Growing up as the oldest of 12 children on a dairy farm in Mexico, New York, John Schenck was an inquisitive little kid. Early on he developed a great work ethic and a love for science – two qualities that have remained the backbone of his being for the past 70+ years.
John graduated as class valedictorian from the Mexico Academy and Central School in 1957 and was the first central New York recipient of a National Merit Scholarship. He packed his bags and headed east to Rensselaer Polytechnic Institute in Troy, New York where he earned a bachelor’s degree in physics. Four years later in 1965 and still at RPI, John earned a Ph.D. in solid-state physics, which in laymen’s terms, is the study of the structure and properties of solid matter.
“My thesis on superconductivity helped me secure a staff scientist position at the GE Electronics Laboratory back in central New York,” Dr. Schenck said. “I spent four years working on semiconductor devices for radar and other applications and also became a faculty member of the electrical engineering department at Syracuse University.”
A few years into his academic career Dr. Schenck found himself attending lectures on neuroscience, prompted by a series of lunchtime conversations with a fellow professor who happen to have multiple sclerosis.
“I was surprised to realize that there are parallels between the disabilities he was experiencing – such as intention tremors – and feedback instabilities in electrical engineering control systems,” he said. “I wanted to learn more about the brain and how it worked with the body.”
Dr. Schenck started a very popular electrical engineering graduate course exploring the relations between neurophysiology and electrical circuit theory. And rather than opt to attend more lectures or take a few classes, Dr. Schenck made a bold move; he stepped away from SU and cut his status with GE to part time so he could attend medical school. He went to and graduated from Albany Medical College in Albany, New York and completed an internal medicine internship at the neighboring Albany Medical Center Hospital. By 1978 Dr. Schenck held a Ph.D., an M.D., and a crazy amount of motivation to put all his knowledge to work.
Without missing a beat he returned to GE full time, working for Red Redington as a senior scientist at Global Research in Niskayuna, New York. At the time Redington had led and just completed the very large and very successful computed tomography (CT) development program at the GE research labs in the mid-1970s. CT had transitioned almost entirely to GE’s Medical Systems business in Wisconsin and several of Redington’s staff followed the opportunity. Redington’s staff was down to just a couple of people and his focus was shifting to magnetic resonance (MR) as a medical tool. Dr. Schenck became the first full-time team member to join his effort.
“I had no particular knowledge of the technology, but several staff members – particularly Howard Hart and Richard Likes – had been investigating MR on a part-time basis. They had become familiar with imaging work at (what would now be called) low field strengths – underway in the UK and at Stony Brook in the US – using resistive, air-core magnets or electromagnets,” said Dr. Schenck, but at the time GE did not have an imaging magnet of its own.
These competing groups had already had success in scaling-up nuclear magnetic resonance (NMR) from its original test tube sample size to human-scale imaging, but with the use of low field magnets, generally in the 0.1 – 0.2 Tesla (T) range. These companies were already in the process of commercializing their products so Redington, Dr. Schenck, and the team were concerned about how GE could compete.
“In addition to concerns about the tough, well organized competition, there was a lot of hesitation internally partly because NMR imaging had several esoteric, and potentially problematic, aspects; putting human subjects into large powerful magnets was only one of them,” Dr. Schenck said. “The size of the potential clinical market was very uncertain and there was concern over the investment GE had just put into its CT development program. Also, Also, CT had rapidly become a booming and highly competitive business and had major continuing development needs. At that time many people worried that eventually either MR would eliminate CT from the marketplace or vice versa, but obviously that hasn’t turned out to be the case.”
At the time, Oxford Instruments (OI) out of the UK was the primary producer of “high powered” magnets, ranging between 0.1 – 0.35 T. But Dr. Schenck caught word of researcher Britton Chance and his 1.4 T mid-size bore superconducting magnet at the University of Pennsylvania. Chance was a world-famous biophysicist and biochemist, an Olympic gold medalist, and a very wealthy man; he had purchased the magnet from OI using his own money.
“GE suggested I contact him to see if it was possible to become familiar with his lab and this magnet,” Dr. Schenck said. “I was nervous and intimidated when I called him because he was an extremely famous scientist and had been prominent in my medical school textbooks.”
To Dr. Schenck’s surprise, Chance was very friendly and open about his research and invited the GE team to come try some of their ideas using his magnet. “We’re talking about a magnet costing hundreds of thousands of dollars, which at that time was a lot of money,” Dr. Schenck said. “He was doing some pretty interesting tests but without gradient coils, as his magnet was designed for human spectroscopy studies, not imaging.”
