WE-DE-206-04: MRI Pulse Sequences - Spin Echo, Gradient Echo, EPI, Non-Cartesia

2016 ◽  
Vol 43 (6Part40) ◽  
pp. 3816-3816
Author(s):  
R. Pooley
Keyword(s):  
Spin Echo ◽  
Pulse Sequences ◽  
Gradient Echo

Experimental intracerebral and subarachnoid/intraventricular haemorrhages: MR detectability at 0.5 T and 1.5 T

2002 ◽  
Vol 43 (5) ◽  
pp. 464-473
Author(s):  
M. Alemany Ripoll ◽  
R. Raininko
Keyword(s):  
Cerebrospinal Fluid ◽  
Mr Imaging ◽  
Spin Echo ◽  
Autologous Blood ◽  
Pulse Sequences ◽  
Proton Density ◽  
Gradient Echo ◽  
The Brain ◽  
Formalin Fixed

Purpose: To compare the detectability of small experimental intracranial haemorrhages on MR imaging at 0.5 T and 1.5 T, from hyperacute to subacute stages. Material and Methods: 1 ml of autologous blood was injected into the brain of 15 rabbits to create intraparenchymal haematomas. Since the blood partially escaped into the cerebrospinal fluid (CSF) spaces, detectability of subarachnoid and intraventricular blood was also evaluated. MR imaging at 0.5 T and at 1.5 T was repeated up to 14 days, including T1-, proton density- and T2-weighted (w) spin-echo (SE), FLAIR and T2*-w gradient echo (GE) pulse sequences. The last MR investigation was compared to the formalin-fixed brain sections in 7 animals. Results: The intraparenchymal haematomas were best revealed with T2*-w GE sequences, with 100% of sensitivity at 1.5 T and 90–95% at 0.5 T. Blood in the CSF spaces was significantly ( p < 0.05) better detected at 1.5 T with T2*-w GE sequences and detected best during the first 2 days. The next most sensitive sequence for intracranial blood was FLAIR. SE sequences were rather insensitive. Conclusion: 1.5 T equipment is superior to 0.5 T in the detection of intracranial haemorrhages from acute to subacute stages. T2*-w GE sequences account for this result but other sequences are also needed for a complete examination.

scholarly journals Quantitative Radiomics: Impact of Pulse Sequence Parameter Selection on MRI-Based Textural Features of the Brain

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
John Ford ◽  
Nesrin Dogan ◽  
Lori Young ◽  
Fei Yang
Keyword(s):  
Pulse Sequence ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Parameter Selection ◽  
Inversion Recovery ◽  
Textural Features ◽  
Imaging Data ◽  
Gradient Echo ◽  
The Impact ◽  
The Brain

Objectives. Radiomic features extracted from diverse MRI modalities have been investigated regarding their predictive and/or prognostic value in a variety of cancers. With the aid of a 3D realistic digital MRI phantom of the brain, the aim of this study was to examine the impact of pulse sequence parameter selection on MRI-based textural parameters of the brain. Methods. MR images of the employed digital phantom were realized with SimuBloch, a simulation package made for fast generation of image sequences based on the Bloch equations. Pulse sequences being investigated consisted of spin echo (SE), gradient echo (GRE), spoiled gradient echo (SP-GRE), inversion recovery spin echo (IR-SE), and inversion recovery gradient echo (IR-GRE). Twenty-nine radiomic textural features related, respectively, to gray-level intensity histograms (GLIH), cooccurrence matrices (GLCOM), zone size matrices (GLZSM), and neighborhood difference matrices (GLNDM) were evaluated for the obtained MR realizations, and differences were identified. Results. It was found that radiomic features vary considerably among images generated by the five different T1-weighted pulse sequences, and the deviations from those measured on the T1 map vary among features, from a few percent to over 100%. Radiomic features extracted from T1-weighted spin-echo images with TR varying from 360 ms to 620 ms and TE = 3.4 ms showed coefficients of variation (CV) up to 45%, while up to 70%, for T2-weighted spin-echo images with TE varying over the range 60–120 ms and TR = 6400 ms. Conclusion. Variability of radiologic textural appearance on MR realizations with respect to the choice of pulse sequence and imaging parameters is feature-dependent and can be substantial. It calls for caution in employing MRI-derived radiomic features especially when pooling imaging data from multiple institutions with intention of correlating with clinical endpoints.

