Radiofrequency thermal ablation of hepatocellular carcinoma: using contrast-enhanced harmonic power doppler sonography to assess treatment outcome

OBJECTIVE: We evaluated the accuracy of contrast-enhanced harmonic power Doppler sonography in assessing the outcome of radiofrequency thermal ablation of hepatocellular carcinoma. SUBJECTS AND METHODS: Fifty patients with 65 hepatocellular carcinoma nodules (1-5 cm in diameter; mean diameter, 2.5 cm) were studied using unenhanced and contrast-enhanced harmonic power Doppler sonography before and after IV administration of a microbubble contrast agent. The examinations were repeated after treatment of the tumors with radiofrequency ablation. Findings of the Doppler studies were compared with those of dual-phase helical CT, which were used as points of reference for assessing treatment outcome. RESULTS: Before radiofrequency treatment, intratumoral blood flow was revealed by unenhanced power Doppler sonography in 48 (74%) of 65 hepatocellular carcinoma nodules. After injection of the contrast agent, intratumoral enhancement was observed in 61 (94%) of 65 hepatocellular carcinomas (p < 0.01). After radiofrequency treatment, all 51 (84%) of the 61 hepatocellular carcinomas found to be necrotic on helical CT scans failed to show enhancement on power Doppler sonograms. In nine of the 10 lesions that showed a residual viable tumor on helical CT scans, persistent intratumoral enhancement-matching the enhancing areas on helical CT images-was revealed by power Doppler sonography. These nine hepatocellular carcinomas were subjected to repeated radiofrequency thermal ablation with the guidance of contrast-enhanced power Doppler sonography. Complete necrosis was seen after the second treatment session in six of the nine lesions. CONCLUSION: Contrast-enhanced harmonic power Doppler sonography is an accurate technique for assessing the outcome of radiofrequency thermal ablation of hepatocellular carcinoma and may be useful in guiding additional treatment in patients with incomplete response to initial efforts.     

Percutaneous ablation therapy guided by contrast-enhanced sonography for patients with hepatocellular carcinoma

OBJECTIVE: The newly developed contrast-enhanced harmonic gray-scale sonography technique enables us to improve the real-time detectability of viable tumor tissue in hepatocellular carcinoma lesions. We evaluated the usefulness of real-time percutaneous ablation therapy under guidance with this method for patients with hepatocellular carcinoma that is not depicted on conventional sonography. SUBJECTS AND METHODS: We examined 30 patients with 56 hepatocellular carcinomas using real-time contrast-enhanced harmonic gray-scale sonography after injection of a galactose-palmitic acid contrast agent and compared the results with the findings of contrast-enhanced helical CT. We performed percutaneous ablation therapy guided by this modality for treatment of viable hepatocellular carcinoma lesions that could not be detected using conventional sonography. RESULTS: High detection rates of viable hepatocellular carcinoma lesions were obtained using real-time contrast-enhanced harmonic gray-scale sonography (52/56 lesions, 93%); these rates were comparable to those of helical CT (54/56 lesions, 96%). Nine (90%) of the 10 lesions that were not detected on conventional sonography but were depicted on real-time contrast-enhanced harmonic gray-scale sonography (incomplete local treatment, n = 4; small new lesion, n = 6) were successfully treated with percutaneous ablation therapy guided by this method. CONCLUSION: Real-time contrast-enhanced harmonic gray-scale sonography improved the sensitivity for the detection of viable hepatocellular carcinoma lesions. Percutaneous ablation therapy guided by this modality may be useful in patients with hypervascular hepatocellular carcinoma lesions that cannot be detected using conventional sonography.     

Radiofrequency ablation of hepatocellular carcinoma: therapeutic response using contrast-enhanced coded phase-inversion harmonic sonography

