Robert Mulkern, PhD
Associate Professor of Radiology
Department of Radiology
Boston Children’s Hospital
Harvard Medical School
The Brigham was a hot bed of magnetic resonance activity in the 1980’s with proton relaxation measurements of tissues playing an important role in understanding the science behind the amazing tissue contrast just becoming appreciated by the world. Some of these early works, including some early 31P spectroscopy studies to examine the biological effects of “destructive energy” driven by Ferenc Jolesz and others in those early days are reviewed in order to understand the impetus to go from ex vivo tissue measurements to in vivo imaging measurements. In particular the development of multi-spin echo sequences for T2 measurement in the early 1990’s and its role in the “spin-off” of what has become most probably the busiest MR sequence in the business, the so-call fast or turbo spin-echo sequence, is highlighted along with Ferenc’s leadership role in its rapid dissemination. Further considerations of both T2 and T2* measurement and subtleties involved, including spectroscopic methods based on multiple echoes, the separation of reversible from irreversible transverse relaxation effects and the role of frequency distributions that have evolved over the last 20 years are then provided. Finally, measurements of T2 from individual metabolite signals in tissue using a careful analysis of the differences between the “left” and “right” sides of a single spectroscopically sampled spin-echo are presented.
Bob obtained his physics degree from Cornell University in 1978 and his PhD in physics from Brown in 1986. Since then he has been actively involved in the field of medical and biophysical applications of magnetic resonance imaging and spectroscopy. He has contributed to the development and application of fast imaging techniques, spectroscopy and spectroscopic imaging methods, advanced diffusion imaging schemes and unique approaches to the study of MR relaxation. All stem from a longstanding interest in applying quantitative MR methods for tissue characterization and for understanding the MR signals from tissue from a scientific perspective. In today’s lecture he hopes to impart some of the motivation for this longstanding interest by reviewing the “excited state” of MR relaxation studies he encountered in the very early days of MR at the Brigham and Women’s Hospital with Ferenc Jolesz and his colleagues. He will then focus on sustained efforts through the present in the measurement, understanding and application of transverse relaxation processes in tissue, culminating in a method for extracting metabolite T2 values from brain or muscle in vivo from one single spectroscopically sampled spin echo.