A radiation imaging apparatus irradiates a subject with a radioactive ray emitted from a radiation generation unit to capture a radiographic image based on a radioactive ray that has penetrated through the subject. Upon dislodgement, a user may be provided with guidance to help reposition and secure the navigational reference to the initial reference location, or the navigational reference may be automatically repositioned and secured to the initial reference location. The cushion upper half portion has a tubular inflated pillow region that extends toward the occupant further than the tubular inflated ring surrounding the central unfilled region, to thereby provide an enlarged pillow surface for supporting the occupant head. A processor and sensor provide for detection of relative positions between the units. The preprocessed face images are preferably used to train a neural network ensemble having a first stage made up of a bank of face recognition neural networks each of which is dedicated to a particular pose range, and a second stage constituting a single fusing neural network that is used to combine the outputs from each of the first stage neural networks. After demodulating the digital frequency-modulated signal for generating the signal’s amplitude and differential phase value, the amplitude of the demodulated signal is compared with a constant at determined sampling times.