OBJECTIVE: This study was performed to evaluate the usefulness of contrast-enhanced coded phase-inversion harmonic sonography in assessing the therapeutic response of percutaneous radiofrequency ablation in patients with hepatocellular carcinoma. SUBJECTS AND METHODS: Sixty-seven patients with a total of 107 examinations on 91 hepatocellular carcinoma nodules underwent coded harmonic angio, a technique of coded phase-inversion harmonic sonography, using the IV microbubble contrast agent Levovist before and after percutaneous radiofrequency ablation. The intratumoral blood vessels and tumor parenchymal stain were detected in the early arterial phase and the late vascular phase, respectively. The results of contrast-enhanced imaging with coded harmonic angio were compared with those of three-phase dynamic CT. RESULTS: Before treatment, all examined 107 hepatocellular carcinoma nodules were found to be hypervascular on contrast-enhanced imaging with coded harmonic angio. After radiofrequency ablation, contrast-enhanced coded harmonic angio detected persistent signal enhancement in 41 examined nodules (38.3%), whereas this technique showed no intratumoral enhancement in the remaining 66 (61.7%) examined nodules. Compared with dynamic CT, the sensitivity, specificity, and diagnostic accuracy of contrast-enhanced coded harmonic angio were 95.3%, 100%, and 98.1%, respectively. With contrast-enhanced coded harmonic angio, we found that it was difficult to identify the safety margin that can be detected on dynamic CT. CONCLUSION: Contrast-enhanced imaging with coded harmonic angio may provide an alternative approach that has high diagnostic agreement with dynamic CT in assessing the therapeutic effect of radiofrequency ablation in hypervascular hepatocellular carcinomas, in spite of having limitations in identifying the safety margin.     

Using contrast-enhanced sonography to assess the effectiveness of transcatheter arterial embolization for hepatocellular carcinoma

OBJECTIVE: We evaluated the usefulness of contrast-enhanced wideband harmonic gray-scale sonography in assessing the therapeutic effects of transcatheter arterial embolization for patients with hepatocellular carcinoma and compared the findings of this imaging modality with those of helical CT. SUBJECTS AND METHODS: Twenty-nine patients with 39 hepatocellular carcinoma lesions were examined. We scanned lesions before and after therapy using contrast-enhanced wideband harmonic gray-scale sonography after injection of a galactose-palmitic acid contrast agent. All patients held their breath for 20--50 sec after injection while the vascularity of the tumor was observed. We then monitored tumor enhancement between 60 and 180 sec after injection with patients breath-holding for a few seconds. Lesions were considered to exhibit viable tumor residue if hypervascular enhancement was observed in the tumor. We compared this enhancement with helical CT findings. RESULTS: After therapy, 36 of the 39 lesions showed viable tumor residue on contrast-enhanced wideband harmonic gray-scale sonography, with no artifacts from iodized oil. Helical CT revealed a high-attenuation area in 12 of the 36 lesions, whereas 24 of the 36 lesions could not be evaluated for tumor residue as a result of artifacts from iodized oil accumulation in the tumor. The remaining three lesions showed complete deposition of iodized oil and complete necrosis on contrast-enhanced wideband harmonic gray-scale sonography. CONCLUSION: Contrast-enhanced wideband harmonic gray-scale sonography is useful in evaluating the therapeutic effects of transcatheter arterial embolization for hepatocellular carcinoma.     

Creation of radiofrequency lesions in a porcine model: correlation with sonography, CT, and histopathology

OBJECTIVE: We studied the correlation between sonographic and CT appearances of radiofrequency thermal lesions created in porcine liver and histopathologic findings to evaluate the accuracy of these techniques in revealing the extent of tissue necrosis. MATERIALS AND METHODS: We used sonographic guidance and a 2.0-cm-diameter, eight-prong retractable radiofrequency electrode to view 12 hepatic lesions that were created in five pigs. Biphasic helical CT was performed 12-48 hr after ablation. The animals were sacrificed immediately after CT, and their livers were histopathologically examined. The maximum lesion size in the long and short axes as measured on CT and sonography was then correlated with the histopathologically determined lesion size. RESULTS: On sonography, lesions changed rapidly within 5 min after the termination of ablation. An early echogenic cloud became peripherally hypoechoic with a variable thin echogenic rim. Early (0-2 min after ablation) sonograms led to an underestimation of true lesion sizes on histopathology (r = 0.3-0.49; p < 0.05). Delayed (2-5 min after ablation) sonograms also led to an underestimation of true lesion size (r = 0.5-0.62; p < 0.05); however, lesions were larger and better demarcated. Biphasic contrast-enhanced helical CT revealed avascular lesions surrounded by hyperemic rims that closely correlated with true pathologic lesions size (r = 0.93-0.95; p < 0. 05). Lesions with hyperemic rims that were measured on CT led to overestimations of true lesion size. CONCLUSION: Sonography led to underestimations of the true size of ablated lesions within the first 5 min after creation; however, delayed images provided better results. The avascular lesion measured on contrast-enhanced helical CT closely correlated with the size of ablated tissue; therefore, contrast-enhanced CT is preferred for serially monitoring the effect of radiofrequency ablation.     

