Within the last few years, and especially since the introduction of the Coolidge tube, much has been accomplished in the establishment of suitable dosage for the therapy of superficial and benign skin lesions with the roentgen ray. The lethal dose for cancer cells, however, has not, so far as we are aware, been accurately determined for filtered rays of short wave length such as are now used for deep therapy. The experiments described below were, therefore, undertaken in 1916, with tissue growing in culture as well as in the living animal.
There is a distinct advantage in the use of animal tumors, as they furnish an easily reproducible standard for biologic calibration of the output of any roentgenray machine and of the effects of filters, while human material is extremely variable in its resistance to the rays, ranging from the basal-cell epitheliomas, which often yield to a single erythema dose,
WOOD FC, PRIME F. LETHAL DOSE OF ROENTGEN RAYS FOR CANCER CELLS. JAMA. 1920;74(5):308–312. doi:10.1001/jama.1920.02620050016006