Preoperative RFA simulation for liver cancer using a CT virtual ultrasound system

Ultrasound fusion imaging technologies for guidance in ablation therapy for liver cancer

With advances in imaging technology, images from ultrasound (US) and computed tomography (CT) or magnetic resonance imaging (MRI) can be displayed simultaneously and in real time, according to the angle of the transducer. CT/MR-US fusion imaging improves the visualization of inconspicuous hepatocellular carcinoma (HCC) and helps us to understand the three-dimensional relationship between the liver vasculature and HCC. US fusion imaging guidance facilitates improvement in the treatment response for HCC with poor conspicuity, and the rates of technical success of ablation and local tumor progression for inconspicuous HCC range from 94.4 to 100% and 0 to 8.3%, respectively. Moreover, the development of image fusion has made it possible to compare and overlay pre- and post-ablation US images. This US-US fusion imaging allows side-by-side comparison of the ablative margin, while US-US overlay fusion can visualize the ablative margin because the tumor image is projected onto the ablative hyperechoic zone. Thus, US-US overlay fusion guidance is highly effective for safety margin achievement in local ablation therapy for HCC, providing a lower risk of local tumor progression. This manuscript reviews the current status of ultrasound fusion imaging for percutaneous ablation therapy of HCC.

Ultrasound fusion imaging of hepatocellular carcinoma: a review of current evidence

With advances in technology, imaging techniques that entail fusion of sonography and CT or MRI have been introduced in clinical practice. Ultrasound fusion imaging provides CT or MRI cross-sectional multiplanar images that correspond to the sonographic images, and fusion imaging of B-mode sonography and CT or MRI can be displayed simultaneously and in real time according to the angle of the transducer. Ultrasound fusion imaging helps us understand the three-dimensional relationship between the liver vasculature and tumors, and can detect small liver tumors with poor conspicuity. This fusion imaging is attracting the attention of operators who perform radiofrequency ablation (RFA) for the treatment of hepatic malignancies because this real-time, multimodality comparison can increase monitoring and targeting confidence during the procedure. When RFA with fusion imaging was performed on small hepatocellular carcinomas (HCCs) with poor conspicuity, it was reported that the rates of technical success and local tumor progression were 94.4-100% and 0-8.3%. However, there have been no studies comparing fusion imaging guidance and contrast-enhanced sonography, CT or MRI guidance in ablation. Fusion imaging-guided RFA has proved to be effective for HCCs that are poorly defined on not only conventional B-mode sonography but also contrast-enhanced sonography. In addition, fusion imaging could be useful to assess the treatment response of RFA because of three-dimensional information. Here, we give an overview of the current status of ultrasound fusion imaging for clinical application in the liver.

The feasibility study of US-MRI virtual navigation in the shoulder

PURPOSE

The aim of this study was to evaluate the feasibility of ultrasound sonography (US)-magnetic resonance imaging (MRI) virtual navigation in the shoulder.

METHODS

We selected 10 healthy volunteers and 10 patients with supraspinatus tendinitis to fuse in the shoulder with a Virtual Navigator System. We selected five internal marks as follows: (1) ① acromion, ② the point of junction between the supraspinatus muscle and the tendon, ③ the point of the middle in the surface of the head of humerus in the plane of ②, ④ the point of attachment of the supraspinatus tendon in the great tuberosity of humerus, and ⑤ the point of the middle in the surface of the head of humerus in the plane of ④. To make three, four, and five marks in different combinations in the process of image fusion successively, it should be based on these points. The observed targets included coincidence, stability, and accuracy in the sonography and magnetic resonance images by two radiologists.

RESULTS

The supraspinatus tendon of the 10 volunteers and the lesions of 10 patients with supraspinatus tendinitis could be fused between the sonography image and the magnetic resonance image. The effect of the combination of ②+③+④+⑤ in the group with four-point internal marks was most satisfactory (P<.05).

CONCLUSION

The process of the combination of ②+③+④+⑤ in the group with four-point internal marks is considered the best method, and the application of US-MRI virtual navigation is regarded feasible in the shoulder.