Therapeutic effect of transcatheter arterial chemoembolization on hepatocellular carcinoma: evaluation with contrast-enhanced harmonic power Doppler ultrasound

The aim of this study was to investigate the usefulness of contrast-enhanced harmonic power Doppler ultrasound (US) for the detection of residual viable hepatocellular carcinoma (HCC) after treatment with transcatheter arterial chemoembolization (TACE). Forty-seven patients with 68 HCC lesions 1.8–9.5 cm in diameter (mean ± SD 4.3 ± 1.7 cm) underwent contrast-enhanced power Doppler US, in the harmonic mode, before and after treatment with TACE. Unenhanced spiral CT and contrast-enhanced dynamic MR imaging were also performed to help establish the outcome of therapy. Before treatment, intratumoral blood flow signals were detected at contrast-enhanced harmonic power Doppler US in 65 (95 %) of 68 lesions. After TACE, flow signals were no longer detectable in 22 of these 65 lesions, which showed complete response at spiral CT and dynamic MR imaging. In 38 (88 %) of the 43 lesions with partial response, intratumoral flow signals were still identified at contrast-enhanced harmonic power Doppler US. Twenty-eight of these 38 lesions underwent additional treatment with percutaneous ethanol injection (PEI) using contrast-enhanced harmonic power Doppler US guidance. Complete response was seen after PEI in 23 of 28 lesions. Contrast-enhanced harmonic power Doppler US proved useful for assessing the therapeutic effect of TACE on HCC and for guiding additional treatment with PEI in cases of partial response. Received: 25 January 2000; Revised: 21 April 2000; Accepted: 25 April 2000     

Color Doppler sonography of hepatocellular carcinoma before and after treatment by transcatheter arterial embolization.

Color Doppler sonographic findings on 38 lesions in 31 patients who had primary hepatocellular carcinoma were evaluated before and after transcatheter arterial embolization and compared with dynamic CT and hepatic arteriographic findings. All lesions that were observed with dynamic CT or arteriography were correctly identified on color Doppler sonography. Peritumoral pulsatile flow was the predominant color Doppler flow seen in all lesions. Mixed pulsatile and continuous flow were noted in larger tumors and in tumors with a higher degree of vascularity, as determined by arteriography. Two weeks after treatment, color Doppler flow was still identified in 18 lesions (47%), corresponding to dynamic CT or arteriographic findings documenting residual tumor. Histopathologic examination, performed in 10 other lesions, showed that the tumor was completely necrotic in five. These five necrotic tumors were not visible on color Doppler flow images after treatment. Viable tumor was observed in the five remaining lesions, all of which were shown on color Doppler flow images after treatment. During the 6- to 16-month follow-up period, color Doppler flow images showed recurrence of 13 (50%) of 26 lesions, corresponding to tumor recurrence as shown by CT and arteriography. We conclude that color Doppler sonography is useful for imaging hepatocellular carcinoma, for evaluating residual tumor after treatment, and for imaging tumor recurrence during follow-up.     

Radiofrequency Ablation of Liver Cancer: Early Evaluation of Therapeutic Response with Contrast-Enhanced Ultrasonography

The early assessment of the therapeutic response after percutaneous radiofrequency (RF) ablation is important, in order to correctly decide whether further treatment is necessary. The residual unablated tumor is usually depicted on contrast-enhanced multiphase helical computed tomography (CT) as a focal enhancing structure during the arterial and portal venous phases. Contrast-enhanced color Doppler and power Doppler ultrasonography (US) have also been used to detect residual tumors. Contrast-enhanced gray-scale US, using a harmonic technology which has recently been introduced, allows for the detection of residual tumors after ablation, without any of the blooming or motion artifacts usually seen on contrast-enhanced color or power Doppler US. Based on our experience and reports in the literature, we consider that contrast-enhanced gray-scale harmonic US constitutes a reliable alternative to contrast-enhanced multiphase CT for the early evaluation of the therapeutic response to RF ablation for liver cancer. This technique was also useful in targeting any residual unablated tumors encountered during additional ablation.     

