Opacity to the X-ray of silica glasses incorporated with lead

Brachytherapy is a procedure that involves the implantation of radioactive seeds directly into the tumor region, allowing patients to receive higher radioactive dose than is possible with external irradiation with less normal tissue damage. The location and orientation of the seeds in the tumor region are determined through opacity to X-ray by radiographic techniques. For this purpose, some metals such as silver, gold and lead are used. In this work, the procedure of obtention of silica-lead glasses employing sol-gel process with tetramethyl-orthosilicate as precursor, HNO3 as catalyst and lead nitrate as simulator element of opacity to X-ray is presented. The opacity to X-ray was evaluated for samples with different lead contents through optical density of radiographic images. The nitrogen adsorption and mercury pycnometer techniques were employed for structural characterization of the glasses. The process parameters obtained here will be valuable to develop seeds of iodine-125. (author)