Efficacy of fusion imaging combining sonography and hepatobiliary phase MRI with Gd-EOB-DTPA to detect small hepatocellular carcinoma

OBJECTIVE

We evaluated the efficacy of fusion imaging that fuses conventional sonography images with hepatobiliary phase contrast-enhanced MR images obtained with gadolinium-ethoxybenzyl-diethylenetriamine pentaacetic acid (Gd-EOB-DTPA) as the reference image for the detection of hepatocellular carcinomas (HCCs).

SUBJECTS AND METHODS

Eighty-seven HCCs with a maximum diameter of between 1 and 3 cm at the time of diagnosis were enrolled in this prospective study. We compared the detection rates of HCCs using three sonography modalities: conventional sonography, late phase of contrast-enhanced sonography with Sonazoid, and fusion imaging combining conventional sonography and the hepatobiliary phase of contrast-enhanced MRI with Gd-EOB-DTPA as the reference image. The comparisons were made using the McNemar test.

RESULTS

The detection rate of HCCs using fusion imaging (98%, 85/87) was significantly higher than the detection rates using conventional sonography (76%, 66/87) and contrast-enhanced sonography (83%, 72/87) (p<0.01, for both). For small HCCs (maximum diameter, 1-2 cm), the detection rate using fusion imaging (97%, 59/61) was also significantly higher than those using conventional sonography (66%, 40/61) and contrast-enhanced sonography (80%, 49/61) (p<0.01, for both). The detection rate for atypical HCCs was also significantly higher using fusion imaging (95%, 18/19) than using conventional sonography (53%, 10/19) and contrast-enhanced sonography (26%, 5/19) (p<0.01, for both).

CONCLUSION

Fusion imaging combining conventional sonography and the hepatobiliary phase of contrast-enhanced MRI with Gd-EOB-DTPA is more sensitive than conventional sonography or contrast-enhanced sonography for detecting HCCs, especially small or atypical HCCs.

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.

Magnetic navigation in ultrasound-guided interventional radiology procedures

AIM

To evaluate the usefulness of magnetic navigation in ultrasound (US)-guided interventional procedures.

MATERIALS AND METHODS

Thirty-seven patients who were scheduled for US-guided interventional procedures (20 liver cancer ablation procedures and 17 other procedures) were included. Magnetic navigation with three-dimensional (3D) computed tomography (CT), magnetic resonance imaging (MRI), 3D US, and position-marking magnetic navigation were used for guidance. The influence on clinical outcome was also evaluated.

RESULTS

Magnetic navigation facilitated applicator placement in 15 of 20 ablation procedures for liver cancer in which multiple ablations were performed; enhanced guidance in two small liver cancers invisible on conventional US but visible at CT or MRI; and depicted the residual viable tumour after transcatheter arterial chemoembolization for liver cancer in one procedure. In four of 17 other interventional procedures, position-marking magnetic navigation increased the visualization of the needle tip. Magnetic navigation was beneficial in 11 (55%) of 20 ablation procedures; increased confidence but did not change management in five (25%); added some information but did not change management in two (10%); and made no change in two (10%). In the other 17 interventional procedures, the corresponding numbers were 1 (5.9%), 2 (11.7%), 7 (41.2%), and 7 (41.2%), respectively (p=0.002).

CONCLUSION

Magnetic navigation in US-guided interventional procedure provides solutions in some difficult cases in which conventional US guidance is not suitable. It is especially useful in complicated interventional procedures such as ablation for liver cancer.

Percutaneous sonographically guided radio frequency ablation of hepatocellular carcinoma: causes of mistargeting and factors affecting the feasibility of a second ablation session

OBJECTIVES

The purposes of this study were to evaluate the causes of mistargeting during percutaneous sonographically guided radio frequency ablation in patients with hepatocellular carcinoma and to determine factors affecting the feasibility of a second ablation session.

METHODS

This study received Institutional Review Board approval, and informed consent was waived. Among 2213 percutaneous sonographically guided radio frequency ablations performed in our hospital, we searched for mistargeting cases and analyzed the causes of mistargeting. To determine which factors affected the feasibility of a second ablation session, univariate and multivariate analyses were performed.

