MRISIMUL

ENHANCED MRI PHYSICS SIMULATOR

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 Obiettivo del progetto (Objective)

'We propose the design and development of an enhanced comprehensive computer simulation platform of MRI physics, which will integrate realistic aspects of the MRI experiment (such as motion and strain) from signal generation up to and including image reconstruction for the explicit purposes of 1) better understanding the mechanisms involved in artifact and contrast generation in cardiovascular MRI and 2) effectively teaching MRI physics to non-technical personnel. This comprehensive computer simulation of MRI physics and image reconstruction will allow us to better understand realistic artifact generating mechanisms in cardiovascular MRI and will help in defining exam protocols that are optimized for suppressing such artifacts without resorting to animal and/or human experimentation. This research will allow for detailed evaluation of cardiovascular pulse sequences and protocols such as Phase Contrast (PC) velocity mapping, myocardial tagging and Displacement Encoding with Stimulated Echoes (DENSE). With the design and development of the proposed simulator platform, the parameter space of different protocols will be tested and evaluated in detail without the time constraint imposed by experimentation in an MRI scanner. The simulations will be designed and developed with a variant of a four-vector formalism. A deforming model of the heart will be implemented as part of the simulator to allow visualization and analysis of imaging techniques that map myocardial motion and strain. Last, the simulation will allow for noise injection, respiratory motion modeling and multi-coil signal acquisition. We will apply this tool to allow researchers, technologists, physicians and students to visualize the effects of motion and/or strain, on tissue contrast, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in models of acute myocardial infarction. This will allow for further research in optimizing MRI protocols and also for training of non-technical personnel.'

Introduzione (Teaser)

Magnetic resonance imaging (MRI) helps detect and diagnose pathologies in most tissues in the body. A novel MRI simulator that recreates heart and respiratory motion will aid in optimisation of algorithms and training of new personnel.

Descrizione progetto (Article)

Since it does not use ionising radiation, MRI is a very safe, non-invasive method to determine both static and dynamic properties of biological tissues. With EU support of the project 'Enhanced MRI physics simulator' (http://mri.dib.uth.gr/ (MRISIMUL)), scientists have developed a realistic simulation tool that runs on a single computer.

The impetus was to integrate realistic aspects of an MRI experiment to understand artefact generation mechanisms during cardiovascular MRI. This will facilitate better exam protocols without the need for more complicated and expensive human or animal experiments.

Scientists developed a MATLAB platform that supports development of custom MRI pulse sequences and their application to model objects. MRISIMUL exploits Bloch simulation, the most accurate way to study the effect of pulse sequence on magnetisation.

Following analysis of computational power, the team determined that prohibitively long execution times of several days were required even with a high-end personal computer. Researchers replaced the central processor unit (CPU)-based approach with a large number of processing cores integrated with a graphic processing unit (GPU), again on a single computer.

Now the computationally demanding core services (kernel) are executed in parallel within the GPU environment for a speed-up of about 228 times compared to serial processing with a CPU. This means, for example, that instead of 5 full days (120 hours), a simulation now requires approximately half an hour. In multi-node, multi-GPU systems, MRISIMUL demonstrated an almost linearly scalable performance with increasing number of available GPU cards.

The team has now developed a detailed 3D model of the human heart and torso that simulates relevant motions, including respiration, heart and simple flow. The model can be installed from the project website. There, users will also find a 'fuzzy' spatial distribution of the brain, including 11 tissue types.

MRISIMUL has been warmly welcomed by the scientific community with its first description in the Journal of Cardiovascular Magnetic Resonance, acquiring the designation 'highly accessed' within less than a month of its publication. The project also paves the way for extension to other biomedical fields. EU citizens can soon expect better diagnoses and care for a variety of illnesses.