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Cobalt therapy is the medical use of gamma rays from the radioisotope cobalt-60 to treat conditions such as cancer. Beginning in the 1950s, cobalt-60 was widely used in external beam radiotherapy (teletherapy) machines, which produced a beam of gamma rays which was directed into the patient's body to kill tumor tissue.
It is estimated that almost 80 percent of people received a dose less than 500 mrem (equivalent to 5 mSv); 18 percent, between 0.5 and 25 rems (5–25 mSv); and only two percent (about 80 people) received doses greater than 25 rems (250 mSv). Of these, five people received a dose between 300 and 700 rems (3–7 Sv) over a period of two months. [3]
Between March and July 1962, a radiation incident in Mexico City occurred when a ten-year-old boy took home an industrial radiography source that was not contained in its proper shielding. Five individuals received significant doses of radiation from the 200- gigabecquerel cobalt-60 capsule, [1] four of whom died. [2]
Cobalt-60 (60 Co) is a synthetic radioactive isotope of cobalt with a half-life of 5.2714 years. [ 3 ] [ 4 ] : 39 It is produced artificially in nuclear reactors . Deliberate industrial production depends on neutron activation of bulk samples of the monoisotopic and mononuclidic cobalt isotope 59
The dose is fractionated to about 2 Gy per day for curative treatment, which allows normal tissues to undergo repair, allowing them to tolerate a higher dose than would otherwise be expected. The dose to the targeted tissue mass must be averaged over the entire body mass, most of which receives negligible radiation, to arrive at a whole-body ...
e. Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m 2, resulting from mass in kilograms (kg) and height in metres (m). The BMI may be determined first by measuring its components by means of a ...
Cobalt-60 Teletherapy Capsule. The radiotherapy accident in Costa Rica occurred within the Alcyon II radiotherapy unit at San Juan de Dios Hospital in San José, Costa Rica. It was related to a cobalt-60 source that was being used for radiotherapy in 1996. An accidental overexposure of radiotherapy patients treated during August and September ...
In 1974, Axt calibrated a cobalt-60 teletherapy unit with an incorrect decay curve. The calculated decay rate was more rapid than the real source, leading to a dose rate underestimated by 10–45% and an overestimated treatment time. [2] [3] No other calibrations and checks were performed between May 1974 and January 1976. Axt later attributed ...