Rebecca Waugh^1,2, Maria Gusseva^3,4, Gerald Greil², Dominique Chapelle^3,4, Tarique Hussain², and Radomir Chabiniok^2
1UT Dallas, Dallas, TX, United States, ²Pediatrics, UT Southwestern Medical Center, Dallas, TX, United States, ³Inria, Palaiseau, France, ⁴LMS, Ecole Polytechnique, Palaiseau, France

Biomechanical models coupled with cardiovascular MRI (CMR) have the potential to provide non-invasively physiological parameters of clinical interest. The approach is presented and validated on a group of 10 patients who underwent CMR and invasive catheterization. Patient-specific models are built based on CMR data and maximum/minimum arterial pressure. The stroke work, derived from ventricular pressure-volume (P-V) loops, was comparable between the measured and simulated P-V loops, suggesting the high quality of the in silico loops. An excellent correlation of the model-derived myocardial contractility with maximum time-derivative of ventricular pressure gives an opportunity for the non-invasive characterization of patients’ inotropic state.

Jihye Jang¹, Yansong Zhao¹, Jouke Smink², Andrew J Powell³, Lorna Browne⁴, and Mehdi H Moghari^4
1Philips Healthcare, Gainsville, FL, United States, ²Philips Healthcare, Best, Netherlands, ³Boston Children’s Hospital and Harvard Medical School, Boston, MA, United States, ⁴Children's Hospital Colorado and University of Colorado, Aurora, CO, United States

Phase-contrast (PC) MRI enables non-invasive quantification of blood velocity and flow. The velocity encoding factor (venc) selected by the operator is chosen to maximize the velocity-to-noise ratio (VNR) while preventing aliasing artifacts. To minimize the acquisition time increase associated with an additional venc, a dual-venc dual-echo (DVDE) technique has been proposed where both venc images are acquired within a single TR as dual-echo images. Compared to the single-venc PC-MRI, DVDE allows simultaneous imaging of arterial and venous blood flow with an enhanced VNR and similar blood flow and velocity.

Genki Nambu¹, Naoki Ohno¹, Tosiaki Miyati¹, Fumiki Sugita¹, Yuki Makino², Momoka Ikeda¹, Noam Alperin³, Toshifumi Gabata¹, and Satoshi Kobayashi^1
1Division of Health Sciences, Graduate School of Medical Sciences, Kanazawa University, Kanazawa, Ishikawa, Japan, ²Department of Radiology, Kanazawa University Hospital, Kanazawa, Ishikawa, Japan, ³Department of Radiology, University of Miami, Miami, FL, United States

Perfusion-related diffusion coefficient (D^*) in intravoxel incoherent motion analysis is closely correlated with the regional cerebral blood flow (rCBF). However, the D^* is only a semiquantitative relative value of rCBF, which makes absolute rCBF quantification challenging. To solve this problem, we developed a novel method of diffusion imaging with phase contrast (DIP), in which the total CBF (tCBF) from phase-contrast (PC)-MRI was used to convert the perfusion-related parameters in the brain to absolute rCBF. Using this method, we measured rCBF in gray matter and white matter. Each value was consistent with literature values assessed using [¹⁵O]-water positron emission tomography.

Freya Allery^1,2, Daniel P. Bulte¹, Embla Hocking¹, Nicholas P. Blockley^3,4, James W. Harkin⁵, and Joana Pinto^1
1Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Oxford, United Kingdom, ²Institute of Health Informatics, University College London, London, United Kingdom, ³Sir Peter Mansfield Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom, ⁴School of Life Sciences, University of Nottingham, Nottingham, United Kingdom, ⁵Poole Hospital NHS Foundation Trust, Poole, United Kingdom

ASL inversion efficiency is often assumed as a pre-defined value or estimated by acquiring an additional phase-contrast MR image. While the former approach might be inaccurate in certain conditions, the latter can be time-consuming. Here, we propose a simplified method that estimates blood flow velocity and inversion efficiency solely using the ASL data. This novel strategy was tested using multi-PLD pCASL datasets with two different blood flow dynamics (normo- and hypercapnia). Our results show the feasibility of this approach and highlight the need for subject/condition-specific inversion efficiency estimation for a more accurate quantification of CBF. 

