Treatment response assessment of radiofrequency ablation for hepatocellular carcinoma: Usefulness of virtual CT sonography with magnetic navigation
Division of Gastroenterology and Hepatology, Department of Internal Medicine, Kinki University School of Medicine, 377-2 Ohno-Higashi, Osaka-Sayama 589-8511, Japan. European journal of radiology
(Impact Factor: 2.37).
03/2011; 81(3):e277-80. DOI: 10.1016/j.ejrad.2011.02.026
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.
Available from: Lena Maier-Hein
- "Remote virtual sonography (RVS) involves fusion of US and CT/MRI images and is often achieved by tracking the US probe using EM technology . This technique is sometimes used for guidance of punctures without tracking the puncture needle itself, but instead using conventional US-guidance for needle insertion. "
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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.
Available from: ajronline.org
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ABSTRACT: The objective of our study was to evaluate the feasibility rate and the reasons for infeasibility of percutaneous radiofrequency ablation of hepatocellular carcinomas (HCCs) at planning sonography.
We retrospectively evaluated 248 patients who had been referred for planning sonography at our department between October 2005 and February 2006. We reviewed the radiologic reports of 256 planning sonography examinations in terms of the rate of feasible cases and the reasons for infeasibility. The reasons for infeasibility were classified in six categories: an inconspicuous tumor, an inadequate electrode path, an organ vulnerable to collateral thermal damage, a tumor that was too large or too many tumors, and a high risk of the heat sink effect. In addition, we assessed the treatment modality for the patients who were determined to have HCCs for which percutaneous radiofrequency ablation was not feasible.
In 141 (55%) of the 256 planning sonography examinations, percutaneous radiofrequency ablation was feasible. The remaining 115 (45%) planning sonography examinations revealed that radiofrequency ablation was not a feasible procedure. The reasons for infeasibility included an inconspicuous tumor in 77 patients (55.8%), an inadequate electrode path in 33 patients (23.9%), an organ vulnerable to collateral thermal damage in 14 patients (10.1%), a tumor that was too large or too many tumors in eight patients (5.8%), a high risk of the heat sink effect in five patients (3.6%), and a portal vein thrombosis in one patient (0.7%). One reason for infeasibility was found in 96 patients, two reasons in 19 patients, and four reasons in one patient. Seventy (61.9%) of 113 patients for whom radiofrequency ablation was not feasible underwent transcatheter arterial chemoembolization as an alternative treatment.
In approximately half of the patients for whom percutaneous radiofrequency ablation of HCC is requested, the procedure is not feasible, mainly due to inconspicuous tumors, at planning sonography. Additional objective criteria for assessing the feasibility of radiofrequency ablation and therapeutic strategies according to the reasons for infeasibility should be investigated further.
Available from: Adrian Saftoiu
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ABSTRACT: Contrast enhanced ultrasound has recently been introduced and is recommended in daily practice in many circumstances, mainly for the detection and characterization of focal liver lesions. Also, contrast enhanced ultrasound has the potential of becoming the primary liver-imaging modality, preceding CT or MR, for the diagnosis of hepatocellular carcinoma in patients with cirrhosis, detection of liver metastases in oncology patients and guidance and assessment of the outcome of percutaneous tumor ablation procedure. Recently, a new imaging technique that combines in real-time, transabdominal ultrasound with CT or MR, has been introduced in clinical practice. Real-time virtual sonography uses a magnetic positioning system attached to the ultrasound probe in order to calculate the spatial position and to display both imaging methods in real-time. Benefits include an increased diagnostic confidence, direct comparison of the lesions using different imaging modalities, more precise monitoring of interventional procedures and reduced radiation exposure. We describe the role of real-time contrast-enhanced and real-time virtual sonography in the assessment of malignant liver lesions.
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