Evaluation of virtual CT sonography for enhanced detection of small hepatic nodules: a prospective pilot study

WFUMB Review Paper. Incidental Findings in Otherwise Healthy Subjects, How to Manage: Liver

An incidental focal liver lesion (IFLL) is defined as a hepatic lesion identified in a patient imaged for an unrelated reason. They are frequently encountered in daily practice, sometimes leading to unnecessary, invasive and potentially harmful follow-up investigations. The clinical presentation and the imaging aspects play an important role in deciding if, and what further evaluation, is needed. In low-risk patients (i.e., without a history of malignant or chronic liver disease or related symptoms), especially in those younger than 40 years old, more than 95% of IFLLs are likely benign. Shear Wave liver Elastography (SWE) of the surrounding liver parenchyma should be considered to exclude liver cirrhosis and for further risk stratification. If an IFLL in a low-risk patient has a typical appearance on B-mode ultrasound of a benign lesion (e.g., simple cyst, calcification, focal fatty change, typical hemangioma), no further imaging is needed. Contrast-Enhanced Ultrasound (CEUS) should be considered as the first-line contrast imaging modality to differentiate benign from malignant IFLLs, since it has a similar accuracy to contrast-enhanced (CE)-MRI. On CEUS, hypoenhancement of a lesion in the late vascular phase is characteristic for malignancy. CE-CT should be avoided for characterizing probable benign FLL and reserved for staging once a lesion is proven malignant. In high-risk patients (i.e., with chronic liver disease or an oncological history), each IFLL should initially be considered as potentially malignant, and every effort should be made to confirm or exclude malignancy. US-guided biopsy should be considered in those with unresectable malignant lesions, particularly if the diagnosis remains unclear, or when a specific tissue diagnosis is needed.

A review of virtual reality in radiology

Virtual reality (VR) is not new to the field of medicine or radiology but has grown exponentially in recent years. Exploration of VR in medicine to augment educational experiences and aid in procedural training began in the 1990s. Surgeons have benefited from VR, both for training and planning purposes. The use of VR has been applied throughout the field of radiology with applications in imaging interpretation and procedural training. VR systems have been developed for integration with computed tomography (CT)-guided interventions and ultrasound (US)-guided interventions, and there is a growing amount of information available about the applications of the technology developed specifically for various organ systems, including breast, prostate, liver, renal, lung, cardiovascular, and thyroid. This review provides an overview and update of the use of VR in radiology.

Real-time virtual sonography-assisted radiofrequency ablation in liver tumors with conspicuous or inconspicuous images or peritumoral landmarks under ultrasonography

Objectives

The objectives of this study were to determine the primary technique effectiveness (PTE), to compare the complete response and local recurrence rates between conspicuous and inconspicuous tumors using single and switching electrodes of real-time virtual sonography (RVS)-assisted radiofrequency ablation (RFA) in conspicuous and inconspicuous hepatic tumors under conventional ultrasonography (US).

Subjects and method

We compared the complete ablation of inconspicuous tumors with and without anatomical landmark (N = 54) with conspicuous liver tumors (N = 272). Conventional US imaging was done initially, and then these images were fused with CT or MRI arterial-venous-wash-out cross-sectional studies and synchronized with real-time US images.

Results

RVS-assisted RFA was technically feasible in all patients. The PTE rate after the first ablation was 94% (245/261) for conspicuous tumors, 88% (7/8) in inconspicuous tumors with landmark, and 78% (36/46) in inconspicuous tumors without landmark. The complete response (p = 0.1912 vs. p = 0.4776) and local recurrence rate (p = 0.1557 vs. p = 0.7982) were comparable in conspicuous tumors of both HCC and liver metastasis group when single or multiple switching was used. The cumulative local recurrence in the conspicuous and inconspicuous tumors of the HCC group (p = 0.9999) was almost parallel after 12 (10% vs. 4%) and 24 (13% vs. 4%) months of follow-up. In the liver metastasis group, the cumulative local recurrence for conspicuous tumors (p = 0.9564) was nearly equal after 12 and 24 months of monitoring (24% vs. 27%) while no recurrence was incurred for the inconspicuous tumors.

Conclusion

RVS-assisted RFA is an effective tool for the treatment of conspicuous and inconspicuous HCC and hepatic metastasis.

