Seeds (ca. 1940s to 1960s)
These metal "seeds" contained a radioactive material and were intended to be permanently implanted into a tumor or other diseased tissue. The seeds shown in the photo are of two kinds. The single gold seed, immediately below the penny, would have been filled with radon. The rest of the seeds are made of titanium. They were probably used to hold iodine-125.
Today, the two radionuclides most commonly used in implantable seeds are iodine-125 and palladium-103. They are primarily used to treat prostate cancer. Gold-198, and to a far lesser extent, cobalt-60, have also been used.
Radon seeds were usually 0.75 to 1.0 mm in diameter and 4 to 7.5 mm long. They were made by filling a hollow 24K gold tube (ca. 0.3 mm wall thickness) with radon and using pliers to pinch the tube off into the appropriate lengths. The activities might range from 0.05 to 5 millicuries per seed. Since radon has a 3.8 day half-life, it was common to leave the gold seeds in the patient permanently. Nevertheless, they would contain some residual activity due to the long lived radon decay product lead-210.
The idea of using gold originated with Gino Failla (ca. 1920) at Memorial Hospital in New York. Until then, radon had been sealed in glass, but the betas emitted by the radon decay products caused necrosis of the tissue in the immediate vicinity of the seeds. Gold, on the other hand, filtered out the betas while still allowing the gamma rays (which did the real work of killing off the diseased tissue) to escape.
Radon seeds were implanted in a wide range of tissues: cervix, mouth, tongue, tonsils, rectum, bladder, etc. In the 1960s, radon seeds fell out of favor and were replaced with gold-198 grains.
Learn more about the bad things that could happen when spent gold seeds were recycled.
- U.S. Public Health Service. Radiological Health Aspects of Spent Radon Seeds. radiological health Data and Reports Vol. 10 (5) p.185-190. 1969.
- Radium Chemical Company catalog. Radium Radon. No date. ca. 1940s, 1950s.
- E.R.N. Grigg. The Trail of the Invisible Light. Charles C Thomas. Springfield. 1965.
- Richard Mould. A Century of X-rays and Radioactivity in Medicine. Institute of Physics Publishing. Bristol. 1993.
- Walter Murphy. Radiation Therapy. W.B. Saunders Company. Philadelphia. 1959.