Patent ID: 8062203

Claim:
A method for attenuating radiation selectively to protect sensitive patient tissues during a brachytherapy radiation treatment, comprising: selecting a catheter for delivery of ionizing radiation and an ionizing radiation source carried by the catheter, selecting an attenuator mask to mask a portion of radiation from the source, the selection based on the radiation to be delivered and the presence of sensitive tissue within the region of radiation that will need protection from over-radiation, placing the attenuator mask so that the mask is supported on or to be adjacent to the catheter, by fixing the mask to a catheter element that is interposed over and surrounds the radiation source, positioning the catheter and mask properly to attenuate radiation at one or more specific locations relative to the radiation source, the mask comprising a discrete attenuating spot between the source and the specific locations, such that the mask will throw a limited-angle attenuation shadow toward tissue to attenuate radiation within a selected volume that includes tissue to be protected, the selected volume being a small part of total volume surrounding the source, the attenuator mask including an attenuating material with atomic number in the range of 40 to 53, and irradiating target tissue with the catheter within a patient while masking the sensitive tissue using the attenuator mask, whereby the mask attenuates the radiation by a desired constant factor essentially consistently throughout the distance range of the radiation in the direction of said specific locations.