[Echocardiography. Advantages and limitations related to unidimensional and bidimensional technics in real time].
Mode-M echocardiography is the most valuable non invasive technique in cardiology, but as a one-dimensional technique it displays the cardiac structure in an unfamiliar form without resemblance to the cardiac anatomy. Two-dimensional ultrasonic imaging of the heart overcomes this disadvantage. However, the definition of these scanners leaves much to be desired and becomes very poor when the stop-frame mode is used. The major disadvantages of the "multiscan" are the length of the multicrystal transducer, distortion of the picture, spurious echoes and verticalization. The sector scanner has smaller transducers fitting the "echocardiographic window" and permitting an apical, subxiphoid and suprasternal approach. However, with this system resolution is usually poor in the first anterior 3.5--4 cm after the thoracic wall. The mechanical scanner causes a vibrating sensation occasionally irritating to the patient. The electronic sector scanner has the widest angle and provides the best quality images. Unfortunately, its cost is markedly higher than that of other two-dimensional systems.