[Note: For a report on the installation of the 7T MRI at Johns Hopkins Kennedy Krieger F.M. Kirby Research Center, read the January 2009 issue of DOTmed Business News.]

An exclusive DOTmed Business News e-mail interview with leading experts at Kennedy Krieger's F.M. Kirby Research Center providing details on their new magnet.

Information provided by Peter van Zijl, Ph.D., Director, and Joe Gillen, B.S., Staff Scientist, of the F.M. Kirby Research Center at Kennedy Krieger Institute.

Q: What will the MRI be used for?
A: The MRI will be used for research on brain function and physiology in normal volunteers and the many patient populations at Kennedy Krieger Institute, Johns Hopkins University, the University of Maryland, and several other institutions.

Q: Is this a research or clinical/human application?
A: This is a research application. Human patient studies will be carried out but no clinical reimbursement studies will take place.


Q: Who made the MRI?
A: The system was developed at Philips Medical Systems, Cleveland, OH and Best, Netherlands. The magnet is made by Magnex Scientific, Oxford, England.

Q: What type of machine is it?
A: 7 Tesla Achieva Magnetic Resonance Imager. It uses the same console as Philips 1.5T and 3T Achieva systems but with modifications to the RF system for 7 Tesla operation. This allows our research modifications to the Philips product MR pulse sequences developed for 3T to be immediately used at 7T.

Q: Describe your work; areas of research.
A: Currently there are about 100 users of the F.M Kirby Research Center who study a variety of diseases, including metabolic disorders, ADHD, reading disability, Alzheimer's disease, Multiple Sclerosis, autism, cancer, stroke, and other conditions.

Q: How will this high-powered magnet help? What will it allow you to do that a "regular" MRI can't?
A: There are several advantages, the most important one is that images can be acquired at higher resolution, allowing us to study more anatomical detail. Secondly, the study of brain function becomes easier as the MRI effects due to brain activity are proportional to field strength. It will help us detect smaller effects not visible at low field. Third, 7T will allow the detection of several chemical compounds that can not be detected very well at low field. For example, several neurotransmitters. Finally, detection of physiological parameters such as blood flow can be done more accurately.

Q: Where is it to be installed, in an office building, laboratory, other setting?
A: It will be installed in the basement level of the new Kennedy Krieger Institute Clinical Research Building in East Baltimore. The site is near the Johns Hopkins Medical Institutions campus. (Note: The MRI is in place and scheduled to be operational in March.)

Q: Explain the challenges overcome to put a technology of this capability in place.
A: [Explaining several types of challenges]

Magnet -- Production of a 7T whole-body superconducting magnet was a challenge for the magnet manufacturers. We believe the first system with ultra high field magnet was the 8T magnet at Ohio State University in 1998. 7T followed at University of Minnesota in 1999. Currently there are about twenty-two 7T systems operating in the world plus the OSU 8T and a 9.4T at University of Illinois at Chicago.

Transmit homogeneity of the radiofrequency (RF) field -- An MRI uses radiofrequency similar to local radiostations. Producing a homogeneous RF excitation at 7T is a challenge due to the higher frequency used at 7T (300 MHz). This corresponds to a wavelength smaller than the human brain. The solution appears to be the use of arrays of transmitter coils in similar fashion to the arrays of receivers commonly used in clinical scanners today.

Magnetic shielding -- The magnet is not self shielded as 1.5T and 3T scanners for clinical use are. Due to the high field strength the spread of the magnetic field higher than 5 Gauss would be quite large. Therefore, the scanner is placed in a 440 ton (400 metric ton) six sided steel box that forms the largest part of the MR examination room. The box is made of annealed, high-silicon steel plates, 16 inches thick at the center of the room closest to the magnet, tapering to 8 inches thick at the head and foot ends of the box. This magnetic shield brings down the 5 Gauss lines to a manageable size, about 30 feet by 60 feet. Due to the large forces exerted by the magnet on the box, the magnet must be perfectly centered in the box and the box is constructed to 1/8 inch tolerance. The steel erector was Richard Lee of Shreveport, LA (whom I believe you have already contacted) who is a contractor of Imedco America, Inc. of Noblesville, IN who designed the shield in concert with the magnet manufacturer, Magnex Scientific, Inc.

Vibration -- The Baltimore Metro runs underground in front of this new building - and a station is directly across from the building. Also there is a large amount of vehicle traffic on the 2 streets adjacent to the building. Due to vibrations from these two sources, the entire MR examination room was placed on air springs manufactured by Hammond Kinetics of Dublin, Ohio. These 26 air springs will be inflated when the construction is complete and will lift the examination room, with the 440 ton shield, 35 ton magnet and all interior finishes (1.25 million pounds total) about 1/4 inch off their supports. Optical sensors in three locations sense the position of the room and controllers adjust the pressure in the air springs to keep the room level. This system will completely isolate the MR scanner from outside vibrations.