Radon seeds

Radon can be isolated from radium by several methods. An aqueous solution of radium salt such as radium bromide is heated, liberating radon. Radioactive bombardment then decomposes water to oxygen and hydrogen. Radon is separated from the gaseous mixture by condensation in tiny tubes placed in liquid air. The tubes then are sealed by melting. A gold or platinum coating is applied to form the radon seeds used in radiation therapy. 

Medical uses of radon in the United States began as early as 1914. Treatments were primarily for malignant tumors. The radon was encapsulated in gold seeds and then implanted into the site of malignancy. During the period of 1930 to 1950, radon seeds were used for dermatological disorders, including acne. 

First he had to shift his laboratory to a different part of the Cavendish building, and that delayed him then he had to prepare a strong polonium source. In the matter of polonium he was lucky. Norman Feather had spent the 1929-30 academic year in Baltimore, in the physics department at Johns Hopkins, and there befriended an English physician who was in charge of the radium supply at Baltimore s Kelly Hospital. The physician had stored away several hundred used radon seeds together, Feather remembers, they contained almost as much polonium as was available to Curie and Joliot in Paris. The hospital donated them to the Cavendish and Feather brought them home. Chadwick accomplished the dangerous chemical separation that autumn. 

Example 1 Radon seeds, radon collected from radium bromide and sealed in capillary tubing, are used for cancer therapy. The half-life for radon, Wn- g Po -f- JHe, Is 3.825 days, (a) Starting wifo 0.0200 mg, how many milligrams will remain after 11,475 days (b) A radon seed initially emitted 7.0 x lo a particles per second it now emits 2.1 X 10 a particles per second. What is the age of the seed ... 

Radon, sealed in small capsules called seeds , has been used as a radioactive substance in medicine, but is being superseded by more convenient artificially-produced radioisotopes. 

Radon is still produced for therapeutic use by a few hospitals by pumping it from a radium source and sealing it in minute tubes, called seeds or needles, for application to patient. This... 

Radon is used in implant seeds for the therapeutic treatment of localized tumors. Radon is found in the atmosphere with a concentration estimated to be 1 in 10 parts of air. 

L.A. Braby (Pacific Northwest Laboratories) is studying the malignant transformation of mammalian cells exposed to alpha particles that pass through the cell nuclei in an attempt to elucidate the mechanisms of action of radiation. The mechanisms of cell killing by alpha particles (M. Raju, Los Alamos Laboratories), cell neoplastic transformation from alpha particles (S.B. Curtis, Lawrence Berkeley Laboratory), and pulmonary tissue injury from radon/radon daughter exposure (T.M. Seed, Argonne National Laboratory) are also under investigation. 

Radon has been produced commercially for use in radiation therapy but for the most part has been replaced by radionuclides made in accelerators and nuclear reactors. Radiopharmaceutical companies and a few hospitals pump the radon from a radium source into tubes called "seeds" or "needles" which may be implanted in patients (Cohen 1979). Research laboratories and universities produce radon for experimental studies. 

Marie Curie s Radium Institute at the east end of the Rue Pierre Curie in the Latin Quarter, built just before the war with funds from the French government and the Pasteur Foundation, had the advantage in any studies that required polonium. Radon gas decays over time to three only mildly radioactive isotopes lead 210, bismuth 210 and polonium 210, which thus become available for chemical separation. Medical doctors throughout the world then used radon sealed into glass ampules— seeds —for cancer treatment. When the radon decayed, which it did in a matter of days, the seeds no longer served. Many physicians sent them on to Paris as a tribute to the woman who discovered radium. They accumulated to the world s largest source of polonium. 

Mineralization probably occurs both by increasing the size of the seed and by the formation of new crystals. It is not known how much each one of these processes contributes to mineralization. Some indirect evidence for the increase in crystal size has been obtained. Animals whose bones contain radium in the mineral phase exhale less radon—a gas derived from the disintegration of radium—as they increase in age. The radium in the bone is found within the lattice of the crystal. If the crystal size is considerably increased, then instead of blasting its way through the crystal, the radon remains trapped inside the crystal. 

From experimental beginnings, radiation therapy soon developed into a separate branch of medicine, with its own specialists, practices, and standards. X-rays had to be applied from an external machine, but radium could be introduced right into the patient. This approach, known as brachytherapy, was pioneered early in the century. The radium was put in gold needles that were inserted into cancerous tissue, in tubes that were placed in body cavities, or in moulds applied to the outside of the body. During tumour surgery, doctors permanently implanted gold capsules, or seeds, filled with short-lived radon to help kill residual cancerous cells. 

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