Therapeutic response assessment of percutaneous radiofrequency ablation for hepatocellular carcinoma: utility of contrast-enhanced agent detection imaging

PURPOSE: To assess the utility of contrast-enhanced agent detection imaging (ADI) in the assessment of the therapeutic response to percutaneous radiofrequency (RF) ablation in patients with hepatocellular carcinoma (HCC). MATERIALS AND METHODS: Ninety patients with a total of 97 nodular HCCs (mean, 2.1+/-1.3 cm; range, 1.0-5.0 cm) treated with percutaneous RF ablation under the ultrasound guidance were evaluated with contrast-enhanced ADI after receiving an intravenous bolus injection of a microbubble contrast agent (SH U 508A). We obtained serial contrast-enhanced ADI images during the time period from 15 to 90 s after the initiation of the bolus contrast injection. All of the patients underwent a follow-up four-phase helical CT at 1 month after RF ablation, which was then repeated at 2-4 month intervals during a period of at least 12 months. The results of the contrast-enhanced ADI were compared with those of the follow-up CT in terms of the presence or absence of residual unablated tumor and local tumor progression in the treated lesions. RESULTS: On contrast-enhanced ADI, technical success was obtained in 94 (97%) of the 97 HCCs, while residual unablated tumors were found in three HCCs (3%). Two of the three tumors that were suspicious (was not proven) for incomplete ablation were subjected to additional RF ablation. The remaining one enhancing lesion that was suspicious of a residual tumor on contrast-enhanced ADI was revealed to be reactive hyperemia at the 1-month follow-up CT. Therefore; the diagnostic concordance between the contrast-enhanced ADI and 1-month follow-up CT was 99%. Of the 94 ablated HCCs without residual tumors on both the contrast-enhanced ADI and 1-month follow-up CT after the initial RF ablation, five (5%) had CT findings of local tumor progression at a subsequent follow-up CT. CONCLUSION: Despite its limitations in predicting local tumor progression in the treated tumors, contrast-enhanced ADI is potentially useful for evaluating the early therapeutic effect of percutaneous RF ablation for HCCs.     

Advanced dynamic flow imaging with contrast-enhanced ultrasonography for the evaluation of tumor vascularity in liver tumors

To examine the usefulness of advanced dynamic flow imaging in diagnosing hepatic tumor and in assessing therapeutic effects in patients with hepatocellular carcinoma (HCC) and metastatic hepatic tumor, we performed contrast-enhanced ultrasonography (US) with Levovist, a microbubble contrast agent. Twenty-two patients of 35 HCC nodules infected with hepatitis C virus (HCV) and six patients with metastatic liver nodules were studied. They were diagnosed as having HCC or metastasis with helical dynamic computed tomography (CT) and/or celiac angiography. Tumor vascularities in the early arterial and postvascular phases were assessed by real-time scanning of advanced dynamic flow imaging and intermittent interval-delay scanning of contrast pulse subtraction imaging with a wide-band power Doppler technology. All patients showed hypervascular enhancement of HCC on contrast-enhanced US and/or dynamic CT. The advanced dynamic flow could be obtained as vascular and perfusion images of hepatic tumors. Tumor vascularities, including tumor vessels and parenchymal flow, were able to demonstrate in 27 of 29 nodules including 17 patients with 27 HCC nodules and 2 patients with 2 metastatic nodules before radiofrequency ablation (RFA) treatment by the advanced dynamic flow on contrast-enhanced harmonic US. Two nodules gave insufficient dynamic flow which were located approximately 12 cm in depth from the body surface. The advanced dynamic flow, which was done 7-10 days after RFA, indicated disappearance of the tumor vessels in 27 of visible 27 nodules. The study on early phase of helical dynamic CT revealed the same results as noted in early vascular phase of dynamic flow US. No major complication of RFA procedure was noted. The results indicated that contrast-enhanced advanced dynamic flow imaging on US clearly depicted intratumoral vascularity in real time and thus it is useful to diagnose and assess therapeutic efficacy in patients with HCC and metastatic liver tumor.     

