Yen-Yu Ian Shih¹, Li Guang¹, Bryan H De La Garza¹, Eric R Muir¹, and Timothy Q Duong^1
1Research Imaging Institute, University of Texas Health Science Center at San Antonio, San Antonio, TX, United States

The retina is sandwiched by retinal and choroidal vasculature and has an avascular layer in between. This study employed high resolution spin-echo, gradient-echo MRI and MION to reveal ∆R2 and ∆R2* profiles across the retinal thickness at an 11.7T scanner using a retina linearization analysis. The MRI-based vessel density index was also tabulated. This technique has potential to serve as an alternative method of postmortem fluorescence microscopy-based vessel density measurement, which has been widely used to quantify retinal and choroidal vascular degeneration or neovascularization in retinal diseases.

Myriam Marianne Chaumeil¹, Samuel Rose², Subramanian Sukumar¹, Hagit Dafni¹, Manish Aghi², and Sabrina M Ronen^1
1Radiology, University of California San Francisco, San Francisco, CA, United States, ²Neurological Surgery, University of California San Francisco, San Francisco, CA, United States

Macromolecular dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) at 14.1Tesla was used to quantitatively measure the effect of antiangiogenic treatment with a Bevacizumab analogue in two glioblastoma (GBM) models: one responsive (U87) and one resistant (SF7796). Whereas no significant differences between GBMs were observed prior to treatment, antiangiogenic treatment induced a significant decrease in the mean values of permeability (PS, p=0.03) and blood volume fraction (fBV, p=0.001) in the responsive GBM model and no significant changes in the resistant one. Histogram analysis was also performed for both tumor types, allowing assessment of the heterogeneity of tumor response to treatment.

Fotios Vlachos¹, Yao-Sheng Tung¹, Jameel Feshitan², Mark Borden², and Elisa Konofagou^1,3
1Biomedical Engineering, Columbia University, New York, New York, United States, ²Chemical Engineering, Columbia University, New York, New York, United States,³Radiology, Columbia University, New York, New York, United States

This study investigates the permeability dependence of the focused ultrasound-induced blood-brain barrier opening on different acoustic pressures and microbubble diameters. Dynamic contrast-enhanced MR images of the sonicated murine hippocampus were acquired and fitted to the generalized Tofts-Kermode kinetic mode. The BBB-opened region volume and the K_trans values in the sonicated area were both found to depend on the acoustic pressure and the bubble size. Thus, the permeability maps may constitute a diagnostic tool for the assessment of the therapeutic agent uptake in the BBB-opened region.

Guillaume Duhamel¹, Mohamed Tachrount¹, Patrick J. Cozzone¹, David C. Alsop², and Virginie Callot^1
1CRMBM / CNRS 6612, Faculté de Médecine, Université de la Méditerranée, Marseille, France, ²Department of Radiology, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States

Despite the use of high field, improvements of MR sequences for small animal studies are still required to obtain high spatial resolution images. The recent pCASL technique might be the best candidate for mouse brain perfusion since it overcomes the main limitations of CASL while giving higher efficiency than PASL. However, at very high field, pCASL could be challenged by a loss of the inversion efficiency caused by increased B1 and B0 inhomogeneities. This work presents the development of pCASL techniques at very high field (11.75T) and their performances relatively to a PASL sequence fully optimized for mouse brain perfusion.

Yuguang Meng¹, Alberto Vazquez¹, and Seong-gi Kim^1
1Neuroimaging Center, Department of Radiology, University of Pittsburgh, Pittsburgh, PA, United States

Cortical arterial oxygen saturation level is lower than the systemic level and can increase during stimulation. In previous oxygen tension measurements of pial arterial vessels, an arterial oxygen saturation level of ~85% was observed, which is much less than systemic levels (near 100%). T₂ is sensitive to the blood oxygen saturation and can be used to determine the baseline arterial oxygen saturation level, which can be an important physiological parameter. In this work, continuous arterial spin labeling was used to isolate arterial blood signals and measure the arterial blood T₂ value of isoflurane-anesthetized rats at 9.4 T.