Ultrasound 2020 - Diagnostics & Therapy: On the Way to Multimodal Ultrasound: Contrast-Enhanced Ultrasound (CEUS), Microvascular Doppler Techniques, Fusion Imaging, Sonoelastography, Interventional Sonography

BACKGROUND

 Ultrasound as a non-ionizing imaging procedure is one of the most important diagnostic procedures in everyday clinical practice. The technology is widely used. Due to constant technical innovations, sonographic procedures, such as contrast-enhanced ultrasound (CEUS), sonoelastography, new microvascular Doppler modalities and, as an example of interventional procedures, sonographically controlled microwave ablation (MWA), are becoming increasingly important in diagnostic imaging and interventional medicine alongside CT and MRI. However, this also requires greater expertise, specialization and qualification on the part of users.

METHOD

 This review article provides information about the range of technical innovations in ultrasound in recent years and describes the underlying technology, the clinical applications, and their diagnostic value. These are presented in the context of the current literature, explaining their advantages and disadvantages and their clinical value.

RESULTS AND CONCLUSION

 Contrast-enhanced ultrasound (CEUS), microvascular Doppler modalities, fusion imaging and elastography complement B-scan ultrasound and conventional Doppler procedures for various problems. Microwave ablation (MWA) has a firm place as an ablative procedure for local tumor therapy in different organ systems and can be performed under ultrasound guidance. Thanks to new developments, the possibilities of ultrasound are now greater than ever. Knowledge of the technology, indications, and possible applications of newer procedures is essential for adequate patient care.

KEY POINTS

  · Contrast-enhanced ultrasound (CEUS) allows an increase in sensitivity and specificity in the assessment of parenchymal lesions.. · CEUS allows the microperfusion to be visualized and quantified. For larger vessels, CEUS is an important instrument in diagnosing endoleak after stenting.. · Microvascular Doppler techniques with clutter suppression algorithms allow a more accurate representation of the smallest vessels than regular color or power Doppler.. · Elastography of the liver in diffuse hepatopathies is a noninvasive diagnostic tool to exclude higher grade fibrosis/cirrhosis.. · Microwave ablation (MWA) also offers sonographically controlled ablation of tumors..

CITATION FORMAT

· Kloth C, Kratzer W, Schmidberger J et al. Ultrasound 2020 - Diagnostics & Therapy: On the Way to Multimodal Ultrasound: Contrast-Enhanced Ultrasound (CEUS), Microvascular Doppler Techniques, Fusion Imaging, Sonoelastography, Interventional Sonography . Fortschr Röntgenstr 2021; 193: 23 - 32.

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.

Clinical Value of Real-Time Ultrasonography-MRI Fusion Imaging for Second-Look Examination in Preoperative Breast Cancer Patients: Additional Lesion Detection and Treatment Planning

BACKGROUND

This study was conducted to evaluate the clinical effect of real-time magnetic resonance imaging (MRI)-navigated ultrasonography (US) for preoperative second-look examination in patients with breast cancer.

PATIENTS AND METHODS

Between October 2013 and February 2015, 232 patients with breast cancer underwent MRI for staging; second-look US was performed in 70 patients to evaluate additional lesions suspected to be disease detected using MRI. We retrospectively included 67 lesions in 55 patients. Lesions were classified as detected on conventional US (group 1), and not visible on conventional US, but detected on MRI-navigated US (group 2). The imaging features between groups 1 and 2 were compared using Student t, χ², or Fisher exact tests. We compared the detection rate and histopathology of additional lesions using a McNemar test.

RESULTS

Heterogeneous background echotexture (69.6% [16 of 23] vs. 34.1% [14 of 41]) and lesion isoechogenicity (65.2% [15 of 23] vs. 7.3% [3 of 41]) on US and middle or posterior lesion depth on MRI (78.3% [18 of 23] vs. 46.3% [19 of 41]) were more common in group 2 (P < .05). More lesions were detected using MRI-navigated US (64 of 67; 95.5%) than conventional US (41 of 67; 61.2%; P < .01). Using MRI-navigated US we found more high-risk or malignant lesions than conventional US (21 vs. 11; P < .01). The optimal treatment plan was determined for 9 of 16 (56.3%) patients by virtue of MRI-navigated US.

CONCLUSION

Real-time MRI-navigated US significantly improved the detection of additional high-risk or malignant lesions during second-look US in preoperative evaluation of patients with breast cancer and ultimately determined the optimal treatment plan.

Real-Time MRI Navigated Ultrasound for Preoperative Tumor Evaluation in Breast Cancer Patients: Technique and Clinical Implementation

Real-time magnetic resonance imaging (MRI) navigated ultrasound is an image fusion technique to display the results of both MRI and ultrasonography on the same monitor. This system is a promising technique to improve lesion detection and analysis, to maximize advantages of each imaging modality, and to compensate the disadvantages of both MRI and ultrasound. In evaluating breast cancer stage preoperatively, MRI and ultrasound are the most representative imaging modalities. However, sometimes difficulties arise in interpreting and correlating the radiological features between these two different modalities. This pictorial essay demonstrates the technical principles of the real-time MRI navigated ultrasound, and clinical implementation of the system in preoperative evaluation of tumor extent, multiplicity, and nodal status in breast cancer patients.

