Visualisation of liver tumours using hand-held real-time strain imaging: results of animal experiments

Focal liver lesions found incidentally

Incidentally found focal liver lesions are a common finding and a reason for referral to hepatobiliary service. They are often discovered in patients with history of liver cirrhosis, colorectal cancer, incidentally during work up for abdominal pain or in a trauma setting. Specific points should considered during history taking such as risk factors of liver cirrhosis; hepatitis, alcohol consumption, substance exposure or use of oral contraceptive pills and metabolic syndromes. Full blood count, liver function test and tumor markers can act as a guide to minimize the differential diagnosis and to categorize the degree of liver disease. Imaging should start with B-mode ultrasound. If available, contrast enhanced ultrasound is a feasible, safe, cost effective option and increases the ability to reach a diagnosis. Contrast enhanced computed tomography should be considered next. It is more accurate in diagnosis and better to study anatomy for possible operation. Contrast enhanced magnetic resonance is the gold standard with the highest sensitivity. If doubt still remains, the options are biopsy or surgical excision.

Application of Real-Time Tissue Elastography with a Low Frequency Convex Array Probe: A Noninvasive Approach to Differential Diagnosis of Liver Tumors

To evaluate diagnostic performance of real-time tissue elastography (RTE) with a low frequency convex array probe for distinguishing benign from malignant hepatic tumors through trans-abdominal examination, elasticity images of 210 liver tumors were obtained by EUB-7500 (Hitachi Medical Systems and 3.5 MHz probe) and eventually 121 liver tumors were analyzed in the study. Elasticity images were classified into four types, from type a to d. Regarding type a or b as benign tumors and type c or d as malignant ones, sensitivity, specificity, and accuracy were calculated and the consistency between the findings of RTE and the pathohistological diagnosis was evaluated. The sensitivity, specificity, and accuracy were separately 97.2%, 88.0%, and 93.4% (P < 0.001). Moreover, there was a good consistency between the findings of RTE and the pathological diagnosis (kappa value 0.86). Among elasticity images of all the malignant tumors, the hepatocellular carcinomas (HCCs) mainly appeared in type c, and liver metastatic cancers in type d. Thus, RTE utilized as a novel noninvasive imaging examination method enables us to distinguish benign from malignant liver tumors. Moreover, it provides certain information for the differential diagnosis between HCCs and liver metastatic cancers.

Intraoperative ultrasound and tissue elastography measurements do not predict the size of hepatic microwave ablations

RATIONALE AND OBJECTIVES

Image-guided thermal ablation is used to treat primary and secondary liver cancers. Evaluating completeness of ablation is difficult with standard intraoperative B-mode ultrasound. This study evaluates the ability of B-mode ultrasound (US) and tissue elastography to adequately measure the extent of ablation compared to pathologic assessment.

MATERIALS AND METHODS

An in vivo porcine model was used to compare B-mode ultrasonography and elastography to pathologic assessment of the microwave ablation zone area. In parallel, intraoperative ablations in patients were used to assess the ability of B-mode US and elastographic measures of tissue strain immediately after ablation to predict ablation size, compared to postprocedural computed tomography (CT).

RESULTS

In the animal model, ablation zones appeared to decrease in size when monitored with ultrasound over a 10-minute span with both B-mode US and elastography. Both techniques estimated smaller zones than gross pathology, however, the differences did not reach statistical significance. Biopsies from the edges of the ablation zone, as assessed by US, contained viable tissue in 75% of the cases. In the human model, B-mode US and elastography estimated similar ablation sizes; however, they underestimate the final size of the ablation defect as measured on postprocedure CT scan (median area [interquartile range]: CT, 7.3 cm(2) [5.2-9.5] vs. US 3.6 cm(2) [1.7-6.3] and elastography 4.1 cm(2) [1.4-5.1]; P = .005).

CONCLUSIONS

Ultrasound and elastography provide an accurate gross estimation of ablation zone size but are unable to predict the degree of cellular injury and significantly underestimate the ultimate size of the ablation.

Elastography for hepato-biliary-pancreatic surgery

Palpation is a subjective and non-sharable diagnostic method. Recently, palpation has been supported and replaced by elastography, which provides a novel parameter of “stiffness” as a visual representation or quantified value. Today, elastography is performed using two major modalities: strain elastography and shear wave elastography. Strain elastography converts the extent of deformation during external compression into colors, displaying these colors as a strain map in a motion picture representing the relative elasticity inside the region of interest. Shear wave elastography can quantify the elasticity of a target by calculating the velocity of shear waves generated by a probe. In addition to superficial organs, elastography has also been applied to upper abdominal organs, including the liver, pancreas and spleen. The visualization of the stiffness of focal lesions in the liver or the pancreas has enabled a more sensitive and specific depiction of small, non-palpable nodules, which are difficult to depict using B-mode ultrasonography. The quantification of stiffness also enables non-invasive estimates of liver fibrosis, the risk of postoperative liver insufficiency and the risk of recurrence of viral hepatitis after transplantation. In this article, we review the major reports that have recently been published describing the effective application of elastography to solid upper abdominal organs in a clinical setting.

Clinical impact of ultrasound-related techniques on the diagnosis of focal liver lesions

Since its introduction in clinical practice, ultrasound technology has greatly impacted patient management, particularly in the case of liver diseases, where hepatologists usually perform ultrasound examinations. Clinicians are increasingly aware of the great potential of ultrasound waves and of the recent innovations that exploit the mechanical properties of ultrasound waves. Thus, at present, not only B-mode ultrasound but also contrast-enhanced ultrasound and, more recently, elastosonography are used worldwide in various settings. This review aims to describe why clinicians should be aware of ultrasound-based techniques, how they should use these techniques for assessing focal liver lesions, and how these techniques impact patient management. We will review the clinical potential of ultrasound-related techniques, starting from lesion detection, moving to characterization, and concluding with their utility in guiding treatments and analyzing their effects.