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https://www.readbyqxmd.com/read/28092785/integrated-ssfp-for-functional-brain-mapping-at-7t-with-reduced-susceptibility-artifact
#1
Kaibao Sun, Rong Xue, Peng Zhang, Zhentao Zuo, Zhongwei Chen, Bo Wang, Thomas Martin, Yi Wang, Lin Chen, Sheng He, Danny J J Wang
Balanced steady-state free precession (bSSFP) offers an alternative and potentially important tool to the standard gradient-echo echo-planar imaging (GE-EPI) for functional MRI (fMRI). Both passband and transition band based bSSFP have been proposed for fMRI. The applications of these methods, however, are limited by banding artifacts due to the sensitivity of bSSFP signal to off-resonance effects. In this article, a unique case of the SSFP-FID sequence, termed integrated-SSFP or iSSFP, was proposed to overcome the obstacle by compressing the SSFP profile into the width of a single voxel...
December 30, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28092527/block-matching-distortion-correction-of-echo-planar-images-with-opposite-phase-encoding-directions
#2
Renaud Hedouin, Olivier Commowick, Elise Bannier, Benoit Scherrer, Maxime Taquet, Simon Warfield, Christian Barillot
By shortening the acquisition time of MRI, Echo Planar Imaging (EPI) enables the acqui- sition of a large number of images in a short time, com- patible with clinical constraints as required for diffusion or functional MRI. However such images are subject to large, local distortions disrupting their correspondence with the underlying anatomy. The correction of those distortions is an open problem, especially in regions where large deformations occur. We propose a new block-matching registration method to perform EPI distortion correction based on the acquisition of two EPI with opposite phase encoding directions (PED)...
January 9, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28090656/real-time-monitoring-of-tissue-displacement-and-temperature-changes-during-mr-guided-high-intensity-focused-ultrasound
#3
Pierre Bour, Fabrice Marquet, Valéry Ozenne, Solenn Toupin, Erik Dumont, Jean-François Aubry, Matthieu Lepetit-Coiffe, Bruno Quesson
PURPOSE: The therapy endpoint most commonly used in MR-guided high intensity focused ultrasound is the thermal dose. Although namely correlated with nonviable tissue, it does not account for changes in mechanical properties of tissue during ablation. This study presents a new acquisition sequence for multislice, subsecond and simultaneous imaging of tissue temperature and displacement during ablation. METHODS: A single-shot echo planar imaging sequence was implemented using a pair of motion-encoding gradients, with alternated polarities...
January 16, 2017: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28079398/feasibility-evaluation-of-diffusion-weighted-imaging-using-an-integrated-mri-radiotherapy-system-for-response-assessment-to-neoadjuvant-therapy-in-rectal-cancer
#4
Narek Shaverdian, Yingli Yang, Peng Hu, Steven Hart, Ke Sheng, James Lamb, Minsong Cao, Nzhde Agazaryan, David Thomas, Michael Steinberg, Daniel A Low, Percy Lee
OBJECTIVES: To evaluate the feasibility of on-board DWI with an integrated low-field MRI-radiotherapy system to assess responses to neoadjuvant chemoradiation (NAC) in rectal cancer. METHODS: A spin echo-based planar imaging diffusion sequence on a 0.35 T MRI-radiotherapy system was acquired over the course of NAC. The apparent diffusion coefficients (ADC) from the tumor region of interest (ROIs) were calculated. A functional diffusion map (fDM) was created showing a pixel-wise ADC analysis of the ROI over the course of treatment...
January 12, 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/28067973/simultaneous-multislice-readout-segmented-echo-planar-imaging-for-accelerated-diffusion-tensor-imaging-of-the-mandibular-nerve-a-feasibility-study
#5
Andrei Manoliu, Michael Ho, Marco Piccirelli, Daniel Nanz, Lukas Filli, Evelyn Dappa, Wei Liu, Dominik A Ettlin, Andreas Boss, Gustav Andreisek, Felix P Kuhn
PURPOSE: To assess the feasibility of diffusion tensor imaging (DTI) using simultaneous multislice (SMS) acquisition with blipped controlled aliasing in parallel imaging (CAIPI) for accelerated readout-segmented echo planar imaging (rs-EPI) of the mandibular nerves. DTI of the mandibular nerves using EPI is challenging due to susceptibility artifacts. Rs-EPI is less prone to artifacts but associated with longer scan durations. MATERIALS AND METHODS: Eight asymptomatic volunteers were imaged at 3T using a 64-channel head/neck coil...