Initial experience with contrast-enhanced sonography of the prostate

OBJECTIVE: We investigated the usefulness of contrast-enhanced sonography to depict vascularity in the prostate and improve the detection of prostatic cancer. SUBJECTS AND METHODS: Twenty-six patients with an elevated prostate-specific antigen level (> or = 4 ng/ml) or an abnormal digital rectal examination were enrolled in a phase II study of an i.v. injected sonographic contrast agent. Continuous gray-scale, intermittent gray-scale, phase inversion gray-scale, and power Doppler sonography of the prostate were performed. Sonographic findings were correlated with sextant biopsy results. RESULTS: After the administration of contrast material, gray-scale and Doppler images revealed visible enhancement (p < 0.05). Using intermittent imaging, we found focal enhancement in two isoechoic tumors that were not visible on baseline images. No definite focal area of enhancement was identified in any patient without cancer. Contrast-enhanced images revealed transient hemorrhage in the biopsy tracts of three patients. CONCLUSION: Enhancement of the prostate can be seen on gray-scale and Doppler sonographic images after the administration of an i.v. contrast agent. Contrast-enhanced intermittent sonography of the prostate may be useful for the selective enhancement of malignant prostatic tissue.     

Contrast-enhanced harmonic ultrasound imaging in ablation therapy for primary hepatocellular carcinoma

The success rate of percutaneous radiofrequency (RF) ablation for hepatocellular carcinoma (HCC) depends on correct targeting via an imaging technique. However, RF electrode insertion is not completely accurate for residual HCC nodules because B-mode ultrasound (US), color Doppler, and power Doppler US findings cannot adequately differentiate between treated and viable residual tumor tissue. Electrode insertion is also difficult when we must identify the true HCC nodule among many large regenerated nodules in cirrhotic liver. Two breakthroughs in the field of US technology, harmonic imaging and the development of second-generation contrast agents, have recently been described and have demonstrated the potential to dramatically broaden the scope of US diagnosis of hepatic lesions. Contrast-enhanced harmonic US imaging with an intravenous contrast agent can evaluate small hypervascular HCC even when B-mode US cannot adequately characterize tumor. Therefore, contrast-enhanced harmonic US can facilitate RF ablation electrode placement in hypervascular HCC, which is poorly depicted by B-mode US. The use of contrast-enhanced harmonic US in ablation therapy for liver cancer is an efficient approach.     

Sonazoid-enhanced sonography for guiding radiofrequency ablation for hepatocellular carcinoma: better tumor visualization by Kupffer-phase imaging and vascular-phase imaging after reinjection

Purpose  The purpose of this study was to assess the usefulness of contrast harmonic sonography with a newly developed sonographic contrast agent as a means of guidance for percutaneous radiofrequency (RF) ablation of hepatocellular carcinoma (HCC). Materials and methods  A total of 52 consecutive HCC lesions in 42 patients with HCC who underwent percutaneous RF ablation were included in this study. Altogether, 40 lesions in 35 patients were untreated HCC, and 12 lesions in 7 patients were local tumor progression of an HCC that had already been treated by other methods. We investigated tumors by Kupffer-phase imaging and vascular-phase imaging after reinjection. We performed RF ablation guided by Sonazoid-enhanced sonography using Kupffer-phase imaging and vascular-phase imaging after reinjection. Results  Conventional sonography identified 30 (57%) of 52 HCCs, whereas Sonazoid-enhanced sonography detected 50 (96%) of 52 HCCs (P < 0.01, McNemar’s χ² test). Complete ablation was achieved at a single session in 48 of 50 tumors. Conclusion  Sonazoid-enhanced sonography is a useful technique for guiding RF ablation of HCCs, even when treating local progression of a previously treated HCC.     

Contrast-enhanced subtraction harmonic sonography for evaluating treatment response in patients with hepatocellular carcinoma

OBJECTIVE: Our objective was to assess the usefulness of contrast-enhanced subtraction harmonic sonography in evaluating the treatment response of patients with hepatocellular carcinoma. SUBJECTS AND METHODS: Thirty-two hepatocellular carcinoma lesions in 26 patients (age range, 44-85 years; mean age, 66 years) were examined with Levovist-enhanced intermittent harmonic imaging before and after therapy. A Toshiba Powervision 8000 was used. A subtraction image was obtained by digitally subtracting the last-frame harmonic image from the first-frame image when multishot mode was preset. Results of contrast-enhanced CT were compared with the results of subtraction harmonic imaging. RESULTS: Before therapy, an enhancement pattern of tumor vascularity was seen for 93.8% (30/32) of hepatocellular carcinoma nodules on subtraction harmonic imaging. After therapy, subtraction harmonic imaging showed 46.7% (14/30) enhancement (incomplete tumor necrosis) and 53.3% (16/30) no enhancement (complete tumor necrosis). When dynamic CT was the gold standard, the sensitivity, specificity, and accuracy of subtraction harmonic imaging were 93.3%, 100%, and 96.7%, respectively. Intratumoral flow signals in hepatocellular carcinoma after therapy on harmonic imaging were used as a guide to target additional percutaneous therapy. CONCLUSION: Digital subtraction contrast-enhanced harmonic imaging can depict tumor vascularity in hepatocellular carcinoma after therapy sensitively and accurately. Because it is easy to perform and provides real-time needle insertion guidance, it may be preferable to perform after localized therapy to monitor treatment response, which will reduce unnecessary CT scanning.     

