Detection of hepatic metastases with low MI real time contrast enhanced sonography and SonoVue.

AIM: SonoVue is the first ultrasound contrast agent which allows repeated continuous examination of the liver in real time. The aim of this study was to compare low mechanical index (MI) real time contrast enhanced ultrasound of the liver, using the contrast agent SonoVue, with conventional B-mode sonography for the detection of hepatic metastases. METHOD: 40 patients with known malignancy and at least one liver lesion on conventional B-mode sonography were included. Conventional B-mode sonography was performed followed by contrast enhanced ultrasound (CEUS) of the liver in the arterial (< 30 sec), portal-venous (40-120 sec) and delayed phase (> 120 sec) after injection of SonoVue. CEUS was performed using contrast specific imaging and low MI (< 0.3). Number, location and size of metastases on baseline and CEUS were compared with CT or MRI (blinded reader). RESULTS: 37 patients had 128 metastases on CT or MRI. Baseline US showed 74 metastases confirmed by reference examination (69%), while CEUS yielded 109 metastases (sensitivity 90%) (p < 0.001). On CEUS, 35 additional metastases not seen on baseline but confirmed by reference imaging were detected in 14 patients (36%). In 8 patients, CEUS showed 13 metastases not seen on reference imaging. CONCLUSION: Detection of hepatic metastases is substantially improved by low MI real time contrast enhanced ultrasound with SonoVue compared to conventional B-mode sonography.

Liver metastases in cancer: detection with contrast-enhanced ultrasonography.

In patients with known or suspected malignancy, ultrasonography (US) is often the first choice for liver imaging because of its widespread availability and low cost. Compared with contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI), the sensitivity of conventional US for detecting hepatic metastases is relatively poor. The advent of microbubble contrast agents changed this situation. Sensitivity and specificity increased substantially with the use of these contrast agents and contrast-specific imaging modes in recent years. Currently, numerous US imaging methods exist, based on Doppler techniques or harmonic imaging. They exploit the complex nonlinear behavior of microbubbles in a sound field to achieve marked augmentation of the US signal. Although microbubble contrast agents are essentially blood pool agents, some have a hepatosplenic specific late phase. Imaging during this late phase is particularly useful for improving the detection of malignant liver lesions and allows US to perform similarly to spiral CT as shown by recent studies. In addition, this late phase imaging is very helpful for lesion characterization. Low mechanical index imaging with the newer perfluor agents permits real-time imaging of the dynamic contrast behavior during the arterial, portal venous, and late phases and is particularly helpful for lesion characterization. The use of US for hemodynamic studies of the liver transit time may detect blood flow changes induced by micrometastases even before they become visible on imaging. In this field of functional imaging, further research is required to achieve conclusive results, which are not yet available.

Detection and characterisation of liver metastases.

Modern liver imaging of cancer patients requires an imaging modality that is not only highly sensitive in detecting lesions but also provides reliable characterisation of lesions and thus allows differentiation of metastases from frequently found benign lesions. Conventional ultrasound (US) has a relatively poor sensitivity and specificity for imaging liver metastases and US used to be inferior to CT and MRI mainly due to a lack of contrast agents. This has changed with the advent of microbubble contrast agents for US. The use of recent contrast agents such as SonoVue (Bracco, Italy) combined with low mechanical index contrast-specific imaging techniques such as Contrast Pulse Sequencing provides dynamic real time imaging of focal liver lesions in the arterial, portal venous and delayed phase. This improves lesion detection and characterisation. To investigate the benefit of SonoVue for detecting liver metastases we studied 40 cancer patients with liver lesions on reference imaging (CT or MRI), 37 of them had metastases. The mean number of reference confirmed metastases per patient increased from 1.85+/-1.79 on conventional ultrasound to 2.73+/-2.50 post SonoVue (p < 0.05). CEUS showed more individual metastases than baseline in 12 (34%) patients. Using CT or MRI as the reference, the mean sensitivity to individual metastases increased from 69% on baseline US to 90% post contrast (p < 0.0005). The role of SonoVue in characterisation of focal liver lesions was evaluated in 63 patients. One lesion was studied per patient. Based on standardised dynamic enhancement criteria for each lesion type, the number of correctly diagnosed lesions improved from 41 (65%) on baseline US to 58 (92%) post contrast (p < 0.001). On CEUS all 27 metastases were correctly diagnosed, while baseline US misinterpreted 2 of these. The number of correctly diagnosed benign lesions (n = 28) increased from 12 (43%) on baseline to 25 (89%) post SonoVue. In conclusion, detection and characterisation of focal liver lesions by US are markedly improved by the use of SonoVue. Contrast agents add a new dimension to sonography allowing it to rival CT and MRI, especially for lesion characterisation.

[Characterization of focal liver lesions with contrast-enhanced low MI real time ultrasound and SonoVue]. / Charakterisierung fokaler Leberläsionen mit kontrastmittelgestütztem "low MI real time" Ultraschall und SonoVue.

PURPOSE: SonoVue is a new microbubble ultrasound contrast agent that for the first time allows continuous real time examination during the different phases of contrast enhancement using low transmission power, expressed as mechanical index (MI). This study investigates whether low MI real time phase inversion imaging with SonoVue can improve the characterization of focal liver lesions in comparison to unenhanced sonography and power Doppler sonography. MATERIALS AND METHODS: Sixty-three patients with 35 malignant and 28 benign liver lesions were studied with unenhanced ultrasound (US) including B-mode and power Doppler, followed by contrast-enhanced al MI (0.1 - 0.3) real time phase inversion US during arterial, portal-venous and delayed liver phase (> 2 min after injection). Findings of the scans obtained before and after administration of contrast agent were compared with each other and with reference examinations (biopsy, MRI, CT or intraoperative US). RESULTS: The number of correctly diagnosed lesions increased from 41 (65%) without contrast agent to 58 (92%) with contrast agent (p < 0.001). The differentiation of malignant from benign lesions improved from 43 (68 %) to 60 (95 %, p < 0.001). After administration of the contrast agent, all 35 malignant lesions were correctly recognized and 3 of the 28 benign lesions were misclassified. All 27 metastases showed little or no enhancement on portal-venous and delayed phase imaging, independent of their arterial features. All 6 hepatocellular carcinomas (HCC) enhanced markedly during arterial phase and 5 showed less contrast uptake than normal liver in the late phase. Ten of 11 hemangioma displayed arterial peripheral nodular enhancement followed by progressive centripetal fill-in. Nine of 11 focal nodular hyperplasias (FNHs) showed profuse arterial enhancement (5 with a transient "spokewheel") and contrast uptake similar to normal liver thereafter. One FNH showed a subtle central scar. CONCLUSION: Low MI real time US with SonoVue markedly improves the characterization of focal hepatic lesions in comparison with unenhanced sonography.