PROPELLER DUO DWI序列+常规MRI在直肠癌术前T分期中的应用价值

目的研究螺旋桨采集技术扩散加权成像(PROPELLER DUO DWI)+核磁共振成像(MRI)诊断直肠癌术前T分期的应用价值。方法选取我院2018年6月至2020年6月直肠癌患者65例,均进行MRI及DWI扫描检查,以病理学诊断结果为“金标准”。比较常规MRI与常规MRI+DWI诊断直肠癌T分期的结果及准确率。结果65例直肠癌患者常规MRI诊断T1~T2期33例,T3期22例,T4期10例。MRI+PROPELLER DUO DWI诊断T1~T2期37例,T3期21例,T4期7例。MRI+PROPELLER DUO DWI诊断总准确率为92.3%(60/65),高于MRI[80.0%(52/65,P<0.05)]。结论与MRI常规序列比较,PROPELLER DUODWI技术+常规MRI在直肠癌患者术前T分期诊断中准确率更高,有助于临床治疗方案的制定。     

Detectability of Neural Tracts and Nuclei in the Brainstem Utilizing 3DAC‐PROPELLER

Despite clinical importance of identifying exact anatomical location of neural tracts and nuclei in the brainstem, no neuroimaging studies have validated the detectability of these structures. The aim of this study was to assess the detectability of the structures using three‐dimensional anisotropy contrast‐periodically rotated overlapping parallel lines with enhanced reconstruction (3DAC‐PROPELLER) imaging. Forty healthy volunteers (21 males, 19 females; 19‐53 years, average 23.4 years) participated in this study. 3DAC‐PROPELLER axial images were obtained with a 3T‐MR system at four levels of the brainstem: the lower midbrain, upper and lower pons, and medulla oblongata. Three experts independently judged whether five tracts (corticospinal tract, medial lemniscus, medial longitudinal fasciculus, central tegmental and spinothalamic tracts) and 10 nuclei (oculomotor and trochlear nuclei, spinal trigeminal, abducens, facial, vestibular, hypoglossal, prepositus, and solitary nuclei, locus ceruleus, superior and inferior olives) on each side could be identified. In total, 240 assessments were made. The five tracts and eight nuclei were identified in all the corresponding assessments, whereas the locus ceruleus and superior olive could not be identified in 3 (1.3%) and 16 (6.7%) assessments, respectively. 3DAC‐PROPELLER seems extremely valuable imaging method for mapping out surgical strategies for brainstem lesions.     

螺旋桨(PROPELLER)技术的原理及应用

周期性旋转重叠平行线采集和增强后处理重建(PROPELLER)技术是磁共振成像中一种能减少运动伪影的崭新数据采集和重建方法。该方法同时具有K空间中心部分过采样和获取人体组织内在“导航波”信息的优势,它能纠正受检对象层面内平移和旋转引起的运动伪影,以及部分层面间的运动伪影。本文就PROPELLER技术的基本原理、研究进展及临床应用进行综述。     

Motion correction in periodically‐rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and turboprop MRI

Periodically‐rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and Turboprop MRI are characterized by greatly reduced sensitivity to motion, compared to their predecessors, fast spin‐echo (FSE) and gradient and spin‐echo (GRASE), respectively. This is due to the inherent self‐navigation and motion correction of PROPELLER‐based techniques. However, it is unknown how various acquisition parameters that determine k‐space sampling affect the accuracy of motion correction in PROPELLER and Turboprop MRI. The goal of this work was to evaluate the accuracy of motion correction in both techniques, to identify an optimal rotation correction approach, and determine acquisition strategies for optimal motion correction. It was demonstrated that blades with multiple lines allow more accurate estimation of motion than blades with fewer lines. Also, it was shown that Turboprop MRI is less sensitive to motion than PROPELLER. Furthermore, it was demonstrated that the number of blades does not significantly affect motion correction. Finally, clinically appropriate acquisition strategies that optimize motion correction are discussed for PROPELLER and Turboprop MRI. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Eliminating side excitations in PROPELLER‐based 2D‐selective RF excitations

Recently, spatially two‐dimensional selective radiofrequency excitations based on the PROPELLER trajectory have been presented and were applied to minimize partial volume effects in single‐voxel MR spectroscopy. Thereby, residual side excitations appeared due to limitations of the Voronoi diagram that was used to consider the nonconstant sampling density, and trajectory distortions caused by eddy currents varying between the differently rotated blades. In this extension, one of the refocusing radiofrequency pulses of a PRESS‐based pulse sequence is applied in the blip direction of each segment to eliminate the side excitations. This corresponds to an infinitely dense sampling of the blade and the required sampling density correction can easily be calculated. Thus, signal contributions from outside the desired region‐of‐interest are completely avoided. The feasibility of this approach to acquire single‐voxel MR spectra of anatomically defined regions‐of‐interest is demonstrated in the human brain in vivo on a 3T whole‐body MR system. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

Aliasing artifacts with the BLADE technique: causes and effective suppression

Purpose:

To elucidate the causes of aliasing artifacts with the BLADE technique and clarify the effective suppression methods.

Materials and Methods:

We separately observed the aliasing artifacts of BLADE from features inside and then outside the defined field‐of‐view (FOV) using phantom studies. The effectiveness of suppressing them with phase oversampling (POS) and presaturation pulses (SAT) was evaluated. Finally, our observations were confirmed for a healthy volunteer.

Results:

Characteristic aliasing artifacts were observed from both inside and outside the FOV. Those from inside the FOV were sufficiently suppressed by using a POS of 25%, considering the acquisition time prolongation. Those from outside the FOV were nearly suppressed using SAT outside the FOV without selecting needless receiver coils. Aliasing artifacts on the coronal images of the head and neck with a healthy volunteer were completely suppressed by a combination of using a POS of 25% and using SAT on all four sides outside the FOV.

Conclusion:

The characteristic aliasing artifacts of BLADE are caused from both inside and outside the defined FOV. They can be effectively suppressed by a combination of using a POS of 25% and using SAT on all four sides outside the FOV. J. Magn. Reson. Imaging 2011;33:432–440. © 2011 Wiley‐Liss, Inc.     

Iterative image reconstruction for PROPELLER‐MRI using the nonuniform fast fourier transform

Purpose:

To investigate an iterative image reconstruction algorithm using the nonuniform fast Fourier transform (NUFFT) for PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) MRI.

Materials and Methods:

Numerical simulations, as well as experiments on a phantom and a healthy human subject were used to evaluate the performance of the iterative image reconstruction algorithm for PROPELLER, and compare it with that of conventional gridding. The trade‐off between spatial resolution, signal to noise ratio, and image artifacts, was investigated for different values of the regularization parameter. The performance of the iterative image reconstruction algorithm in the presence of motion was also evaluated.

Results:

It was demonstrated that, for a certain range of values of the regularization parameter, iterative reconstruction produced images with significantly increased signal to noise ratio, reduced artifacts, for similar spatial resolution, compared with gridding. Furthermore, the ability to reduce the effects of motion in PROPELLER‐MRI was maintained when using the iterative reconstruction approach.

Conclusion:

An iterative image reconstruction technique based on the NUFFT was investigated for PROPELLER MRI. For a certain range of values of the regularization parameter, the new reconstruction technique may provide PROPELLER images with improved image quality compared with conventional gridding. J. Magn. Reson. Imaging 2010;32:211–217. © 2010 Wiley‐Liss, Inc.