Magnetic Resonance Imaging: Comparative Study of Radiofrequency Pulse Techniques in the Evaluation of Focal Cerebral Ischemia

Neurosurgery ◽  
1985 ◽  
Vol 16 (4) ◽  
pp. 502-510 ◽  
Author(s):  
Joseph M. Zabramski ◽  
Robert F. Spetzler ◽  
Benjamin Kaufman
Keyword(s):  
Magnetic Resonance ◽  
Mr Imaging ◽  
Focal Cerebral Ischemia ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Artery Occlusion ◽  
Primate Model ◽  
Cross Sectional ◽  
Tissue Contrast ◽  
Rf Pulse

Abstract The recently developed technique of magnetic resonance (MR) imaging utilizes radiofrequency (RF) radiation in the presence of a strong magnetic field to provide cross sectional displays of body anatomy similar to computed tomography, When utilizing MR, the operator alters tissue contrast electronically by changing RF pulse sequences. The three most frequently used RF pulse sequences are partial-saturation (PS), inversion-recovery (IR), and spin-echo (SE). We evaluated the sensitivity of these RF sequences to detect ischemic changes in our primate model. Serial MR scans were carried out using all three pulse formats 5 to 60 hours after middle cerebral artery occlusion (MCAO) in four animals. SE- and IR-sequenced proton MR images readily identified areas of evolving infarct 5 to 6 hours after MCAO, whereas PS scans that were performed during this acute period appeared normal. From 24 to 60 hours after MCAO, PS-sequenced scans showed focal areas of progressively decreasing signal intensity. However, SE and IR scans performed at the same intervals always demonstrated more extensive tissue changes. The basis of MR imaging, the effects of altering RF pulse sequences, and the resulting interpretation of changes observed in MR sections are presented. (Neurosurgery 16: 502-510, 1985)

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.

Application of magnetic resonance neurography in the evaluation of patients with peripheral nerve pathology

1996 ◽  
Vol 85 (2) ◽  
pp. 299-309 ◽  
Author(s):  
Aaron G. Filler ◽  
Michel Kliot ◽  
Franklyn A. Howe ◽  
Cecil E. Hayes ◽  
Dawn E. Saunders ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Time Course ◽  
Spin Echo ◽  
Fast Spin Echo ◽  
Mr Neurography ◽  
Magnetic Resonance Neurography ◽  
Cross Sectional ◽  
Content Type ◽  
Direct Nerve ◽  
Fine Print

✓ Currently, diagnosis and management of disorders involving nerves are generally undertaken without images of the nerves themselves. The authors evaluated whether direct nerve images obtained using the new technique of magnetic resonance (MR) neurography could be used to make clinically important diagnostic distinctions that cannot be readily accomplished using existing methods. The authors obtained T2-weighted fast spin—echo fat-suppressed (chemical shift selection or inversion recovery) and T1-weighted images with planes parallel or transverse to the long axis of nerves using standard or phased-array coils in healthy volunteers and referred patients in 242 sessions. Longitudinal and cross-sectional fascicular images readily distinguished perineural from intraneural masses, thus predicting both resectability and requirement for intraoperative electrophysiological monitoring. Fascicle pattern and longitudinal anatomy firmly identified nerves and thus improved the safety of image-guided procedures. In severe trauma, MR neurography identified nerve discontinuity at the fascicular level preoperatively, thus verifying the need for surgical repair. Direct images readily demonstrated increased diameter in injured nerves and showed the linear extent and time course of image hyperintensity associated with nerve injury. These findings confirm and precisely localize focal nerve compressions, thus avoiding some exploratory surgery and allowing for smaller targeted exposures when surgery is indicated. Direct nerve imaging can demonstrate nerve continuity, distinguish intraneural from perineural masses, and localize nerve compressions prior to surgical exploration. Magnetic resonance neurography can add clinically useful diagnostic information in many situations in which physical examinations, electrodiagnostic tests, and existing image techniques are inconclusive.

Comparison of breath-hold fast spin-echo and conventional spin-echo pulse sequences for T2-weighted MR imaging of liver lesions.

