%),and T1 and T4(-0.3750%,0.2825%).R2* of the liver,spleen and spine increased significantly after injection(P<0.0001).CONCLUSION Using the IDEAL-IQ sequence to measure the FF,we can obtain results that will not be affected by Gd-EOB-DTPA.The high reproducibility of the IDEAL-IQ sequence makes it available in the scanning interval to save time during multiphase examinations.
文摘Purpose: Commonly used diffusion weighted (DW) imaging such as DW spin echo (SE) type echo planar imaging (DW-SE-EPI) is known to be a snapshot-like acquisition and to have a relatively high signal-to-noise ratio. Spiral MRI sequence (SPIRAL) has characteristics similar to these of EPI, but it has rarely been used for diffusion-weighted imaging (DWI). In vivo DW-SPIRAL of the rat brain has almost never been reported. Our purpose in this study was to examine the potential of SE-type two-dimensional (2D) multi-shot spiral acquisition MRI for apparent diffusion coefficient (ADC) mapping of the rat brain in vivo. Materials and Methods: We made an SE-type DW-2D-spiral MRI sequence (DW-SPIRAL) which was prepared on a 2.0-T animal-experiment MR scanner. Comparing the phantom experimental result of DW-SPIRAL with the phantom experimental result of DW SE-type echo-planar imaging (DW-SE-EPI) and conventional DW spin echo imaging (DW-SE), we estimated the characteristics of DW-SPIRAL and assessed the clinical application of DW-SPIRAL in an animal experiment on the rat brain. Results: There was not much difference between the calculated water/glycerol phantom diffusion coefficient of DW-SPIRAL and the calculated diffusion coefficient of DW-SE. This result shows that the DW-SPIRAL sequence is appropriate for use in diffusion weighted imaging. There were fewer phantom image distortions and ghosting artifacts with DW-SPIRAL than with DW-SE-EPI, and this tendency was similar in the animal experiment on the rat brain. Conclusion: The DW-SPIRAL sequence had been successfully tested in phantom experiments and rat brain experiments. It has been demonstrated that the DW-SPIRAL sequence is capable of producing in vivo rat brain DWI.
文摘The contrast agent concentration, the time of repetition (TR) and magnetic field strength are significant parameters that influence for the accurate signal intensity (SI) in quantitative Magnetic Resonance Imaging (MRI). Therefore, this study was conducted to investigate and refine the dependence and the optimal effect of Time of Repetition (TR) on the relationship between signal intensity and Gd-DTPA (Gadolinium-diethylene-triaminepenta-acetic acid) concentration, after applying two-dimensional (2D) Spin Echo (SE) pulse sequence under low-field MRI. In addition to that, the optimal concentration of Gd-DTPA at given sequence parameters at low-field MRI was also evaluated. A water-filled phantom was constructed for a range of Gd-DTPA concentrations (0 - 6 mmol/L) and the mean signal intensities (SIs) were assessed in the defined region of interest on T1-weighted images with different TR values (40 - 2000 ms). The generated signal-concentration curves for Gd-DTPA revealed that increasing TR was associated with the increase of the overall SIs and the maximum relationship between SI to concentration. Moreover, the required Gd-DTPA concentration to produce the maximum SI was associated to decrease with the increase of TR. In addition to this, the application of beyond 100 ms TR values in this study with relatively higher concentrations (beyond 1 - 2 mmol/L) has resulted predominantly non-linear patterns in the signal-concentration curves and it appears the saturation or decay of the SIs due to T2 effect. From these results, it can be suggested that the selection of relatively lower Gd-DTPA concentration ( mmol/L) with less than 800 ms (<800 ms) TR values can produce a better linear relationship between the concertation and SIs in T1-weighted SE low field contrast-enhanced MRI. Furthermore, this study also outlined the significance and necessity of the optimization of TR in SE sequence in low field MRI prior to a particular examination.
文摘Purpose: To increase the efficiency of densely encoded magnetization transfer imaging of the brain, we time-multiplex multiple slices within the same readout using simultaneous echo refocusing FLASH imaging with magnetization transfer (MT) preparation (MT-SER-FLASH). Materials and Methods: Inefficiency in total scan time results from the number of frequency samples needed for sufficient quality of quantitative parameter maps for a binary spin bath model. We present a highly efficient multiplexing method, simultaneous echo refocused magnetization transfer imaging (MT-SER-FLASH) for reducing the total scan time of MT imaging by one-third. The specific absorption rate (SAR) was also reduced by reducing the number of MT-pulses per volume. Results: 2D-MT-SER-FLASH is performed in 19 minutes rather than 1 hour, acceptable for routine clinical application. The SAR could be reduced to 69% instead of more than 100% with a standard 2D or 3D-FLASH with MT-preparation. Conclusion: The net reduction of scan time and SAR enables the use of quantitative model based magnetization transfer imaging within a clinical environment.