RESULTS

Forty-one cases of mistargeting occurred during the first ablation session, and 4 cases occurred during the second session. Of the 41 patients with mistargeted hepatocellular carcinomas during the first session, 39 who underwent replanning sonography were able to be analyzed for causes of mistargeting. The most common cause of mistargeting was confusion with cirrhotic nodules (87.2% [34 of 39]), followed by poor conspicuity of the hepatocellular carcinoma (69.2% [27 of 39]), a poor sonic window (28.2% [11 of 39]), a poor electrode path (7.7% [3 of 39]), and inaccurate electrode placement (2.6% [1 of 39]). Artificial ascites (P = .035) and the presence of more than 3 mistargeting causes (P = .017) were independent factors affecting feasibility.

CONCLUSIONS

The most common cause of mistargeting was confusion with cirrhotic nodules, followed by poor conspicuity of the hepatocellular carcinoma, a poor sonic window, a poor electrode path, and inaccurate electrode placement. The use of artificial ascites and the presence of more than 3 mistargeting causes were factors affecting the feasibility of a second radio frequency ablation session.

Recurrent hepatocellular carcinoma after transcatheter arterial chemoembolization: planning sonography for radio frequency ablation

OBJECTIVES

The purposes of this study were to evaluate the sonographic findings of recurrent hepatocellular carcinoma after transcatheter arterial chemoembolization and to determine how often the lesion conspicuity of the recurrent hepatocellular carcinoma makes it suitable for percutaneous sonographically guided radio frequency ablation.

METHODS

A radiologist prospectively classified the echogenicity of recurrent hepatocellular carcinomas compared to that of the surrounding liver. In addition, the margin of the tumor was classified as follows: grade 1, absolutely indistinguishable; grade 2, less than 50%; grade 3, greater than 50%; and grade 4, clearly demarcated. The lesion conspicuity was also classified as follows: grade 1, absolutely invisible, thus ineligible for percutaneous sonographically guided radio frequency ablation; grade 2, poorly visible, thus unsuitable for ablation; and grade 3, visible and conspicuous, thus suitable for ablation.

RESULTS

A total of 37 consecutive patients (31 men and 6 women; mean age, 59.4 years) with 38 hepatocellular carcinomas were enrolled. The echogenicity of the recurrent hepatocellular carcinomas varied, with the most common finding being a heterogeneous hypoechoic lesion (31.6%), followed by an isoechoic lesion (23.7%), a heterogeneous hyperechoic lesion (18.4%), a homogeneous hypoechoic lesion (13.2%), a lesion with a hypoechoic halo (10.5%), and a homogeneous hyperechoic lesion (2.7%). The margin of the recurrent hepatocellular carcinomas was clearly demarcated in only 28.9% of tumors, whereas 23.7% of the tumors were absolutely indistinguishable from the surrounding liver. The lesion conspicuity was classified as grade 3 in only 60.5% of the recurrent hepatocellular carcinomas.

CONCLUSIONS

The echogenicity and margins of recurrent hepatocellular carcinomas after transcatheter arterial chemoembolization varied. The lesion conspicuity was suitable for sonographically guided radio frequency ablation in only 60.5% of cases.

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.

Contrast-enhanced sonography-guided radiofrequency ablation for the local recurrence of previously treated hepatocellular carcinoma undetected by B-mode sonography

BACKGROUND.: The purpose of this study was to assess the usefulness of contrast-enhanced sonography (CEUS) with Sonazoid to demonstrate local recurrence of hepatocellular carcinoma previously treated with radiofrequency ablation (RFA) and not seen on conventional sonography, prior to repeat RFA. METHODS.: This study included 16 cirrhotic patients with 17 cases of hypervascular locally recurrent hepatocellular carcinoma found by contrast-enhanced multidetector row CT (MDCT) but not seen on noncontrast sonography. We used Kupffer-phase imaging and vascular-phase imaging after re-injection. The morphologic patterns of local recurrence detected on CEUS were compared with those on MDCT. We performed repeat RFA guided by CEUS using Kupffer-phase imaging after re-injection. RESULTS.: We were able to detect on CEUS the location of all local recurrences with positive enhancement after re-injection. The morphologic patterns of local recurrence on CEUS were in concordance with those found on MDCT in all lesions. Repeat percutaneous RFA was successfully performed in all lesions. CONCLUSIONS.: The CEUS appearance of local recurrences correlated well with those on MDCT. A wider use of CEUS to guide repeat of percutaneous RFA may be possible with Sonazoid.

