Basic probe positioning and screen orientation for an arterial duplex ultrasound
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.
Figure 1. The duplex ultrasound probe has an orientation notch on one side. When holding the probe, this notch should be oriented towards the thumb side of your hand.
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.
Figure 2. On duplex ultrasound images, the artery looks like a horizontal tube in the longitudinal view. In the transverse view, the artery is cross-sectioned.
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.
Figure 3. When using a longitudinal view, hold the probe so that the orientation notch is towards the patient’s head. When using a transverse view, keep the notch pointed towards the patient’s right side.
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.
Figure 4. In the longitudinal view of a common femoral artery, the duplex ultrasound screen is oriented so that the right of the image is cranial, the left is caudad, the top of the image is the patient’s left, and the bottom is the patient’s right.
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.
Figure 5. In the transverse view of a superficial femoral artery, the duplex ultrasound screen is oriented so that the top of the image is cranial, the bottom is caudad, the right of the image is the patient’s left side, and the left of the image is the patient’s right side.
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