ISMRM 24th Annual Meeting & Exhibition • 07-13 May 2016 • Singapore

Scientific Session: New Techniques: It's Time to See How it Works!

Wednesday, May 11, 2016
Summit 1
13:30 - 15:30
Moderators: Hans Hoogduin, Stephen Riederer

Accurate T1 and T2 mapping by direct least-squares ellipse fitting to phase-cycled bSSFP data
Yulia Shcherbakova1, Cornelis A.T. van den Berg2, Jan J.W. Lagendijk3, Chrit T.W. Moonen4, and Lambertus W. Bartels5
1Center for Imaging Sciences/Imaging Division, UMC Utrecht, Utrecht, Netherlands, 2Dept. of Radiotherapy/Imaging Division, UMC Utrecht, Utrecht, Netherlands, 3Department of Radiotherapy/Centre for Image Sciences, UMC Utrecht, Utrecht, Netherlands, 4Center for Imaging Sciences/ Imaging Division, UMC Utrecht, Utrecht, Netherlands, 5Image Sciences Institute/Department of Radiology, UMC Utrecht, Utrecht, Netherlands
Björk et al. proposed to use the balanced steady-state free precession (bSSFP) pulse sequence with multiple phase-cycled acquisitions to estimate the values of  T1 and T2 using a non-linear fitting approach. Unfortunately, they found that this non-linear approach would face large uncertainties for realistic SNRs. The purpose of our work was to demonstrate that by reformulating the signal model in the complex plane, an elliptical model can be fitted to the data points using a linear least squares method , allowing for more robust, accurate and simultaneous estimation of  T1 and T2 values.

Influence of pulse length and shape on variable flip angle T1 mapping of the human brain
Yosef Al-Abasse1 and Gunther Helms1
1Medical Radiation Physics, Lund University, Lund, Sweden
Effects of the macromolecular pool are usually neglected in T1 mapping using the variable flip angle (VFA) method. To demonstrate the influence of magnetization transfer (MT) on the estimated T1, VFA experiments were performed using sinc and rect pulses of different pulse lengths (0.5 ms ≤ TRF ≤ 2.0 ms). Substantial variations in T1 (11-21 %) were observed. Longer rect pulses yielded lower T1 values than those obtained by inversion recovery. This can be explained by varying saturation of macromolecules and inherent MT. A simplified model for the influence of TRF on the T1 estimates is suggested for low-power rect pulses.

B0 and B1 Insensitive Robust Fat Suppression using Frequency Offset Corrected Inversion (FOCI)
Xinzeng Wang1, Joshua S. Greer1,2, Ivan E. Dimitrov3,4, and Ananth J. Madhuranthakam1,3
1Radiology, UT Southwestern Medical Center, Dallas, TX, United States, 2Bioengineering, University of Texas at Dallas, Richardson, TX, United States, 3Advanced Imaging Research Center, UT Southwestern Medical Center, Dallas, TX, United States, 4Philips Medical Systems, Cleveland, OH, United States
STIR uses adiabatic non-selective hyperbolic secant (HS) inversion pulse to achieve uniform fat suppression even in the presence of B1 inhomogeneities. However, in the regions of increased B0 and B1 inhomogeneities, particularly at 3T and higher field strengths, the increased bandwidth of the HS pulse comes at the expense of higher adiabatic threshold. In this work, we evaluated C-FOCI pulse to achieve robust fat suppression with broader bandwidth and increased robustness to B1 variations compared to HS pulse. We also derived an analytical expression for the adiabatic threshold of C-FOCI pulse and show robust performance against B0 and B1 inhomogeneities.

Real-time multi-slice MRI during CPAP reveals dynamic changes in upper airway in response to pressure change
Weiyi Chen1, Ziyue Wu2, Sally L. Davidson Ward3, Michael C.K. Khoo4, and Krishna S. Nayak1
1Electrical Engineering, University of Southern California, Los Angeles, CA, United States, 2Alltech Medical Systems USA, Solon, OH, United States, 3Children's Hospital Los Angeles, Los Angeles, CA, United States,4Biomedical Engineering, University of Southern California, Los Angeles, CA, United States
We demonstrate a novel experiment that captures the upper airway’s instantaneous response to changes in air pressure.  We apply rapid changes in continuous positive airway pressure (CPAP) during real-time simultaneous multi-slice MRI. This reveals the airway area does NOT only depend on pressure level but also different airway sections and previous muscle tone status. This technique also enables characterization of airway collapsibility, and is relevant to the assessment of obstructive sleep apnea (OSA) and treatment planning. 