It was soon decided that, although it was going to be very expensive, GE should acquire its own research magnet. Though contacts provided by Chance, Dr. Schenck met with OI management who came to the Niskayuna labs to propose various options for the GE program. They talked about several options for an MR research magnet, including a mid-size bore that would have permitted high-field studies of pig imaging but was too small to perform human studies. The most ambitious (and most expensive) option was a unique, one-meter bore magnet designed to operate at 1.5 – 2.0 T. Easily large enough for human imaging, the field strength would be about four times as large as any existing magnet, improving the possibility of a better clinical performance compared to any existing magnet.
OI had never built a human whole-body magnet anywhere near that strength but their design calculations indicated it was technically feasible. A major risk of this approach was that at 1.5 T, the NMR signal from the body would be near 64 MHz. At the time, many leading researchers maintained that human MRI would be impossible at frequencies above 10 – 15 MHz because of radiofrequency absorption (skin effect) in the human body. Interestingly enough, this proposed absorption limitation in humans was based entirely on calculations and had never actually been demonstrated experimentally.
Despite the high level of risk involved, the possibility of a leapfrog breakthrough was decisive and in 1980 GE’s top management approved the ordering of the high-end, high-cost, high-risk magnet. Management also approved two new staff positions for the program and, after a brief search, Bill Edelstein and Paul Bottomley, two researchers who had each just completed successful post-doctoral research in low field strength MRI at universities in the UK, also joined the team and soon made major contributions.
Because it would take approximately 18 months to complete the OI magnet, an interim, low field resistive 0.12 T magnet was acquired and used for initial imaging studies. Work also began on a small outbuilding to house the magnet and the research team to ensure the powerful magnet and its still somewhat mysterious properties would not interfere with other laboratory programs and vice versa.
For Dr. Schenck though, his focus was two-fold because in addition to his research work at GE, he was also serving as an emergency room physician at nearby Ellis Hospital in Schenectady, New York. It was a passion of his for 11 years and since you can’t quite beat first-hand experience, Dr. Schenck served as GE’s longtime go-to guy for industry related information. Questions like “What kind of patients will benefit from this technology?” to “Will the potential medical benefits outweigh the cost?” and “How will we verify the safety of this technique?” were explored time and again throughout GE’s MRI development process.
“I always intended on practicing medicine and my position at Ellis kept me in tune with what was going on in clinical medicine,” he said. “This knowledge transferred to the MR work we were doing at GE and helped us navigate a number of challenges and answer questions that were critical to MRI development.”
The magnet arrived at GE in the spring of 1982 and was rapidly cooled to liquid helium temperature brought up to field. Although designed to operate as high as 2 T, the magnet was found to develop a drift in field strength once the field exceeded 1.5 T; it was decided that the operating field for further experiments would be 1.5 T.
Dr. Schenck’s clinical experience came in handy on May 26, 1982 when he and GE clinic nurse Peggy Porter, RN collected the first formal safety studies at this field strength by measuring Dr. Schenck’s vital signs before and after an extended period inside the magnet. Although technicians from OI had worked inside the magnet and experienced the field during its construction, this was the first formal effort to demonstrate that a person’s vital signs were not affected by exposure to this field strength.
Fast forward a few months to November 1982… the team had used these months to prepare the interior of the magnet as a complete imaging system. Dr. Schenck was placed inside the magnet on a makeshift wooden table.. His friend and co-worker Dr. Howard Hart was at the controls, preparing the system’s settings for head scanning.
“He was operating a supplementary current supply that had to be carefully adjusted to stabilize the field against the slight magnet drift in order to collect the imaging data,” said Dr. Schenck.
After hours of adjusting and readjusting, in the early morning hours of November 22, 1982, the pair obtained the first human head images at 64 MHz. “We were surprised and pleased to see that there was no evidence of signal loss from the deepest parts of the brain, indicating that proton human imaging at 1.5 T (64 MHz) would be practical,” said Dr. Schenck. “This was imaging obtained at roughly four times as high a field strength than was previously attained with a human whole-body magnet. We knew our images were going to bring big changes to the field of MRI.”
The first formal presentation of the team’s findings occurred in February 1983 at the First Annual Meeting of the Society for Magnetic Resonance Imaging (a precursor society to today’s International Society for Magnetic Resonance in Medicine (ISMRM)). A paper given by Dr. Schenck and coauthored by five of his GE colleagues, NMR Imaging at Very High Fields: Issues and Theories, Results and Conjectures, was named the meeting’s best and paved the way for additional publications and presentations. By and large the GE Global Research MR program was a success, which permitted the GE Medical Imaging business to focus on commercializing MRI technology at the 1.5 T field strength.
“At first there was a lot of controversy as to what strength was optimum for MRI and GE’s business decision to jump in at 1.5 T was rather risky and courageous at the time,” said Dr. Schenck. “But by 1985 1.5 T had become the dominant field strength for advanced MRI and still today, 1.5 T scanners constitute the largest volume of new systems.”
