The concept of the image and its mathematical description. Mathematical and physical discussion of image characteristics: contrast, geometric resolution, noise, detection quantum efficiency, modulation transfer function, signal-to-noise ratio. Imaging methods: transmission, emission and excitation techniques. Imaging with gamma photons. Gamma radiation sources. Projection radiography: stages of imaging and mathematical modelling. Parameters of conventional film-based and electronic systems. Transmission tomography: measurement of projections and review of reconstruction algorithms (analytical-algebraic and model-based). Factors influencing the image characteristics. Emission tomography: SPECT and PET. Overview of scanning and emission image reconstruction algorithms. Factors influencing the image characteristics. Nuclear medicine. Physics and techniques of magnetic resonance imaging (MRI). Ultrasound imaging procedures. Comparative complex evaluation of imaging procedures.