Perfusion MRI: DSC & DCE MRI
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Friday May 13th
Room 710B  10:30 - 12:30 Moderators: Geoffrey J.M. Parker and Matúš Straka

10:30 784.   Separation of Intra- and Extra-Vascular Spaces in Human Brain with DCE-MRI and 11C- verapamil PET 
Xiaoping Zhu1, John R Cain1, Shaonan Wang1, Maria Feldmann1,2, Gerry Thompson1, Ka-Loh Li1, Marie Claude Asselin1, and Alan Jackson1
1Wolfson Molecular Imaging Centre, University of Manchester, Manchester, United Kingdom, 2Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom

Conventional multi-compartment kinetic models designed to identify the intra- and extravascular spaces in human brain failed in separating Ktrans from Vp due to the well-known covariance errors in the fitting procedure. An extended first pass model (EFPM) was implemented to reduce these errors. The new DCE-MRI method using EFPM significantly improved differentiation. Excellent accordance was found between the 3D EFPM permeability maps from DCE-MRI and 3D VPM-PET images. Strong separation between CP and surrounding veins has practical significance for partial volume correction of PET images. Good separation of Ktrans and Vp will help understanding roles of CP in drug delivery

10:42 785.   Whole-brain CBF measurements using DCE-MRI and 3D k-t PCA 
Henrik Pedersen1, Adam E. Hansen1, and Henrik B.W. Larsson1
1Functional Imaging Unit (KFNA), Glostrup Hospital, Glostrup, Denmark

T1-weighted dynamic contrast enhanced (DCE) MRI has emerged as a promising technique for quantifying cerebral blood flow (CBF) and other vascular properties. However, the clinical feasibility of DCE-MRI perfusion imaging is currently limited by low SNR and poor spatial coverage. The recently proposed k-t PCA technique allows a considerable data reduction in dynamic MRI by jointly exploiting the separation of the aliased signals in x-f space and the sparsity of dynamic data when subjected to principal component analysis (PCA).This paper investigates the quality of whole-brain CBF measurements using DCE-MRI and 3D k-t PCA with 20 slices.

10:54 786.   Accurate brain tumor blood volume estimation using DCE-MRI with Bookend T1 measurements and phase-derived AIFs 
Greg O. Cron1, Claire Foottit1, Jean Francois Mercier1, Rebecca Thornhill1, Viviane Thanh-Van Nguyen2, Ian Cameron1, Mark E Schweitzer1, J J Shankar1, John Sinclair1, John Woulfe1, Matthew J Hogan3, and Thanh B Nguyen1
1The Ottawa Hospital, Ottawa, Ontario, Canada, 2University of Montreal, 3Neuroradiology, University of Ottawa, Ottawa, Ontario, Canada

For quantitative DCE-MRI of human brain tumors, there is no single, widely implemented data acquisition protocol. This lack of standardization makes it difficult to compare different studies, especially between institutions. We propose standardizing the data acquired with any DCE pulse sequence by saving phase data during DCE and by performing Bookend T1 measurements before and after DCE. The phase and bookends enable reliable estimation of the AIF and tissue function, both in terms of absolute concentrations. Initial evaluation has shown that DCE-MRI tumor blood volume values are consistent with equivalent CT perfusion estimates, thus supporting the strategy.

11:06 787.   Discriminant Analysis to Classify the glioma grading using DCE MRI and immunohistochemical markers 
Rishi Awasthi1, Prativa Sahoo2, Nuzhat Husain3, Priyanka Soni3, Ashish Awasthi4, Rohit Kumar Singh5, Sanjay Behari5, Chandra M Pandey4, Ram Kishan Singh Rathore6, and Rakesh Kumar Gupta1
1Radiodiagnosis, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, 2Indian Institute of Technology, Kanpur, Kanpur, Uttar Pradesh, India, 3Pathology, Chatrapati Sahu ji Maharaj Medical University, Lucknow, Uttar Pradesh, India, 4Biostatistics, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, 5Neurosurgery, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, 6Mathematics & Statistics, Indian Institute of Technology, Kanpur, Kanpur, Uttar Pradesh, India

Seventy six patients of brain tumor (55 high grades and 21 low grades) with a postoperative diagnosis of either high or low grade glioma were imaged using conventional, and DCE MRI. On discriminant analysis, rCBV, Kep, Ve and HIF-1α were proved to be significant discriminators of tumor grade and these parameters were able to classify high and low grade tumors with 92.1% accuracy at a significance level of p<0.001.

11:18 788.   Spin- and Gradient-Echo EPI for Imaging of Brain Perfusion with MRI 
Heiko Schmiedeskamp1, Matus Straka1, Greg Zaharchuk1, Nancy J Fischbein1, Marteen G Lansberg2, Jean-Marc Olivot2, Greg W Albers2, Michael E Moseley1, and Roland Bammer1
1Department of Radiology, Stanford University, Stanford, CA, United States, 2Department of Neurology, Stanford University, Stanford, CA, United States

A spin- and gradient-echo (SAGE) EPI sequence was used for simultaneous acquisition of spin- and gradient-echo weighted perfusion maps through the acquisition of 5 echo trains per readout. Hereby, perfusion parameters were calculated from estimates of R2 and R2*, rather than relative changes in signal intensity, with the goal to produce T1-independent, more quantitative PWI maps and to facilitate vessel size imaging.

