Right choice is (a) Gamma Camera
The best explanation: A gamma camera had detectors made of PMTs to help form an image. Since PET produces 2 photons/gamma rays, correlation of the image formed at the two ends is used to form a proper image. However, SPECT produces only 1 photon so if they need to be collected properly to form an image. Thus, a gamma camera, a camera specializing in capturing images by taking the impulses from the photons in used in SPECT.