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    • 2. 发明授权
    • Magnetic resonance imaging of short T.sub.2 species with improved
contrast
    • 短T2物种的磁共振成像具有改善的对比度
    • US5150053A
    • 1992-09-22
    • US645859
    • 1991-01-25
    • John M. PaulySteven M. ConollyDwight G. Nishimura
    • John M. PaulySteven M. ConollyDwight G. Nishimura
    • A61B5/055G01R33/48G01R33/50G01R33/56G01R33/561
    • G01R33/446G01R33/50G01R33/56
    • Magnetic resonance signals for imaging species having short spin-spin relaxation times (T.sub.2) are obtained without the need for a refocusing lobe. A series of RF excitation pulses are applied to the species with magnetic resonance signals being detected after each RF excitation pulse is applied. The magnetic resonance signals are then combined to provide the imaging signals. In one embodiment, each RF excitation pulse is half of a conventional slice-selective pulse with each pulse being slewed to zero. Contrast between the imaged short T.sub.2 species and longer T.sub.2 species can be enhanced by first applying an RF signal having sufficient amplitude to excite the longer T.sub.2 species but insufficient amplitude to excite the short T.sub.2 species whereby the longer T.sub.2 species are tipped by the RF signal. A magnetic gradient can then be applied to dephase the tipped nuclei of the longer T.sub.2 species. The imaging signals are then obtained from magnetic resonance signals from the short T.sub.2 species.
    • 获得具有短自旋 - 自旋弛豫时间(T2)的成像物质的磁共振信号,而不需要重新聚焦波瓣。 在施加每个RF激励脉冲之后,对具有磁共振信号的物种施加一系列RF激励脉冲。 然后将磁共振信号组合以提供成像信号。 在一个实施例中,每个RF激励脉冲是常规切片选择脉冲的一半,其中每个脉冲被转换为零。 可以通过首先施加具有足够振幅的RF信号来激发较长的T2物种但不足的幅度来激发短的T2物种,从而通过RF信号使更长的T2物种倾斜,可以增强成像的短T2物种与较长的T2物种之间的对比。 然后可以应用磁梯度来去除较长T2物种的尖端核。 然后从来自短T2物种的磁共振信号获得成像信号。
    • 4. 发明授权
    • RF pulses for long T2 suppression in MRI
    • 射频脉冲在MRI中长T2抑制
    • US07288936B2
    • 2007-10-30
    • US11180339
    • 2005-07-12
    • Peder E. LarsonJohn M. PaulySteven M. Conolly
    • Peder E. LarsonJohn M. PaulySteven M. Conolly
    • G01V3/00
    • G01R33/446
    • In imaging a first species having a short T2 magnetic resonance parameter in the presence of a second and third species having longer T2 parameters, a method of suppressing signals from the longer T2 species comprises the steps of: a) applying a RF saturation pulse with multiple suppression bands for the second and third species to excite nuclei spins of the longer T2 species with the magnitude of the RF pulse being sufficiently low so as not to excite nuclei spins of the short T2 species, the RF saturation pulse being sufficiently long to rotate the longer T2 species nuclei spins into a transverse plane, and b) dephasing the longer T2 species nuclei spins in the transverse plane. An imaging pulse sequence is then applied to image the short T2 species. Alternatively, the method can comprise the steps of a) applying a first inversion pulse for selective inverting species of the second longer T2 species, b) obtaining first image signals after step a, c) applying a second inversion pulse for selectively inverting species of the third longer T2 species, d) obtaining second image signals after step c), and e) combining the first image signals and the second image signal to image the first short T2 species with the longer second and third species cancelling in the combination. In each of these methods, either the second or third longer T2 species can be suppressed without suppressing the other by applying the RF saturation or inversion pulse only to the species to be suppressed.
