DAILY INTERMITTENT MULTIPORTAL THERAPY FOLLOWED BY STEREOTAXIC BOOST (DIMT-SB) FOR TREATMENT OF SMALL INTRACRANIAL LESIONS: TECHNICAL ASPECTS AND PRELIMINARY RESULTS

A treatment technique has been developed for small intracranial lesions that preserves the high therapeutic ratio of dose fractionation and takes advantage of the preciseness of stereotaxic apparatus. The fixed-field conformational radiotherapy, which has been named, “daily intermittent multiportal therapy”(DIMT), utilizes sixteen to 32 ports for a target volume in a trans-axial single plane, irradiating two parallel opposed portals each treatment day. The total dose distribution is similar to conventional conformational rotation therapy, but the biological dose distribution is expected to be different because of the dose fractionation in space and time. An immobilizing plastic mask used in DIMT has been shown to preduce an accuracy of about 2 mm. Stereotaxic boost is given with a metal frame fixed to the skull following the DIMT. Localization of the treatment center by the metal frame has been demonstrated to be accurate to less than 1 mm. Examples of preliminary results of DIMT followed by stereotaxic boost (DIMT-SB) are given. No definite conclusion about clinical benefits is available yet, because of the few patients and short follow-up period.