Jan Petr¹, Niels Verburg², Joost P.A. Kuijer³, Thomas Koopman³, Vera C. Keil⁴, Esther A.H. Warnert⁵, Frederik Barkhof^3,6, Jörg van den Hoff¹, Ronald Boellaard³, Philip C. de Witt Hamer², and Henri J.M.M. Mutsaerts^3,7
1Institute of Radiopharmaceutical Cancer Research, Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany, ²Neurosurgical Center Amsterdam, Amsterdam University Medical Center, location VU, Amsterdam, Netherlands, ³Department of Radiology & Nuclear Medicine, Amsterdam University Medical Center, location VU, Amsterdam, Netherlands, ⁴Department of Neuroradiology, Bonn University Hospital, Bonn, Germany, ⁵Department of Radiology and Nuclear Medicine, Erasmus MC, Rotterdam, Netherlands, ⁶UCL Institutes of Neurology and Healthcare Engineering, London, United Kingdom, ⁷Ghent Institute for Functional and Metabolic Imaging (GIfMI), Ghent University, Ghent, Belgium

While agreement between ASL, DSC, and PET perfusion is well established in healthy volunteers, an analogous comparison in gliomas is still missing and more challenging. We compared ASL and DSC perfusion measurements with the gold-standard of ¹⁵O-H₂O-PET perfusion measurements in eight patients diagnosed with gliomas. We showed the importance of normalization to the contralateral hemisphere, and identified several examples of different regional perfusion as assessed with ASL and DSC and interpreted them using the PET reference.

Isabell K. Bones¹, Suzanne L. Franklin^1,2, Anita A. Harteveld¹, Matthias J.P. van Osch², Sophie Schmid², Jeroen Hendrikse³, Chrit Moonen¹, Marijn van Stralen¹, and Clemens Bos^1
1Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, ²C.J.Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, ³Department of Radiology, University Medical Center Utrecht, Utrecht, Netherlands

VSASL for renal application has constraints on the cut-off velocity, as low V_c in the presence of respiratory motion causes spurious labeling of moving tissue. With higher V_c, label could be generated more upstream in the vascular tree, potentially introducing ATT sensitivity. To study label dynamics of renal VSASL using a V_c compatible with free-breathing (V_c of 10cm/s), data at multiple time points were acquired. High ASL signal was already observed at early time points, thus supporting that spatially non-selective VSASL in the kidney generates label close to, or even inside the target tissue, also using a free-breathing compatible V_c.

Suzanne L. Franklin^1,2,3, Isabell K. Bones², Anita A. Harteveld², Lydiane Hirschler¹, Marijn van Stralen², Anneloes de Boer², Hans Hoogduin², Matthias J.P. van Osch^1,3, Sophie Schmid^1,3, and Clemens Bos^2
1C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Netherlands, ²Center for Image Sciences, University Medical Center Utrecht, Utrecht, Netherlands, ³Leiden Institute for Brain and Cognition, Leiden University, Leiden, Netherlands

Different flow-based arterial spin labeling (ASL)-techniques were proposed in recent years. In this multi-organ study four flow-based ASL-techniques were compared, with pCASL in brain, and with both pCASL and FAIR in kidney. ASL-techniques were compared based on temporal-SNR, sensitivity to perfusion changes (in brain) and robustness to respiratory motion (in kidney). In brain, Velocity-Selective Inversion showed superior temporal-SNR and sensitivity to perfusion changes. In kidney, flow-based ASL-techniques showed decreased temporal-SNR compared to FAIR, although their settings can be improved to increase robustness to B₁-inhomogeneity. All ASL-techniques were relatively robust to respiratory motion, showing potential for free-breathing kidney-ASL at 3T.

Briana Meyer¹, Lydiane Hirschler^2,3, Jan Warnking², Emmanuel Barbier², and Matthew Budde^4
1Biophysics, Medical College of Wisconsin, Wauwatosa, WI, United States, ²Univ. Grenoble Alpes, Inserm, U1216, Grenoble Institut des Neurosciences, Grenoble, France, ³C.J. Gorter Center for High Field MRI, Radiology, Leiden University Medical Center, Leiden, Netherlands, ⁴Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States

Pseudo-continuous arterial spin labeling (pCASL) to monitor spinal cord perfusion and hemodynamics has the potential to inform the clinical care of spinal cord injury and other disorders. This work demonstrates successful implementation and application of pCASL of the rodent cervical spinal cord at high field.

