- Person
- Robert Hofstadter
- Lived
- 1915–1990
- Field
- Physics
- From
- American
The story
Robert Hofstadter was born in Manhattan in 1915 to Polish Jewish immigrants and studied at the free City College of New York before taking his doctorate at Princeton. After war work at the National Bureau of Standards, he returned to Princeton in 1946 and set out to build better detectors for gamma rays, the high-energy light given off by radioactive atoms.
Scientists knew that some organic crystals give off a tiny flash of light when struck by radiation, and that a light-sensitive tube could count the flashes. Hofstadter, an expert on solid crystals, tried inorganic salts instead. In 1948 he found that sodium iodide activated with a little thallium was an excellent scintillator, and he filed a patent that year. The crystal is transparent to its own light, it is dense, and iodine is a heavy atom that stops gamma rays well. In 1950, with J. A. McIntyre, he showed that well-formed crystals could also measure the energy of each gamma ray, so they could tell one radioactive substance from another.
Thallium-activated sodium iodide became one of the most widely used radiation detectors in the world, and it is still the standard scintillator for gamma-ray detection. Its most familiar use is in nuclear medicine. A gamma camera contains a large flat crystal of the material that records the gamma rays coming from a radioactive tracer given to a patient. Doctors use these cameras for cardiac stress tests, lung scans and SPECT imaging, in which detectors rotate around the body to build three-dimensional pictures of organs and blood flow.
When President Reagan presented Hofstadter with the National Medal of Science in 1986, the citation credited him with developing the sodium iodide scintillation counter and noted its use across science and technology, including imaging in medicine. Hofstadter, who won the 1961 Nobel Prize in Physics for measuring the size and structure of the proton and neutron, never lost his love of detectors, and in later years he worked on sodium iodide arrays for particle physics and on NASA’s EGRET gamma-ray telescope.
Why it matters
Every gamma-camera heart scan, lung scan or SPECT image relies on the sodium iodide crystal detector that Hofstadter discovered in 1948.
About Robert Hofstadter
Stanford physicist who invented the sodium iodide gamma-ray detector still used in hospital gamma cameras, and first measured the size and shape of the proton and neutron.
More about Robert Hofstadter
Sources
- Gamma camera Wikipedia
- Robert Hofstadter, Biographical Memoirs vol. 79 National Academy of Sciences
- Robert Hofstadter, National Medal of Science National Science Foundation
- Robert Hofstadter, Biographical NobelPrize.org
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.