Leonidas D. Marinelli

Marinelli was born of Italian parents in Buenos Aires, Argentina, on November 28, 1906, eldest son of 6 children of bank owner Vincenzo Marinelli and Amelia Sammartino Marinelli. He was age 11 when his father died of a heart attack and he returned with his widowed mother and her children to the family seat in Agnone, Italy, where the Marinelli family established their bell foundry in the 12th century. Leonidas graduated the Volta Institute of Naples, October, 1925, with highest honors and a gold Queen Victoria coin. Two months after his nineteenth birthday, he emigrated to New York City and supported himself as a meter tester while working his way through Cooper Union Night School of Electrical Engineering. In 1929 he was hired by Dr. Gioacchino Failla, former student of Marie Curie, to the biophysical laboratory at Memorial Cancer Hospital, New York City, known today as Memorial Sloan Kettering Cancer Center). Hardly a year later, Leonidas measured the gamma ray intensities of radium, previously unquantified, in electrostatic units which were convertible to the x-ray roentgen unit. This made possible the comparison of xrays and gamma rays, later useful to evaluations of cancer therapies. By 1933 he coauthored his first publication with Failla, Edith Quimby, and John E. Rose. In 1935 he became Assistant Physicist. In 1938 he completed all course requirements for the PhD at Columbia University and had published 5 papers in radiological journals.

In the 1940s Marinelli became an independent scientist. In 1941 his papers dealt with post-irradiation blood studies and with early tracer work on cancer; in 1942 with the production of chromosomal breaks in plant cells and with the theory of time distribution of radiation treatments. In February, 1942, he published the theoretical basis for internal radiation dosimetry that provided the basis for nuclear medicine. In 1946, he published its systematic application to the radioactive treatment of functional cancer of the thyroid. This breakthrough was followed by autoradiography techniques and by a Review of Modern Physics report on beta rays. The explosive growth of radiation medicine enlarged his responsibilities as Head of Physics at Memorial-Sloan Kettering Institute. In 1948 he added to his publication of internal radiation dosimetry the supplementary biological considerations contributed by Edith Quimby.

In 1948 he moved to the Argonne National Laboratory, with a position on the University of Chicago faculty. Here, with John Rose, he provided early leadership and scientific direction of the Radiological Physics Division and concurrently the Biology and Medical Ressearch Division.[12]

He authored review articles on dosimetry in the Annual Review of Nuclear Science, in Radiation Biology, and in the Handbook of Medical Radiology. His studies of physics dealt now with electron diffusion from point sources in air, and with the cosmic ray background. In radiology he pioneered the detection of minimal burdens of radioactivity in humans, studying their distribution and variation in tissues and the epidemiology of chronic low levels of radiation[13] The Center for Human Radiobiology, which now has the responsibility for all AEC-supported research on the effects of internally deposited radioisotopes, grew out of his effort.[14]

In 1950, Marinelli pioneered the Whole Body Counter, a low-level gamma-ray detector, and applied it to study the long-term effects of radium in people injected with radium in the 1920s and 1930s.[15] The WBC used thallium-activated sodium iodide crystals.[16] In radiology, he detected radium distribution and variation in tissues, and the epidemiology of chronic low levels of radiation[17]

US Patent 2,795,703A - Isadore B. Berlman and Leonidas D. Marinelli, "Apparatus for counting fast neutrons in the presence of gamma rays", issued 1957, applied for 1954. Under military supervision, this patent was assigned to the Atomic Energy Commission.[18]

Marinelli devised and applied the “twin” scintillator method for the dosimetry and spectrometry of fast neutrons to the measurement of cosmic neutron background. In 1955, he developed sensitivity of the method to measure the body’s total natural potassium (K-40) content. His spectrometric method was copied in many laboratories throughout the world and has yielded insights into the human metabolisms of many elements and their compounds.[19]

• Marinelli Road in Rockville, Maryland is named in his honor and the site for the US Nuclear Regulatory Commission headquarters office.

• 1958 Janeway Medal awarded by the American Radium Society. Janeway Lecture: Radioactivity in Man
• 1951 Radiological Society of North America: Certificate of Merit: Exhibit on Radium Toxicity
• 1952 American Academy of Orthopaedic Surgeons: Scientific Exhibit on Clinical Investigation of Radium Toxicity.
• 1964 Failla Memorial Lecture: New York Chapter of Health Physics Society
• 1978 “Biological Effects of Ra-224 and Thorotrast,” Proceedings of the International Symposium, at Alta, Utah, 21 – 13 July 1974, dedicated to “Leonidas D. Marinelli, 1906-1974.” (Health Physics Journal, July, 1978, Vol. 35, 5-6. Editor, Charles W. Mays. Pergamon Press, New York, 1978.)