Radio-frequency ablation of VX2 rabbit tumors: assessment of completeness of treatment by using contrast-enhanced harmonic power Doppler US

PURPOSE: To assess contrast material-enhanced harmonic power Doppler and fundamental color Doppler ultrasonography (US) in the detection of residual viable tumor tissue after radio-frequency (RF) ablation in tumors embedded in fat. MATERIALS AND METHODS: Twenty-eight VX2 tumors were implanted into the retroperitoneum of 14 rabbits. Tumors were examined with contrast-enhanced fundamental color Doppler US and harmonic power Doppler US before and 10 minutes after RF ablation. Saline-enhanced RF ablation (30 mL/h) was performed over 10 minutes with 28-W RF power. Follow-up included repeat US examinations. Necropsies and histopathologic assessment were performed after detection of residual untreated tumor at US or 3 weeks after ablation. RESULTS: VX2 tumors reached a mean size of 21 mm +/- 9 (SD) (size range, 6-43 mm) 25 days after implantation. All tumors larger than 31 mm showed signs of central necrosis at US. Before ablation, intense vascularity was detected in all tumors with both contrast-enhanced US modes. Histopathologic assessment at the end of the follow-up period revealed local relapses due to incomplete ablation in 14 (50%) of 28 cases. Detection of residual tumor was missed in all cases with contrast-enhanced color Doppler US. Contrast-enhanced harmonic power Doppler US depicted residual flow in 12 of the 14 cases (sensitivity, 86%) in which local relapses occurred. There was a significant (P <.005, McNemar test) improvement in detection of residual tumor when the harmonic power Doppler mode was used. CONCLUSION: Contrast-enhanced harmonic power Doppler US has greater sensitivity than contrast-enhanced color Doppler US for detecting residual VX2 tumor following ablation. Therefore, contrast-enhanced harmonic power Doppler US may be a useful additional method for the detection of residual tumors after RF ablation.     

Use of fusion imaging combining contrast-enhanced ultrasonography with a perflubutane-based contrast agent and contrast-enhanced computed tomography for the evaluation of percutaneous radiofrequency ablation of hypervascular hepatocellular carcinoma

Objective

We evaluated the efficacy of fusion imaging, which fuses contrast-enhanced ultrasonography images with arterial-phase, contrast-enhanced CT images as a reference on a single screen in real time, for the evaluation of the effectiveness of radiofrequency ablation for treatment of hypervascular hepatocellular carcinoma.

Materials and methods

Eighty hepatocellular carcinoma lesions with a maximum diameter of between 1 and 3 cm that were scheduled for treatment with radiofrequency ablation were enrolled in this prospective study. After bolus injection of perflubutane-based contrast agent, fusion imaging combining contrast-enhanced ultrasonography images and arterial-phase, contrast-enhanced CT images was performed one day after radiofrequency ablation. We used two functions, which were subsets of the fusion imaging, to confirm the location of the hepatocellular carcinoma lesions in the ablated areas and to evaluate the presence or absence of an adequate safety margin. Contrast-enhanced CT was performed one month after the ablation. Two blinded observers reviewed the images obtained using both modalities to evaluate the effect of ablation.

Results

When the one-month contrast-enhanced CT images were used as the reference standard, the sensitivity, specificity, and accuracy of the one-day fusion imaging for the diagnosis of adequate ablation were 97%, 83%, and 96%, respectively; the kappa value for the agreement between the findings obtained using the two modalities was 0.75.

Conclusion

Fusion imaging combining contrast-enhanced ultrasonography images and arterial-phase, contrast-enhanced CT images as a reference appears to be a useful method for the early evaluation of the efficacy of radiofrequency ablation for the treatment of hypervascular hepatocellular carcinoma.     

