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Richard L. Ehman, MD, Professor of Radiology, Mayo Clinic, Rochester, MN, ehman.richard@mayo.edu
Moderator: Ferenc Jolesz, MD, CIMIT Co-Program Leader, Image Guided Therapy; Director, Division of MRI and Director, Image Guided Therapy Program, Brigham and Women's Hospital; Director, National Center for Image Guided Therapy; Professor of Radiology, Harvard Medical School, fjolesz@partners.org
Many disease processes cause profound changes in the mechanical properties of tissues. This accounts for the efficacy of palpation for detecting abnormalities and provides motivation for developing practical methods to quantitatively image tissue elasticity. Magnetic Resonance Elastography (MRE) is an emerging imaging technique that uses a modified phase-contrast MRI technique to visualize propagating acoustic waves generated by surface drivers, inertial effects, acoustic radiation pressure, or endogenous mechanisms. MRE acquisition sequences are capable of visualizing waves of less a micron in amplitude in vivo. Inversion algorithms are used to process the wave data to generate maps of properties such as stiffness, viscosity, attenuation, and anisotropic behavior, providing access to a new range of previously unexplored tissue imaging biomarkers.
Human studies have demonstrated that it is feasible to quantitatively image the mechanical properties of skeletal muscles, gray and white matter in the brain, thyroid, myocardium, kidney, liver, and skin. The first established clinical application of the technology is for detection of hepatic fibrosis. Emerging evidence suggests that in addition to being safer, more comfortable, and less expensive, MRE is at least as accurate as liver biopsy for this diagnosis. Other clinical and scientific applications await the development of specialized acoustic driver systems
MRI Strain Imaging: Fundamentals & Applications for Diagnosis and Therapy
Ehud Schmidt, PhD, Director, Engineering Physics,
Radiology, Brigham and Women's Hospital, eschmidt3@partners.org
Moderator: Van Wedeen, MD, Assistant in Neuroscience,
Massachusetts General Hospital and Associate Professor in Radiology,
Harvard Medical School, van@nmr.mgh.harvard.edu
Strain constitutes a change in the dimensions (compression, dilation) and/or shape (shear, torsion) of a sample tissue element due to external forces, such as pressure. Elastic deformation constitutes a sub-set of the above changes which is reversible in nature. Information on elastic deformation can be obtained in MRI with multiple imaging techniques. Cardiac MRI strain has been obtained via analysis of wall-motion cine, myocardial tagging, HARP and DENSE. Focusing on the Displacement Encoding Stimulated Echo Technique (DENSE) technique, it is possible to obtain multidirectional strain components in practical acquisition times (<20 seconds). Since changes in tissue elastic constants are associated with multiple physiological conditions and changes, Strain imaging can be used in the diagnosis and therapy of many diseases. We will demonstrate applications of DENSE imaging to the diagnosis of acute ischemia in the heart, to monitoring therapy for mitral regurgitation and heart failure, to visualizing ablation injury created by Electro-physiology RF ablation in the left atrium. Finally, MR Radiation Force Imaging (MR-ARFI), a variant of Strain imaging that includes a synchronized force-displacement field, can visualize micrometer-scale displacement fields produced by low-power focused ultrasound beams, fields that produce only minute (0.2 Celsius) Temperature changes. MR-based strain techniques will be compared to Ultrasound-based imaging in flexibility, spatial and temporal resolution. Images contributed by researchers at MGH, NAMC, NIH and BWH are gratefully acknowledged.
A woman in Japan has been arrested for the murder of her husband after their sudden divorce. That headline is simple enough, one that anyone in the world has heard before numerous times. Except, it wasn’t ‘really’ her husband. And he isn’t ‘really’ dead. Yet she really does sit in jail.
No, this is not Days of Our Lives – This is Alternate Reality. Everyone understands the concepts of online worlds where people share and interact. It could be gaming oriented like World of WarCraft where four and five generations of Ann DeMarle’s family play and talk to one another in real time every Thursday night. Or it could be Second Life, where hospitals and governments are retooling their planning and experimenting with how life works in rhythm or how it might work.
In Japan they have Maple Story, a similar type of online world where people live their lives everyday just like we all do, except they get to live it in any way they wish so long as it is within the established reality of the world’s parameters.
Many video games (15%) have violence and killing in them, but there is a difference between killing and murder, isn’t there? In this particular case we see true murder. This was not killing as part of a game or a storyline or pointless brutal violence, but instead murder built into an otherwise peaceful online world.
Of course this was not the life of a real person, but the time and energy participants put into their virtual persona is deeply personal to them. More so than your car, more so than your home. The time and thought participants put into crafting their virtual lives far outweighs what most of us spend on… anything. Even work. I personally find this type of activity to be wasteful and I do not participate in these types of worlds, but I’m not going to make value judgments on what others enjoy.
But the question is: Is this the first step toward a Bill of Virtual Rights? But not one with impact on the virtual world, rather one with implications on our physical world. Will rights be granted to crafted online profiles that restrict how we in the real world treat them? Will how we live, vote and eat be changed by the way we live in the virtual?
But just as #3 of the Ten Commandments on the Maple Story website clearly states:
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