The Value of a Multi-perforated Screen in Deep X-ray Therapy

Abstract

THE deleterious effect on the skin of delivering large doses of x-rays to an underlying tumor has been frequently the main deterrent to the successful treatment of malignancies. The method at present proposed to circumvent this difficulty is based on the fact, well known to all x-ray therapists, that when small areas of skin are treated, as in epitheliomas or verrucæ, large doses of radiation (from four to six erythema doses to an area 1 cm. in diameter) can be given with safety. Apparently the presence of adjoining normal tissue protects the small radiated area from vesiculation and ulceration. Taking advantage of this observation, the author began a study of the effects of radiating deep structures through numerous small areas simultaneously (say, from 200 to 400 areas per large portal). The radiation is delivered through a multi-perforator, a sheet of lead from 1.5 mm. to 2 mm. in thickness, with uniform perforations regularly spaced and comprising a definite percentage of the total square area. This perforated lead sheet is placed on the skin. The perforations obviously can be of different sizes and shapes, exposing more or less of the skin to direct radiation, and leaving greater or smaller isthmuses of normal skin, protected by lead, to act as centers of healing in case the radiation is of such magnitude as to cause ulceration of the radiated skin. Some of the designs tried out were as follows: 1. Strips of lead 1 cm. wide and 20 cm. long, 10 in number, fastened to a 20 × 20 cm. piece of celluloid, 1 cm. space between the strips of lead. This design was found not to be servicable on account of insufficient protection to the skin. 2. Lead squares, 1 × 1 cm. each, arranged in a checkerboard fashion, fastened to a piece of celluloid, alternating the lead squares with equal spaces. This method was found to be unserviceable on account of the difficulties of proper construction and insufficiency of protection. 3. A latticework effect in a sheet of lead, obtained by punching out squares, lozenge shapes, or hexagonal perforations, leaving an area of one-half the original area. This method has been found to be unserviceable when (1) the perforations are of 1 sq. cm. area, on account of too narrow, uniform isthmuses of protected skin, resulting in insufficient protection ; (2) when perforations are of less than 0.5 sq. cm. area, the angles interfering with delivery of maximum radiation, especially if the perforator has to be bent over the treated area, and forms an angle with a perpendicular to the central ray. 4. Round or oval perforations of varying sizes from 2 to 8 mm. in diameter, the perforated area comprising two-thirds, one-half, or one-fourth of the total area. This type is not difficult of construction and offers the maximum skin protection, especially if the perforations are less than 8 mm. in diameter.