Characterization of lymphomatous lymph nodes in dogs using contrast harmonic and power doppler ultrasound

Doppler ultrasound has been used in humans to determine angioarchitecture of lymph nodes as the criterion for the determination of malignancy. We hypothesized that the vascular and perfusion patterns of a canine malignant lymph node could be characterized with intravenous microbubble ultrasound contrast media and that contrast harmonic ultrasound could provide better conspicuity of the angioarchitecture when compared with Power Doppler ultrasound. In this study, 11 peripheral lymph nodes in dogs with histologically verified malignant lymphoma were imaged with fundamental ultrasound, Power Doppler ultrasound, and three contrast harmonic pulse sequences to characterize the vascular pattern and perfusion. Vascular imaging was greatly enhanced in these nodes with 2.13 times more vessels seen with contrast harmonic ultrasound compared with Power Doppler ultrasound (P < 0.01). The angioarchitecture of lymphomatous lymph nodes of dogs in this study were similar to those previously described in malignant superficial lymph nodes in human patients; 45.5% of the nodes had displacement of the central hilar vessel, 45.5% had aberrant vessels, 63.6% had pericapsular vessels, 36.4% had subcapsular vessels, and 81.8% had loss of the central hyperechoic band in fundamental sonography. Poor perfusion, indicated by a lower mean pixel intensity increase between pre- and postcontrast administration images, was seen in 36.4% of the lymph nodes while 63.6% had fair to good perfusion. The perfusion patterns in nine of the 11 lymph nodes were homogenous and two showed focal hypoperfused regions. We conclude that Power Doppler and contrast harmonic ultrasound are beneficial in accurately depicting angioarchitechture and can provide additional information in determining the presence of malignant vascular characteristics within lymphomatous nodes in dogs.