Intra-lumen polyp detection

An apparatus, comprising:

• a capsule configured to be swallowed by a subject and to pass through a gastrointestinal (GI) tract of the subject, the capsule comprising:
• a capsule housing;
• at least one radiation source configured to emit radiation from the capsule;
• a rotatable collimator configured to rotate with respect to the housing and to collimate the radiation emitted by the at least one radiation source;
• at least one radiation detector positioned next to the collimator and coupled with the collimator to rotate together, the radiation detector being configured to detect radiation comprising particles generated responsive to the radiation emitted from the capsule, wherein the generated particles that are detected are directed back toward the radiation detector and collimator in an opposite direction of the radiation emitted from the capsule;
• electronic circuitry programed to serve as a control unit to analyze data regarding the detected particles;
• and
• a shield for covering and uncovering the radiation source, the shield is configured to rotate with the collimator and detector and comprises wings that cover openings on the shield, the wings are configured to rotate open and expose the radiation source;
• wherein the wings are disposed on the shield, within the capsule housing to avoid contact with walls of the gastrointestinal tract;
• and wherein the wings are held closed by a spring when the shield is not rotating.