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December 1947


Author Affiliations

From the Wilmer Ophthalmologic Institute of the Johns Hopkins Hospital and University.

Arch Ophthalmol. 1947;38(6):827-830. doi:10.1001/archopht.1947.00900010850008

THE VALUE of beta irradiation in the treatment of certain ocular lesions is well recognized, but the difficulty in obtaining the radon for the Burnam applicator has greatly limited its use. Accordingly, a beta ray radium applicator was designed which would as nearly approach as possible the performance of the Burnam applicator. In order to understand the use of this radium applicator, the differences between radon and radium must be appreciated and the construction of the applicator understood.

Radon is a gas, a breakdown product of radium, and one hundred thousand times as active, weight for weight, as the radium in the form of salt. It is thus possible to concentrate in a very small space an extremely high potential of radioactivity. The breakdown rate of the radon is extremely rapid, as the half transformation time is 3.83 days. In the Burnam applicator a radon seed of 5 mm. diameter,

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