Positioning the probe during a duplex ultrasound is simple. Every probe has an orientation notch that is a small marker or grooved line on one side of the probe. Begin by holding the probe with the thumb side of your hand near the orientation notch or groove.
Next, it’s important to realize that there are two planes used for peripheral arterial duplex studies:
On longitudinal ultrasound images, the artery looks like a horizontal tube. On the other hand, transverse ultrasound images are a cross-section of the artery.
How to orient the ultrasound probe
When using the longitudinal orientation, hold the probe so that the orientation notch is pointing towards the patient’s head. When using the transverse orientation, the notch should be towards the patient’s right side. This will orient your screen to the corresponding plane.
Duplex ultrasound screen orientation
When looking at the ultrasound screen in the longitudinal orientation, the patient’s head will be to the left of the image and their legs will be to the right. Longitudinal ultrasound images are taken parallel to the vessel—which is why the artery looks like a horizontal tube.
Keep in mind that velocities are only taken in the longitudinal view.
In transverse images, the artery looks like a cross-sectional circle. As such, any plaque jutting out into the lumen can be easily seen. Transverse views are also useful for finding a vessel’s location.
The probe is held perpendicular to the vessel, which provides the sharpest image. The notch is to the patient’s right when using the transverse view.
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