Electrocardiography

At around the same time, Ian Donald of the Glasgow Royal Maternity Hospital struck up a relationship with boilermakers Babcock & Wilcox in Renfrew, where he used their industrial ultrasound equipment to conduct experiments assessing the ultrasonic characteristics of various in vitro preparations. With fellow obstetrician John MacVicar and medical physicist Tom Brown, Donald refined the equipment to the point where it could be used successfully on live volunteer patients. These findings were reported in The Lancet on June 7, 1958 as "Investigation of abdominal masses by pulsed ultrasound."

Nuclear magnetic resonance (NMR) in molecules was first described by Isidor Rabi in 1938. His work was followed up eight years later by Felix Bloch and Edward Mills Purcell, who, working independently, noticed that magnetic nuclei such as hydrogen and phosphorus, when placed in a magnetic field of a specific strength, absorb radio-frequency energy, a situation described as being " in resonance."

For the next 20 years NMR found purely physical applications in chemistry and physics, and it was not until 1971 that Raymond Damadian showed that the nuclear magnetic relaxation times of different tissues, especially tumors, differed, thus raising the possibility of using the technique to detect disease. Magnetic resonance imaging (MRI) was first demonstrated on small test tube samples in 1973 by Paul Lauterbur, and in 1975 Richard Ernst proposed using phase and frequency encoding and the Fourier transform, the technique that still forms the basis of MRI.

The first commercial nuclear magnetic imaging scanner allowing imaging of the body appeared in 1980 using Ernst's technique, which allowed a single image to be acquired in approximately 5 minutes. By 1986, the imaging time was reduced to about 5 seconds without sacrificing too much image quality. In the same year, the NMR microscope was developed, which allowed approximately 10-mm resolution on approximately 1-cm samples. In 1993, functional MRI (fMRI) was developed, thus permitting the mapping of function in various regions of the brain.

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