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Clinical Radiation Dosage, Part III: A Biological Factor in Radon and Isotope Dosage

Radiation Therapy Department, Johannesburg General Hospital

This excerpt was created in the absence of an abstract.

It has been shown that when relatively short-lived radioactive sources are used in therapy, there is a critical interval of time during which the biological efficacy is approaching a maximum. Clinical dosage prescriptions must be calculated for this critical interval. Doses based on longer or shorter time intervals are likely to prove excessive. A formula is given whereby the critical biological interval can be determined for isotopes having various half-lives; and a nomogram relates tissue tolerance and cancer lethal doses to the half-life of the -ray source used. It is suggested that permanent implants of moderately long-lived sources may have certain clinical advantages.