scholarly journals Variable Refocusing Flip Angle Single-Shot Imaging for Sedation-Free Fast Brain MRI

2020 ◽  
Vol 41 (7) ◽  
pp. 1256-1262
Author(s):  
R. Jabarkheel ◽  
E. Tong ◽  
E.H. Lee ◽  
T.M. Cullen ◽  
U. Yousaf ◽  
...  
Keyword(s):  
Brain Mri ◽  
Flip Angle ◽  
Single Shot ◽  
Variable Refocusing Flip Angle

Variable refocusing flip angle single-shot fast spin echo imaging of liver lesions: increased speed and lesion contrast

2017 ◽  
Vol 43 (3) ◽  
pp. 593-599
Author(s):  
Robert M. Hicks ◽  
Andreas M. Loening ◽  
Michael A. Ohliger ◽  
Shreyas S. Vasanawala ◽  
Thomas A. Hope
Keyword(s):  
Spin Echo ◽  
Flip Angle ◽  
Fast Spin Echo ◽  
Single Shot ◽  
Liver Lesions ◽  
Variable Refocusing Flip Angle ◽  
Fast Spin

scholarly journals Multiparametric mapping in post-mortem perinatal MRI: a feasibility study

2020 ◽  
Vol 93 (1111) ◽  
pp. 20190952
Author(s):  
Amy R McDowell ◽  
Susan C Shelmerdine ◽  
Sara Lorio ◽  
Wendy Norman ◽  
Rod Jones ◽  
...  
Keyword(s):  
Flip Angle ◽  
Whole Body ◽  
Proton Density ◽  
Single Shot ◽  
Post Mortem ◽  
Variable Flip Angle ◽  
High Quality ◽  
Isotropic Resolution ◽  
Tissue Contrast ◽  
Magnetic Transfer

Objectives: To demonstrate feasibility of a 3 T multiparametric mapping (MPM) quantitative pipeline for perinatal post-mortem MR (PMMR) imaging. Methods: Whole body quantitative PMMR imaging was acquired in four cases, mean gestational age 34 weeks, range (29–38 weeks) on a 3 T Siemens Prisma scanner. A multicontrast protocol yielded proton density, T1 and magnetic transfer (MT) weighted multi-echo images obtained from variable flip angle (FA) 3D fast low angle single-shot (FLASH) acquisitions, radiofrequency transmit field map and one B0 field map alongside four MT weighted acquisitions with saturation pulses of 180, 220, 260 and 300 degrees were acquired, all at 1 mm isotropic resolution. Results: Whole body MPM was achievable in all four foetuses, with R1, R2*, PD and MT maps reconstructed from a single protocol. Multiparametric maps were of high quality and show good tissue contrast, especially the MT maps. Conclusion: MPM is a feasible technique in a perinatal post-mortem setting, which may allow quantification of post-mortem change, prior to being evaluated in a clinical setting. Advances in knowledge: We have shown that the MPM sequence is feasible in PMMR imaging and shown the potential of MT imaging in this setting.

Three-dimensional T2-weighted imaging for liver MRI: Clinical values of tissue-specific variable refocusing flip-angle turbo spin echo imaging

2014 ◽  
Vol 41 (2) ◽  
pp. 339-346 ◽  
Author(s):  
Yukihisa Takayama ◽  
Akihiro Nishie ◽  
Yoshiki Asayama ◽  
Yasuhiro Ushijima ◽  
Nobuhiro Fujita ◽  
...  
Keyword(s):  
Spin Echo ◽  
Three Dimensional ◽  
Flip Angle ◽  
Turbo Spin Echo ◽  
Liver Mri ◽  
Tissue Specific ◽  
Specific Variable ◽  
Turbo Spin ◽  
Variable Refocusing Flip Angle

scholarly journals Applications of Continuous Wave Free Precession Sequences in Low-Field, Time-Domain NMR

