Which veins is duplex ultrasound suitable for?
However, different probes and different ultrasound frequencies need to be used to get optimal results.
The first and simplest is the linear probe. In a linear probe, the piezoelectric crystals are positioned in a straight line. They all fire parallel to each other and the resulting image is a rectangle. These probes tend to be used for more superficial veins that are near the surface.
The second probe used is the curved probe. In a curved probe, the piezoelectric crystals are positioned on a curved surface. When they fire, the impulses spread out like a fan. These probes tend to be used for deeper veins, such as veins deep in the abdomen or deep in the thigh muscles in the leg.
Finally, there are specialist probes, such as the transvaginal probe. When the pelvic veins are being examined for pelvic vein reflux and pelvic venous congestion, the most accurate duplex ultrasound image is produced by a transvaginal approach. By using the vagina to access the pelvis, the ultrasound probe can be brought very close to the ovarian and internal iliac veins, and so a very accurate duplex ultrasound examination can be performed.
However it is impossible to use one of the larger probes that are used for the usual external examinations, and so the tranvaginal probe is a very long and thin probe, specifically made for transvaginal examinations.
However the different ultrasound frequencies have different properties when travelling within the body.
The lower frequencies penetrate deeper and the higher frequencies penetrate far more superficially. However, the higher frequencies can give far higher detail in the images that they produce.
Thus, although different machines and different operators might have personal preferences, as a general indication:
- 2 – 3 MHz – Used for deep veins in the Abdomen or Thigh
- 5 MHz – Used for the deep veins and large truncal veins (Great and Small Saphenous veins)
- 8 MHz – Truncal veins and more superficial veins
- 10 – 15 MHz – Reticular veins and feeding veins
Which veins are not suitable for duplex ultrasound examination?
However other veins can be more difficult; Perforator veins are small and deep, and can be set at strange angles; Pelvic veins are not usually examined and it has only been in the last decade that the importance of pelvic venous reflux has been identified as a cause of varicose veins. As such, many vein clinics are not experienced in transvaginal duplex ultrasonography of the pelvic veins.
In reality, there are no veins that need to be imaged for phlebology that are not suitable for duplex ultrasound examination. However, to be able to image them all, the correct machine and selection of probes needs to be available, and most importantly, a highly trained and experienced duplex scan operator is need to perform the scans and interpret the results. Please click here to find your nearest ultrasound technologist.