Treatment response assessment of radiofrequency ablation for hepatocellular carcinoma: Usefulness of virtual CT sonography with magnetic navigation

ArticleinEuropean journal of radiology 81(3):e277-80 · March 2011with3 Reads
DOI: 10.1016/j.ejrad.2011.02.026 · Source: PubMed
Abstract
Virtual CT sonography using magnetic navigation provides cross sectional images of CT volume data corresponding to the angle of the transducer in the magnetic field in real-time. The purpose of this study was to clarify the value of this virtual CT sonography for treatment response of radiofrequency ablation for hepatocellular carcinoma. Sixty-one patients with 88 HCCs measuring 0.5-1.3 cm (mean±SD, 1.0±0.3 cm) were treated by radiofrequency ablation. For early treatment response, dynamic CT was performed 1-5 days (median, 2 days). We compared early treatment response between axial CT images and multi-angle CT images using virtual CT sonography. Residual tumor stains on axial CT images and multi-angle CT images were detected in 11.4% (10/88) and 13.6% (12/88) after the first session of RFA, respectively (P=0.65). Two patients were diagnosed as showing hyperemia enhancement after the initial radiofrequency ablation on axial CT images and showed local tumor progression shortly because of unnoticed residual tumors. Only virtual CT sonography with magnetic navigation retrospectively showed the residual tumor as circular enhancement. In safety margin analysis, 10 patients were excluded because of residual tumors. The safety margin more than 5 mm by virtual CT sonographic images and transverse CT images were determined in 71.8% (56/78) and 82.1% (64/78), respectively (P=0.13). The safety margin should be overestimated on axial CT images in 8 nodules. Virtual CT sonography with magnetic navigation was useful in evaluating the treatment response of radiofrequency ablation therapy for hepatocellular carcinoma.
    • "Hence, some specific cases in open surgery in which line-of-sight is blocked, also seem a field of application for EM tracking. Remote virtual sonography (RVS) involves fusion of US and CT/MRI images and is often achieved by tracking the US probe using EM technology [112]. This technique is sometimes used for guidance of punctures without tracking the puncture needle itself, but instead using conventional US-guidance for needle insertion. "
    [Show abstract] [Hide abstract] ABSTRACT: Object tracking is a key enabling technology in the context of computer-assisted medical interventions. Allowing the continuous localization of medical instruments and patient anatomy, it is a prerequisite for providing instrument guidance to subsurface anatomical structures. The only widely used technique that enables real-time tracking of small objects without lineof- sight restrictions is electromagnetic (EM) tracking. While EM tracking has been the subject of many research efforts, clinical applications have been slow to emerge. The aim of this review paper is therefore to provide insight into the future potential and limitations of EM tracking for medical use. We describe the basic working principles of EM tracking systems, list the main sources of error, and summarize the published studies on tracking accuracy, precision and robustness along with the corresponding validation protocols proposed. State-of-the-art approaches to error compensation are also reviewed in depth. Finally, an overview of the clinical applications addressed with EM tracking is given. Throughout the paper, we report not only on scientific progress, but also provide a review on commercial systems. Given the continuous debate on the applicability of EM tracking in medicine, this paper provides a timely overview of the state-of-the-art in the field.
    Full-text · Article · May 2014
    • "Several studies address the relation between microvascular invasion of HCC cells and tumor size. Kojiro et al [22] reported that the tumor invades the portal vein in 27% of cases even in early HCC (lesions < 2 cm in dimension). Esnaola et al [26] found the frequency of microvascular invasion to be 25% and 31% for tumors < 2 cm and 2-4 cm in the greatest dimension, respectively. "
    [Show abstract] [Hide abstract] ABSTRACT: Radiofrequency ablation (RFA) is commonly applied for the treatment of hepatocellular carcinoma (HCC) because of the facile procedure, and the safety and effectiveness for the treatment of this type of tumor. On the other hand, it is believed that HCC cells should spread predominantly through the blood flow of the portal vein, which could lead to the formation of intrahepatic micrometastases. Therefore, monitoring tumor response after the treatment is quite important and accurate assessment of treatment response is critical to obtain the most favorable outcome after the RFA. Indeed, several reports suggested that even small HCCs of ≤ 3 cm in diameter might carry intrahepatic micrometastases and/or microvascular invasion. From this point of view, for preventing local recurrences, RFA should be performed ablating a main tumor as well as its surrounding non-tumorous liver tissue where micrometastases and microvascular invasion might exist. Recent advancement of imaging modalities such as contrast-enhanced ultrasonic, computed tomography, and magnetic resonance imaging are playing an important role on assessing the therapeutic effects of RFA. The local recurrence rate tends to be low in HCC patients who were proven to have adequate ablation margin after RFA; namely, not only disappearance of vascular enhancement of main tumor, but also an adequate ablation margin. Therefore, contrast enhancement gives important findings for the diagnosis of recurrent HCCs on each imaging. However, hyperemia of non-tumorous liver surrounding the ablated lesion, which could be attributed to an inflammation after RFA, may well obscure the findings of local recurrence of HCCs after RFA. Therefore, we need to carefully address to these imaging findings given the fact that diagnostic difficulties of local recurrence of HCC. Here, we give an overview of the current status of the imaging assessment of HCC response to RFA.
    Full-text · Article · Apr 2014
    • "Interventional MRI or PET–CT are rarely available [16, 17]. Fusion imaging between previously acquired CT or MRI and real-time ultrasound recently described need improvement in terms of motion correction in order to bypass the problem of respiratory motion18192021. In 2004, Adam et al. first described the technique of coil-assisted RFA of hepatic tumors invisible on US and poorly visible on unenhanced-CT in a short series of five patients [6]. A metallic coil was percutaneously inserted via a fine needle under CT guidance within the targeted hepatic tumor during the phase of contrast enhancement. "
    [Show abstract] [Hide abstract] ABSTRACT: This study was designed to determine the effectiveness of a percutaneously inserted coil as a landmark before radiofrequency ablation (RFA) of poorly visible liver tumors on unenhanced computed tomography and ultrasound. This was a single-center, retrospective study of 46 consecutive patients treated from January 2008 to June 2012 with RFA under CT guidance for 57 poorly visible liver tumors after percutaneous coil insertion. Effectiveness was evaluated by the rate of local tumor progression (LTP), and the risk factors of LTP were evaluated by multiple univariate analysis. After a mean follow-up of 15.9 months, the overall rate of LTP was 22.8 % (13/57). An increase in the distance between the coil and the center of the tumor was a predictive factor of LTP (p = 0.005) and resulted in an increase in time to place the RFA probe. LTP was significantly reduced in case of coil placed within the tumor (10 vs. 43.5 %, p = 0.009). The effectiveness of the "coil-assisted" RFA for poorly visible liver tumors is improved by centering the coil in the tumor in order to facilitate the placement of the RFA probe and equal to the results of RFA under direct image guidance.
    Article · Aug 2013
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