2019 ◽  
Vol 9 (7) ◽  
pp. 1312 ◽  
Author(s):  
Tiago Bueno Moraes ◽  
Tatiana Monaretto ◽  
Luiz Colnago
Keyword(s):  
Time Domain ◽  
Continuous Wave ◽  
Signal To Noise Ratio ◽  
Flip Angle ◽  
Time Interval ◽  
Single Shot ◽  
Free Precession ◽  
Signal To Noise ◽  
Low Field ◽  
Noise Ratio

This review discusses the theory and applications of the Continuous Wave Free Precession (CWFP) sequence in low-field, time-domain nuclear magnetic resonance (TD-NMR). CWFP is a special case of the Steady State Free Precession (SSFP) regime that is obtained when a train of radiofrequency pulses, separated by a time interval Tp shorter than the effective transverse relaxation time (T2*), is applied to a sample. Unlike regular pulsed experiments, in the CWFP regime, the amplitude is not dependent on T1. Therefore, Tp should be as short as possible (limited by hardware). For Tp < 0.5 ms, thousands of scans can be performed per second, and the signal to noise ratio can be enhanced by more than one order of magnitude. The amplitude of the CWFP signal is dependent on T1/T2; therefore, it can be used in quantitative analyses for samples with a similar relaxation ratio. The time constant to reach the CWFP regime (T*) is also dependent on relaxation times and flip angle (θ). Therefore, T* has been used as a single shot experiment to measure T1 using a low flip angle (5°) or T2, using θ = 180°. For measuring T1 and T2 simultaneously in a single experiment, it is necessary to use θ = 90°, the values of T* and M0, and the magnitude of CWFP signal |Mss|. Therefore, CWFP is an important sequence for TD-NMR, being an alternative to the Carr-Purcell-Meiboom-Gill sequence, which depends only on T2. The use of CWFP for the improvement of the signal to noise ratio in quantitative and qualitative analyses and in relaxation measurements are presented and discussed.

scholarly journals Assessment of third ventriculostomy patency with the 3D-SPACE technique: a preliminary multicenter research study

2015 ◽  
Vol 122 (6) ◽  
pp. 1347-1355 ◽  
Author(s):  
Oktay Algin ◽  
Murat Ucar ◽  
Evrim Ozmen ◽  
Alp Ozgun Borcek ◽  
Pinar Ozisik ◽  
...  
Keyword(s):  
Sagittal Plane ◽  
Third Ventricle ◽  
Brain Mri ◽  
Flip Angle ◽  
Third Ventriculostomy ◽  
Mr Images ◽  
3D Space ◽  
Scan Time ◽  
Space Technique ◽  
Flow Void

OBJECT The goal of this study was to determine the value of the 3D sampling perfection with application-optimized contrasts using different flip-angle evolutions (3D-SPACE) technique in the evaluation of endoscopic third ventriculostomy (ETV) patency. METHODS Twenty-six patients with ETV were examined using 3-T MRI units. Sagittal-plane 3D-SPACE with variant flip-angle mode, 3D T1-weighted (T1W), and 3D heavily T2-weighted (T2W) images were obtained with isotropic voxel sizes. Also, sagittal-axial plane phase-contrast cine (PC)-MR images were obtained. The following findings were evaluated: diameters of stoma and third ventricle, flow-void sign on 3D-SPACE and PC-MR images, integrity of the third ventricle on heavily T2W images, and quantitative PC-MRI parameters of the stoma. Obtained sequences were evaluated singly, in combination with one another, and all together. RESULTS The mean area, flow, and velocity values measured at the level of stoma in patients with patent stoma were significantly higher than those measured in patients with closed stoma (p < 0.05). There was significant correlation among PC-MRI, 3D-SPACE, and 3D heavily T2W techniques regarding assessment of ETV patency (p < 0.001). The 3D-SPACE technique provided the lowest rate of ambiguous results. CONCLUSIONS The 3D-SPACE technique seems to be the most efficient one for determination of ETV patency. The authors suggest the use of 3D-SPACE as a stand-alone first-line sequence in addition to routine brain MRI protocols in assessing patients with ETV, thereby decreasing scan time and reserving the use of a combination of additional sequences such as PC-MRI and 3D heavily T2W images in suspicious or complex cases.

