ABSTRACT
Ultrasound, magnetic resonance, endoscopic procedures, and other sources of information are competing with X-rays and in many cases delivering complementary information. Clinical routine requires robust, easy-to-use, cost-effective solutions, which fit the overall workflow. X-ray imaging has been one of the well-developed modalities and is still improving. Ultrasound, and echocardiology, has been taking a dramatic development path as well. Miniaturization of probes, color Doppler methods, cost-efficient use, immediate availability in consulting rooms without the necessity of magnetic or X-ray shielding, the lack of ionizing radiation, or rapid changes of the magnetic flux, which may heat metal implants, make this modality extremely attractive. During the sequence of passage of the beam through a composite object, not only does the intensity diminish but also its spectrum successively hardens, as the strength of attenuation is monotonically falling with the energy for most part of the spectrum.
