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

Abstract

Objective: Surgical resection is the only curative option for colorectal hepatic metastases. Intra-operative localisation of these metastases during hepatic resection is performed by intra-operative B-mode imaging and palpation. Because liver metastases are stiffer than normal tissues, elastography may be a useful complement to B-mode imaging. This paper reports quantitative measures of the image quality attained during intra-operative real-time elastographic visualisation of liver metastasis. Methods: VX2 tumours were implanted in the liver of eight rabbits and were scanned in vivo. Measurements of the tumour dimensions obtained via elastography were compared with those obtained using B-mode imaging and with gross pathology. Results: Measurements of tumour diameters were similar when obtained by intraoperative elastography and pathological measurement methods (mean difference ¡ standard deviation, 0.1¡0.9 mm). The contrast between tumours and normal tissues was significantly higher (p,0.05) in elastograms (26¡10 dB contrast) than in sonograms (1¡1 dB contrast). Sensitivity and specificity for detecting tumours using intra-operative elastography were 100% and 88%, respectively, and positive and negative predictive values were 89% and 100%, respectively. In two cases elastograms were able to detect a tumour that was ambiguous in B-mode images. Conclusion: Combined hand-held B-mode/strain imaging may provide additional information that is relevant for detection of liver metastases that may be missed by standard B-mode imaging alone, such as small and/or isoechoic tumours. Colorectal cancer is the fourth most common cancer in males and the third most common cancer in females worldwide [1,2]. Approximately half of these patients either present with hepatic metastases or develop them during the course of their disease. Although ablative therapies are frequently used, resection of liver metastases, when possible, remains the preferred therapy for potential cure [3,4]. The overall 5 year survival rates are in the range of 35-58% in several studies reporting on the results of hepatectomy conducted with curative intent [4,5]. The pre-operative and intra-operative staging of metastases is essential to remove all metastases and increase the rate of cure. At the pre-operative stage, contrast-enhanced CT is the most commonly used modality to screen for metastases. It is highly sensitive, particularly since the introduction of helical CT and multidetector systems capable of scanning the entire liver in a few seconds, allowing for several scans during the liver's different circulatory phases [6]. MRI is very sensitive as well, and has the advantage of liver-specific contrast if required. MRI is also used for screening purposes, despite the fact that it is more time-consuming than other methodologies and may be subject to motion artefacts [7]. According to different reports, these modalities detect .90% of liver metastases if their diameter is .5 mm [7,8]. There is still a group of patients who undergo hepatic surgery without c...

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

“…Moreover, another study by Inoue et al [ 14 ] on freehand RTE of live lesion in an intraoperative setting also reported similar effect mimicking “visual palpation”. Besides clinical research, an animal experiment [ 15 ] applying combined hand-held B-mode/strain imaging on rabbit hepatic metastases also provided valuable evidences for detection of liver metastases that might be missed by standard B-mode imaging alone.…”

Thermal ablation by high-intensity-focused ultrasound using a toroidal transducer for the treatment of colorectal liver metastases during an open procedure. Clinical results

“…Compared to an extracorporeal device, an open procedure facilitates the protection of adjacent viscera and the intraabdominal staging of malignancies. The lesions not detected with preoperative imaging may be discovered intraoperatively 21,22 . Nevertheless, the use of an extracorporeal HIFU device is clinically feasible, as demonstrated by the treatment of hepatocellular carcinoma 23 , but only a small part (approximately 30%) of the liver is accessible using a noninvasive HIFU device unless a partial rib resection is performed 24 .…”

Focal liver lesions found incidentally

“…Few studies are available concerning its application to the liver, particularly for the evaluation of liver fibrosis. Apart from its use for characterization, RT elastography has been studied for the detection of liver nodules in animal models and during surgery [16,17] . In the latter setting, it has been demonstrated to have a higher diagnostic accuracy than B-mode intraoperative USS in detecting lesions surrounded by a heterogeneous background or with an iso echoic pattern (96% vs 89%).…”