A Black Hole in Honor of Jack Leigh

Dr. John "Jack" Leigh, a scientific genius, prolific reader and oddball eccentric, sadly passed away last week. Jack's desk sits about 10 feet from my own and has an assortment of gadgets like bar magnets, canned beaver and a book of crude yiddish vocabulary. The corner of his filing cabinet has innumerable beer bottle caps which are suspended from bar magnets.



I wrote an article a couple of years ago on an infrequently used (overstatement) technique called an off-resonance rotary echo and its application to MR imaging. While writing, I had a conversation with Jack that went something like this:

Me: When you transform to the tilted rotating frame you can show that the off-resonance rotary echo refocuses the magnetization...
Jack: Tilted rotating frame? That's bullsh$t!

Dr. Ari Borthakur wrote to me his thoughts, 'Over the years, I have related several stories to you of his genius in topics such as physics (e.g. approximating how long a human can survive immersed in freezing water) to love ("You don't really want to be with a promiscuous girl. People just says these things. You want a girl that is happy being with you sometimes and is quite content being without you too.").

This year Siemens licensed from the University of Pennsylvania some awesome, endogenous contrast, technology that was developed by Jack and other clever Penn scientists called arterial spin labeling. Using slice selection and spin inversion, flowing blood is 'tagged' as it flows to the brain. The initial tagging alters blood flow contrast and is used for perfusion imaging. The Center for Functional Neuroimaging at Penn investigates many of these techniques for vascular disease, substance abuse and sleep studies.

Jack + brain will be sorely missed.

Unrelated, but interesting: There is a small chance - as in monkeys typing Shakespeare kinds of odds - that the world will end when CERN attempts to replicate the first several nanoseconds of the Universe's existence. The New York Times wrote an article about the two individuals who decided to sue CERN to protect humanity. Largely the issue is jurisdictional; a court in Hawaii cannot force a massive, multi-University/Institution organization in Europe to halt its experiments.

In general, scientists are driven by curiousity and not by evil intent. More likely, although not much more likely, are our chances of using the black hole as a nearly infinite renewable energy source or to travel rapidly to a solar system with a planet with clear blue water and soft sandy beaches. From a moral and recreational perspective, I think particle physicists are obligated to create the black hole.

Grab some popcorn, it's your heart - now at theaters everywhere.

Is it possible to make a film of the human heart beating without performing surgery? Today it can be common practice using an MRI technique called CINE.

Coming soon... cine of my heart.

To understand how this works, it helps to think about how you can make a movie out of set of single still images. Your digital camcorder collects single images at a given frame rate, usually measured in frames per second (fps). To make the 'jumps' between consecutive still images appear undetectable to the human eye, 24-30+ frames need to appear every second (24-30+ fps).

Cardiac movie-making is slightly more complicated. Using the fastest scanning techniques available, an MR scanner is capable of producing a single high resolution image once every 100-300 ms. This means we collect only 10 fps if we were scanning as fast as possible. Even more problematic is that the normal human heart beats slightly faster than once per minute. Contraction of the 4 chambers of the heart (systole) takes even less time.

To fully (time) resolve the heart beating, cine plays a trick on your eyes. Instead of acquiring single images over a single heart beat, it acquires fractions of images over multiple heart beats and reconstructs these images as a single heart beat afterwards. This is all well and good for predictable hearts, but if a heart beats asynchronously during a time period shorter than the total scan time (15 s - minutes), we're out of luck.

So what are the top researchers investigating now?

At the National Heart Lung and Blood Institute (NHLBI) at the National Institutes of Health (NIH) in Bethesda, Maryland, measurements of heart depolarization (electrical activity) are correlated with functional activity by EKG and cine MRI. Check out the work here.

Abroad, at the Institute for Biomedical Engineering at ETH in Zurich, Switzerland, the composition of plaques that develop during atherosclerosis is investigated using MRI. Check it out here.

Seven Tesla

The University of Pennsylvania became the proud owner of a Siemens 7T MRI system on Saturday. The magnet weighed in at a trim 36+ tons and was secured to 4 rigs each capable of holding 15 tons. The magnet arrived on a flatbed truck after being delivered on a ship from Germany. Check out the press here.


For nearly an hour, the riggers eyeballed the system of chains and platforms used to secure the device. Slowly the magnet creeped toward a hole where it would be lowered into the basement of labs where the MMRRCC facility is located. As the magnet approached the hole, the chief rigger decided the track along which the magnet rode was not secure. The magnet was brought out, the harness was secured and the creep continued. Each side of the magnet was lowered manually and asynchronously from the ground floor to the basement of Stellar-Chance. There was some (small) risk that overloading a single 15 ton capable pulley could send the magnet plummeting 20+ feet. Here is a view from the basement as the magnet is lowered from the ground floor.


So why 7T? There is a strong desire among researchers to acquire images at 7T because of the better resolution, the ability to separate resonances in separate chemical environments and changes in relaxation times. Several sites in the country have already installed full-body 7T or greater MR sytems, including OSU and UCSF.

It should be another 2 months before the magnet is ready to be used for research. And besides the magnet itself, RF coils need to be manufactured for nuclear excitation and image acquisition. Two such coils, designed for both proton and sodium imaging, are already in the works for the Penn site.