Contrast-enhanced second-harmonic sonography in the detection of pseudocapsule in renal cell carcinoma

OBJECTIVE: Our purpose was to assess the capacity of contrast-enhanced second-harmonic sonography to detect a pseudocapsule in renal masses compared with conventional gray-scale sonography. SUBJECTS AND METHODS. Thirty-two patients with 40 renal masses suspicious for renal cancer (mean diameter, 3.1 cm) were prospectively studied with contrast-enhanced second-harmonic sonography during IV administration of a second-generation sonographic contrast agent. The sonographic criteria for the presence of a pseudocapsule were a peritumoral hypoanechoic halo on conventional gray-scale imaging and a rim of perilesional enhancement, increasing in the tardive phase of the examination, on contrast-enhanced second-harmonic imaging. Multiphasic helical CT or dynamic MRI or both were performed in all patients. RESULTS: Final diagnoses of the 40 renal masses were as follows: hemorrhagic cysts, five; angiomyolipomas, four; lymphomas, four; metastasis from lung cancer, one; and renal cell carcinomas (RCCs), 26. Histologic diagnosis of RCC was surgically obtained in all patients. Nephron-sparing surgery was performed in 12 of 26 RCCs, and radical nephrectomy was performed in the remaining 14. At pathologic examination, pseudocapsule was found in 14 (53.8%) of 26 RCCs. On conventional sonography, the presence of a pseudocapsule was detected in 3 of 14 RCCs (sensitivity, 21%). Sonographic contrast-enhanced harmonic imaging revealed the presence of pseudocapsule in 12 of 14 RCCs (sensitivity, 85.7%). In the remaining 12 RCCs with either absent or extensive neoplastic infiltration of pseudocapsule seen at pathologic evaluation, pseudocapsule was not visible on either conventional or contrast-enhanced second-harmonic sonography. The pseudocapsule was not visible in any of the 14 noncancerous renal masses on either conventional or contrast-enhanced sonography. CONCLUSION: Sonographic contrast-specific imaging with a second-generation contrast agent is effective in improving the sonographic visualization of tumoral pseudocapsule. This finding could be useful both in the sonographic diagnosis and in the choice of conservative surgery for renal cell carcinoma. The potential role of second-harmonic contrast-enhanced sonography in the management of renal cell carcinoma should be investigated in larger series and compared with the findings of state-of-the-art MRI and CT.     

Assessment of the ablated area after radiofrequency ablation by contrast-enhanced sonography; comparison with virtual sonography with magnetic navigation

This study investigated whether contrast-enhanced sonography can accurately predict the ablated area by radiofrequency ablation using virtual sonography by computed tomography as a gold standard.Thirty-one hepatocellular carcinoma nodules were treated by radiofrequency ablation and then examined. The defect of contrast-enhanced sonography (puncture direction: r=.868, P<.0001; perpendicular direction; r=.925, P<.0001) was closely correlated with the unenhanced area of virtual sonography.Contrast-enhanced sonography can be used for early and accurate prediction of the ablated area and is helpful for assessing local control of radiofrequency ablation.     

Hepatocellular carcinoma treated with radio-frequency ablation: spectrum of imaging findings.

Contrast material-enhanced Doppler or gray-scale harmonic ultrasonography (US) may help determine the completeness or long-term therapeutic efficacy of radio-frequency (RF) ablation of hepatocellular carcinoma (HCC). Successfully treated HCC is devoid of vascularity at color or power Doppler US. When the tumor is not completely treated, residual viable tumor can be detected. These contrast-enhanced US techniques may also help identify residual tumor when performed during repeat RF ablation, when accurate localization of viable tumor is needed. To date, contrast-enhanced computed tomography (CT) has been the most widely used imaging modality in the evaluation of therapeutic response after RF ablation of HCC. At follow-up CT, successfully ablated lesions appear as low-attenuation areas with no foci of contrast enhancement either within or at the periphery of the treated lesion, whereas any foci of enhancement indicate residual or recurrent tumor. Reactive hyperemia in tissue surrounding the ablated lesion, iatrogenic arterioportal shunting, and small intralesional air pockets are frequently seen at immediate follow-up CT. Gadolinium-enhanced dynamic magnetic resonance imaging is also useful in assessing therapeutic response following RF ablation of HCC, particularly when CT findings are inconclusive. Familiarity with these imaging findings is helpful in this setting. Copyright RSNA, 2003.     

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

Purpose

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.

Patients and methods

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.

Results

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.

Conclusion

Virtual CT sonography with magnetic navigation was useful in evaluating the treatment response of radiofrequency ablation therapy for hepatocellular carcinoma.