Yulia Shcherbakova¹, Cornelis A.T. van den Berg², Jan J.W. Lagendijk³, Chrit T.W. Moonen⁴, and Lambertus W. Bartels^5
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.

Yosef Al-Abasse¹ and Gunther Helms^1
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 T_RF on the T₁ estimates is suggested for low-power rect pulses.

Xinzeng Wang¹, Joshua S. Greer^1,2, Ivan E. Dimitrov^3,4, and Ananth J. Madhuranthakam^1,3
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.

Weiyi Chen¹, Ziyue Wu², Sally L. Davidson Ward³, Michael C.K. Khoo⁴, and Krishna S. Nayak^1
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. 

Caroline Guglielmetti¹, Tanguy Boucneau², Peng Cao², Annemie Van der Linden³, Peder Larson², and Myriam M Chaumeil^1
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.

Cheng-Chieh Cheng¹, Lena Franziska Schaefer¹, Jeffrey Duryea¹, and Bruno Madore^1
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.

Jinseong Jang¹, Taejoon Eo¹, and Dosik Hwang^1
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.

Abhishek Pandey^1,2, Umit Yoruk³, Puneet Sharma¹, Diego R. Martin¹, Maria Altbach¹, Ali Bilgin^1,2,4, and Manojkumar Saranathan^1,4
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.

 

Russell Butler¹, Guillaume Gilbert², and Kevin Whittingstall^3
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). 

Yu Kang¹, Bing Wu², Shikuo Fu², and Nan Hong^1
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.