Perfusion & Permeability

Thursday 15 May 2014    10:30 - 11:30

Space 1/Power Poster Theatre & Traditional Poster Hall
Moderators: Fernando Calamante, Ph.D. & Linda Knutsson, Ph.D.

Click on this video icon to view the introductory session.

Xingxing ZHANG¹, Eidrees Ghariq¹, Sophie Schmid¹, Wouter Teeuwisse¹, and Matthias J.P. van Osch^1
1C.J. Gorter Center for High Field MRI, Department of Radiology, Leiden University Medical Center, Leiden, Zuid-Holland, Netherlands

Vessel selective dynamic arterial spin labeling (VS-DASL) combined with 3D Turbo-Field Echo-Planar Imaging (TFEPI) was proposed to achieve fast whole brain flow territory mapping. The results showed good agreement with traditional vessel selective ASL (VS-ASL) as proven by the Dice similarity coefficient. These results imply that 3D VS-DASL has the potential to map whole brain flow territories within 30 seconds, enabling clinical use both in standard cerebrovascular imaging protocols as well as in the acute setting, i.e. patients with acute stroke.

David Feinberg^1,2, Liyong Chen^1,2, and Alexander Beckett^1,2
1Helen Wills Neuroscience Institute, University of California, Berkeley, California, United States, ²Advanced MRI Technologies, LLC, Sebastopol, California, United States

Simultaneous multi-slice EPI has been combined with pulsed ASL to record several times more images than conventional EPI. Comparison of quantitative CBF maps and perfusion weighted images show good agreement to EPI. Comparisons to segmented 3D GRASE ASL shows differences in scan times and susceptibility artifacts with advantages of background suppression and higher SNR in 3D GRASE, while both achieve whole brain slice coverage.

Ke Zhang¹, Seong Dae Yun¹, and N. Jon Shah^1,2
1Institute of Neuroscience and Medicine 4, Forschungszentrum Jülich GmbH, Jülich, Germany, ²Faculty of Medicine, Department of Neurology, JARA, RWTH Aachen University, Aachen, Germany

To quantitatively measure CBF with ASL, multiple readout with different post-labeling delay is preferred incase of various blood arrival time. One approach for sampling the tracer kinetics curve with increasing post-labeling delays is using Look-Locker imaging. Due to the signal recovery of the labeled blood, the slice number in the readout is limited. In this study, multiband excitation technique was applied in Look-locker readout to triple the readout slices for the dynamic pCASL. Preliminary results show that the quantitative CBF can be acquired with whole brain coverage using multiband technique in the same measurement time as using singleband excitation.

Tae Kim¹, Yoojin Lee¹, and Kyongtae Ty Bae^1
1Radiology, University of Pittsburgh, Pittsburgh, PA, United States

Multi-band (MB) excitation for data acquisition was successfully implemented into cerebral arterial blood volume (CBVa) and evaluated on healthy volunteers at 3T. CBVa quantification for MB excitation was highly comparable with that of a conventional single-band acquisition. Our study demonstrates that the MB technique facilitates an accelerated acquisition of high resolution, whole-brain CBVa quantification maps

Federico von Samson-Himmelstjerna¹, Jan Sobesky², and Matthias Günther^1
1Fraunhofer MEVIS, Bremen, Bremen, Germany, ²Center for Stroke Research (CSB), Charité University Medicine Berlin, Berlin, Germany

Time encoded (a.k.a Hadamard) pseudo continuous ASL decodes N-1 time steps from N image acquisitions. All N images are necessary for correct decoding. This means, that corrupted images, e.g. by motion, can lead to erroneous decoding and, thus, complete loss of data. To overcome this limitation a Walsh-ordered and extended Hadamard matrix is proposed for encoding. It allows the reconstruction of perfusion data from the second image acquisition on and a time resolution that increases with the number of acquisitions. This renders the technique robust against complete loss of data e.g. by motion of agitated patients in the clinical setup.

Yuriko Suzuki¹, Wouter M Teeuwisse², Sophie Schmid², Peter Koken³, Marc Van Cauteren⁴, Michael Helle³, and Matthias JP van Osch^2
1Philips Electronics Japan, Minato-ku, Tokyo, Japan, ²C.J.Gorter Center for High Field MRI, Departement of Radiology, Leiden University Medical Center, Leiden, Netherlands, ³Philips Research Laboratories, Hamburg, Germany, ⁴Philips Healthcare Asia Pasific, Tokyo, Japan

Both 4D magnetic resonance angiography (4D-MRA) and perfusion imaging have proved their value in the characterization of hemodynamic pathology in cerebrovascular disease, and their complementary information provides a complete picture of the hemodynamic status, which may prove especially important in conditions such as acute stroke. In this study, we propose the simultaneous acquisition of ASL-based perfusion image and MRA by combining a time-encoded ASL preparation with two sequential readout modules which have different spatial resolution: a high-resolved sequence for 4D MRA immediately followed by low resolution sequence for perfusion imaging.

