The purpose of this study was to demonstrate a simple and fast method for solving the time-dependent Bloch-McConnell equations describing the behavior of magnetization in magnetic resonance imaging (MRI) in the presen...The purpose of this study was to demonstrate a simple and fast method for solving the time-dependent Bloch-McConnell equations describing the behavior of magnetization in magnetic resonance imaging (MRI) in the presence of multiple chemical exchange pools. First, the time-dependent Bloch- McConnell equations were reduced to a homogeneous linear differential equation, and then a simple equation was derived to solve it using a matrix operation and Kronecker tensor product. From these solutions, the longitudinal relaxation rate (R1ρ) and transverse relaxation rate in the rotating frame (R2ρ) and Z-spectra were obtained. As illustrative examples, the numerical solutions for linear and star-type three-pool chemical exchange models and linear, star- type, and kite-type four-pool chemical exchange models were presented. The effects of saturation time (ST) and radiofrequency irradiation power (ω1) on the chemical exchange saturation transfer (CEST) effect in these models were also investigated. Although R1ρ and R2ρ were not affected by the ST, the CEST effect observed in the Z-spectra increased and saturated with increasing ST. When ω1 was varied, the CEST effect increased with increasing ω1 in R1ρ, R2ρ, and Z-spectra. When ω1 was large, however, the spillover effect due to the direct saturation of bulk water protons also increased, suggesting that these parameters must be determined in consideration of both the CEST and spillover effects. Our method will be useful for analyzing the complex CEST contrast mechanism and for investigating the optimal conditions for CEST MRI in the presence of multiple chemical exchange pools.展开更多
本文通过比较 7 T 场强下化学交换饱和转移(chemical exchange saturation transfer,CEST)成像技术不同量化方式在急性帕金森氏病小鼠模型研究中的应用效果,探讨了客观无创的帕金森氏病研究方案.使用 Bruker PharmaScan7 T小动物磁共振...本文通过比较 7 T 场强下化学交换饱和转移(chemical exchange saturation transfer,CEST)成像技术不同量化方式在急性帕金森氏病小鼠模型研究中的应用效果,探讨了客观无创的帕金森氏病研究方案.使用 Bruker PharmaScan7 T小动物磁共振成像(Magnetic Resonance Imaging,MRI)扫描仪,对经 1-甲基-4-苯基-1,2,3,6-四氢吡啶(1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine,MPTP)急性造模前及造模后第3、10天的小鼠黑质、皮层及海马进行扫描,计算弛豫时间 T1、T2、MTRasym(magnetization transfer ratio based on asymmetry analysis)、MTRrex(magnetization transfer ratio yielding Rex)、AREX(apparent exchange-dependent relaxation)及5池拟合后的胺峰面积 Areaamine、酰胺峰面积 Areaamide.结果显示仅黑质中融合了倒Z谱分析和5池洛仑兹拟合所得的量化指标 MTRrex、AREX及Areaamine在造模后显著减小,与黑质免疫组化结果一致,而 T1、T2以及基于Z谱非对称性分析的 MTRasym未见统计学差异,这表明此量化方式消除了直接饱和效应及磁化转移效应的影响,准确性上要优于Z谱非对称分析法,更能正确地提示帕金森氏病黑质的变化.展开更多
文摘The purpose of this study was to demonstrate a simple and fast method for solving the time-dependent Bloch-McConnell equations describing the behavior of magnetization in magnetic resonance imaging (MRI) in the presence of multiple chemical exchange pools. First, the time-dependent Bloch- McConnell equations were reduced to a homogeneous linear differential equation, and then a simple equation was derived to solve it using a matrix operation and Kronecker tensor product. From these solutions, the longitudinal relaxation rate (R1ρ) and transverse relaxation rate in the rotating frame (R2ρ) and Z-spectra were obtained. As illustrative examples, the numerical solutions for linear and star-type three-pool chemical exchange models and linear, star- type, and kite-type four-pool chemical exchange models were presented. The effects of saturation time (ST) and radiofrequency irradiation power (ω1) on the chemical exchange saturation transfer (CEST) effect in these models were also investigated. Although R1ρ and R2ρ were not affected by the ST, the CEST effect observed in the Z-spectra increased and saturated with increasing ST. When ω1 was varied, the CEST effect increased with increasing ω1 in R1ρ, R2ρ, and Z-spectra. When ω1 was large, however, the spillover effect due to the direct saturation of bulk water protons also increased, suggesting that these parameters must be determined in consideration of both the CEST and spillover effects. Our method will be useful for analyzing the complex CEST contrast mechanism and for investigating the optimal conditions for CEST MRI in the presence of multiple chemical exchange pools.
基金supported by the Fundamental Research Funds for the Central Universities(WK2060000020)the National Natural Science Foundation of China(22175168)+1 种基金the Collaborative Innovation Program of Hefei Science Center,CAS(2021HSC-CIP012)the National Key R&D Program of China(2022YFA1305100)。
基金the National Natural Science Foundation of China(61671228,61728107)
文摘本文通过比较 7 T 场强下化学交换饱和转移(chemical exchange saturation transfer,CEST)成像技术不同量化方式在急性帕金森氏病小鼠模型研究中的应用效果,探讨了客观无创的帕金森氏病研究方案.使用 Bruker PharmaScan7 T小动物磁共振成像(Magnetic Resonance Imaging,MRI)扫描仪,对经 1-甲基-4-苯基-1,2,3,6-四氢吡啶(1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine,MPTP)急性造模前及造模后第3、10天的小鼠黑质、皮层及海马进行扫描,计算弛豫时间 T1、T2、MTRasym(magnetization transfer ratio based on asymmetry analysis)、MTRrex(magnetization transfer ratio yielding Rex)、AREX(apparent exchange-dependent relaxation)及5池拟合后的胺峰面积 Areaamine、酰胺峰面积 Areaamide.结果显示仅黑质中融合了倒Z谱分析和5池洛仑兹拟合所得的量化指标 MTRrex、AREX及Areaamine在造模后显著减小,与黑质免疫组化结果一致,而 T1、T2以及基于Z谱非对称性分析的 MTRasym未见统计学差异,这表明此量化方式消除了直接饱和效应及磁化转移效应的影响,准确性上要优于Z谱非对称分析法,更能正确地提示帕金森氏病黑质的变化.
文摘酰胺质子转移(amide proton transfer,APT)成像基础为细胞内游离蛋白及多肽酰胺质子与自由水中的氢质子发生交换,肿瘤恶性程度越高,细胞内游离蛋白质及多肽含量越多,APT信号增高。本文汇总APT成像诊断直肠癌的国内外相关文献,希望将APT成像用于直肠癌临床早期诊断及疗效评估,提高直肠癌患者生存率。国内外文献研究APT成像诊断直肠癌主要集中在以下几个方面:评估直肠癌组织学分级,预测直肠癌化疗疗效,预测大鼠肉瘤病毒癌(Kirsten rat sarcoma,KRAS)基因是否突变,预测直肠癌侵袭性。与常规MRI序列相比,APT成像可以无创性预测直肠癌侵袭性,进一步观察分子生物学改变。APT成像目前最常用于脑部肿瘤,空腔脏器所含成分复杂,因此临床应用受限,故本文汇总相关文献,探索人为均匀磁场方法,将APT成像这一反映蛋白质代谢的分子生物学检查方法用于直肠癌,开辟APT成像临床应用新领域。