scholarly journals Correction of respiratory artifacts in MRI head motion estimates

2018 ◽  
Author(s):  
Damien A. Fair ◽  
Oscar Miranda-Dominguez ◽  
Abraham Z. Snyder ◽  
Anders Perrone ◽  
Eric A. Earl ◽  
...  
Keyword(s):  
Real Time ◽  
Functional Mri ◽  
Brain Mri ◽  
Body Motion ◽  
Head Motion ◽  
Single Shot ◽  
Resting State Functional Connectivity ◽  
Novel Approach ◽  
Field Fluctuations ◽  
Functional Connectivity Mri

AbstractHead motion represents one of the greatest technical obstacles for brain MRI. Accurate detection of artifacts induced by head motion requires precise estimation of movement. However, this estimation may be corrupted by factitious effects owing to main field fluctuations generated by body motion. In the current report, we examine head motion estimation in multiband resting state functional connectivity MRI (rs-fcMRI) data from the Adolescent Brain and Cognitive Development (ABCD) Study and a comparison ‘single-shot’ dataset from Oregon Health & Science University. We show unequivocally that respirations contaminate movement estimates in functional MRI and that respiration generates apparent head motion not associated with degraded quality of functional MRI. We have developed a novel approach using a band-stop filter that accurately removes these respiratory effects. Subsequently, we demonstrate that utilizing this filter improves post-processing data quality. Lastly, we demonstrate the real-time implementation of motion estimate filtering in our FIRMM (Framewise Integrated Real-Time MRI Monitoring) software package.

Abstract 18972: Iron Quantification in Carotid Artery Atherosclerosis Predicts Downstream Injury by Magnetic Resonance Imaging

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Travis P Sharkey-Toppen ◽  
Tam Tran ◽  
Suzanne Smart ◽  
Beth McCarthy ◽  
Xuan Nguyen ◽  
...  
Keyword(s):  
Brain Injury ◽  
Carotid Artery ◽  
Carotid Plaque ◽  
Carotid Artery Disease ◽  
Brain Mri ◽  
Flip Angle ◽  
Ischemic Brain Injury ◽  
Ischemic Brain ◽  
Carotid Artery Atherosclerosis ◽  
Artery Disease

Introduction: Luminal stenosis is the primary imaging parameter used to guide management of patients with carotid artery atherosclerosis (CAA). However, neuroimaging identifies subclinical events in patients with CAA not meeting anatomic guidelines for intervention. Strategies to characterize atherosclerotic plaque beyond %stenosis may help reduce the downstream ischemic burden of atherosclerotic disease. Hypothesis: Using noncontrast MRI T2* tissue mapping that we have previously validated for plaque iron characterization, we tested the hypothesis that carotid plaque T2* better predicts ischemic injury by brain MRI than symptom history. Methods: We enrolled 26 individuals with carotid artery stenosis ≥50%. Each subject underwent MRI that included carotid plaque T2* mapping (TR=75ms, 5 TEs, 20° flip angle, 0.44x0.44x2mm resolution), brain diffusion weighted imaging (TR=4436ms, TE=93ms, 0.9x0.9x3mm resolution) and brain fluid attenuated inverse recovery imaging (TR=13970ms, TE=2500ms, 150° flip angle, and 0.9x0.9x3mm resolution). Plaque T2* quantification and brain MRI were independently assessed by experienced observers blinded to patient history and other results. Brain MRIs with Wahlund score ≥2 were classified as positive for ischemic damage. Results: Patients with brain imaging positive for ischemic damage had shorter intraplaque T2* compared to patients with negative brain MRI (17.2±2.9 vs. 20.3±3.2ms, p=.012, Figure). Conversely, presence/absence of brain injury did not correlate with symptoms (p=.352). Conclusions: Noncontrast atherosclerosis imaging using an MRI biomarker of intraplaque iron in patients with carotid artery disease can discriminate between patients with vs. those without ischemic brain injury. Prospective studies that couple plaque characterization with anatomic and clinical factors may better identify at-risk patients with carotid artery disease before significant ischemic brain injury has accrued.

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