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For example, M-mode is used to measure the length of the ventricular cavity, allowing to estimate many
important physiological parameters. Indeed, these allows to see the trajectory of the layers, allowing to
reconstruct profile velocity and dimension of layers (e.g. thickness of the wall of the heart varying in min-
max range). Mitral and cardiac valves are the most investigated one. Since heart is located inside the thoracic
cage, here is required a small and convex probe, to optimal fit two consecutive ribs and prospectively
avoiding all the reflection from them (high reflecting surfaces like bones produce bad results with US). Many
echographic systems are used also with an ECG system to study the synchronization between the heart
electrical signal and the mechanical pumping of the heart.
Harmonic imaging is the US modality in which there is a specific attention in the suppression of acoustic
noise, which usually clouds the image and makes difficult to clearly identify the morphological structures of
the investigated tissue. These spurious echoes, often called clutter noise, are particularly noticeable in fluid
filled areas (e.g. heart or cyst) and are common problem when imaging large patients. With this technique,
the assumptions made previously are expressly taken in consideration, trying to limit the drawbacks that rise
from this facts in the final imaging rendition. Theoretically, the launched frequency of an US pulse is assumed
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to be one, called nominal frequency. In reality, the piezoelectric produces a whole range of frequencies, that
are essentially useless:
The pulsed wave has a different spectrum, centred on the nominal frequency but containing also other