January 9, 2017: Journal of Magnetic Resonance Imaging: JMRI
https://www.readbyqxmd.com/read/28065851/high-resolution-distortion-free-diffusion-imaging-using-hybrid-spin-warp-and-echo-planar-psf-encoding-approach
#6
Myung-Ho In, Oleg Posnansky, Oliver Speck
High-resolution diffusion-weighted imaging (DWI) has great potential to provide unique information about tissue microstructure in-vivo. Although single-shot echo-planar imaging (EPI) is a most popular tool for DWI, its application for high-resolution DWI is limited due to T2⁎ blurring and susceptibility- and eddy-current-induced geometric distortions, especially at ultra-high field (UHF) such as 7T. In this study, we adapt a hybrid spin-warp and echo-planar encoding strategy inspired by point spread function (PSF) mapping and optimize it for high-resolution and distortion-free diffusion imaging applications...
January 5, 2017: NeuroImage
https://www.readbyqxmd.com/read/28063447/accelerating-two-dimensional-nuclear-magnetic-resonance-correlation-spectroscopy-via-selective-coherence-transfer
#7
Qimiao Ye, Lin Chen, Wenqi Qiu, Liangjie Lin, Huijun Sun, Shuhui Cai, Zhiliang Wei, Zhong Chen
Nuclear magnetic resonance (NMR) spectroscopy serves as an important tool for both qualitative and quantitative analyses of various systems in chemistry, biology, and medicine. However, applications of one-dimensional (1)H NMR are often restrained by the presence of severe overlap among different resonances. The advent of two-dimensional (2D) (1)H NMR constitutes a promising alternative by extending the crowded resonances into a plane and thereby alleviating the spectral congestions. However, the enhanced ability in discriminating resonances is achieved at the cost of extended experimental duration due to necessity of various scans with progressive delays to construct the indirect dimension...
January 7, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28061381/hyperpolarized-13-c-pyruvate-mouse-brain-metabolism-with-absorptive-mode-epsi-at-1t
#8
Vesselin Z Miloushev, Valentina Di Gialleonardo, Lucia Salamanca-Cardona, Fabian Correa, Kristin L Granlund, Kayvan R Keshari
The expected signal in echo-planar spectroscopic imaging experiments was explicitly modeled jointly in spatial and spectral dimensions. Using this as a basis, absorptive-mode type detection can be achieved by appropriate choice of spectral delays and post-processing techniques. We discuss the effects of gradient imperfections and demonstrate the implementation of this sequence at low field (1.05T), with application to hyperpolarized [1-(13)C] pyruvate imaging of the mouse brain. The sequence achieves sufficient signal-to-noise to monitor the conversion of hyperpolarized [1-(13)C] pyruvate to lactate in the mouse brain...
December 21, 2016: Journal of Magnetic Resonance
https://www.readbyqxmd.com/read/28048467/su-g-jep2-08-image-guided-radiation-therapy-using-synthetic-cts-in-brain-cancer
#9
R G Price, J Kim, W Zheng, I J Chetty, C Glide-Hurst
PURPOSE: Synthetic-CTs(synCTs) are essential for MR-only treatment planning. However, the performance of synCT for IGRT must be carefully assessed. This work evaluated the accuracy of synCT and synCT-generated DRRs and determined their performance for IGRT in brain cancer radiation therapy. METHODS: MR-SIM and CT-SIM images were acquired of a novel anthropomorphic phantom and a cohort of 12 patients. SynCTs were generated by combining an ultra-short echo time (UTE) sequence with other MRI datasets using voxel-based weighted summation...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28048042/tu-ab-bra-07-distortion-free-3d-diffusion-mri-on-an-mri-guided-radiotherapy-system-for-longitudinal-tumor-response-assessment
#10
Y Gao, Y Yang, N Rangwala, M Cao, D Low, P Hu
PURPOSE: To develop a reliable, 3D distortion-free diffusion MRI technique for longitudinal tumor response assessment and MRI-guided adaptive radiotherapy(RT). METHODS: A diffusion prepared 3D turbo spin echo readout (DP-TSE) sequence was developed and compared with the conventional diffusion-weighted single-shot echo-planar-imaging (DW-ssEPI) sequence in a commercially available diffusion phantom, and one head-and-neck and one brain cancer patient on an MRI-guided RT system (ViewRay)...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047531/su-g-iep1-15-towards-accurate-cerebral-blood-flow-quantification-with-distortion-corrected-pseudo-continuous-arterial-spin-labeling
