1.5 Harmonic Imaging Sonography with microbubble contrast agent improves characterization of hepatocellular carcinoma

Contrast-enhanced ultrasound in the preoperative, intraoperative and postoperative assessment of liver lesions

The use of contrast agents (CA) with liver ultrasound (US) has gained recently an established role for the diagnosis of various hepatic diseases due to their safety, high versatility and low costs (contrast-enhanced ultrasound: CEUS). The purpose of this review is to provide a state-of-the-art summary of the available evidence for their use in the characterization of focal liver lesions. A published work search was conducted for all preclinical and clinical studies involving CA on hepatic US imaging. CEUS increases the sensitivity for lesion detection and the specificity to differentiate between benign and malignant diseases due to the enhanced visualization of the tumor microcirculation. Results achieved seem at least equivalent to those of spiral computed tomography or magnetic resonance imaging. The association of CA with intraoperative ultrasound has changed the surgical approach in 25% of patients and guarantees complete ablations by a single session in most of them. CEUS provides detailed information about tumor vasculature, improves the preoperative characterization and therefore the therapeutic strategy, and can evaluate the intraoperative completeness of the ablation.

Contrast-enhanced sonography with abdominal virtual sonography in monitoring radiofrequency ablation of hepatocellular carcinoma

BACKGROUND

Contrast-enhanced CT is regarded as the gold standard for monitoring radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC). Recently, 3-dimensional volume data from CT have been used to create cross-sectional multiplanar reconstruction images. Using this technique, we can reconstruct 2-dimensional CT images identical in orientation to ultrasound (US) images, which we call virtual sonographic (VUS) images. The present prospective randomized control trial compared the number of CT scans needed to assess the efficacy of RFA of HCC using VUS-contrast-enhanced ultrasonography (CEUS) versus CT.

METHOD

Subjects comprised 50 patients (50 HCCs) treated with US-guided RFA between May 2005 and August 2006, randomized to undergo assessment by CT (Group 1; 25 HCC nodules) or VUS-CEUS (Group 2; 25 HCC nodules). All patients were followed for 1 year. Primary endpoint was whether the number of CT scans could be reduced using VUS-CEUS.

RESULT

Mean number of CT scans required was 1.64 +/- 0.7 in Group 1 and 1.1 +/- 0.2 in Group 2 (p < 0.001).

CONCLUSION

VUS-CEUS can be used to assess the efficacy of HCC of RFA, with the potential to reduce the number of CT scans required for that purpose.

Delta-projection imaging on contrast-enhanced ultrasound to quantify tumor microvasculature and perfusion

RATIONALE AND OBJECTIVES

The aim of this study was to assess the Delta-projection image processing technique for visualizing tumor microvessels and for quantifying the area of tissue perfused by them on contrast-enhanced ultrasound images.

MATERIALS AND METHODS

The Delta-projection algorithm was implemented to quantify perfusion by tracking the running maximum of the difference (Delta) between the contrast-enhanced ultrasound image sequence and a baseline image. Twenty-five mice with subcutaneous K1735 melanomas were first imaged with contrast-enhanced grayscale and then with minimum-exposure contrast-enhanced power Doppler (minexCPD) ultrasound. Delta-projection images were reconstructed from the grayscale images and then used to evaluate the evolution of tumor vascularity during the course of contrast enhancement. The extent of vascularity (ratio of the perfused area to the tumor area) for each tumor was determined quantitatively from Delta-projection images and compared to the extent of vascularity determined from contrast-enhanced power Doppler images. Delta-projection and minexCPD measurements were compared using linear regression analysis.

RESULTS

Delta-projection was successfully performed in all 25 cases. The technique allowed the dynamic visualization of individual blood vessels as they filled in real time. Individual tumor blood vessels were distinctly visible during early image enhancement. Later, as an increasing number of blood vessels were filled with the contrast agent, clusters of vessels appeared as regions of perfusion, and the identification of individual vessels became difficult. Comparisons were made between the perfused area of tumors in Delta-projections and in minexCPD images. The Delta-projection perfusion measurements were correlated linearly with minexCPD.

CONCLUSION

Delta-projection visualized tumor vessels and enabled the quantitative assessment of the tumor area perfused by the contrast agent.

Usefulness of contrast-enhanced ultrasonography with abdominal virtual ultrasonography in assessing therapeutic response in hepatocellular carcinoma treated with radiofrequency ablation

OBJECTIVE

Contrast-enhanced computed tomography (CECT) is regarded as the gold standard for assessing the efficacy of radiofrequency ablation (RFA) against hepatocellular carcinoma (HCC). We evaluated the efficacy of virtual ultrasonography (VUS) with contrast-enhanced ultrasonography (CEUS) vs. CECT for assessing the response to RFA.

MATERIALS AND METHODS

Study 1: The therapeutic responses in 22 patients with 26 HCC nodules were assessed by CEUS with VUS as well as by CECT. The efficacy of treatment was based on whether the safety margin was greater than 5 mm after RFA. Study 2: In seven patients with seven HCC nodules, the nodules were treated by RFA and the therapeutic efficacy was assessed by CEUS with VUS. The number of RFA sessions was assessed.

RESULTS

Compared with CECT, CEUS with VUS had a specificity of 77%, a sensitivity of 91.6%, and an accuracy of 84%. When the therapeutic response to RFA was analyzed by CECT only, 1.86 +/- 0.69 assessments (mean) were required, while when response was assessed by CEUS with VUS, 1.14 +/- 0.38 CECT assessments were required (P = 0.03).

CONCLUSION

CEUS with VUS is effective in assessing the therapeutic response to RFA of HCC. Moreover, the number of CECT scans required is reduced by this approach.