 |
| Fig. 17 |
To obtain parasternal views, the subject is inclined slightly toward
the left lateral position. The transducer is placed over the intercostal
space as for an M-mode examination (Fig.
17). For the long-axis view, the scan plane is aligned from
the right shoulder to the left kidney, with the transducer index
mark toward the shoulder so the aorta will appear on the right-hand
side of the display. From this position, the transducer is rotated
clockwise through 90 degrees to obtain short-axis views (the index
mark should now point toward the left midclavicle). Since the right-
hand side of the short-axis scan tends to be obscured by lung, the
transducer should be positioned as close to the sternal border as
possible. It may help to turn the subject more toward the left,
and to record during forced exhalation. In difficult subjects, such
maneuvers may be necessary even to obtain minimal visualization
of cardiac structures.
It is normal to obtain a series of parasternal short-axis views,
from the apex to the pulmonary artery, by tilting the transducer
along the line of the long axis. When the transducer is aimed toward
the apex, a tomographic section is obtained at the level of the
papillary muscles. Progressive tilting up the long axis shifts the
section first to the mitral valve, then to the left ventricular
outflow tract, the aortic and pulmonary valves, and finally to the
main pulmonary artery.
2004