scholarly journals Anatomy-guided Inverse-phase-encoding Registration Method for Correcting Susceptibility Artifacts in Sub-millimeter fMRI

2019 ◽  
Author(s):  
Soan T. M. Duong ◽  
Son L. Phung ◽  
Abdesselam Bouzerdoum ◽  
Harriet G. Boyd Taylor ◽  
Alexander M. Puckett ◽  
...  
Keyword(s):  
Brain Function ◽  
Ground Truth ◽  
Planar Imaging ◽  
Phase Encoding ◽  
Susceptibility Artifacts ◽  
Registration Method ◽  
Structural Image ◽  
Magnetic Resonance Imaging Mri ◽  
Registration Scheme ◽  
Echo Planar

AbstractEcho planar imaging (EPI) is a fast and non-invasive magnetic resonance imaging (MRI) technique that supports data acquisition at spatial and temporal resolutions suitable for brain function studies. However, susceptibility artifacts are unavoidable distortions in EPI. These distortions are especially strong in high spatial resolution images and can lead to misrepresentation of brain function in fMRI experiments. A common method for correcting susceptibility artifacts is based on a registration scheme which uses two EPI images acquired using identical sequences but with inverse phase-encoding (PE) directions. In this paper, we present a new method for correcting susceptibility artifacts by integrating a T1-weighted (T1w) image into the inverse-PE based registration, since the T1w structural image is considered as a ground-truth measurement of the brain. Furthermore, the T1w image is used as a criterion to select automatically the regularization parameters of the proposed image registration. Evaluations on two high-resolution EPI-fMRI datasets, acquired at 3T and 7T scanners, confirm that the proposed method provides more robust and sharper corrections and runs faster compared with two other state-of-the-art inverse-PE based susceptibility artifact correction methods, i.e. HySCO and TOPUP.

scholarly journals MRI Powered and Triggered Current Stimulator for Concurrent Stimulation and MRI

2019 ◽  
Author(s):  
Ranajay Mandal ◽  
Nishant Babaria ◽  
Jiayue Cao ◽  
Kun-Han Lu ◽  
Zhongming Liu
Keyword(s):  
Scale Up ◽  
Small Animal ◽  
7 Tesla ◽  
Planar Imaging ◽  
Novel Device ◽  
Peripheral Muscle ◽  
Gradient Fields ◽  
Magnetic Resonance Imaging Mri ◽  
Small Animal Mri ◽  
Echo Planar

AbstractBioelectric stimulation during concurrent magnetic resonance imaging (MRI) is of interest to basic and translational studies. However, existing stimulation systems often interfere with MRI, are difficult to use or scale up, have limited efficacy, or cause safety concerns. To address these issues, we present a novel device capable of supplying current stimulation synchronized with MRI while being wirelessly powered by the MRI gradient fields. Results from testing it with phantoms and live animals in a 7 Tesla small-animal MRI system suggest that the device is able to harvest up to 72 (or 18) mW power during typical echo-planar imaging (or fast low angle shot imaging) and usable for stimulating peripheral muscle or nerve to modulate the brain or the gut, with minimal effects on MRI image quality. As a compact and standalone system, the plug-and-play device is suitable for animal research and merits further development for human applications.

A thermometry software tool for monitoring laser-induced interstitial thermotherapy

2019 ◽  
Vol 64 (4) ◽  
pp. 449-457 ◽  
Author(s):  
Babak Bazrafshan ◽  
Ahmad Koujan ◽  
Frank Hübner ◽  
Christian Leithäuser ◽  
Norbert Siedow ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Software Tool ◽  
Biological Tissues ◽  
Planar Imaging ◽  
Imaging Sequence ◽  
Mri Thermometry ◽  
Visualization Toolkit ◽  
Magnetic Resonance Imaging Mri ◽  
Echo Planar ◽  
Interstitial Thermotherapy

