Tumor Incidence in Rat Skin Following Proton Irradiation in a Sieve Pattern.

Abstract

The dorsal skin of 183 male, albino rats was irradiated with 8.0 Mev protons at various doses in a uniform pattern and at two doses in sieve patterns with pore diameters of 5.0 mm, 2.0 mm and 0.5 mm. The depth-dose curve of the proton beam was modified so that it was approximately linear with a maximum penetration of about 0"8 mm. Skin lesions were noted every 4 weeks for 80 weeks and at the end of the experiment were examined histologically.The results indicated that the sieve pattern did not significantly affect the tumor incidence per unit irradiated area or the incidence of damaged hair follicles at any pore size. This contrasts ---' to the results of earlier experiments with electrons where a sieve pattern produced a significant protective effect at a pore diameter of 2.5 mm. Possible explanations for this discrepancy are discussed.'. \ 4t'7.

Tumorigenic action of beta, proton, alpha and electron radiation on the rat skin

“…Whether tumor incidence is proportional to the amount of tissue irradiated was studied by irradiating rat skin in grid and sieve patterns of various pore sizes with electrons, protons and low energy X-rays. A consistent finding was the localized dose patterns were less oncogenic than uniform patterns for low linear energy transfer (LET) radiation, electrons (2) and X-rays (4), but not for high LET protons (9). It was estimated from geometrical considerations that the interaction distance between irradiated and unirradiated tissue was approximately 170 microns and mice are less sensitive.than rats (10).…”

TUMORIGENIC ACTION OF BETA, PROTON, ALPHA, AND ELECTRON RADIATION ON THE RAT SKIN. Progress Report, August 1, 1971--July 31, 1972.

“…In previous work under the present contract, a number of significant results have been obtained which will now be summarized (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16) . For rat skin in the resting phase of hair growth, skin tumors were produced only if the radiation penetrated at least to a depth of about 0.3 mm which roughly corresponded to the depth of the follicles (3).…”

“…The tumor incidence per unit irradiated area was found to be: less for a sieve pattern•than for a uniform pattern for electron irradiation • (2), but for protons which have a relatively high LET the sieve pattern did not produce a reduction of the tumor incidence (11). In all experiments a correlation was found between the incidence of atrophic follicles and the incidence of tumors…”

“…A paper was published which•described the effect of proton irradiation in a sieve pattern on the incidence of skin tumors (11).…”

Tumorigenic action of beta, proton, alpha and electron radiation on the rat skin. Progress report, August 1, 1977--January 31, 1979

“…A consistent finding was that localized dose patterns were less oncogenic than uniform patterns for low linear energy transfer (LET) radiation, electrons (2) and X-rays (4) , but not for high LET Rrotons (9) • It was estimated from geometrical considerations that the interaction distance between irradiated and unirradiated tissue was approximately 170 microns.…”