Patent ID: 7604405

Claim:
A quality assurance marker for determining alignment of an image guided radiation treatment delivery system, comprising: a housing being translucent to a radiation beam of a therapeutic radiation source of the radiation treatment delivery system and translucent to an imaging guidance system of the radiation treatment delivery system; a void within the housing to support an alignment target being opaque to the therapeutic radiation source for casting a shadow in an exposure image of the quality assurance marker, wherein the void comprises a spherical void to support a spherical target; and a ring void within the housing to support a ring target being opaque to the therapeutic radiation source, wherein the ring void comprises a first ring void and the ring target comprises a first ring target, the quality assurance marker further comprising: a second ring void within the housing to support a second ring target being opaque to the therapeutic radiation source, wherein the first and second ring voids are positioned to have first and second ring axes aligned with a trajectory passing through a center of the spherical void; and wherein ring centers of the first and second ring voids have a diameter larger than the spherical void.