Stefan M Spann¹, Doris Grössinger², Christoph Stefan Aigner^1,3, Josef Pfeuffer⁴, Guilherme Wood^2,5, and Rudolf Stollberger^1,5
1Institute of Medical Engineering, Graz University of Technology, Graz, Austria, ²Institute of Psychology, University of Graz, Graz, Austria, ³Physikalisch-Technische Bundesanstalt (PTB), Braunschweig and Berlin, Germany, ⁴Application Development, Siemens Healthcare, Erlangen, Germany, ⁵BioTechMed-Graz, Graz, Austria

Real-time neurofeedback (RT-NF) fMRI allows the subjects to regulate their own brain activity by providing them a neurofeedback. Functional ASL is perfectly suited for RT-NF studies due to the absolute quantification of activation related changes in the cerebral blood flow (CBF). In this study we implemented a real-time solution for ASL data processing and feedback generation which includes the following steps: data acquisition, image reconstruction, post-processing and neurofeedback presentation. The results of this RT-NF fASL study show that subjects were able to learn to regulate their own brain activation during a finger tapping experiment.

Yang Li¹, Michael Schär¹, Dengrong Jiang¹, and Hanzhang Lu^1
1Johns Hopkins University Department of Radiology, Baltimore, MD, United States

Vascular compliance is an important predictor of cardiovascular disease and stroke. Here we proposed a technique to map vascular compliance along the entire intracranial arterial tree. We applied the ASL MRA to acquire k-space data in radial fashion. Then the k-space data was retrospectively grouped by cardiac phases and reconstructed by the GRASP algorithm. A series of cardiac-phase-resolved angiography images were obtained, allowing quantification of vascular compliance.

Ekin Karasan¹, Michael Lustig¹, and Zhiyong Zhang^1,2
1Department of Electrical Engineering, University of California, Berkeley, CA, United States, ²Institute for Medical Imaging Technology, School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China

Displacement spectrum imaging (DiSpect) performs multiple scans with increasing displacement (DENSE) encodings. It can resolve the multi-dimensional spectrum of displacements that spins exhibit over the mixing time between tagging and imaging. This work presents two innovations: 1) Imaging dynamic displacement spectra by repeatedly imaging after tagging, each image  corresponding to an increased mixing time. 2) Post acquisition, it is possible to retrospectively select source vessels from the displacement maps and display only their contribution to perfusion in the imaging slice. We demonstrate feasibility in flow phantom and in-vivo brain at 3T.

Jonas Schollenberger¹, Luis Hernandez-Garcia^1,2, and C. Alberto Figueroa^1,3
1Biomedical Engineering, University of Michigan, Ann Arbor, MI, United States, ²fMRI Laboratory, University of Michigan, Ann Arbor, MI, United States, ³Surgery, University of Michigan, Ann Arbor, MI, United States

Collateral flow patterns in the circle of Willis play a major role in maintaining adequate blood supply to the brain in the presence of cerebrovascular occlusive disease. In this work, we present a strategy to quantify collateral flow by calibrating patient-specific computational fluid dynamic models of cerebral blood flow with perfusion data from arterial spin labeling. For a patient with right carotid stenosis, the collateral flow patterns in the circle of Willis obtained with the calibrated computational model show good agreement with territorial perfusion maps acquired with vessel-selective arterial spin labeling.

Zixuan Lin¹, Dengrong Jiang¹, Yang Li¹, Pan Su¹, Jay J. Pillai¹, and Hanzhang Lu^1
1Department of Radiology, Johns Hopkins University, Baltimore, MD, United States

A new scheme of water-extraction-with-phase-contrast-arterial-spin-tagging (WEPCAST) MRI was proposed for non-invasive assessment of blood-brain-barrier (BBB) permeability to water. In this scheme, venous bolus-arrival-time was measured first by Look-Locker WEPCAST and then applied to single-delay long-labeling-duration WEPCAST scan to estimate water extraction fraction. The results showed an improved accuracy for estimation of BBB permeability.