Eleanor F Cox¹, Venkata Rukmini Latha Gullapudi^2,3, Charlotte E Buchanan¹, Kelly White³, Sebastian Coleman¹, Daniel Cocking¹, Isma Kazmi^2,3, Katrin Köhler⁴, Bernard Canaud⁴, Maarten W Taal^2,3, Nicholas M Selby^2,3, and Susan T Francis^1
1Sir Peter Mansfield Imaging Centre, University of Nottingham, Nottingham, United Kingdom, ²Centre for Kidney Research and Innovation, University of Nottingham, Derby, United Kingdom, ³Renal Unit, University Hospitals of Derby and Burton NHS Foundation Trust, Derby, United Kingdom, ⁴Center of Excellence Medical Europe, Middle East and Africa, Fresenius Medical Care, Bad Homburg, Germany

Twelve patients underwent serial cardiac, cerebral and renal multiparametric 3T MRI scans before, during and after haemodialysis. During dialysis, there was a significant decline in cardiac and stroke index and myocardial strain, with increased diastolic dysfunction. This was accompanied by a reduction in blood flow to both the heart and brain. White matter T₁ increased during dialysis suggesting fluid shifts increasing water content resulting in local oedema. Total kidney volume, renal cortex T₁ and T₂* all reduced during dialysis likely reflecting reduced renal blood volume and change in renal tissue water. These results highlight the acute multi-organ effects of dialysis.

Prativa Sahoo¹, Jost M Kollmeier², and Steffi Dreha Kulaczewski^1
1University Medicine Göttingen, Göttingen, Germany, ²Max Planck Institute for Biophysical Chemistry, Göttingen, Germany

Venous system pathologies have increasingly been linked to disorders of CSF circulation whereas the exact coupling mechanisms still remain unknown. Using real-time phase-contrast MRI fluid dynamics of both systems were studied during normal and forced breathing in healthy subjects at spinal lumbar level L3. The aim was to provide experimental evidence that respiration couples CSF and venous flow. A correlation between CSF and venous flow could be observed during forced breathing. The findings point to a dynamic interplay between the fluid systems to regulate intracranial volume. Further insights will expand our understanding of the pathophysiology of different forms hydrocephalus.

Dounia El Hamrani¹, Julie Magat¹, Jérôme Naulin¹, Céline Ayez¹, Marilyne Campagnac², Frédéric Perros³, Christelle Guibert², David Benoist¹, and Bruno Quesson^1
1IHU Liryc, Bordeaux, France, ²CRCTB-INSERM U1045, Bordeaux, France, ³Université Paris–Saclay, AP-HP, INSERM UMR_S 999, Le Kremlin Bicêtre, France

 Transgenic rats with Bmpr2 mutation is a model of heritable pulmonary arterial hypertension (PAH). This study aims to evaluate cardiac alterations of Bmpr2-mutants associated with a risk factor (hypoxia) by MRI and ³¹P-MRS. Transgenic rats exposed to chronic hypoxia showed a drastic dilatation of the RV along with an increased wall thickness and no variation of ejection fraction, thus resembling right heart failure with preserved ejection fraction. The cardiac energy balance is disturbed in Bmpr2 rats under hypoxia indicating a metabolic insult. Bmpr2 mutation associated with chronic hypoxia can aggravate right heart failure and thereby accentuated the onsets of PAH. 

Fikunwa Kolawole^1,2,3, Mathias Peirlinck⁴, Tyler E Cork^1,2,5, Marc E Levenston^1,3, Ellen Kuhl³, and Daniel Ennis^1,2
1Radiology, Stanford University, Stanford, CA, United States, ²Radiology, Veterans Administration Health Care System, Palo Alto, CA, United States, ³Mechanical Engineering, Stanford University, Stanford, CA, United States, ⁴Biomechanical Engineering, Technische Universiteit Delft, Delft, Netherlands, ⁵Bioengineering, Stanford University, Stanford, CA, United States

MRI-driven computational constitutive modeling can be used to obtain subject-specific myocardial passive stiffness. Verifying the accuracy and precision of this technique requires overcoming the challenge of obtaining ground-truth in vivo myocardial stiffness. We developed a controllable in vitro diastolic filling setup which incorporates a soft heart phantom of known myocardium-mimicking mechanical stiffness and MRI properties. Using the setup we demonstrate that uncertainties in quantifying cardiac reference geometry can lead to errors in estimating myocardial passive stiffness. The in vitro setup is designed to enable us to achieve our overarching goal: to extensively validate in vivo MRI-based myocardial passive stiffness estimation.