11:30 789.   Independent Component Analysis of Dynamic Susceptibility Contrast MRI in Brain Tumor: a New Biomarker for Measuring Tumor Perfusion Patterns 
Peter Sherman LaViolette1, Alex D Cohen1, Scott D Rand2, Wade Mueller3, and Kathleen M Schmainda1,2
1Biophysics, Medical College of Wisconsin, Milwaukee, WI, United States, 2Radiology, Medical College of Wisconsin, Milwaukee, WI, United States, 3Neurosurgery, Medical College of Wisconsin, Milwaukee, WI, United States

It is well known that tumor growth beyond a size of about 2 mm requires the development of its own blood vessels, a process termed angiogenesis. While physiologic angiogenesis, such as that occurs with wound healing, results in the formation of well-ordered mature vessels, pathologic angiogenesis such as that observed with tumors, results in the formation of chaotic and immature vessels. It is therefore not surprising that the resulting tumor perfusion patterns are likewise altered. We hypothesized that application of ICA (independent component analysis) to DSC-MRI signals would provide a new approach for distinguishing tumor from normal tissue, thus demonstrating the potential to serve as a novel biomarker to predict response to anti-angiogenic drugs thought to normalize tumor vasculature.

11:42 790.   Improved Differentiation of Brain Tumors by Phase Contrast Calibration of Dynamic Susceptibility Contrast MRI: Combined Use with Extravasation Correction  -permission withheld
David Bonekamp1, and Peter B Barker1
1Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States

The purpose of this study is to implement a PC-MRA calibration for absolute quantification of CBF with DCE-MRI that is clinically feasible in routine examinations and to test the method and compare it with quantitative DCE-MRI CBF measurements with and without enhancement correction in patients with brain tumors. Twenty-six consecutive patients with gliomas (n=15), meningiomas (n=7, 6 WHO I, 1 WHO III), non-neoplastic lesions (n=2; hemorrhage and gliosis) or metastases (n=2) were included. Calibration of quantitative DSC-MRI CBF measurements significantly improves the differentiation between brain tumors compared to quantitative DSC-MRI with or without the use of extravasation correction alone.

11:54 791.   Does DSC-derived CA extravasation correlate with DCE Ktrans? 
Kyrre E Emblem1,2, Kim Mouridsen1, Ronald JH. Borra1, Gregory Sorensen1, Tracy T Batchelor3, Rakesh K Jain4, and Atle Bjornerud2,5
1A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, Massachusetts, United States, 2The Interventional Center, Oslo University Hospital - Rikshospitalet, Oslo, Norway, 3Pappas Center for Neuro-Oncology, Massachusetts General Hospital, Boston, Massachusetts, United States, 4Department of Radiation Oncology, Massachusetts General Hospital, Boston, Massachusetts, United States, 5Department of Physics, University of Oslo, Oslo, Norway

A ‘byproduct’ of DSC-based leakage correction methods is the leakage term reflecting estimated contrast agent extravasation into the interstitial space. Potentially, if properly understood and corrected for, this parameter could provide estimates similar to that of DCE Ktrans. In this study, we have compared contrast agent extravasation from DSC and DCE using simulations and patient data.

12:06 792.   Can we separate the contributions of permeability and diffusion of contrast agent? A simulation study. 
Clément Stephan Debacker1,2, Nicolas Pannetier1,2, Franck Mauconduit1,2, Thomas Christen1,3, and Emmanuel Luc Barbier1,2
1INSERM - U836, Grenoble, France, 2Grenoble Institut des Neurosciences, Université Joseph Fourier, Grenoble, France, 3Department of Radiology, Stanford University, Stanford, California, United States

There is a growing interest in Dynamic Contrast Enhanced (DCE) MRI to characterize tumor perfusion and microvasculature. Current DCE approaches generally use a global parameter which concatenates two phenomena: permeability and diffusion of the CA in the interstitium. In this study, we evaluate, using numerical simulations, an MR experiment designed to estimate separately these two contributions. Accounting for relaxivity and susceptibility effects, results indicate that permeability measured at short echo times are not sensitive to the diffusion of CA. Moreover, at long echo times, it seems that the diffusion of CA in interstitium could be characterized.

12:18 793.   Dynamic ratio Capital Greek DeltaR2GE/Capital Greek DeltaR2SE3/2 in DSC perfusion imaging reveals the relative arterial and venous blood volume fraction 
Chao Xu1, Valerij Kiselev2, Peter Brunecker1, and Jochen Fiebach1
1Center for Stroke Research Berlin (CSB), Berlin, Berlin, Germany, 2Department of Diagnostic Radiology, University Hospital Freiburg, Freiburg, Germany

The characterization of the cerebral microvascular morphology can be achieved by assessing the ratio Capital Greek DeltaR2GE/Capital Greek DeltaR2SE3/2 during DSC perfusion imaging. Rather than following a reversible line, the dynamic ratio forms a counter-clockwise loop in normal brain tissue. We simulated the dynamic involvement of microvasculature during the bolus passage and found out that the counter-clockwise loop results from the higher blood volume of venous blood than that of arterial blood. We suggest that the direction of the loop may indicate the local arterial and venous volume contribution.