Imaging myelin with ultrashort-echo time (UTE) in a Multiple Sclerosis model on a clinical 7T system
Caroline Guglielmetti1, Tanguy Boucneau2, Peng Cao2, Annemie Van der Linden3, Peder Larson2, and Myriam M Chaumeil1
1University of California San Francisco, San Francisco, CA, United States, 2Department of Radiology and Biomedical Imaging, University of California San Francisco, San Francisco, CA, United States, 3University of Antwerp, Antwerp, Belgium
Many advances in neuroimaging have improved diagnosis and care of Multiple Sclerosis (MS) patients. However, current clinical methods fail to detect the majority of cortical lesions. In this work, we used the well characterized cuprizone mouse model for brain demyelination to  evaluate the sensitivity of in vivo ultra-short echo time (UTE) measurements for the non-invasive detection of grey and white matter alterations. We showed that UTE enabled the detection of cortical lesions and the assessment of myelin integrity in the white matter following demyelination and spontaneous remyelination.

Simultaneous DESS imaging and T2 mapping, for knee osteoarthritis studies
Cheng-Chieh Cheng1, Lena Franziska Schaefer1, Jeffrey Duryea1, and Bruno Madore1
1Radiology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, United States
The ‘dual-echo in the steady state’ (DESS) sequence is often the method of choice for assessing cartilage damage. A modified DESS method was developed that provides images of similar quality to regular DESS while also providing T2 values, a proven biomarker for the early stages of osteoarthritis. The method exploits the fact that the two signal pathways sampled in a DESS sequence decay differently during the TR period, allowing T2 and T2* to be quantified. The resulting method can assess cartilage volume seemingly as well as regular DESS, while also providing relevant T2 information, without increasing scan time.

Quality evaluation scheme for no-reference MR images using pre-scanned MR big data
Jinseong Jang1, Taejoon Eo1, and Dosik Hwang1
1Electrical and Electronic Engineering, Yonsei University, Seoul, Korea, Republic of
This study demonstrated the feasibility of no reference (NR) image quality  assessment (IQA) for magnetic resonance imaging. Especially, this method used pre-scanned images from other subjects. So by using prior big data, MRI can be evaluated in no reference environments.

Multiresolution imaging using golden angle stack-of-stars and compressed sensing
Abhishek Pandey1,2, Umit Yoruk3, Puneet Sharma1, Diego R. Martin1, Maria Altbach1, Ali Bilgin1,2,4, and Manojkumar Saranathan1,4
1Department of Medical Imaging, University of Arizona, Tucson, AZ, United States, 2Electrical and Computer Engineering, University of Arizona, Tucson, AZ, United States, 3Electrical Engineering, Stanford University, Stanford, CA, United States, 4Biomedical Engineering, University of Arizona, Tucson, AZ, United States
Dynamic contrast enhanced MRI requires measurement of arterial input function with great accuracy while maintaining high spatial resolution. Golden angle stack-of-stars radial acquisition was used to get reconstructions at multiple temporal resolutions. A multiresolution reconstruction scheme is used to generate AIFs using a very small temporal window. The accuracy of the reconstruction method was checked on a realistic phantom and then applied to an in vivo data. Results show that compressed sensing reconstruction works best with high temporal resolution (HTR) AIF giving both diagnostic image quality and accurate GFR estimate.


Ultra-short echo time sequence for electrode locations in simultaneous EEG-FMRI
Russell Butler1, Guillaume Gilbert2, and Kevin Whittingstall3
1University of Sherbrooke, Sherbrooke, QC, Canada, 2MR Clinical Science - Philips Healthcare, Markham, ON, Canada, 3Diagnostic Radiology, University of Sherbrooke, Sherbrooke, QC, Canada
Precise and accurate knowledge of EEG sensors relative to underlying cortical tissue enhances simultaneous EEG-FMRI studies, but to date no specialized sequence for providing these locations exists. We propose an ultra-short echo time sequence (UTE) to highlight the plastic casing and wiring of a 64 channel MR compatible EEG cap. We show that the UTE resolves electrode components up to 6mm from the surface of the scalp, allowing to locate the precise contact point of electrode with skin and direction of wire leading away from the electrode in all subjects (n=8). 

Can Zero TE imaging be a viable alternative to micro CT in dentistry imaging : application in tooth implanting and extraction ?
Yu Kang1, Bing Wu2, Shikuo Fu2, and Nan Hong1
1Peking University people's hospital, Beijing, China, People's Republic of, 2GE healthcare MR Research China, Beijing, China, People's Republic of
Micro CT is currently used for dentistry imaging. Not only it is associated with radiation, it also offers poor contrast of the mandible canal, whose position needs to be precisely known during tooth implantation and extraction. Conventional MRI fails for this case due to the short T2 time of the teeth as well as the susceptibility in the oral cavity. Zero TE imaging, due to its technical uniqueness, seems to be a viable solution to this. In this work, imaging of the the jaw of a patient with both CT, conventional MR and zTE imaging was performed.

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