Abstract The purpose of this study was to develop a thermometry software tool for temperature monitoring during laser-induced interstitial thermotherapy (LITT). C++ programming language and several libraries including DICOM Toolkit, Grassroots DICOM library, Insight Segmentation and Registration Toolkit, Visualization Toolkit and Quasar Toolkit were used. The software’s graphical user interface creates windows displaying the temperature map and the coagulation extent in the tissue, determined by the magnetic resonance imaging (MRI) thermometry with the echo planar imaging sequence and a numerical simulation based on the radiation and heat transfer in biological tissues, respectively. The software was evaluated applying the MRI-guided LITT to ex vivo pig liver and simultaneously measuring the temperature through a fiber-optic thermometer as reference. Using the software, the temperature distribution determined by the MRI method was compared with the coagulation extent simulation. An agreement was shown between the MRI temperature map and the simulated coagulation extent. Furthermore, the MRI-based and simulated temperatures agreed with the measured one – a correlation coefficient of 0.9993 and 0.9996 was obtained, respectively. The precision of the MRI temperature amounted to 2.4°C. In conclusion, the software tool developed in the present study can be applied for monitoring and controlling the LITT procedure in ex vivo tissues.

scholarly journals Slice-direction geometric distortion evaluation and correction with reversed slice-select gradient acquisitions

2021 ◽  
Author(s):  
Anna I Blazejewska ◽  
Thomas Witzel ◽  
Jesper LR Andersson ◽  
Lawrence L Wlad ◽  
Jonathan R Polimeni
Keyword(s):  
High Resolution ◽  
Strong Field ◽  
Pulse Sequence ◽  
Geometric Distortion ◽  
Single Shot ◽  
Planar Imaging ◽  
Phase Encoding ◽  
Spatial Alignment ◽  
Ultrahigh Field Mri ◽  
Echo Planar

Accurate spatial alignment of MRI data acquired across multiple contrasts in the same subject is often crucial for data analysis and interpretation, but can be challenging in the presence of geometric distortions that differ between acquisitions. It is well known that single-shot echo-planar imaging (EPI) acquisitions suffer from distortion in the phase-encoding direction due to B0 field inhomogeneities arising from tissue magnetic susceptibility differences and other sources, however there can be distortion in other encoding directions as well in the presence of strong field homogeneities. High-resolution ultrahigh-field MRI typically uses low bandwidth in the slice-encoding direction to acquire thin slices and, when combined with the pronounced B0 inhomogeneities, is prone to an additional geometric distortion in the slice direction as well. Here we demonstrate a presence of this slice distortion in high-resolution 7T EPI acquired with a novel pulse sequence allowing for the reversal of the slice-encoding gradient polarity that enables the acquisition of pairs of images with equal magnitudes of distortion in the slice direction but with opposing polarities. We also show that the slice-direction distortion can be corrected using gradient reversal-based method applying the same software used for conventional corrections of phase-encoding direction distortion.

scholarly journals Mapping of Absolute Host Concentration and Exchange Kinetics of Xenon Hyper-CEST MRI Agents

2021 ◽  
Vol 14 (2) ◽  
pp. 79 ◽  
Author(s):  
Martin Kunth ◽  
Christopher Witte ◽  
Leif Schröder
Keyword(s):  
Spin Exchange ◽  
Chemical Exchange ◽  
Chemical Exchange Saturation Transfer ◽  
Planar Imaging ◽  
Internal Reference ◽  
Cest Mri ◽  
Exchange Kinetics ◽  
Magnetic Resonance Imaging Mri ◽  
Echo Planar

Xenon magnetic resonance imaging (MRI) provides excellent sensitivity through the combination of spin hyperpolarization and chemical exchange saturation transfer (CEST). To this end, molecular hosts such as cryptophane-A or cucurbit[n]urils provide unique opportunities to design switchable MRI reporters. The concentration determination of such xenon binding sites in samples of unknown dilution remains, however, challenging. Contrary to 1H CEST agents, an internal reference of a certain host (in this case, cryptophane-A) at micromolar concentration is already sufficient to resolve the entire exchange kinetics information, including an unknown host concentration and the xenon spin exchange rate. Fast echo planar imaging (EPI)-based Hyper-CEST MRI in combination with Bloch–McConnell analysis thus allows quantitative insights to compare the performance of different emerging ultra-sensitive MRI reporters.

