Ablative safety margin depicted by fusion imaging with post-treatment contrast-enhanced ultrasound and pre-treatment CECT/CEMRI after radiofrequency ablation for liver cancers

Treatments and cancer: implications for radiologists

This review highlights the critical role of radiologists in personalized cancer treatment, focusing on the evaluation of treatment outcomes using imaging tools like Computed Tomography (CT), Magnetic Resonance Imaging (MRI), and Ultrasound. Radiologists assess the effectiveness and complications of therapies such as chemotherapy, immunotherapy, and ablative treatments. Understanding treatment mechanisms and consistent imaging protocols are essential for accurate evaluation, especially in managing complex cases like liver cancer. Collaboration between radiologists and oncologists is key to optimizing patient outcomes through precise imaging assessments.

Research Progress on Contrast-Enhanced Ultrasound (CEUS) Assisted Diagnosis and Treatment in Liver-Related Diseases

Liver-related diseases, such as hepatocellular carcinoma (HCC) and cirrhosis, are globally prevalent and significantly contribute to mortality rates. Despite the availability of various imaging techniques for liver evaluation, a consensus regarding the selection of an accurate and safe method remains elusive. As a non-invasive imaging approach, the effectiveness of contrast-enhanced ultrasound (CEUS) in assisting the diagnosis and treatment of liver-related diseases has been established. Compared to conventional methods, CEUS offers notable advantages, including high safety, convenience, accuracy, and cost-effectiveness. Recent advancements have demonstrated the expanded utility of CEUS in liver-related diseases. In addition to diagnosing focal liver lesions, CEUS is increasingly employed for guiding local treatments, assessing liver transplantation suitability, and planning surgical interventions. However, its application requires caution due to the high technical proficiency demanded of operators, time-sensitive imaging processes, and susceptibility to visual interference. This review summarizes the current applications and recent advancements in CEUS-assisted diagnosis and treatment of liver-related diseases, explores its future potential, and proposes possible improvements. The objective is to enhance the accuracy and versatility of non-invasive liver assessments and provide a reference for the broader and more effective utilization of CEUS in liver disease diagnosis and management.

The value of contrast-enhanced ultrasound fusion imaging in percutaneous liver biopsy for liver lesions invisible on conventional B-mode ultrasound

Background

Ultrasound (US) is the most commonly used imaging method for guiding percutaneous liver biopsies. For lesions that are invisible on B-mode ultrasound (BMUS), contrast-enhanced ultrasound (CEUS) improves the contrast between neoplasms and liver parenchyma, while emerging fusion imaging techniques can enhance the localization of lesions. Therefore, our study aimed to assess the value of CEUS fusion imaging in detecting and guiding percutaneous liver biopsy for lesions invisible on BMUS.

Methods

Patients with focal liver lesions (FLLs) identified on computed tomography (CT) or magnetic resonance imaging (MRI) but not visible on BMUS were retrospectively included at Nanjing Drum Tower Hospital, Affiliated Hospital of Medical School, Nanjing University from September 2019 to December 2023. All patients underwent BMUS fusion imaging and CEUS fusion imaging. We evaluated the lesion visibility, detection rate of BMUS fusion, and CEUS fusion before liver biopsy and the rate of technical success and diagnostic success after CEUS fusion-guided biopsy.

Results

This study included 70 FLLs from 61 patients. The mean visibility score of the 70 lesions on BMUS was 1.51±0.52. BMUS fusion detected 31 (31/70, 44.3%) lesions, yielding a mean visibility score of 1.81±1.03. CEUS fusion detected 63 (63/70, 90%) lesions, and achieved a mean visibility score of 2.90±0.30, which was significantly higher than that of BMUS fusion. Subgroup analysis corroborated the superiority of CEUS fusion in detecting infiltrative lesions and lesions <2 cm. Finally, CEUS fusion-guided liver biopsy achieved a technical success rate of 98.4% and a diagnostic success rate of 82.0% (50/61).

Conclusions

Compared with conventional BMUS or BMUS fusion imaging, the combination of CEUS and fusion imaging enabled an increase in the detection rate and lesion visibility of BMUS-invisible lesions, particularly for infiltrative masses and small-sized lesions, thereby increasing operators' confidence and success rate during the percutaneous liver biopsy.

3D-CEUS/MRI-CEUS fusion imaging vs 2D-CEUS after locoregional therapies for hepatocellular carcinoma: a multicenter prospective study of therapeutic response evaluation

OBJECTIVES

To compare the diagnostic accuracy of 3D contrast-enhanced ultrasound (CEUS)/MRI-CEUS fusion imaging with 2D-CEUS in assessing the response of hepatocellular carcinoma (HCC) to locoregional therapies in a multicenter prospective study.

