Contrast-enhanced ultrasonography (CEUS) in canine liver examination

Abstract

Ultrasonography is a noninvasive diagnostic tool used to image size, shape, parenchyma and vascularization of various body organs. Unfortunately, the ultrasonographic image is characterized by a low contrast due to similar acoustic properties of the soft tissue. The Doppler mode provides information about blood flow, but is incapable of imaging small vessels and capillaries because of their low blood flow velocity (1 mm/s). However, a possibility to increase the effectiveness of ultrasonographic diagnostics exists, thanks to intravenous ultrasound contrast agents (UCAs) consisted of gas microbubbles.The purpose of this review paper is to characterize specific imaging techniques necessary to conduct a contrast-enhanced liver examination and indications for CEUS as an alternative diagnostic method.Key words: ultrasonography, liver, canine, neoplasm, differential diagnostics Specific contrast-enhanced imaging techniquesThe basic B-mode (Haers and Saunders 2009) is not effective enough for ultrasound contrast agent detection in tissue, so it can not be used in contrast-enhanced ultrasonography (CEUS). All Doppler modalities are too sensitive to the microbubbles and this hypersensitivity causes artifacts such as "color blooming" (color Doppler) and "flash" (power Doppler), which decreases the usefulness of these modes. "Color blooming" artifact (Nilsson 2001) presents itself as extravascular color induced by reverberation and/or a high gain setting. The "flash" artifact appears when tissue or transducer movement disturbs the desired flow signal.Specific contrast-enhanced imaging techniques (Haers and Saunders 2009) are deprived of these Correspondence to: M. Wdowiak, e-mail: ktmtombstone@interia.pl defects and bring satisfying clinical results and artifact reduction. Many techniques have been created e.g. second harmonic imaging, pulse/phase inversion harmonic imaging, cadence-contrast pulse sequencing and power (amplitude) modulation.These specific imaging techniques take advantage of the nonlinear properties of UCAs which manifests in asymmetrical oscillation of the gas microbubbles under ultrasonic wave influence. The nonlinear properties of UCAs (Quaia 2007) increase contrast detection in tissues, thus increasing the contrast to tissue ratio and decreasing artifacts and noise.The principles of the second harmonic imaging are to create an image based on a frequency twice the value of the wave emitted by the transducer. The fundamental wave is filtered. If the fundamental wave is 2 MHz, then the second harmonic is 4 MHz, third harmonic 6 MHz and so on. Conventional USG sys-

Description of the use of contrast‐enhanced ultrasonography in four dogs with pancreatic tumours

“…Although pancreatic nodular hyperplasia is a common finding in older dogs compared to humans, no information is available regarding CEUS contrast patterns in pancreatic hyperplastic lesions. However, in liver and spleen, CEUS of nodular hyperplasia showed a diffuse and homogeneous contrast pattern, which was iso-or hypoechogenic in the arterial phase and homogeneously isoechoic during the wash-out phase (Rossi et al 2008;Wdowiak et al 2010).…”

Imaging Diagnosis—cholangiocellular Adenoma: Contrast‐enhanced Ultrasonographic Findings of a Benign Tumor Mimicking Malignant Neoplasia in a Dog

“…The use of CEUS has been reported to improve accuracy in diagnosing focal liver lesions and differentiating between benign nodules and primary or metastatic masses in dogs . The usefulness of CEUS for liver evaluation is based on the liver's unique vascular supply, characterized by both arterial and venous portal feeding, representing the 20–30% and 70–80% of hepatic blood supply, respectively . Contrast‐enhanced ultrasonographic characterization of focal liver lesions is based on the comparison between contrast uptake patterns of lesions vs. that of the surrounding liver parenchyma .…”

“…Contrast‐enhanced ultrasonographic characterization of focal liver lesions is based on the comparison between contrast uptake patterns of lesions vs. that of the surrounding liver parenchyma . Both in humans and dogs, benign lesions usually show a variable pattern during the arterial phase, but they are consistently isoechoic with respect to the surrounding parenchyma during the portal and late phases . However, some cases of hepatic nodular hyperplasia and one case of hepatoma have been described to have heterogeneous contrast uptake during peak enhancement.…”

Ultrasonographic tools used in the evaluation of the canine spleen: A review

“…Additionally, pulmonary contrast elimination may limit its use in patients with pulmonary diseases. Some adverse effects of contrast were observed in humans (headaches, diarrhea, neutropenia, nausea, skin reactions, dyspnoea, rhinorrhagia), but not in small animals (Wdowiak et al, 2010). In experimental studies with sheep, dexamethasone was used to prevent pseudoanaphylaxis and pulmonary hypertension due to acute and transient reactions (right ventricular dilatation and pulmonary pressure increase) reported in pigs after contrast administration (Antoine et al, 2014).…”