A torque detection apparatus includes a resolver having a rotor core and a stator core, and a computation unit having a multiple rotation amount computation section, a multiple rotation amount accumulation section, and an abnormality determination section. The distal section of the catheter is quite flexible yet it has sufficient transverse or radial rigidity to prevent significant distortion of the transverse cross-sectional shape of the catheter. The method determines areas with both low color gradient values and high relative intensity. Wavelength selection element 19 has pixels arranged in lattice pattern, for bringing a pixel at a position corresponding to to-be-selected channel and wavelength into a reflective state. In another technique, parameters employed to trigger the recording of diagnostic data are adaptively modified to reduce the likelihood of any unnecessary recording of such data.