Eleanor S K Berry¹, Peter Jezzard¹, and Thomas W Okell^1
1FMRIB Centre, University of Oxford, Oxford, Oxfordshire, United Kingdom

An automated method of calculating optimised encodings to label vessels using vessel-encoded pseudo-continuous arterial spin labelling is presented. The resulting encoding schemes have greater simulated SNR efficiency than those from other methods for a variety of vessel numbers and geometries. Preliminary healthy subject scans have resulted in images with higher SNR. The method requires further validation in subjects and more vessel scenarios.

Erin K Englund¹, Zachary B Rodgers², Michael C Langham³, Emile R Mohler III⁴, Thomas F Floyd⁵, and Felix W Wehrli^3
1University of Pennsylvania, Philadelphia, PA, United States, ²Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, United States,³Department of Radiology, University of Pennsylvania, Philadelphia, PA, United States, ⁴Department of Medicine, University of Pennsylvania, Philadelphia, PA, United States, ⁵Department of Anesthesiology, Stony Brook University, Stony Brook, NY, United States

A method to simultaneously measure perfusion, arterial velocity, venous oxygen saturation, and skeletal muscle T₂* using an interleaved pulsed arterial spin labeling and velocity-encoded multi-echo GRE sequence is presented. The method, termed velocity-encoded Perfusion, Intravascular Venous Oxygen saturation and T₂* (velocity-encoded PIVOT) was assessed in healthy subjects during a series of ischemia reperfusion paradigms. Results demonstrate that the method is capable of faithfully measuring all four parameters at 3-second temporal resolution. Dynamic measurement of these parameters was also completed during isometric plantar flexion contractions. Results suggest that this technique may be useful in developing biophysical models of muscle metabolism.

Benjamin Lemasson^1,2, Alexis Broisat^3,4, Pauline Busieau^1,2, Régine Farion^1,2, Mitra Ahmadi^3,4, Sandrine Bacot^3,4, Catherine Ghezzi^3,4, Chantal Rémy^1,2, and Emmanuel Barbier^1,2
1U836, Inserm, GRENOBLE, France, ²Grenoble Institut des Neurosciences, Université Joseph Fourier, GRENOBLE, France, ³U1039, Inserm, GRENOBLE, France, ⁴Radiopharmaceutiques Biocliniques, Université Joseph Fourier, GRENOBLE, France

We evaluated the impact of the local hematocrit (Hct) when mapping the brain tumor oxygen saturation (StO₂). A multimodal experiment (MRI and autoradiography of 2 different isotopes) was performed on 8 rats bearing a brain tumor. The tumor Hct level, assessed by autoradiography, was significantly reduced as compared to healthy striatum. Using, for each animal, the Hct to compute the StO₂ voxel-wise led to a significant reduction in tumor oxygenation in comparison to that of the healthy striatum. Our results indicate that change in Hct should not be overlooked when assessing oxygenation in brain tumors or in other brain diseases.

Xin Li¹, Csanad Varallyay², Seymur Gahramonov², William D Rooney¹, and Edward A Neuwelt^2
1Advanced Imaging Research Center, Oregon Health & Science University, Portland, Oregon, United States, ²Department of Neurology, Oregon Health & Science University, Portland, Oregon, United States

Though widely adopted for brain perfusion measurement, Dynamic Susceptibility Contrast (DSC) Magnetic Resonance Imaging (MRI) with low molecular weight Gadolinium (Gd) contrast reagent (CR) is often confounded by CR’s leakage into intersitium space. Based on pharmacokinetic first principles, we demonstrate a fast leakage correction method similar to that of the Patlak plot. This linearization approach uniquely identifies the leakage rate constant and significantly simplifies relative cerebral blood volume (rCBV) quantification.