Dr. Schenck and the GE Global Research team soon turned their attention to coil development; their inventions in the areas of radiofrequency and gradient coils remain critical to MRI function even today and are among his proudest accomplishments. Dr. Schenck remained on staff with Ellis Hospital until 1989 and joined the University of Pennsylvania, Philadelphia as an adjunct assistant professor of radiology and Albany Medical College as an adjunct research professor of neurology.
“I continued to practice medicine, develop coil technology, and teach,” he said. “I presented GE’s research via white papers and high-profile industry lectures; we had earned our place as a technological leader in the field and our influence was strong, but the technology was in its infancy so we had to remain vigilant in our R&D efforts.”
In 1987 the team acquired a much more powerful whole-body magnet also built by OI and operating at 4.0 T. In 1993 the American Association of Physicists in Medicine presented Dr. Schenck with its SS Greenfield Award for best paper published in the association publication, Medical Physics, that year. The paper, titled Human Exposure to 4.0-Tesla Magnetic Fields in a Whole-Body Scanner, was co-authored by five of Dr. Schenck’s GE coworkers. The trend of going to ever higher magnetic field strengths for MRI continues today.
Dr. Schenck wrote extensively about MR safety, the role of magnetic susceptibility in MRI, and the development of interventional MRI. His papers have and continue to be cited by the FDA in their guidelines for MR safety and compatibility. Further demonstrating his commitment to safety, in 1996 Dr. Schenck chaired a workshop on advances in MR safety and compatibility in McLean, Virginia.
Circling back to his interest in how the human brain works with the body, Dr. Schenck started conducting extensive studies on the use of high-field MRI to investigate brain iron abnormalities in neurodegenerative disorders such as Alzheimer’s and Parkinson’s disease. His studies provided critical insight as to how MRI can help in promoting earlier detection of these debilitating diseases. From 2001 to 2012 he served as director of a joint Albany Medical College/GE Global Research effort devoted to high-field MR research on neurodegenerative diseases. As his work progressed, GE Global research promoted Dr. Schenck to principal scientist.
Dr. Schenck is a Fellow of the American Physical Society and the ISMRM and holds a Coolidge Fellowship, which is highest individual award for technical excellence at GE Global Research. In 2009 he received the ISMRM Gold Medal, the society’s highest award and he was recently inducted into the RPI Alumni Hall of Fame.
Since 2014 Dr. Schenck has served as a senior principal scientist for GE Global Research, focused on high-performance, high-field human brain imaging, particularly the recently introduced technique called quantitative susceptibility mapping (QSM). This technique has important implications for understanding the function and disorders of the brain, particularly depression. It will also be valuable for guiding neurosurgical procedures such as deep brain stimulation.
From this start 33 years ago 1.5 T MRI was rapidly adopted into clinical practice and high field MRI machines are now found in nearly every hospital. Also, the total number of patient studies/year increased rapidly. Precise numbers are not available, but, an informed estimate in 2012 was that approximately 80,000,000 MRI studies were performed worldwide per year and, since the mid-1980s, there have been more than 700,000,000 clinical studies performed. During all that time, 1.5 T scanners served as the standard platform for high-performance MRI.
Since approximately the year 2000, whole-body scanners operating at 3 T have become available and provide certain performance advantages. Scanners operating at this field strength are becoming gradually more common. It was also estimated in 2012 that there were approximately 24,000 whole-body superconducting scanners in clinical service worldwide and of these approximately 22,000 operated at 1.5 T and 2,000 at 3 T. There were also approximately 50 whole-body superconducting research scanners operating at field strengths of 7 T or higher. In 2015, 1.5 T scanners still represent the most common field strength for new installations.
As implied by the large number of scans being performed, the impact of MRI on medical practice has been dramatic. In 2001 a group of 225 general internists was asked to rank the importance of 30 medical innovations of the previous 25 years. Despite the fact that these 25 years had seen the introduction of many revolutionary medical technologies – coronary artery bypass grafts, medical therapies for depression, diabetes, joint diseases, etc. – these clinicians selected MRI, along with computed tomography, as the most important medical innovation in terms of advancing patient care during this period.
“Imaging is a great tool that’s allowing us to explore and unlock the mysteries of the human brain,” said Dr. Schenck. “Pursuing this avenue of exploration helps us further evolve and fully understand the brain so we can invent solutions to real-life, everyday problems.”
“When I was growing up in the 1950s I think everyone realized that they had a brain and that it was important but I don’t believe people had much feeling for what the brain looked like or what its various components were. Today, however, I believe almost everyone has seen MRI brain images and this is what pops into their heads when they think about their brain and how it determines who and what they are,” said Dr. Schenck. “A little over 30 years ago that technology did not exist.”
It may be hard to imagine a time when most people hadn’t seen detailed pictures of the deep brain structures, but thanks to Dr. Schenck and his colleagues, the next generation of scientists can focus their attention on the technology’s potential to further change the healthcare industry as we know it today.