scholarly journals Sir Peter Mansfield. 9 October 1933—8 February 2017

2021 ◽  
Vol 70 ◽  
pp. 313-334
Author(s):  
P. G. Morris
Keyword(s):  
Magnetic Resonance ◽  
High Speed ◽  
Imaging Technique ◽  
Functional Brain Imaging ◽  
Planar Imaging ◽  
X Ray ◽  
X Ray Crystallography ◽  
Mri Scans ◽  
Magnetic Resonance Imaging Mri ◽  
Echo Planar

Peter Mansfield's rise from humble origins to founding father of magnetic resonance imaging (MRI) is an inspirational and remarkable story. His first scientific contributions were in the field of solid state nuclear magnetic resonance (NMR), and it was whilst trying to develop an NMR version of X-ray crystallography that he developed the underpinning methodology for MRI. At that time (the early 1970s) NMR was an analytical tool, ubiquitous in chemistry departments. For most of those working in the field, there was no hint that it could be developed into a diagnostic imaging technique that would reveal internal anatomy in unprecedented detail. Yet that was what happened in the space of just a few years. The first MRI scans were slow, and Peter was driven to speed them up, making physiological and later functional brain imaging studies possible. The technical challenges were many, and eschewed by healthcare equipment providers, but Peter persisted and his brainchild, echo-planar imaging, came to dominate the high speed MRI field. Peter was a gifted physicist and archetypal inventor who devoted his life to the development of a technique that has saved millions of lives. In 2003, he shared the Nobel Prize for Physiology or Medicine, in recognition of his achievement.

scholarly journals The Bermuda Triangle of d- and f-MRI sailors - software for susceptibility distortions (SDCFlows)

2021 ◽  
Author(s):  
Oscar Esteban ◽  
Azeez Adebimpe ◽  
Christopher Johnson Markiewicz ◽  
Mathias Goncalves ◽  
Ross W. Blair ◽  
...  
Keyword(s):  
Diffusion Mri ◽  
Petrous Bone ◽  
Planar Imaging ◽  
Phase Encoding ◽  
Small Deviations ◽  
Imaging Parameters ◽  
Fast Acquisition ◽  
Ear Canals ◽  
Brain Data ◽  
Echo Planar

Echo-Planar Imaging (EPI) allows very fast acquisition of whole-brain data, which enables standard functional & diffusion MRI (f/dMRI). However, EPI is notably sensitive to variations in the base B0 field. Small deviations in parts-per-million from the nominal B0 caused by steps in magnetic susceptibility (tissue interfaces) introduce misplacements in the registered location of voxels of up to some cm in standard settings along the phase-encoding direction (PE), apparent as local geometrical distortions of the imaged specimen. In humans, the susceptibility distortion (SD) is prominent starting at the petrous bone and extending towards the ear canals, defining a sort of triangle where signal vanishes (Fig. 1). SD is well-known, but existing solutions require mapping B0 deviations and are sensitive to several imaging parameters. In practice, addressing SDs is error-prone and often overlooked. Here, we introduce SDCFlows (SD Correction Flows), an open-source utility that leverages BIDS1 and several existing software tools to provide standardized, best-effort SD correction.

INTEGRATING MRI AND MRSI INFORMATION INTO TRUS-GUIDED ROBOTIC PROSTATE BIOPSY

2006 ◽  
Vol 03 (04) ◽  
pp. 499-522 ◽  
Author(s):  
WEI SHAO ◽  
RUOYUN WU ◽  
CHOON HUA THNG ◽  
KECK VOON LING ◽  
WAN SING NG
Keyword(s):  
Magnetic Resonance ◽  
Prostate Biopsy ◽  
Transrectal Ultrasound ◽  
Ground Truth ◽  
Poor Quality ◽  
Resonance Spectroscopy ◽  
Detection Rates ◽  
Registration Method ◽  
Magnetic Resonance Imaging Mri ◽  
Set Up

