Monitoring of liver metastases after stereotactic radiotherapy using low-MI contrast-enhanced ultrasound?initial results

Abstract

The purpose of this study was to monitor liver metastases after radiotherapy using contrast-enhanced ultrasound (CEUS). In 15 patients, follow-up examinations after stereotactic, single-dose radiotherapy were performed using CEUS (low mechanical index (MI), 2.4-ml SonoVue) and computed tomography (CT). Besides tumor size, the enhancement of the liver and the metastases was assessed at the arterial, portal venous, and delayed phases. The sizes of the tumor and of a perifocal liver reaction after radiotherapy measured with CEUS significantly correlated with those measured at CT (r=0.93, p<0.001). CEUS found a significant reduction of the arterial vascularization in treated tumors (p<0.05). In the arterial phase, the perifocal liver tissue was hypervascularized compared to the treated tumor (p<0.001); in the late phase, it was less enhanced than the liver (p<0.001) and more than the tumor (p<0.01). The perifocal liver reaction was also seen in CT, but with a variable enhancement at the arterial (50% hyperdense compared to normal liver tissue), venous, or delayed phase (each with 70% hyperdense reactions). CEUS allows for the assessment of tumor and liver perfusion, in addition to morphological tumor examination, which was comparable with CT. Thus, changes of tumor perfusion, which may indicate tumor response, as well as the perifocal liver reaction after radiotherapy, which must be differentiated from perifocal tumor growth, can be sensitively visualized using CEUS.

Contrast-enhanced ultrasound for examining tumor biology

“…), contrast-enhanced ultrasound (CEUS) clearly shows a high arterial enhancement of the untreated liver metastasis, its reduction after therapy and an arterially hypervascularized perifocal liver reaction after therapy. From [28] , with permission.…”

“…In liver metastases treated with stereotactic radiotherapy, for example, we can study how arterial perfusion decreases as a consequence of the sterilization of the tissue (Fig. 2) [28] . In another, as yet unpublished study on liver metastases treated with chemotherapy, it was found that before initiating treatment the arterial contrast enhancement was stronger in later responders than in non-responders.…”

Detection of Colorectal Cancer Hepatic Metastases with Contrast-Enhanced Ultrasound: Comparison with Conventional B-Mode Ultrasound

“…The introduction of ultrasound contrast agents and the advances in ultrasound apparatuses that are now able to detect these agents in real time have improved the overall accuracy of US in the characterization of focal liver lesions [3,4] , in liver metastases detection [5][6][7][8][9][10] and in monitoring the effect of therapy in liver metastases [11] .…”

Evaluation of quantitative contrast harmonic imaging to assess malignancy of liver tumors: A prospective controlled two-center study

“…Since no www.wjgnet.com single diagnostic tool has been able to clarify this question with sufficient reliability up to now, histological analysis remains the gold standard. Characterization of focal hepatic lesions with imaging techniques is an important part of radiological diagnosis and is still the focus of scientific research because of technical innovations of existing methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] . Special attention has been paid to the validation of new methods, especially the further development of contrast-enhanced ultrasound techniques because ultrasound is the most common and best available imaging technique [1][2][3][5][6][7][8][9][10][11][12][13][14] .…”