 |
| Fig. 16 |
Much of the skill needed to perform an echocardiographic examination
lies in being able to direct the ultrasound beam at cardiac structures
of interest in such a way that echoes from them can be detected.
The principles of cardiac anatomy and recording technique relevant
to M-mode apply equally to two-dimensional echocardiography. The
stationary ultrasound beam used for M-mode can be thought of as
a flashlight, illuminating only a small area of the heart at a time;
a two-dimensional transducer is like a circular saw, rotating around
the point where it rests on the chest, with the blade aligned with
the index mark on the transducer (Fig.
16). The side of the transducer with the index mark corresponds
to the right-hand side of the display.
When performing a two-dimensional examination, therefore, more
complex maneuvers are necessary to order to align the scan plane
with the desire anatomic axis of the heart. Manipulation of the
transducer can be described as follows (Fig.
16). Rotating the transducer pivots the scan plane about the
transducer axis. Rotation through 90 degrees is used, for example,
to change from the parasternal long axis to the short axis. Tilting
the transducer displaces the scan to form a series of radial planes,
like the faces of the segments of an orange. Angling the transducer
moves its axis in the plane of the scan, for example to bring an
object at one edge into the center of the field of view.
2004