The development of prostate biopsy robotics can make biopsies both automatic and accurate. However, intervention from urologists is still needed to define the location of biopsy cores. With the aid of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy imaging (MRSI) diagnosis information obtained pre-operationally, it is possible to guide the biopsy needle towards those sites where cancer is suspected, thereby achieving higher detection rates. In this paper, a deformable image registration method is presented for the purpose of merging MRI/MRSI and transrectal ultrasound (TRUS) images. Given the poor quality of ultrasound (US) images and the deformation occurring across modalites, a thin-plate spline transformation is used to match the prostate surfaces and thereafter their volumes. A deformable prostate phantom that simulates the condition in humans was also set up for validation purposes. Fifteen fiducial markers were implanted inside the phantom prostate to act as the reference of "ground truth." The phantom study shows that our method can achieve an accuracy around 1.28 ± 0.50 mm, with voxel dimensions of 0.5 × 0.5 × 0.5 mm3. This result is promising since none of the knowledge about the interior prostate is utilized in the algorithm. Experimental results on patient data are also presented.

scholarly journals Turbo Gradient and Spin Echo PROPELLER-Diffusion Weighted Imaging for Orbital Tumors: A Comparative Study With Readout-Segmented Echo-Planar Imaging

2021 ◽  
Vol 15 ◽  
Author(s):  
Qing Fu ◽  
Xiang-chuang Kong ◽  
Ding-Xi Liu ◽  
Kun Zhou ◽  
Yi-hao Guo ◽  
...  
Keyword(s):  
Diffusion Weighted Imaging ◽  
Diagnostic Performance ◽  
Spin Echo ◽  
Geometric Distortion ◽  
Benign Tumors ◽  
Orbital Tumors ◽  
Planar Imaging ◽  
Susceptibility Artifacts ◽  
Cutoff Value ◽  
Echo Planar

Purpose: To qualitatively and quantitatively compare the image quality and diagnostic performance of turbo gradient and spin echo PROPELLER diffusion-weighted imaging (TGSE-PROPELLER-DWI) vs. readout-segmented echo-planar imaging (rs-EPI) in the evaluation of orbital tumors.Materials and Methods: A total of 43 patients with suspected orbital tumors were enrolled to perform the two DWIs with comparable spatial resolution on 3T. The overall image qualities, geometric distortions, susceptibility artifacts, and lesion conspicuities were scored by using a four-point scale (1, poor; 4, excellent). Quantitative measurements, including contrast-to-noise ratios (CNRs), apparent diffusion coefficients (ADCs), geometric distortion rates (GDRs), and lesion sizes, were calculated and compared. The two ADCs for differentiating malignant from benign orbital tumors were evaluated. Wilcoxon signed-rank test, Kappa statistic, and receiver operating characteristics (ROC) curves were used.Results: TGSE-PROPELLER-DWI performed superior in all subjective scores and quantitative GDR evaluation than rs-EPI (p < 0.001), and excellent interobserver agreement was obtained for Kappa value ranging from 0.876 to 1.000. ADClesion of TGSE-PROPELLER-DWI was significantly higher than those of rs-EPI (p < 0.001). Mean ADC of malignant tumors was significantly lower than that of benign tumors both in two DWIs. However, the AUC for differentiating malignant and benign tumors showed no significant difference in the two DWIs (0.860 vs. 0.854, p = 0.7448). Sensitivity and specificity could achieve 92.86% and 72.73% for TGSE-PROPELLER-DWI with a cutoff value of 1.23 × 10–3 mm2/s, and 85.71% and 81.82% for rs-EPI with a cutoff value of 0.99 × 10–3 mm2/s.Conclusion: Compared with rs-EPI, TGSE-PROPELLER-DWI showed minimized geometric distortion and susceptibility artifacts significantly improved the image quality for orbital tumors and achieved comparable diagnostic performance in differentiating malignant and benign orbital tumors.

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