MATERIALS AND METHODS

A consecutive series of patients with HCC scheduled for locoregional treatment were enrolled between April 2021 and March 2023. Patients were randomly divided into 3D-CEUS/MRI-CEUS fusion imaging group (3D/fusion group) or 2D-CEUS group (2D group). CEUS was performed 1 week before and 4-6 weeks after locoregional treatment. Contrast-enhanced MRI (CE-MRI) 4-6 weeks after treatment was set as the reference standard. CEUS images were evaluated for the presence or absence of viable tumors. Diagnostic performance criteria, including sensitivity, specificity, accuracy, and area under the curve (AUC), were determined for each modality.

RESULTS

A total of 140 patients were included, 70 patients in the 2D group (mean age, 60.2 ± 10.4 years) and 70 patients in the 3D/fusion group (mean age, 59.8 ± 10.6 years). The sensitivity of the 3D/fusion group was 100.0% (95% CI: 75.9, 100.0), higher than that of the 2D group (55.6%, 95% CI: 22.7, 84.7; p = 0.019). The specificity of the 3D/fusion group was 96.3% (95% CI: 86.2, 99.4), which was comparable to that of the 2D group (98.4%, 95% CI: 90.0, 99.9; p = 0.915). The AUC of the 3D/fusion group was 0.98 (95% CI: 0.95, 1.00), higher than that of the 2D group (0.77, 95% CI: 0.56, 0.98; p = 0.020).

CONCLUSION

3D-CEUS/MRI-CEUS fusion imaging exhibits superior diagnostic accuracy in evaluating the treatment response to locoregional therapies for HCC.

CLINICAL RELEVANCE STATEMENT

3D-CEUS/MRI-CEUS fusion imaging can be applied for post-treatment assessment of residual tumors in HCC undergoing locoregional treatment, offering potential benefits in terms of accurate diagnosis and clinical management.

KEY POINTS

Evaluating for HCC recurrence following locoregional therapy is important. 3D-CEUS/MRI-CEUS fusion imaging achieved a higher sensitivity than 2D-CEUS in assessing residual tumors after locoregional therapies. 3D-CEUS/MRI-CEUS fusion imaging can help clinicians intervene early in residual HCC lesions after locoregional treatment.

3D fusion is superior to 2D point-to-point contrast-enhanced US to evaluate the ablative margin after RFA for hepatocellular carcinoma

PURPOSE

To compare the efficiency of three-dimensional (3D) and two-dimensional (2D) contrast-enhanced ultrasound (CEUS)-derived techniques in evaluating the ablative margin (AM) after radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC).

METHODS

In total, 98 patients with 98 HCCs were enrolled. The 2D CEUS point-to-point imaging (2D CEUS-PI) was conducted by comparing the pre- and post-RFA 2D CEUS images manually, and the 3D CEUS fusion imaging (3D CEUS-FI) was conducted by fusing the pre- and post-RFA 3D CEUS images automatically. These two techniques were compared in distinguishing an adequate AM ≥ 5 mm. Risk factors for local tumor progression (LTP) after RFA were analyzed by the Kaplan-Meier method with log-rank test.

RESULTS

The mean registration time of 3D CEUS-FI and 2D CEUS-PI was 5.0 and 9.3 min, respectively (p < 0.0001). The kappa coefficient was 0.680 for agreement between 2D CEUS-PI and 3D CEUS-FI in the evaluation of AM (p < 0.0001). Tumors with AM < 5 mm by 2D CEUS-PI were all identified as AM < 5 mm by 3D CEUS-FI. Nonetheless, 16 (26%) tumors identified as AM ≥ 5 mm by 2D CEUS-PI were re-classified as AM < 5 mm by 3D CEUS-FI. During a median follow-up time of 31.2 months (range, 3.2-66.0 months), LTP was identified in 8 tumors. The estimated 1-/2-/3-year cumulative incidence of LTP was 4.4%, 8.1%, and 10.3%, respectively. Higher estimated cumulative incidence of LTP was identified in tumors with AM < 5 mm by 2D CEUS-PI (at 3-year, 27.2% vs 0%; p < 0.001), and by 3D CEUS-FI (at 3-year, 20.7% vs 0%; p = 0.004).

CONCLUSION

3D CEUS-FI excelled in the evaluation of AM when compared with 2D CEUS-PI. With equivalent efficacy in the prediction of LTP, 3D CEUS-FI was superior to 2D CEUS-PI for its automatic and time-saving procedure.

CLINICAL RELEVANCE STATEMENT

3D CEUS fusion imaging may serve as an effective tool in evaluating ablative margin and predicting local tumor progression after RFA in HCC.

KEY POINTS

• Both 2D and 3D CEUS-derived techniques could evaluate ablative margin (AM) after RFA for hepatocellular carcinoma. • 3D CEUS fusion imaging was more precise in the evaluation of AM compared to 2D CEUS point-to-point imaging, with advantages of its automatic and time-saving procedure. • An inadequate AM < 5 mm evaluated by CEUS-derived techniques was the only risk factor of LTP after RFA for hepatocellular carcinoma (p < 0.001 for 2D CEUS point-to-point imaging, and p = 0.004 for 3D CEUS fusion imaging).