Virtual sonography for novice sonographers: usefulness of SYNAPSE VINCENT® with pre-check imaging of tumor location

PURPOSE

To evaluate the usefulness of a virtual ultrasound (US) imaging device as a tool to assist novice sonographers.

MATERIALS AND METHODS

A prospective blinded pilot study was conducted involving patients with liver lesions. Two sonographers and 2 medical doctors with less than 5 years of experience performed US examinations. The time needed to detect liver lesions on US and the success rate for detecting liver lesions with and without using the virtual US imaging device SYNAPSE VINCENT® (Fujifilm Medical Co., Tokyo, Japan) before US examination were evaluated.

RESULTS

Thirty-two patients with the following 42 liver lesions were included: liver cyst (n = 24), hemangioma (n = 8), hepatocellular carcinoma (n = 6), and liver metastasis (n = 4). The maximal diameter of these lesions ranged from 0.3 to 1.5 cm (mean ± SD, 0.8 ± 0.4). The average time for detecting liver lesions on US was 47.8 s (range, 7-113) with VINCENT and 112.9 s (range, 14-313) without VINCENT before US examination. There were significant differences in the duration of US examination with and without VINCENT (p = 0.0002, Student's t test). The rates for accurately detecting liver lesions were 100 and 76.2% (16/21) in US beginners with and without VINCENT, respectively. Significantly higher detection rates were found in the US beginners who used VINCENT compared to those who did not use VINCENT (p = 0.047, Fisher's exact test).

CONCLUSION

Before US examination, a reference with VINCENT could contribute to the successful detection of liver lesions and could be time-saving for US beginners.

Real-time image fusion for successful percutaneous radiofrequency ablation of hepatocellular carcinoma

Percutaneous radiofrequency ablation (RFA) is an established nonsurgical curative treatment for hepatocellular carcinoma (HCC). Because of its efficiency and safety, sonography is the most commonly used imaging modality when performing RFA. However, the presence of HCC nodules that are inconspicuous when using conventional sonography is a major drawback of RFA and limits its feasibility as a treatment for HCC. However, a new technology has been developed that synthesizes high-resolution multiplanar reconstruction images using 3-dimensional data and is combined with a position-tracking system using magnetic navigation. With this technology, real-time sonograms can be fused with corresponding computed tomographic, magnetic resonance imaging, or even sonographic volume data; this process is known as real-time image fusion. In this article, we describe this novel imaging method as a useful tool for successful RFA treatment 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.

Preliminary study on evaluation of the pancreatic tail observable limit of transabdominal ultrasonography using a position sensor and CT-fusion image

BACKGROUND AND AIM

Transabdominal ultrasonography (US) is commonly used for the initial screening of bilio-pancreatic diseases in Asian countries due to its widespread availability, the non-invasiveness and the cost-effectiveness. However, it is considered that US has limits to observe the area, namely the blind area. The observation of the pancreatic tail is particularly difficult. The goal of this study was to examine the pancreatic tail region that cannot be visualized on transverse scanning of the upper abdomen using US with spatial positional information and factors related to visualization, and observation of the tail from the splenic hilum.

METHODS

Thirty-nine patients with pancreatic/biliary tract disease underwent CT and US with GPS-like technology and fusion imaging for measurement of the real pancreatic length and the predicted/real unobservable (PU and RU) length of the pancreatic tail. RU from US on transverse scanning and the real pancreatic length were used to determine the unobservable area (UA: RU/the real pancreatic length). Relationships of RU with physical and hematological variables that might influence visualization of the pancreatic tail were investigated.

RESULTS

The real pancreatic length was 160.9 ± 16.4mm, RU was 41.0 ± 17.8mm, and UA was 25.3 ± 10.4%. RU was correlated with BMI (R=0.446, P=0.004) and waist circumferences (R=0.354, P=0.027), and strongly correlated with PU (R=0.788, P<0.001). The pancreatic tail was visible from the splenic hilum in 22 (56%) subjects and was completely identified in 13 (33%) subjects.

CONCLUSIONS

Combined GPS-like technology with fusion imaging was useful for the objective estimation of the pancreatic blind area.

