65

The History of Bioelectromagnetism

constant magnetic feld are perturbed by a weak oscillating magnetic feld. Purcell and Bloch shared

the Nobel Prize in Physics in 1952 for their development of new methods for nuclear magnetic precision

measurements and other discoveries in connection.

In 1971, Raymond Vahan Damadian, an American physician and inventor, observed the diference

of the relaxation times between tumors and normal tissues and proposed the use of NMR as imaging

for the detection of cancer (Damadian, 1971). In Japan, during the 1970s, using NMR, Zenmon Abe

(1914–1999), professor at Hokkaido University, Sapporo, and his co-workers proposed and measured

non-invasively biological imaging information by a magnetic focusing method (Abe et al., 1974). Te

basic principle and the technical development of image formation using of NMR was proposed by Paul

Christian Lauterbur (1929–2007), professor at the University of Illinois, USA, and Sir Peter Mansfeld

(1933–2017), professor at the University of Nottingham, UK (Lauterbur, 1973; Mansfeld, 1977). Teir

fundamental concept of NMR is the combination of high static magnetic felds and a gradient (time­

varying) magnetic feld. Afer this invention, they won the Nobel Prize in Physiology or Medicine in

2003 for their discoveries concerning “Magnetic Resonance Imaging.” Te root of MRI is widely known

as NMR. However, to avoid alarming medical experts and the public, the word “nuclear” was deleted

from the term “Nuclear Magnetic Resonance,” although it has nothing to do with radioactivity.

Te actual operation of MRI utilizes basically three diferent types of electromagnetic felds: a high

static magnetic feld, a rapidly changing gradient magnetic feld, and a RF electromagnetic feld. Te

high static magnetic feld is the main magnetic feld in MRI, and is usually generated by a strong super­

conducting magnet. Te gradient magnetic feld with frequencies in the kHz range is used to localize

aligned protons in the image reconstruction process. Te RF electromagnetic felds in the range from 10

to 400 MHz are used to excite the protons within the stable magnetic felds.

Magnetic Resonance Spectroscopy (MRS) is based on in vivo NMR and is also a non-invasive imaging

technique that permits in vivo measurements and quantifcation of the concentration of neurochemical

metabolites. Kurt Wüthrich, professor at the Swiss Federal Institute of Technology (ETH) in Zurich,

Switzerland, won the Nobel Prize in Chemistry in 2002 for his development of NMR spectroscopy for

determining the three-dimensional structure of biological macromolecules in solution. Koichi Tanaka

of Shimazu Corporation shared with Wüthrich the 2002s Nobel Prize in Chemistry for his development

of sof desorption ionization methods for mass spectrometric analyses of biological macromolecules.

Te clinical application of MRS is reviewed by Faghihi (2017). He emphasizes that the in vivo MRS is

a key technique for the investigation of human metabolism. For the development of two-dimensional

NMR spectroscopy, Richard Ernst (1933–2021), professor at ETH in Zurich, won the Nobel Prize in

Chemistry in 1991 for his contributions to the development of the methodology of high resolution NMR.

Interestingly, until now, the invention of NMR and its fundamental research and applications led to 13

Nobel Prizes in Physics, Chemistry, and Physiology or Medicine (Boesch, 2003; Kaufman, 2014).

Te technique to measure brain activity by measuring the cerebral blood fow (CBF) goes back to the

time when Charles Smart Roy (1854–1897), professor of Pathology at the University of Cambridge, and

Charles Scott Sherrington (1857–1952), a British neurophysiologist, reported using dogs, cats, and rab­

bits that changes of CBF refect the neural activity of the brain (Roy and Sherrington, 1890). Tey char­

acterized the relationship between CBF and brain function. Teir observation means that CBF changes

refect tight coupling between cellular energy requirement and vascular delivery of glucose and oxygen

(Lin et al., 2010). Te measurements of brain functions that are made today are based on this report.

Later, in 1932, Sherrington along with Edgar Douglas Adrian (1889–1977), a British neurologist, won the

Nobel Prize in Physiology or Medicine for their discoveries regarding the function of neurons. When

the activity of various functions occurs in the brain, the CBF and metabolism increase in association

with that activity. Te changes are spatially coincident with the site where the neural activity occurred.

By measuring these changes in CBF and metabolism, we can study the functions of the brain.

Tissues are lined with blood vessels that supply oxygen. Te blood reaches the veins from the arter­

ies through the capillaries. Te red blood cells in blood have a lot of hemoglobin, which carries oxy­

gen. Tis hemoglobin is diamagnetic when bound to oxygen molecules, but becomes paramagnetic