Amnah Mahroo¹, Nora-Josefin Breutigam¹, and Matthias Günther^1,2
1MR Physics, Fraunhofer Institute for Digital Medicine MEVIS, Bremen, Germany, ²MR-Imaging and Spectroscopy, University of Bremen, Bremen, Germany

Disrupted blood brain barrier (BBB) is reported to be one of the causes in various neuropathological diseases¹. We assessed the quantified permeability of BBB using blood to tissue water exchange dynamics by employing multi-echo ASL sequence in five healthy individuals. A repeated measurement was conducted to assess the robustness and precision of the method. The average gray matter values were 357 ± 62 ms which are in-accordance with the literature reported values.

Xingfeng Shao¹, Brian T Gold², and Danny JJ Wang^1,3
1Mark & Mary Stevens Neuroimaging and Informatics Institute, Keck School of Medicine, University of Southern California, Los Angeles, CA, United States, ²Department of Neuroscience, College of Medicine, University of Kentucky, Lexington, KY, United States, ³Department of Neurology, University of Southern California, Los Angeles, CA, United States

Abnormally low CSF amyloid-β (Aβ)-42 level is an early biomarker of the Alzheimer’s Disease (AD), however lumbar puncture is required to collect CSF samples. A diffusion prepared arterial spin labeling technique was proposed to measure blood-brain barrier (BBB) water permeability (kw) non-invasively. Associations between water permeability and CSF Aβ42 levels in the “healthy” aging brains were studied. Significant positive correlations were found between kw and CSF Aβ42 and digit symbol scores, which suggests kw may serve as an early imaging marker of AD.

Qihao Zhang¹, Thanh D Nguyen², Jana Ivanidze³, and Yi Wang^3
1Cornell University, Ithaca, NY, NY, United States, ²Weill Cornell Medicine College, New York, NY, United States, ³Weill Cornell Medicine, New York, NY, United States

In this work, we propose an optimized acquisition for high resolution water exchange rate (k_w) mapping, that uses adiabatic RF pulses, 3D fast spin echo readout, regularized inversion to a direct model of the water exchange rate, and fast T1 mapping. Feasibility and superior performance is shown in a regional based analysis in 6 healthy subjects.

Caitlin O'Brien¹, Thomas Okell¹, Mark Chiew¹, and Peter Jezzard^1
1Wellcome Centre for Integrative Neuroimaging (FMRIB), University of Oxford, Oxford, United Kingdom

This work uses remote sensing methods to encode spatial information of venous blood spins in the brain into the longitudinal magnetisation. This information was then decoded remotely from the blood signal in the superior sagittal sinus. A T2-preparation module allowed venous blood T2 and therefore oxygen extraction fraction, to be mapped. An optimum inversion delay (TI) of 2s was found, and the sensitivity of the method to the spatial origins of the blood spins was verified. Low resolution venous T2 maps were obtained in two healthy volunteers. Average values were comparable to global T2 using conventional TRUST. 

Koen P.A. Baas¹, Bram F. Coolen², Gustav J. Strijkers², and Aart J. Nederveen^1
1Radiology and Nuclear Medicine, Amsterdam UMC, Amsterdam, Netherlands, ²Biomedical Engineering & Physics, Amsterdam UMC, Amsterdam, Netherlands

We investigated the reliability of different T₁ and T₂ relaxometry methods for arterial and venous blood. While TRIR enables measurements of both venous blood T₁ and T₂, T₂ estimates from TRIR showed poorer repeatability compared to TRUST. Moreover, significantly higher venous blood T₂ values were observed using TRIR. Lastly, arterial blood T₁ measurements showed a better repeatability compared to venous T₁ measurements using TRIR. These findings advocate for the use of the arterial T₁ measurements instead of venous T₁ and the use of TRUST to measure venous blood T₂.