Virtual CT sonographically guided biopsy of a retroperitoneal mass in a patient with Erdheim-Chester disease

Image fusion between sonography and CT allows real-time synchronization of CT multiplanar reconstructed images with the corresponding sonographic images. This technique has mainly been used in liver imaging. We report the use of image fusion to target and successfully guide the percutaneous biopsy of a retroperitoneal a mass. This technique represents a promising tool in abdominal imaging, and it should be considered for the biopsy of lesions that are difficult to approach with conventional imaging guidance techniques.

Assessing patients with hepatocellular carcinoma meeting the Milan criteria: Is liver 3 tesla MR with gadoxetic acid necessary in addition to liver CT?

PURPOSE

To determine the added value of 3 Tesla liver MR in patients with hepatocellular carcinoma (HCC) within the liver computed tomography (CT) -based Milan criteria.

MATERIALS AND METHODS

Liver CT and MR images of 130 patients with HCC within the Milan criteria based on liver CT were retrospectively reviewed. The number of MR-diagnosed HCCs and that of high risk hypervascular nodules (HRHNs), the effect of obtaining MR on patient management and CT appearances of MR-diagnosed HCCs and those of HRHNs were evaluated. Independent predictor for diagnosing additional HCCs on liver MR was analyzed.

RESULTS

A total of 18.5% (24/130) of patients had additional 39 HCCs on MR, with a 5.4% (7/130) dropout rate from the Milan criteria. 28.5% (37/130) of patients had additional 78 HRHNs. Overall, 39.2% (51/130) of patients required changes in management. The common CT appearances of MR-diagnosed HCCs were arterial enhancing lesions ≥ 0.5cm (38.4%, 15/39), low density nodules < 1.5 cm (30.8%, 12/39) and invisibility (28.2%, 11/39). For MR-diagnosed HRHNs, 55.1% (43/78) were invisible on CT. The presence of inconclusive lesions on CT was an independent predictor for diagnosing additional HCCs on MR.

CONCLUSION

For patients with HCCs within the Milan criteria on liver CT, liver MR may be necessary to detect additional HCCs and HRHNs.

Real-time virtual sonography visualization and its clinical application in biliopancreatic disease

AIM: To evaluate the usefulness of real-time virtual sonography (RVS) in biliary and pancreatic diseases.

METHODS: This study included 15 patients with biliary and pancreatic diseases. RVS can be used to observe an ultrasound image in real time by merging the ultrasound image with a multiplanar reconstruction computed tomography (CT) image, using pre-scanned CT volume data. The ultrasound used was EUB-8500 with a convex probe EUP-C514. The RVS images were evaluated based on 3 levels, namely, excellent, good and poor, by the displacement in position.

RESULTS: By combining the objectivity of CT with free scanning using RVS, it was possible to easily interpret the relationship between lesions and the surrounding organs as well as the position of vascular structures. The resulting evaluation levels of the RVS images were 12 excellent (pancreatic cancer, bile duct cancer, cholecystolithiasis and cholangiocellular carcinoma) and 3 good (pancreatic cancer and gallbladder cancer). Compared with conventional B-mode ultrasonography and CT, RVS images achieved a rate of 80% superior visualization and 20% better visualization.

CONCLUSION: RVS has potential usefulness in objective visualization and diagnosis in the field of biliary and pancreatic diseases.

Fusion imaging-guided percutaneous biopsy of focal hepatic lesions with poor conspicuity on conventional sonography

OBJECTIVES

The purpose of this study was to evaluate the effectiveness of real-time fusion imaging (sonography combined with computed tomography or magnetic resonance imaging) for percutaneous sonographically guided biopsy of focal hepatic lesions with poor sonographic conspicuity.

METHODS

This study was conducted as a retrospective analysis of a prospective database and was approved by the Institutional Review Board. Patients who had target lesions with poor conspicuity on B-mode sonography for percutaneous biopsy were enrolled in the study. Lesion conspicuity was assessed by conventional B-mode sonography first and then by fusion imaging later in the same session. We compared lesion conspicuity and detection rates between B-mode sonography and fusion imaging and evaluated how many cases of initially invisible lesions on B-mode sonography became visible on fusion imaging. The technical success rate was evaluated on the basis of the final diagnoses, which were established by pathologic examination of the biopsy specimens as well as follow-up clinical and radiologic examinations.

RESULTS

A total of 22 patients were enrolled in the study. On fusion imaging, lesion conspicuity was increased in 63.6% of focal hepatic lesions (14 of 22). Moreover, 66.7% of lesions (6 of 9) that were invisible on B-mode sonography became visible on fusion imaging. The true-positive detection rate was significantly different between B-mode sonography and fusion imaging (9 of 22 versus 19 of 22; P = .0044). Percutaneous biopsy was performed for all lesions, including 3 target lesions that were invisible even on fusion imaging. The technical success rate was 95.5% (21 of 22).