Basic pulse sequences

2018 ◽  
pp. 17-25
Author(s):  
Sebastian Kozerke ◽  
Redha Boubertakh ◽  
Marc Miquel
Keyword(s):  
Cardiac Imaging ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Image Sequences ◽  
Black Blood ◽  
Time Varying ◽  
Gradient Echo ◽  
Anatomical Imaging ◽  
Blood Imaging ◽  
Bright Blood

Pulse sequences control the timing of radiofrequency pulses and time-varying gradients that are necessary to create an image. Sequences are divided into different types: gradient echo, spin echo, and hybrid echo sequences. In cardiac imaging, ‘black blood’ spin echo images are used for anatomical imaging, while ‘bright blood’ imaging is used to study function and is based on gradient echo or hybrid echo sequences. Some key applications of those sequences, e.g. water–fat imaging or T2*-mapping to detect iron loading, are discussed. Preparation pulses can be used to modify image contrast to, for example, improve black blood images or for quantitative applications, including T1- and T2-mapping. To help the reader navigate through the sea of sequence acronyms, the chapter ends with a quick guide covering the acronyms used by the main scanner manufacturers.

Evaluation of optimised 3D turbo spin echo and gradient echo MR pulse sequences of the knee at 3T and 1.5T

Radiography ◽  
2020 ◽  
Author(s):  
O.M. Abdulaal ◽  
L. Rainford ◽  
P.J. MacMahon ◽  
P. Kenny ◽  
F. Carty ◽  
...  
Keyword(s):  
Spin Echo ◽  
Pulse Sequences ◽  
Turbo Spin Echo ◽  
Gradient Echo ◽  
Turbo Spin ◽  
Mr Pulse Sequences

scholarly journals MRI and CT venography in the diagnosis of hemodynamic disorders in patients suffering from the lower extremities veins chronic diseases Part I. Possibilities of MRI in visualization of the vascular blood flow of the lower extremities

2020 ◽  
Vol 24 (4) ◽  
pp. 81-101
Author(s):  
E. V. Shajdakov ◽  
A. B. Sannikov ◽  
V. M. Emelyanenko ◽  
L. N. Kryukova ◽  
A. E. Baranova ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Venous Thrombosis ◽  
Mr Angiography ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Lower Extremities ◽  
Maximum Intensity ◽  
Gradient Echo ◽  
Advantages And Disadvantages ◽  
Venous Disorders