Sanna Gevers¹, Pim van Ooij¹, Matthias J.P. van Osch², Sandra van den Berg¹, Karin J. Fijnvandraat³, Charles B.L.M. Majoie¹, and Aart J. Nederveen^1
1Radiology, Academic Medical Center, Amsterdam, Netherlands, ²Radiology, Leiden University Medical Center, Leiden, Netherlands, ³Pediatrics, Academic Medical Center, Amsterdam, Netherlands

Sickle cell disease (SCD) is a hereditary anaemia characterized by chronic haemolytic anaemia and vascular occlusion. One of the complications of SCD is cerebral infarction. Infarction diagnosed on MRI is not always accompanied by neurological deficit but may be associated with decreased neurocognitive functioning and increased risk of new infarcts. Previous ASL studies in SCD have shown perfusion asymmetries. It remains to be investigated whether these asymmetries are reflecting perfusion differences or if they result from technical difficulties like insufficient delay time. Here, we used pseudo-continuous ASL and phase-contrast MRI for flow measurement, to evaluate perfusion asymmetries in SCD patients.

Bhaswati Roy¹, Vimal Paliwal², Puneet Goel³, Siddhant Kumar¹, Ram Kishan Singh Rathore⁴, Sanjay Verma⁴, and Rakesh Kumar Gupta^1
1Department of Radiodiagnosis, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, ²Department of Neurology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, ³Department of Anaesthesiology, Sanjay Gandhi Post Graduate Institute of Medical Sciences, Lucknow, India, Lucknow, Uttar Pradesh, India, ⁴Department of Mathematics & Statistics, Indian Institute of Technology, Kanpur, Kanpur, Uttar Pradesh, India

We report significantly increased CBF in 12 children with cerebral palsy in certain white matter regions which was associated with decrease in FA. Significant inverse correlation observed between FA and CBF values suggests that CBF increase in these abnormal FA regions is an attempt by the body to improve neuronal plasticity. We conclude that ASL based CBF may be used as non invasive marker of brain plasticity in future.

Jingyi Xie¹, Andy Segerdahl^1,2, Irene Tracey^1,2, and Peter Jezzard^1
1Nuffield Dept of Clinical Neurosciences (FMRIB Centre), University of Oxford, Oxford, United Kingdom, ²Nuffield Dept of Clinical Neurosciences (Anaesthetics), University of Oxford, Oxford, United Kingdom

In this study we implemented a novel whole brain ASL method that is capable of detecting functional neuronal activity whilst simultaneously obtaining absolute quantification of key physiological parameters such as cerebral blood flow (CBF) and arterial arrival time (Δt). This is the first demonstration of such an ASL approach within a pain imaging context.

Kim Mouridsen¹, Kyrre Eeg Emblem², Atle Bjørnerud³, Dominique Jennings², and Gregory Sorensen^2
1Center for Functionally Integrative Neuroscience, Aarhus University | Aarhus University Hospital, Aarhus, Denmark, ²Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital, Charlestown, MA, United States, ³Department of Physics, University of Oslo, Interventional Centre, Rikshospitalet, Olso University Hospital, Oslo, Norway

DSC-MRI is used intensively in imaging studies tracking the effect of emerging treatment paradigms, e.g. anti-VEGF therapy in tumors. It is crucial to the success of longitudinal studies to minimize intrapatient reproducibility of perfusion indices, such as CBF, CBV and MTT. We demonstrate substantial improvements in reproducibility in all parameters by revising the AIF search strategy, estimating a patient specific AIF rather than determining the AIF at each scan. We also observe a lower reproducibility using a population-based AIF. This suggests that a patient-level AIF correctly adjusts for variations in systemic circulation while minimizing scan-rescan variability in perfusion values.

Jessy Mouannes Srour¹, John Lee², Colin Derdeyn^2,3, Wanyong Shin⁴, and Timothy J. Carroll^1,5
1Biomedical Engineering, Northwestern University, Chicago, Illinois, United States, ²Radiology, Washington University in Saint Louis, Saint Louis, Missouri, United States,³Neurology and Neurological Surgery, Washington University in Saint Louis, Saint Louis, Missouri, United States, ⁴Imaging Institute, Mellen Center, The Cleveland Clinic, Cleveland, Ohio, United States, ⁵Radiology, Northwestern University, Chicago, Illinois, United States

A new correction model for arterial-tissue delay and dispersion in dynamic susceptibility contrast MR imaging has been developed. It is shown to provide more accurate cerebral blood flow (CBF) values than existing deconvolution methods through numerical simulations. Direct validation of this model is also presented through a correlational analysis of CBF values measured with the Bookend technique for cerebral perfusion quantification and those obtained with gold standard positron emission tomography (PET), in a series of patients with confirmed cerebrovascular occlusive disease.