The Beginning of Nuclear Medicine
courtesy of : http://www.aip.org/history/lawrence/
Ernest Lawrence, invented cyclotron a machine that accelerated atoms and creates radioisotopes, in 1930 at UC Berkley's Donner Lab. The Cyclotron consists of two large dipole magnet designed to produce a semi-circular region of uniform magnetic field These are called Ds because of their D-shape. The two D's are placed back-to-back with their straight sides parallel but slightly separated. An oscillating voltage is applied to produce an electric field across this gap. Particles are injected into the magnetic field region of a D trace out a semicircular path until they reach the gap. The electric field in the gap then accelerates the particles as they pass across it. The particles now have a radioactive isotope so they follow a semi-circular path in the next D with larger radius and so reach the gap again. The electric field frequency must be just right so that the direction of the field has reversed by their time of arrival at the gap. The field in the gap accelerates them and they enter the first D again. Thus the particles gain energy as they spiral around. The trick is that as they speed up, they trace a larger arc and so they always take the same time to reach the gap. This way a constant frequency electric field oscillation continues to always accelerate them across the gap. The limitation on the energy that can be reached in such a device depends on the size of the magnets that form the D's and the strength of their magnetic fields.
courtesy of http://www2.slac.stanford.edu/vvc/accelerators/circular.html
The Father of Nuclear Medicine
courtesy of http://www.lbl.gov/Science-Articles/Archive/nuclear-med-history.html
Ernest Lawrences brother, John Lawrence, recognized the cyclotrons potential to be use in medicine and started at UC Berkley's Donner Laboratory circa 1936. Treating a patient with leukemia, he administered a radioactive isotope of phosphate. It was the first time that a radioactive isotope had been used in the treatment of a human disease as well as the start of a career-long contribution from John Lawrence. He became known as the father of nuclear medicine and his laboratory is considered the birthplace of this field.