#11
M Hoff, S Rane-Levandovsky, J Andre
PURPOSE: Traditional arterial spin labeling (ASL) acquisitions with echo planar imaging (EPI) readouts suffer from image distortion due to susceptibility effects, compromising ASL's ability to accurately quantify cerebral blood flow (CBF) and assess disease-specific patterns associated with CBF abnormalities. Phase labeling for additional coordinate encoding (PLACE) can remove image distortion; our goal is to apply PLACE to improve the quantitative accuracy of ASL CBF in humans. METHODS: Four subjects were imaged on a 3T Philips Ingenia scanner using a 16-channel receive coil with a 21/21/10cm (frequency/phase/slice direction) field-of-view...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28047200/tu-h-206-07-assessment-of-geometric-distortion-in-epi-with-a-spamm-tagged-acquisition
#12
K Hwang, J Meier, J Yung, R Stafford
PURPOSE: Echo planar imaging (EPI) is known to exhibit gross geometric distortion caused by multiple factors, including B0 inhomgeneity and transient eddy currents. However, diffusion weighted (DW) EPI has become indispensable for diagnosis and therapy assessment. We propose a methodology for quantifying distortion in EPI sequences that does not require the use of dedicated spatial accuracy phantoms, enabling flexibility in phantom design for QA of distortion effects in EPI protocols...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046771/su-f-j-93-automated-segmentation-of-high-resolution-3d-wholebrain-spectroscopic-mri-for-glioblastoma-treatment-planning
#13
E Schreibmann, J Cordova, S Gurbani, C Holder, L Cooper, H Shu, H Shim
PURPOSE: We report on an automated segmentation algorithm for defining radiation therapy target volumes using spectroscopic MR images (sMRI) acquired at nominal voxel resolution of 100 microliters. METHODS: Wholebrain sMRI combining 3D echo-planar spectroscopic imaging, generalized auto-calibrating partially-parallel acquisitions, and elliptical k-space encoding were conducted on 3T MRI scanner with 32-channel head coil array creating images. Metabolite maps generated include choline (Cho), creatine (Cr), and N-acetylaspartate (NAA), as well as Cho/NAA, Cho/Cr, and NAA/Cr ratio maps...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046614/tu-h-campus-iep2-01-quantitative-evaluation-of-propeller-dwi-using-qiba-diffusion-phantom
#14
J Yung, H Ai, H Liu, R Stafford
PURPOSE: The purpose of this study is to determine the quantitative variability of apparent diffusion coefficient (ADC) values when varying imaging parameters in a diffusion-weighted (DW) fast spin echo (FSE) sequence with Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) k-space trajectory. METHODS: Using a 3T MRI scanner, a NIST traceable, quantitative magnetic resonance imaging (MRI) diffusion phantom (High Precision Devices, Inc, Boulder, Colorado) consisting of 13 vials filled with various concentrations of polymer polyvinylpyrrolidone (PVP) in aqueous solution was imaged with a standard Quantitative Imaging Biomarkers Alliance (QIBA) DWI spin echo, echo planar imaging (SE EPI) acquisition...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28046496/tu-h-bra-09-relationship-between-b0-and-the-contrast-to-noise-ratio-cnr-of-tumour-to-background-for-mri-radiotherapy-hybrids
#15
K Wachowicz, N DeZanche, E Yip, V Volotovskyy, B Fallone
PURPOSE: To investigate the relationship in MRI between B0 and the contrast-to-noise ratio (CNR) of various tumour/normal tissue pairs. This study is motivated by the current interest in MRI/radiotherapy hybrids, for which multiple magnetic field strengths have been proposed. CNR is the single most important parameter governing the ability of a system to identify a tumour in real time for treatment guidance. The MRI community has long since recognized that the SNR of a well-designed MR system is roughly proportional to B0 , the polarizing magnetic field...
