Provided is a PET scanner system having a PET scanner gantry that is configured for delivering a uniformly distributed cooling air to a plurality of detectors housed in the PET scanner gantry. The PET scanner gantry includes a cooling air delivery manifold that includes a patient tunnel portion; and a front funnel portion. The front funnel portion includes an annular interior wall defining an entry opening of the patient tunnel portion; and an air plenum has an annular structure for carrying a flow of pressurized cooling air received from a remote source supplements the pressurized cooling air with a supply of ambient air and directs it to the plurality of detectors.