How do you obtain that nice long image of the peripheral blood vessel for a longitudinal approach? It is easy to say ‘rotate the probe 90 degrees from the transverse view,’ but there are many subtleties to probe rotation. Many times when we rotate the probe, we do not get the desired longitudinal view, but rather the vessel is seen in part, or obliquely sectioned. Also, the vessel may appear on the left side of the screen or the right side and further fine rotation often makes the vessel disappear. How do we correct for this?
The trick is to understand the many different axes of probe rotation. See the video for an example of :
(i) probe rotation along an axis that goes through the proximal end of the probe (incorrect)
(ii) probe rotation along an axis through the distal end of the probe (incorrect)
(iii) CORRECT probe rotation along an axis through the central portion of the probe (through the transducer wire)
In order to move from a transverse to longitudinal view of a blood vessel without losing track of it, you must:
- Visualize the vessel in the center of the screen (thus, directly beneath the center of the probe)
- Rotate the probe on its CENTRAL axis (through the wire)
- Watch as the vessel transitions from a circle (transverse) to an ellipse (oblique) to two parallel lines (longitudinal)
Go try this on a phantom and with some practice, everyone can get that nice elongated view of the vessel.