文摘Diffusion tensor imaging plays an important role in the accurate diagnosis and prognosis of spinal cord diseases. However, because of technical limitations, the imaging sequences used in this technique cannot reveal the fine structure of the spinal cord with precision. We used the readout segmentation of long variable echo-trains（RESOLVE） sequence in this cross-sectional study of 45 healthy volunteers aged 20 to 63 years. We found that the RESOLVE sequence significantly increased the resolution of the diffusion images and improved the median signal-to-noise ratio of the middle（C4–6） and lower（C7–T1） cervical segments to the level of the upper cervical segment. In addition, the values of fractional anisotropy and radial diffusivity were significantly higher in white matter than in gray matter. Our study verified that the RESOLVE sequence could improve resolution of diffusion tensor imaging in clinical applications and provide accurate baseline data for the diagnosis and treatment of cervical spinal cord diseases.
文摘目的:采用3.0 T MRI非对称回波的最小二乘估算法迭代水脂分离(IDEAL-IQ)技术测量成人腮腺脂肪分数(FF)值,评估其与年龄的相关性。方法:回顾性分析行常规头颈部MRI检查的女性患者120例,分为4组:18~44岁为青年组,45~59岁为中年组,60~74岁为年轻老年组,75~89岁为高龄老年组,每组各30例。测量4组双侧腮腺FF值,比较各组左侧与右侧腮腺FF值的差异,以及各组间BMI、FF值的差异,并评估FF值与年龄及BMI的相关性。结果:4组左侧与右侧腮腺FF值差异均无统计学意义(均P>0.05)。4组双侧腮腺平均FF值两两比较,差异均有统计学意义(均P<0.001);BMI两两比较,差异均无统计学意义(均P>0.05)。腮腺FF值与年龄呈正相关(r=0.443,P<0.001)。结论:成人双侧腮腺脂肪含量不存在差异,腮腺脂肪含量与年龄增长显著相关,在研究干燥综合征时应综合考虑腮腺脂肪含量的增龄性变化。
文摘目的:以MRI测定的全肝脏质子密度脂肪分数(PDFF)为标准,探讨MRI可变容积加速肝脏采集(LAVA-Flex)技术和非对称回波最小二乘估算法迭代水脂分离(IDEAL-IQ)技术测定的代谢相关脂肪性肝病(MAFLD)患者的水相、脂相图肝脏脂肪分数(FF)与PDFF的一致性。探讨LAVA-Flex技术行全肝脏脂肪定量快速检测的可行性。方法:收集97例MAFLD患者及23例健康志愿者。在GE 1.5 T MRI扫描仪上行IDEAL-IQ和LAVA-Flex序列扫描,前者得出PDFF、R2*、水相、脂相、同相位、反相位图,后者得出水相、脂相、同相位、反相位图。使用3D Slicer软件对PDFF、水相、脂相图进行全肝勾画,计算全肝各水相、脂相图的脂肪信号分数(FF_(IQ))和(FF_(Flex))。根据PDFF将120例分成4组:正常组23例,PDFF<5%;轻度组15例,5%≤PDFF<10%;中度组48例,10%≤PDFF<25%;重度组34例,PDFF≥25%。使用Pearson相关性分析评估4组FF_(IQ)、FF_(Flex)与PDFF的一致性,并绘制相关性热图及Bland-Altman图。结果:总体FF_(Flex)与PDFF呈极强相关(r=0.959);正常组FF_(IQ)与PDFF呈极强的相关(r=0.991,P<0.01);轻度组FF_(IQ)与PDFF呈较强相关(r=0.848,P<0.01);中度组FF_(IQ)与PDFF呈极强相关(r=0.997,P<0.01),FF_(Flex)与PDFF呈较强相关(r=0.756,P<0.01);重度组FF_(IQ)、FF_(Flex)均与PDFF呈显著相关(r=0.779,0.793;均P<0.01)。Bland-Altman图显示,FF_(Flex)与FF_(IQ)大部分数据点均落在一致性限内,且中心线接近0,两者与PDFF均具有很好的一致性。结论:IDEAL-IQ和LAVA-Flex技术测定的全肝FF与PDFF呈高度一致性,尤其是在中、重度脂肪肝患者中表现更佳,LAVA-Flex技术以其快速成像的优势为临床肝脏脂肪含量的测定提供了重要工具。
