Brachytherapy, which is the implantation of sealed sources of radioactive material within a tumor, is one of the oldest methods for treating cancer by means of ionized radiation. Interstitial implants are used to treat tumors by inserting afterloading needles into tissue in the vicinity of a tumor and within the tumor itself. See L.W. Brady: Modern Brachytherapy, Masson Ed. Paris, New York, 1987; J.C. Jalabert: Application Methods and Materials of Brachytherapy by Iridium 192, Henri Mondor Hospital.
When straight needles are used, they are usually spaced approximately at 1 to 1.5 cm apart and inserted deep into the tissues as parallel to each other as possible to achieve a uniform dosimetry; nevertheless a great deal of expertise is required for adequate needle placement. In addition, tissue swelling adds significant distortion to the needles, rendering a potentially good implant inappropriate.
The invention described herein provides an accurate radiation dose distribution. The resulting invention provides a shorter operating time with a resulting lessening in risk to the patient during implantation; lower expense; standardization of the dosimetry; elimination of the need for orthogonal films to determine the dosimetry; and less radiation exposure to the implanting physician because of faster loading of the radioactive source into the invention.