Qinyang Shou¹, Xingfeng Shao¹, and Danny Wang^1
1University of Southern California, Los Angeles, CA, United States

Arterial Spin Labelling (ASL) is a noninvasive imaging technique that can quantitatively measure Cerebral Blood Flow (CBF). However, existing ASL techniques generally have a low spatial resolution due to a relative low Signal-to-noise ratio (SNR). In this study, we develop a super-resolution ASL method by combining the Slice Dithered Enhanced Resolution (SLIDER) with multi-band ASL with optimized slice-dependent background suppression to enhance both the resolution and SNR. The reconstructed images achieve a resolution of isotropic 2x2x2 mm³, and show increased spatial and temporal SNR compared to standard high-resolution ASL images.

Manuel Taso¹, Fanny Munsch¹, Li Zhao², and David C. Alsop^1
1Division of MRI research, Department of Radiology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, United States, ²Diagnostic Imaging and Radiology, Children's National Medical Center, Washington, DC, United States

Imaging cortical blood-flow using ASL is relevant to unravel the basis of brain functional autoregulation or response to stimuli, but challenging because of the usual compromise between brain coverage, SNR and spatial resolution in ASL. We here propose to push the limits of volumetric ASL resolution using sparse variable-density FSE and Compressed-Sensing to study the distribution of cortical flow in healthy volunteers. We show through a group surface-based analysis some regional variations in cortical flow, but also depth-dependence of cortical flow. We also propose a high-resolution average ASL perfusion-weighted template that could have benefits for large-scale group studies.

Xingfeng Shao¹, Stefan M Spann², Kai Wang¹, Lirong Yan^1,3, Stollberger Rudolf², 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, ²Institute of Medical Engineering, Graz University of Technology, Graz, Austria, ³Department of Neurology, University of Southern California, Los Angeles, CA, United States

Ultra-high field allows ASL to achieve higher spatial resolution due to increased SNR and prolonged T1 relaxation. We present a single-shot 3D GRASE pCASL technique with 12-fold acceleration using time-dependent 2D CAIPI sampling strategy, and reconstruction of the label/control time series with joint spatial and temporal total-generalized-variation (TGV) regularization. 2D CAIPI under-sampling pattern increases temporal incoherence between measurements which allows joint reconstruction of the highly accelerated ASL time series. Combining the advantages of ultra-high field strength, pTx coils, accelerated acquisition and advanced reconstruction, whole-brain CBF map with 2 mm isotropic resolution was obtained within 5 mins.

Gael Saib¹, Alan Koretsky¹, and S Lalith Talagala^2
1NINDS/LFMI, National Institutes of Health, Bethesda, MD, United States, ²NINDS/NMRF, National Institutes of Health, Bethesda, MD, United States

Pseudo-continuous arterial spin labeling (PCASL) is very sensitive to off-resonance effects. This is especially a problem at higher fields (>3T). Off-resonance effects can be compensated by using an average or a vessel-specific correction integrated into the PCASL tagging/control pulse. Vessel-specific corrections can be performed using a prescan or a field map. In this study, we compared three off-resonance compensation strategies at 7T. Data showed that a large improvement (> 2 times) of the PCASL signal can be obtained with subject specific off-resonance correction with all 3 methods. The field map based method showed slightly better performance over the others.

Merlijn van der Plas¹, Sophie Schmid¹, Martin Craig², Michael Chappell^2,3, and Matthias van Osch^1
1Radiology, C.J. Gorter Center for High Field MRI, Leiden, Netherlands, ²Wellcome Centre for Integrative Neuroimaging, FMRIB, Nuffield Department of Clinical Neurosciences, University of Oxford, Oxford, United Kingdom, ³Institute of Biomedical Engineering, Research Council UK (EP/P012361/1), University of Oxford, Oxford, United Kingdom

A two-component kinetic model allows for the separation of the macrovascular and tissue signal. This model relies on the availability of multi-timepoint data and generates cerebral blood flow, arterial blood volume and arterial transit time maps. The goal of this study was to validate this separation of the macrovascular and tissue signal. A 4D-ASL angiography and densely sampled ASL data were acquired and fitted with different model settings. Fitting the 4D-ASL angiography with a macrovascular component showed the best fit for the model with gamma dispersion included but with limited freedom to change the dispersion parameters.

Mareike Alicja Buck¹ and Matthias Günther^1,2
1Fraunhofer MEVIS, Bremen, Germany, ²MR-Imaging and Spectroscopy, Faculty 01 (Physics, Electrical Engineering), University Bremen, Bremen, Germany

This abstract compares quantified perfusion values of the standard model and a new dispersion model based on an AIF using the ASLIF-sequence. For different ATTs, the voxel´s signal was simulated using the dispersion model. The simulations show that the standard model overestimates the signal. This may result from lack of dispersion effects especially in the inflow phase of the labeled bolus. Consequently, the determined perfusion values vary for different ATTS. Thus, using an AIF based on an acquired patient specific reference bolus instead could improve the stability and robustness of quantified perfusion values.