June 2016: Medical Physics
https://www.readbyqxmd.com/read/28027961/the-clinical-relevance-of-distortion-correction-in-presurgical-fmri-at-7t
#16
Pedro Lima Cardoso, Barbara Dymerska, Beáta Bachratá, Florian Ph S Fischmeister, Nina Mahr, Eva Matt, Siegfried Trattnig, Roland Beisteiner, Simon Daniel Robinson
Presurgical planning with fMRI benefits from increased reliability and the possibility to reduce measurement time introduced by using ultra-high field. Echo-planar imaging suffers, however, from geometric distortions which scale with field strength and potentially give rise to clinically significant displacement of functional activation. We evaluate the effectiveness of a dynamic distortion correction (DDC) method based on unmodified single-echo EPI in the context of simulated presurgical planning fMRI at 7T and compare it with static distortion correction (SDC)...
December 24, 2016: NeuroImage
https://www.readbyqxmd.com/read/28027765/selective-visualization-of-pelvic-splanchnic-nerve-and-pelvic-plexus-using-readout-segmented-echo-planar-diffusion-weighted-magnetic-resonance-neurography-a-preliminary-study-in-healthy-male-volunteers
#17
Rikiya Yamashita, Hiroyoshi Isoda, Shigeki Arizono, Akihiro Furuta, Tsuyoshi Ohno, Ayako Ono, Katsutoshi Murata, Kaori Togashi
PURPOSE: To evaluate the potential of readout-segmented echo-planar diffusion-weighted magnetic resonance neurography (RS-EPI DW-MRN) for the selective visualization of pelvic splanchnic nerve and pelvic plexus in healthy male volunteers. MATERIALS AND METHODS: Institutional review board approval and written informed consent were obtained. RS-EPI DW-MRN images were acquired from thirteen healthy male volunteers aged 25-48 years between September 2013 and December 2013...
January 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28027737/diffusion-mri-for-rectal-cancer-staging-adc-measurements-before-and-after-ultrasonographic-gel-lumen-distension
#18
S Palmucci, M Piccoli, S Piana, P V Foti, R O A Siverino, L A Mauro, P Milone, G C Ettorre
OBJECTIVES: To compare Apparent Diffusion Coefficient (ADC) measurements in rectal neoplastic lesions before and after lumen distension obtained with sonography transmission gel. METHODS: From January 2014 to July 2016, 25 patients (average age 63.7, range 41-85, 18 males) were studied for pre-treatment rectal cancer staging using a 1.5T MRI. Diffusion MRI was obtained using echo-planar imaging with b=800 value; all patients were studied acquiring diffusion sequences with and without rectal lumen distension obtained using sonography transmission gel...
January 2017: European Journal of Radiology
https://www.readbyqxmd.com/read/28019035/estimating-and-eliminating-the-excitation-errors-in-bipolar-gradient-composite-excitations-caused-by-radiofrequency-gradient-delay-example-of-bipolar-spokes-pulses-in-parallel-transmission
#19
Desmond H Y Tse, Christopher J Wiggins, Benedikt A Poser
PURPOSE: To eliminate a slice-position-dependent excitation error commonly observed in bipolar-gradient composite excitations such as spokes pulses in parallel transmission. THEORY AND METHODS: An undesired timing delay between subpulses in the composite pulse and their bipolar slice-selective gradient is hypothesized to cause the error. A mathematical model is presented here to relate this mismatch to an induced slice-position-dependent phase difference between the subpulses...
December 26, 2016: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
https://www.readbyqxmd.com/read/28018165/investigating-the-group-level-impact-of-advanced-dual-echo-fmri-combinations
#20
Ádám Kettinger, Christopher Hill, Zoltán Vidnyánszky, Christian Windischberger, Zoltán Nagy
Multi-echo fMRI data acquisition has been widely investigated and suggested to optimize sensitivity for detecting the BOLD signal. Several methods have also been proposed for the combination of data with different echo times. The aim of the present study was to investigate whether these advanced echo combination methods provide advantages over the simple averaging of echoes when state-of-the-art group-level random-effect analyses are performed. Both resting-state and task-based dual-echo fMRI data were collected from 27 healthy adult individuals (14 male, mean age = 25...
2016: Frontiers in Neuroscience
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