    • 在具有较长T2参数的第二和第三物种存在下成像具有短T2磁共振参数的第一物种时,抑制来自较长T2物种的信号的方法包括以下步骤:a)施加具有多个 第二和第三物种的抑制带激发较长T2物种的核心旋转,其中RF脉冲的幅度足够低,以便不激发短T2物质的核旋转,RF饱和脉冲足够长以旋转 更长的T2物种核转入横向平面,并且b)在横向平面中去除更长的T2种类核自旋。 然后应用成像脉冲序列对短T2物种进行成像。 或者,该方法可以包括以下步骤:a)施加用于第二较长T2种类的选择性反转种类的第一反转脉冲,b)在步骤a之后获得第一图像信号,c)施加第二反转脉冲以选择性地反转 第三较长的T2物种,d)在步骤c)之后获得第二图像信号,以及e)组合第一图像信号和第二图像信号以对组合中较长的第二和第三个物种进行消除的第一短T2物种进行成像。 在这些方法的每一种中,通过仅对要抑制的物质施加RF饱和或反转脉冲,可以抑制第二或第三较长的T2物种,而不会抑制另一个。
    • 9. 发明授权
    • Catalyzing the transient response in steady-state MRI sequences
    • 在稳态MRI序列中催化瞬时反应
    • US06452387B1
    • 2002-09-17
    • US09801424
    • 2001-03-07
    • Brain A. HargreavesShreyas VasanawalaJohn M. PaulyDwight G. Nishimura
    • Brain A. HargreavesShreyas VasanawalaJohn M. PaulyDwight G. Nishimura
    • G01V300
    • G01R33/5613
    • A steady-state condition for tipped nuclear spins is accelerated or catalyzed by first determining magnetization magnitude of the steady state and the scaling magnetization along one axis (Mz) to at least approximate the determined magnetization magnitude. Then the scaled magnetization is rotated to coincide with a real-valued eigenvector extension of the tipped steady-state magnetization. Any error vector will then decay to the steady-state condition without oscillation. In one embodiment, the magnetic resonance imaging utilizes steady-state free precession (SSFP). The scaling and rotating steps are followed by the steps of applying read-out magnetic gradients and detecting magnetic resonance signals from the tipped nuclear spins. The magnetization magnitude is determined by eigenvector analysis, and the eigenvector extension is a real-valued eigenvector determined in the analysis.
    • 通过首先确定稳态的磁化强度和沿着一个轴(Mz)的缩放磁化强度至少接近确定的磁化强度,来加速或催化尖端核自旋的稳态条件。 然后,缩放的磁化被旋转以与尖端稳态磁化的实数特征向量延伸一致。 任何误差矢量都会衰减到稳态,而不会产生振荡。 在一个实施例中,磁共振成像利用稳态自由进动(SSFP)。 缩放和旋转步骤之后是应用读出磁梯度并从尖端核自旋检测磁共振信号的步骤。 磁化强度由特征向量分析确定,特征向量扩展是在分析中确定的实值特征向量。
    • 10. 发明授权
    • Linear combination steady-state free precession MRI
    • 线性组合稳态自由进动MRI
    • US06307368B1
    • 2001-10-23
    • US09312025
    • 1999-05-14
    • Shreyas S. VasanawalaJohn M. PaulyDwight G. Nishimura
    • Shreyas S. VasanawalaJohn M. PaulyDwight G. Nishimura
    • G01V300
    • G01R33/5613G01R33/446
    • A fast, spectrally-selective steady-state free precession (SSFP) imaging method is presented. Combining k-space data from SSFP sequences with certain phase schedules of radiofrequency excitation pulses permits manipulation of the spectral selectivity of the image. For example, lipid and water can be rapidly resolved. The contrast of each image depends on both T1 and T2, and the relative contribution of the two relaxation mechanisms to image contrast can be controlled by adjusting the flip angle. Several applications of the technique are presented, including fast musculoskeletal imaging, brain imaging, and angiography. The technique is referred to herein as linear combination steady-state free precession (LCSSFP) and fluctuating equilibrium magnetic resonance (FEMR).
    • 提出了一种快速,频谱选择性的稳态自由进动(SSFP)成像方法。 将来自SSFP序列的k空间数据与射频激发脉冲的某些相位调度组合允许操纵图像的光谱选择性。 例如,脂质和水可以快速解决。 每个图像的对比度取决于T1和T2,并且可以通过调整翻转角度来控制两个松弛机制对图像对比度的相对贡献。 提出了该技术的几个应用,包括快速肌肉骨骼成像,脑成像和血管造影。 该技术在此被称为线性组合稳态自由进动(LCSSFP)和波动平衡磁共振(FEMR)。