Pei-Lun Yu, Sheng-Min Huang, Cheng-He Li, Sheng-Yan Wu , Chi-Shiun Chiang, Kung-Chu Ho, Fu-Nien Wang

Recently, deuterium oxide (D2O) has been proposed as an alternative contrast agent on rodent brain perfusion by monitoring the attenuation of 1H signal. Since D2O is a highly diffusible contrast agent, the revealed information of Gd chelates and D2O are different. In this study, we aimed to re-investigate the perfusion information carried by D2O with advanced spatial resolution. We speculated that D2O slowly diffused into tumor area and continuously exchanged with tissue water until a balanced concentration. Inside the tumor region, the heterogeneity shown by D2O and Gd-DTPA are somewhat different.

Ruiliang Bai, Charles Springer, Jr., Dietmar Plenz, Peter Basser

Knowledge of transmembrane water exchange kinetics is invaluable for the correct interpretation of many MRI experiments, e.g., DCE-MRI, diffusion MRI, etc. Here we quantitatively studied the transmembrane water exchange  in organotypic cultures from rat brain cortex with an MR relaxation contrast agent. In normal states, we determined the equilibrium cellular water efflux rate constant [k_io] is 2.15 (± 1.28) s^-1 at 34 (± 1)  °C. In the likely cell-swollen state induced by Ouabain perfusion, we, for the first time, quantitatively measured a global increase of the intracellular volume fraction (~104%) together and a large decrease of k_io (~64%). 

Jonathan Doucette, Luxi Wei, Christian Kames, Enedino Hernández-Torres, Rasmus Aamand, Torben Lund, Brian Hansen, Alexander Rauscher

Cerebral white matter tissue perfusion measured with gradient echo dynamic susceptibility contrast (DSC) imaging exhibits a strong dependency on the angle between white matter fibres and the main magnetic field. Here, we investigate how spin echo DSC depends on the orientation of white matter and explain orientation effects by a model of diffusion within a magnetically inhomogenous environment created by a vascular bed with isotropic and anisotropic components. We found that the change in $$$R_2$$$ value for the SE DSC is 20% larger in WM fibres perpendicular to $$$B_0$$$ than for those parallel, compared with 100% larger in GRE DSC.

Elias Kellner, Marco Reisert, Benedikt Poser, Irina Mader, Valerij Kiselev, Michel Herbst

In this work, we combine simultaneous multi-slice acquisition with a multi-echo readout, dedicated to dynamic susceptibility-contrast perfusion imaging (DSC). With this approach, multiple spin and gradient echo images can be obtained at short repetition times to determine both T2 and T1 effects of contrast agent in a robust and stable manner.

Nuno da Silva, N Shah, Rute Lopes, Ezequiel Farrher, Seong Dae Yun

Perfusion weighted imaging (PWI) using dynamic susceptibility contrast (DSC) imaging is a widely used technique in tumour imaging. The use of multi-echo DSC, gradient and spin echo (GESE), allows one to obtain vasculature information. However, trade-off between number of echoes, spatial resolution and brain coverage is required. In this work, the use of EPI with keyhole (EPIK) combined with multi-band is proposed to obtain a whole brain multi-echo GESE-DSC in clinically relevant acquisition times. The method was applied in a cohort of brain tumour patients in a MR-PET scanner enabling localisation of the tumour based on metabolic information from PET.

Leonardo Rivera Rivera, Tilman Schubert, Patrick Turski, Kevin Johnson

Intracranial vascularity is modified in a wide array of diseases including cancer, various forms of dementia, and stroke.  Steady state imaging with Ferumoxytol provides unique opportunities to estimate cerebral blood volume (CBV). In this work, we investigate the correlation between relaxometry changes measured utilizing ultrashort echo time variable flip angle (UTE-VFA) R1 and a multi-echo R2* approaches. Initial results from 8 healthy volunteers shows a high degree of correlation of R1 with R2* measures and improved performance in and around vessels. This, and opportunities to probe disease induced disagreements, suggests potential value in combined R1 and R2* measures. 

Ryan Woodall, Stephanie Barnes, Anna Sorace, David Hormuth II, C Quarles, Thomas Yankeelov

Standard compartmental models for quantitative dynamic contrast enhanced MRI (DCE-MRI) typically assume active delivery of contrast agent that is instantaneously distributed within the extravascular extracellular space within each imaging voxel. The goal of this study is to determine the error accumulated in the estimated pharmacokinetic parameters when these assumptions are not satisfied. Using finite element methods to model contrast agent arrival and diffusion throughout realistic tissue domains (obtained from histological stains of tissue sections from a murine cancer model), it was rigorously determined that parameterization error is highest in regions of low vascularity, and lowest in well-perfused regions.

Cagdas Ulas, Pedro Gomez, Jonathan Sperl, Christine Preibisch, Marion Menzel, Axel Haase, Bjoern Menze

We propose a robust reconstruction model for dynamic perfusion magnetic resonance imaging (MRI) from undersampled k-space data. Our method is based on a joint penalization of the pixel-wise incoherence on temporal differences and patch-wise dissimilarities between spatio-temporal neighborhoods of perfusion image series. We evaluate our method on dynamic susceptibility contrast (DSC)–MRI brain perfusion datasets and demonstrate that the proposed reconstruction model can achieve up to 8-fold acceleration by yielding improved spatial reconstructions and providing highly accurate matching of perfusion time-intensity curves, thus leading to more precise quantification of clinically relevant perfusion parameters over two existing reconstruction methods.

Anneloes de Boer, Tim Leiner, Nico van den Berg

In renal dynamic contrast enhanced (DCE) MRI respiratory motion of the kidneys necessitates registration of the dynamics. Since image contrast varies during contrast agent passage, automatic registration is challenging. We show that on Dixon-derived fat-images this contrast change is virtually absent. Therefore, we propose to perform automated image registration using fat-images and apply the resulting transformation to the water-images. We applied this method to DCE data of 10 patients and show its superiority over a conventional registration approach. Pharmacokinetic fits to a two-compartment model yielded realistic values for renal perfusion and filtration.

Dimitra Flouri, Daniel Lesnic, Constantina Chrysochou, Philip Kalra, Steven Sourbron

Tracer-kinetic model driven motion-correction is a highly effective strategy for 2D free-breathing DCE-MRI. In this study we address the challenge of translation to 3D by improving computational efficiency and evaluating performance in the presence of ghosting artefacts. Results in 8 patient cases show that the optimised algorithm is feasible in realistic computation times and effectively removes between-frame breathing motion despite significant within-frame artefacts. Quantitative evaluation against reference measurements shows a reduction of the bias, but precision is limited by within-frame artefacts and will require an integrated motion-correction and image reconstruction strategy.