Where is the collimator located in a gamma camera system?

Where is the collimator located in a gamma camera system?

• A. Behind the patient
• B. Detector face at photon entrance into camera
• C. Inside the PMT housing
• D. Around the scintillation crystal

Answer: (B)

The key idea is that the collimator sits right at the entrance of the detector, directly in front of the scintillation crystal. It’s a lead structure with holes that only allow gamma photons traveling along certain directions to reach the crystal. By being located at the detector face, it shapes the image by mapping incoming photon directions to specific crystal positions and blocking oblique photons that would blur the image. It isn’t placed behind the patient, inside the PMT housing, or around the crystal, because those placements wouldn’t control the incoming photon angles. So the correct location is at the detector entrance, attached to the detector face.

The key idea is that the collimator sits right at the entrance of the detector, directly in front of the scintillation crystal. It’s a lead structure with holes that only allow gamma photons traveling along certain directions to reach the crystal. By being located at the detector face, it shapes the image by mapping incoming photon directions to specific crystal positions and blocking oblique photons that would blur the image. It isn’t placed behind the patient, inside the PMT housing, or around the crystal, because those placements wouldn’t control the incoming photon angles. So the correct location is at the detector entrance, attached to the detector face.