Radiology ◽  
1995 ◽  
Vol 194 (2) ◽  
pp. 431-437 ◽  
Author(s):  
J N Rydberg ◽  
D J Lomas ◽  
K J Coakley ◽  
D M Hough ◽  
R L Ehman ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Fast Spin Echo ◽  
Breath Hold ◽  
Liver Lesions ◽  
Echo Pulse ◽  
Conventional Spin Echo ◽  
Fast Spin

Characteristics of Incidental Pineal Cysts on Magnetic Resonance Imaging

Neurosurgery ◽  
1989 ◽  
Vol 25 (4) ◽  
pp. 636-640 ◽  
Author(s):  
Jagveer S. Sandhu ◽  
James R. McLaughlin ◽  
Camilo R. Gomez
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Spin Density ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Relaxation Times ◽  
Resonance Imaging ◽  
Characteristic Appearance ◽  
Cystic Changes ◽  
Echo Pulse

Abstract Three patients with different neurological complaints were studied by magnetic resonance imaging. Coincidentally, all studies showed cystic changes within the pineal bodies. These cysts appeared hypointense on T1-weighted, spin-echo pulse sequences and hyperintense on T2-weighted images. Spin-density sequences displayed them as hypointense areas, with relaxation times similar to those of the CSF, suggesting their cystic nature. The increased use of magnetic resonance imaging may result in coincidental imaging of involutional cystic pineal changes of many individuals; their characteristic appearance will allow the differentiation between them and pineal neoplastic conditions.

Superparamagnetic Iron Oxide Hepatic MR Imaging: Efficacy and Safety Using Conventional and Fast Spin-Echo Pulse Sequences

1995 ◽  
Vol 5 (5) ◽  
pp. 566-570 ◽  
Author(s):  
Lawrence H. Schwartz ◽  
Steven E. Seltzer ◽  
Clare M. C. Tempany ◽  
Stuart G. Silverman ◽  
David R. Piwnica-Worms ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Mr Imaging ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Superparamagnetic Iron Oxide ◽  
Fast Spin Echo ◽  
Efficacy And Safety ◽  
Echo Pulse ◽  
Fast Spin

Hyperparathyroidism — Comparison of Flash Imaging with Spin ECHO MR Imaging

1993 ◽  
Vol 34 (6) ◽  
pp. 625-630
Author(s):  
Y. Noguchi ◽  
S. Takashima ◽  
J. Ikezoe ◽  
M. Yoshii ◽  
T. Koide ◽  
...  
Keyword(s):  
Mr Imaging ◽  
Spin Echo ◽  
Flip Angle ◽  
High Signal ◽  
Fat Tissue ◽  
Mr Images ◽  
Flash Sequence ◽  
Tissue Contrast ◽  
T1 And T2

MR images of the neck were prospectively studied in 19 patients with hyperparathyroidism. Fast low angle shot (FLASH) sequence was performed in addition to T1- and T2-weighted spin echo (SE) sequences. FLASH images were obtained with 320/12/20° (TR/TE/flip angle) using presaturation technique. TE of 12 ms was chosen to eliminate high signal of fat tissue. In the evaluation of detectability, a combination of T1-weighted SE and FLASH images (T1WI + FLASH) was compared with a combination of T1- and T2-weighted SE images (T1WI + T2WI). MR imaging correctly depicted 20 of 30 abnormal glands on both T1WI + FLASH and T1WI + T2WI. FLASH imaging effectively eliminated high signal of fat tissue. Nineteen abnormal glands demonstrated higher signal than surrounding tissues on FLASH images, whereas 12 glands were high-intense on T2-weighted SE images. We conclude that FLASH imaging provides improved tissue contrast and anatomic delineation and, thus, may replace T2-weighted SE imaging in the neck.

