Original ContributionAcoustic Radiation Force Impulse Elastography for the Evaluation of Focal Solid Hepatic Lesions: Preliminary Findings
Introduction
Most elastographic imaging of ultrasonography to date has used manual or motorized compression with moving probes. Compression of the liver for elastographic imaging has always been difficult because it is surrounded by the rib cage, which limits using this procedure clinically.
Recently, ultrasound elastography with a short, high-intensity focused ultrasound beam has been introduced for target tissue displacement, i.e., acoustic radiation force impulse (ARFI) elastography (Fahey et al., 2006, Fahley et al., 2005, Nightingale et al., 2002, Walker et al., 2000). This technique has enabled in vivo liver elastography by transmission of the acoustic wave between the ribs or from the subcostal area (Fahey et al., 2008a, Fahey et al., 2008b). Until now, only one in vivo study has characterized liver tumors in humans using ARFI elastography (Fahey et al. 2008a) and that study only included seven liver tumors. Additionally, there are no studies that have evaluated ARFI elastography's usefulness in differentiating liver tumors and no studies have been reported on the quantification of tumor stiffness using shear wave velocity, which may help in the diagnosis of liver tumors.
The present study was performed to investigate the potential usefulness of ARFI elastography for evaluating focal solid hepatic lesions, assuming that different features can be shown on ARFI elastography images according to the type of liver tumor and that quantification of tumor stiffness may be helpful in the diagnosis.
Section snippets
Materials and Methods
Our hospital Institutional Review Board approved this study (IRB number: 0902-039-272) and informed consent was obtained from all patients prior to the ARFI elastography examinations.
Results
Table 1, Table 2 summarize the echogenicity, stiffness and conspicuity of the lesions in the three groups. Of the elastographic images of group I (metastatic tumors and cholangiocarcinomas), 13 of 18 lesions (72%) appeared darker, which indicated that they were stiffer than the surrounding liver parenchyma (Fig. 1, Fig. 2). The stiffer tumors included three cholangiocarcinomas, four metastatic tumors from colon cancer, one metastatic tumor from duodenal cancer, three from neuroendocrine tumors
Discussion
For the abdominal application of ARFI elastography, Fahey et al. first reported the usefulness of ARFI elastography for improving both the conspicuity and contrast of hepatic and renal tumors relative to the use of conventional B-mode images (Fahey et al. 2008a). According to this report, for all seven hepatic tumors that were analyzed including HCCs and metastases, the boundary definition on ARFI images was improved or equivalent to that on B-mode images. HCCs were softer than the regional
Acknowledgments
The authors wish to thank Chris Woo (Korea) and Bonnie Hami, M.A. (USA) for their assistance in preparing and editing this manuscript.
References (9)
- et al.
In vivo guidance and assessment of liver radio-frequency ablation with acoustic radiation force elastography
Ultrasound Med Biol
(2008) - et al.
Acoustic radiation force impulse imaging: In vivo demonstration of clinical feasibility
Ultrasound Med Biol
(2002) - et al.
Quantifying hepatic shear modulus in vivo using acoustic radiation force
Ultrasound Med Biol
(2008) - et al.
Practice Guidelines Committee, American Association for the Study of Liver disease. Management of hepatocellular carcinoma
Hepatology
(2005)