Despite the fact that most vascular surgeons in Russia rarely use magnetic resonance imaging (MRI) in their daily practice, today interest in this method of imaging among specialists in the world is steadily increasing. This is due to the desire of clinicians to have another non – invasive method for diagnosing hemodynamic disorders of both the arterial (Magnetic Resonance Angiography – MRA) and venous vascular bed (Magnetic Resonance Venography – VRA). The development of these methods today is associated with the solution of many technical problems, the development of special pulse sequences and post-processing methods for the resulting image. This literature review analyzes published scientific data on the methodology of MRI in relation to the vascular system and the choice of optimal scanning modes. Taking into consideration the fact that this material is intended primarily for vascular surgeons and phlebologists, and not radiologists, the first part summarizes the basic understanding of the physical phenomena underlying the MRI image, without which a thoughtful analysis of the advantages and disadvantages of MR-Angiography and the search for the most optimal scanning mode for MR-Venography is not possible. Based on the constant desire of clinicians to be self-educated, it seems that this part of the presented material will not be difficult to understand. When describing the developed contrast-free and contrast-free MRA methods, attention is paid to the traditional methods of image processing in 2D mode (TOF, PC) using pulse sequences: spin echo (SE), multi-echo (SE T2), turbo spin echo (TSE), fast Advanced Spin Echo (fast Advanced Spin Echo-FASE), gradient echo (Gradient Echo-GE, GRE) and inversion recovery (Inversion Recovery-IR). In addition, the focus is on the most modern solu tions, including: multiplantar reformatting (MPR), maximum intensity projection (MIP), subvolume maximum intensity, surface rendering (SR), volume rendering (VR) and virtual intraluminal endoscopy (VIE). For all the methods used today, MR-Angiography is shown to be specific and informative, with a detailed analysis of the advantages and disadvantages. The nuances of understanding the resulting angiographic image in T1 and T2-weighted images and the phenomena of “bright blood” and “black blood” are shown. Since the absence of information or a brief mention only about the possibilities of using MRI in the diagnosis of hemodynamic disorders in patients with vascular pathology in Russian scientific literature it seems that this material is relevant and will arouse some interest from various specialists. Of particular interest is the potential use of contrast-free and contrast – free MR Angiography in the study of venous pathology of the lower extremities and pelvis, especially with regard to timely and accurate diagnosis of deep venous thrombosis (deep Vein Thrombosis-DVT) and venous thromboembolism (Venous Thrombosis – Embolism – VTE), which occupy a special position in the structure of patients with chronic venous Disorders of the lower extremities (Chronic Venous Disorders-CVD).

scholarly journals TDM: a temporal decomposition method for removing venous effects from task-based fMRI

2019 ◽  
Author(s):  
Kendrick Kay ◽  
Keith W. Jamison ◽  
Ruyuan Zhang ◽  
Kamil Ugurbil
Keyword(s):  
High Resolution ◽  
Spin Echo ◽  
Pulse Sequences ◽  
High Sensitivity ◽  
Blood Oxygenation ◽  
Dimensional Manifold ◽  
Spatial Accuracy ◽  
Gradient Echo ◽  
Spatial Coverage ◽  
Temporal Decomposition

AbstractMost functional magnetic resonance imaging (fMRI) is conducted with gradient-echo pulse sequences. Although this yields high sensitivity to blood oxygenation level dependent (BOLD) signals, gradient-echo acquisitions are heavily influenced by venous effects which limit the ultimate spatial resolution and spatial accuracy of fMRI. While alternative acquisition methods such as spin-echo can be used to mitigate venous effects, these methods lead to serious reductions in signal-to-noise ratio and spatial coverage, and are difficult to implement without leakage of undesirable non-spin-echo effects into the data. Moreover, analysis heuristics such as masking veins or sampling inner cortical depths using high-resolution fMRI may be helpful, but sacrifice information from many parts of the brain. Here, we describe a new analysis method that is compatible with conventional gradient-echo acquisition and provides venous-free response estimates throughout the entire imaged volume. The method involves fitting a low-dimensional manifold characterizing variation in response timecourses observed in a given dataset, and then using identified early and late timecourses as basis functions for decomposing responses into components related to the microvasculature (capillaries and small venules) and the macrovasculature (veins), respectively. We show that this Temporal Decomposition through Manifold Fitting (TDM) method is robust, consistently deriving meaningful timecourses in individual fMRI scan sessions. Moreover, we show that by removing late components, TDM substantially reduces the superficial cortical depth bias present in gradient-echo BOLD responses and eliminates artifacts in cortical activity maps. TDM is general: it can be applied to any task-based fMRI experiment, can be used with standard- or high-resolution fMRI acquisitions, and can even be used to remove residual venous effects from specialized acquisition methods like spin-echo. We suggest that TDM is a powerful method that improves the spatial accuracy of fMRI and provides insight into the origins of the BOLD signal.

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