Adjustable shunt valve–induced magnetic resonance imaging artifact: a comparative study

2010 ◽  
Vol 113 (1) ◽  
pp. 74-78 ◽  
Author(s):  
Ahmed K. Toma ◽  
Andrew Tarnaris ◽  
Joan P. Grieve ◽  
Laurence D. Watkins ◽  
Neil D. Kitchen
Keyword(s):  
Mr Imaging ◽  
Pulse Sequence ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Fast Spin Echo ◽  
Mr Images ◽  
Shunt Valve ◽  
Adjustable Valve ◽  
Imaging Artifact

Object In this paper, the authors' goal was to compare the artifact induced by implanted (in vivo) adjustable shunt valves in spin echo, diffusion weighted (DW), and gradient echo MR imaging pulse sequences. Methods The MR images obtained in 8 patients with proGAV and 6 patients with Strata II adjustable shunt valves were assessed for artifact areas in different planes as well as the total volume for different pulse sequences. Results Artifacts induced by the Strata II valve were significantly larger than those induced by proGAV valve in spin echo MR imaging pulse sequence (29,761 vs 2450 mm3 on T2-weighted fast spin echo, p = 0.003) and DW images (100,138 vs 38,955 mm3, p = 0.025). Artifacts were more marked on DW MR images than on spin echo pulse sequencse for both valve types. Conclusions Adjustable valve–induced artifacts can conceal brain pathology on MR images. This should influence the choice of valve implantation site and the type of valve used. The effect of artifacts on DW images should be highlighted pending the development of less MR imaging artifact–inducing adjustable shunt valves.

Nuclear Magnetic Resonance of the Spine: Clinical Potential and Limitation

Neurosurgery ◽  
1984 ◽  
Vol 15 (4) ◽  
pp. 583-592 ◽  
Author(s):  
Michael T. Modic ◽  
Russell W. Hardy ◽  
Meredith A. Weinstein ◽  
Paul M. Duchesneau ◽  
David M. Paushter ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Spin Echo ◽  
Intervertebral Discs ◽  
Foramen Magnum ◽  
Conventional Angiography ◽  
Significant Information ◽  
Computed Tomographic ◽  
Plain Films ◽  
Tissue Contrast ◽  
Spin Echo Technique

Abstract Magnetic resonance can visualize the vertebral bodies, discs, neural structures, cerebrospinal fluid (CSF), neural foramina, and extradural structures in the sagittal, axial, and coronal planes. The normal nucleus pulposus can be differentiated from the anulus and changes associated with degeneration. Infection, trauma, and neoplastic conditions can be identified. The signal intensity of the CSF relative to extradural and neural structures can be increased to provide evaluation of the size and configuration of the contents of the thecal sac without the use of an intrathecal contrast medium. Impingement by disc, tumors, fracture segments, and expansile masses can then be accurately evaluted, It is the most accurate modality for the evaluation of the foramen magnum, Chiari malformation, syringomyelia, infection, and degeneration of intervertebral discs. It can identify paravertebral soft tissue and bony changes when plain films and computed tomographic (CT) studies are negative or equivocal. Not only can lesions be localized, but significant information regarding the nature of the process can be obtained. Using variations of the spin-echo technique with appropriate T1 and T2-weighted images, magnetic resonance can produce tissue contrast distinctions not possible with CT scans or conventional angiography.

scholarly journals Theoretical Description of Pulsed RYDMR: Refocusing Zero-Quantum and Single Quantum Coherences

2017 ◽  
Vol 231 (2) ◽  
Author(s):  
Egor A. Nasibulov ◽  
Jan Behrends ◽  
Leonid V. Kulik ◽  
Konstantin L. Ivanov
Keyword(s):  
Magnetic Resonance ◽  
Organic Semiconductors ◽  
Spin Echo ◽  
Pulse Sequences ◽  
Theoretical Description ◽  
Reaction Yield ◽  
Single Quantum ◽  
Paramagnetic Resonance ◽  
Product Operator ◽  
Electron Paramagnetic

AbstractA theoretical description of pulsed reaction yield detected magnetic resonance (RYDMR) is proposed. In RYDMR, magnetic resonance spectra of radical pairs (RPs) are indirectly detected by monitoring their recombination yield. Such a detection method is significantly more sensitive than conventional electron paramagnetic resonance (EPR), but design of appropriate pulse sequences for RYDMR requires additional effort because of a different observable. In this work various schemes for generating spin-echo like signals and detecting them by RYDMR are treated. Specifically, we consider refocusing of zero-quantum coherences (ZQCs) and single-quantum coherences (SQCs) by selective as well as by non-selective pulses and formulate a general analytical approach to pulsed RYDMR, which makes an efficient use of the product operator formalism. We anticipate that these results are of importance for RYDMR studies of elusive paramagnetic particles, notably, in organic semiconductors.

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