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 chi2 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.

Radiofrequency ablation of hepatocellular carcinoma: value of virtual CT sonography with magnetic navigation

OBJECTIVE

Virtual CT sonography with magnetic navigation yields cross-sectional images of CT volume data that correspond to the angle of the transducer in the magnetic field in real time. The purpose of this study was to evaluate the efficiency and feasibility of virtual CT sonography for radiofrequency ablation of hypervascular hepatocellular carcinoma poorly defined on B-mode sonography.

MATERIALS AND METHODS

One hundred one patients enrolled in the study were separated into two groups. Fifty-one patients with 65 hepatocellular carcinomas underwent prospective virtual CT sonography as guidance for radiofrequency ablation. Fifty patients with 63 hepatocellular carcinomas managed with B-mode sonographic guidance were retrospectively selected under the same conditions as the virtual CT sonography group to act as a historical control group.

RESULTS

In the virtual CT sonography group, technically successful ablation was achieved in a single session in 92% (47/51) of the patients and in two sessions in 8% (4/51). In the B-mode sonography group, technical success was achieved in a single session in 72% (36/50) of the patients, in two sessions in 24% (12/50), and in three sessions in 4% (2/50). Treatment analysis showed that the technical success rate after a single treatment session was significantly (p = 0.017) higher for the virtual CT sonography group. The number of treatment sessions was significantly (p = 0.021) lower for the virtual CT sonography group (mean, 1.1 +/- 0.1 vs 1.3 +/- 0.3 sessions).

CONCLUSION

Virtual CT sonographically assisted radiofrequency ablation is an efficient treatment of patients with hepatocellular carcinoma that is poorly defined on B-mode sonography.

Ablation therapy guided by contrast-enhanced sonography with Sonazoid for hepatocellular carcinoma lesions not detected by conventional sonography

OBJECTIVE

We evaluated the usefulness of contrast-enhanced harmonic gray scale sonography with a newly developed sonographic contrast medium as a means of guidance for percutaneous ablation therapy of hepatocellular carcinoma lesions not detected by conventional sonography.

METHODS

We examined 85 patients with 108 hepatocellular carcinoma lesions that were identified as hypervascular by multidetector-row computed tomography by using contrast-enhanced harmonic gray scale sonography after injection of Sonazoid (GE Healthcare, Oslo, Norway), a lipid-stabilized suspension of a perfluorobutane gas microbubble contrast agent. We scanned the whole liver by this modality at a low mechanical index in the late phase to detect lesions not detected by conventional sonography and then scanned the lesions again by this modality at a high mechanical index to visualize tumor vessels and enhancement. We also performed percutaneous ablation therapy guided by this modality to treat viable hepatocellular carcinoma lesions that could not be detected by conventional sonography.

RESULTS

Conventional sonography identified 90 (83%) of 108 hepatocellular carcinoma lesions; 15 (14%) additional viable lesions not detected by conventional sonography were detected in the late phase of contrast-enhanced harmonic gray scale sonography at a low mechanical index, and tumor vessels and enhancement were observed in the late phase at a high mechanical index. Contrast-enhanced harmonic gray scale sonography diagnosed 105 (97%) of the 108 viable hepatocellular carcinoma lesions, and 14 (93%) of the 15 lesions not detected by conventional sonography were successfully treated by percutaneous ablation therapy guided by this modality.

CONCLUSIONS

Contrast-enhanced harmonic gray scale sonography is useful for guidance of percutaneous ablation therapy of hepatocellular carcinoma lesions not detected by conventional sonography.