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150th anniversary of the father of modern ultrasound

THE 150th anniversary of the birth of an eminent French physicist who is the father of modern ultrasound has been marked.

Paul Langevin was born on 23 January 1872 and in 1917, while working with the French and British navies, designed the first piezoelectric ultrasonic transducers using X-cut quartz.

Starting early in 1915, Langevin had worked with the French Navy on a scheme to use ultrasound in pulse-echo mode to locate U-boats. By February 1917, they had built working systems that generated beams of pulsed ultrasound at 100 kHz using mica transducers, and were working on a large area receiver using carbon granules.

But these early technologies could never have formed the basis for the ultrasonic science that resulted from Langevin’s next innovation.

Langevin knew of the Curies’ quartz piézo-électrique, still being used in Marie Curie’s laboratory for measurements on radioactivity. Early in 1917 he realised that if a quartz crystal could act as a piezoelectric receiver of ultrasonic waves, it had to be cut along a different plane, one of three parallel with the main crystal axis.

A few months later, he successfully used a similarly cut crystal as a source of a high intensity ultrasound beam.  Langevin’s discovery was disseminated to the Allied laboratories in Britain, Italy and the USA. By the end of the First World War, successful ultrasonic pulse-echo systems were being tested by both French and British navies.

Langevin published 20 papers and patents on ultrasonics and piezoelectricity between 1916 and 1935. He delivered the first ever course on ultrasonics at the Collége de France in 1923. He helped in the commercial development of an ultrasonic depth-sounder and anticipated the therapeutic use of ultrasound.

All modern medical ultrasound uses derive from Langevin’s pioneering work during WWI. He is honoured in France by his place in the Pantheon in Paris, alongside Marie and Pierre Curie.

More details about Langevin can be found in e-SCOPE for September 2008 and in the forthcoming spring issue of SCOPE.