A Lanthanum Halide scintillator with fast decay time and good timing resolution, as well as high light output and good energy resolution, is used in the design of a PET scanner. The rear plate and the exhaust pipe are sealed by a sealed part obtained by melting a tablet made of amorphous frit glass not containing lead, and a stress working on the sealed part is a tension in the direction of the rear plate and the direction of the exhaust pipe. This allows the user to remain in one position while viewing different parts of the displayed scene corresponding to different viewpoints. The read channel comprises a differentiation circuit for converting the read signal output from the GMR element into the differentiated read signal. The flexible diaphragm is coupled between the cap and the valve housing and is movable from a closed position to an open position.