Jin Zhang¹ and Sungheon Kim^1
1Radiology, New York University, New York, New York, United States

In DCE-MRI studies, accurate estimation of pharmacokinetic model parameters requires B₁-corrected T₁ values. However, it is not trivial to measure B₁and T₁ accurately in addition to the long scan time. In this study, we proposed a novel approach, namely active contrast encoding (ACE) MRI, to measure both B₁ and T₁ values along with kinetic parameters from a single DCE-MRI data. A proof-of-concept study was conducted to demonstrate the proposed method using numerical simulations and an in vivo mouse study, and to show that ACE-MRI can eliminate the need to have separate B₁ and T₁mapping procedures.

Atle Bjornerud^1,2, A. Gregory Sorensen^3,4, Patrick Y Wen⁵, Tracy T Batchelor^6,7, Rakesh K Jain⁶, and Kyrre E Emblem^1,3
1The Intervention Centre, Oslo University Hospital, Oslo, Norway, ²Dept of Physics, University of Oslo, Oslo, Norway, ³Department of Radiology and Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States, ⁴Siemens Healthcare Health Services, Pennsylvania, United States, ⁵Center for Neuro-Oncology, Dana-Farber/Brigham and Women’s Cancer Center and Harvard Medical School, Massachusetts, United States, ⁶Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Massachusetts, United States, ⁷Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Massachusetts, United States

Tumor perfusion (CBF) and capillary permeability transfer constant (Ktrans) have been proposed as sensitive biomarkers to monitor the effect of vascular-targeting and anti-angiogenic agents. Possible inter-dependence of these two metrics may, however complicate their interpretation in clinical data. We used dynamic susceptibility contrast (DSC) MRI to estimate both CBF, Ktrans and the initial contrast agent extraction fraction (E) in 30 patients with recurrent glioblastomas undergoing anti-angiogenic treatment. The results suggest that E is on average below 10% in this patient group and hence Ktrans and CBF can be considered independent parameters in glioblastomas.

Guy Nadav^1,2, Gilad Liberman^2,3, Moran Artzi^2,4, Nahum Kiryati¹, and Dafna Ben Bashat^2,4
1School of Electrical Engineering, Tel Aviv University, Tel Aviv, Israel, ²Functional Brain Center, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel,³3Gonda Multidisciplinary Brain Research Center, Bar Ilan University, Israel, ⁴Sackler Faculty of Medicine and Sagol School of Neuroscience, Tel Aviv University, Tel Aviv, Israel

In order to extract flow from DCE data, a 2-compartment exchange model (2CXM) is needed. In this study we show that flow is misinterpreted as permeability using the standard 1-compartment model (ETM) on simulated data that is based on 2CXM parameters. In real data, obtained from a patient with brain tumor, highly vascularized brain areas (veins and tumor) showed high flow and no permeability using 2CXM, but high permeability using ETM. This study shows that when utilizing ETM, care should be taken when interpreting permeability maps and when temporal resolution allows, the 2CXM should be used.

Dennis Lai-Hong Cheong¹, Bo Zhang¹, Limiao Jiang^1,2, and Thian C Ng^1,2
1Clinical Imaging Research Center, A*STAR & National University of Singapore, 117456, Singapore, ²Department of Diagnostic Radiology, National University of Singapore, 119074, Singapore

It is challenging to find an appropriate AIF in DCE MRI studies. Ideally, AIF is the contrast concentration time curve in incoming blood at the tissue of interest, but this is not measurable directly with current technologies. We estimated the true AIF using a physiological model for AIF that we have developed recently. The model gave good fittings to all concentration time curves measured at vessels. The estimated true AIF was used in tracer kinetic analysis using both a distributed parameter model and the modified Tofts model. This method offers a way to estimate the true AIF at the tissue of interest.

Michael Ingrisch¹, Steven Sourbron², Felix Schwab¹, Mike Notohamiprodjo³, Maximilian F Reiser³, Michael Peller¹, and Olaf Dietrich^1
1Josef Lissner Laboratory for Biomedical Imaging, Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany,²Division of Medical Physics, University of Leeds, Leeds, United Kingdom, ³Institute for Clinical Radiology, Ludwig-Maximilians-University Hospital Munich, München, Germany

The arterial input function (AIF) can be interpreted as the response of the arterial system to the injection of contrast agent, characterized by an unknown ‘arterial response function’ (ARF). This function can be determined from a measured AIF by numerical deconvolution and can be utilized for the generation of synthetic AIFs for arbitrary injection schemes. In this work, we use this approach for a simulation study, investigating the hypothesis that fast injections are required for the determination of plasma flow in tissues with short plasma transit times, whereas in tissues with long transit times slower injections suffice.