CONCLUSIONS

Fusion imaging is effective for percutaneous biopsy of focal hepatic lesions with poor sonographic conspicuity.

Advanced ultrasonography technologies to assess the effects of radiofrequency ablation on hepatocellular carcinoma

Background

Radiofrequency ablation (RFA) is a curative therapy for hepatocellular carcinoma (HCC). In RFA, ultrasonography (US) is most commonly used to guide tumor puncture, while its effects are assessed using dynamic computed tomography or magnetic resonance. The differences in modalities used for RFA and assessment of its effects complicate RFA. We developed a method for assessing the effects of RFA on HCC by combining contrast-enhanced (CE) US and real-time virtual sonography with three-dimensional US data.

Patients and methods

Before RFA, we performed a sweep scan of the target HCC nodule and the surrounding hepatic parenchyma to generate three-dimensional US data. After RFA, we synchronized multi-planar reconstruction images derived from stored three-dimensional US data with real-time US images on the same US monitor and performed CEUS and real-time virtual sonography. Using a marking function, we drew a sphere marker along the target HCC nodule contour on pre-treatment US- multi-planar reconstruction images so that the automatically synchronized sphere marker represented the original HCC nodule contour on post-treatment real-time CEUS images. Ablation was considered sufficient when an avascular area with a margin of several millimeters in all directions surrounded the sphere marker on CEUS.

Results

This method was feasible and useful for assessing therapeutic effects in 13 consecutive patients with HCC who underwent RFA. In 2 patients who underwent multiple sessions of RFA, HCC-nodule portions requiring additional RFA were easily identified on US images.

Conclusions

This method using advanced US technologies will facilitate assessment of the effects of RFA on HCC.

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.

Percutaneous radiofrequency ablation of hepatocellular carcinoma: fusion imaging guidance for management of lesions with poor conspicuity at conventional sonography

OBJECTIVE

The purpose of this study was to determine whether fusion imaging-guided percutaneous radiofrequency ablation (RFA) is effective in the management of hepatocellular carcinoma (HCC) that has poor conspicuity at conventional sonography.

SUBJECTS AND METHODS

Percutaneous RFA of HCC with poor conspicuity was performed under fusion imaging guidance. The time needed for image fusion between the ultrasound and CT or MR images was recorded. The quality of image fusion and the degree of operator confidence in identifying the index tumor were graded on 4-point scales. Technical success and procedure-related complications were evaluated with liver CT immediately after RFA.

RESULTS

Thirty patients with HCC (1.0 ± 0.3 cm) were enrolled. Twenty-seven of the 30 lesions detected at planning ultrasound were identified with fusion imaging. Of the 30 HCC candidate lesions detected with ultrasound, five were found to be pseudolesions close to the index tumor. The time needed for image fusion for the 27 lesions was 3.7 ± 2.1 minutes (range, 1.3-9.0 minutes). The quality of image fusion was graded 3.4 ± 0.6, and the degree of operator confidence in identifying the 30 HCCs, 3.3 ± 0.9. The technical success rate was 90% (27/30) in intention-to-treat analysis and 100% in analysis of actually treated lesions. There were no major RFA-related complications.

CONCLUSION

Fusion imaging-guided percutaneous RFA is effective in the management of HCC that has poor ultrasound conspicuity.

Review of dynamic contrast-enhanced ultrasound guidance in ablation therapy for hepatocellular carcinoma

Local ablative techniques-percutaneous ethanol injection, microwave coagulation therapy and radiofrequency ablation (RFA)-have been developed to treat unresectable hepatocellular carcinoma (HCC). The success rate of percutaneous ablation therapy for HCC depends on correct targeting of the tumor via an imaging technique. However, probe insertion often is not completely accurate for small HCC nodules, which are poorly defined on conventional B-mode ultrasound (US) alone. Thus, multiple sessions of ablation therapy are frequently required in difficult cases. By means of two breakthroughs in US technology, harmonic imaging and the development of second-generation contrast agents, dynamic contrast-enhanced harmonic US imaging with an intravenous contrast agent can depict tumor vascularity sensitively and accurately, and is able to evaluate small hypervascular HCCs even when B-mode US cannot adequately characterize the tumors. Therefore, dynamic contrast-enhanced US can facilitate RFA electrode placement in hypervascular HCC, which is poorly depicted by B-mode US. The use of dynamic contrast-enhanced US guidance in ablation therapy for liver cancer is an efficient approach. Here, we present an overview of the current status of dynamic contrast-enhanced US-guided ablation therapy, and summarize the current indications and outcomes of reported clinical use in comparison with that of other modalities.

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.