Percutaneous image-guided ablation for hepatic metastases

The presence of hepatic metastases indicates advanced disease and is associated with significant morbidity and mortality, especially when the hepatic disease is not amenable to locoregional treatments. The primary tumour of origin, the distribution and extent of metastatic disease, the underlying liver reserve, the patient performance status and the presence of comorbidities are factors that determine whether a patient will benefit from hepatectomy or local curative-intent treatments. For patients with metastatic colorectal cancer, the most common primary cancer that spreads to the liver, several studies have demonstrated a survival benefit for patients who can be treated with hepatectomy and/or percutaneous ablation, compared to those treated with chemotherapy alone. Despite advances in surgical techniques increasing the percentage of patients eligible for surgery, most patients have unresectable disease or are poor surgical candidates. Percutaneous ablation can be used to provide local disease control and prolong survival for both surgical and non-surgical candidates. This is typically offered to patients with small hepatic metastases that can be ablated with optimal (≥10 mm) or at least adequate minimum ablation margins (≥5 mm), as high local tumour control rates can be achieved for these patients which are comparable to surgical resection. This review summarizes available evidence and outcomes following percutaneous ablation of the most frequently encountered types of hepatic metastases in the clinical practice of interventional oncology. Patient selection, technical considerations, follow-up protocols and oncologic outcomes are presented and discussed.

Ablative margins in percutaneous thermal ablation of hepatic tumors: a systematic review

INTRODUCTION

This study aims to systematically review current evidence on ablative margins and correlation to local tumor progression (LTP) after thermal ablation of hepatocellular carcinoma (HCC) and colorectal liver metastases (CRLM).

METHODS

A systematic search was performed in PubMed (MEDLINE) and Web of Science to identify all studies that reported on ablative margins (AM) and related LTP rates. Studies were assessed for risk of bias and synthesized separately per tumor type. Where possible, results were pooled to calculate risk differences (RD) as function of AM.

RESULTS

In total, 2910 articles were identified of which 43 articles were eligible for final analysis. There was high variability in AM measurement methodology across studies in terms of measurement technique, imaging modalities, and timing. Most common margin stratification was < 5 mm and > 5 mm, for which data were available in 25/43 studies (58%). Of these, all studies favored AM > 5 mm to reduce the risk of LTP, with absolute RD of 16% points for HCC and 47% points for CRLM as compared to AM < 5 mm.

CONCLUSIONS

Current evidence supports AM > 5 mm to reduce the risk of LTP after thermal ablation of HCC and CRLM. However, standardization of AM measurement and reporting is critical to allow future meta-analyses and improved identification of optimal threshold value for clinical use.

Efficacy of fusion imaging for immediate post-ablation assessment of malignant liver neoplasms: A systematic review

BACKGROUND

Percutaneous thermal ablation has become the preferred therapeutic treatment option for liver cancers that cannot be resected. Since ablative zone tissue changes over time, it becomes challenging to determine therapy effectiveness over an extended period. Thus, an immediate post-procedural evaluation of the ablation zone is crucial, as it could influence the need for a second-look treatment or follow-up plan. Assessing treatment response immediately after ablation is essential to attain favorable outcomes. This study examines the efficacy of image fusion strategies immediately post-ablation in liver neoplasms to determine therapeutic response.

METHODOLOGY

A comprehensive systematic search using PRISMA methodology was conducted using EMBASE, MEDLINE (via PUBMED), and Cochrane Library Central Registry electronic databases to identify articles that assessed the immediate post-ablation response in malignant hepatic tumors with fusion imaging (FI) systems. The data were retrieved on relevant clinical characteristics, including population demographics, pre-intervention clinical history, lesion characteristics, and intervention type. For the outcome metrics, variables such as average fusion time, intervention metrics, technical success rate, ablative safety margin, supplementary ablation rate, technical efficacy rate, LTP rates, and reported complications were extracted.

RESULTS

Twenty-two studies were included for review after fulfilling the study eligibility criteria. FI's immediate technical success rate ranged from 81.3% to 100% in 17/22 studies. In 16/22 studies, the ablative safety margin was assessed immediately after ablation. Supplementary ablation was performed in 9 studies following immediate evaluation by FI. In 15/22 studies, the technical effectiveness rates during the first follow-up varied from 89.3% to 100%.

CONCLUSION

Based on the studies included, we found that FI can accurately determine the immediate therapeutic response in liver cancer ablation image fusion and could be a feasible intraprocedural tool for determining short-term post-ablation outcomes in unresectable liver neoplasms. There are some technical challenges that limit the widespread adoption of FI techniques. Large-scale randomized trials are warranted to improve on existing protocols. Future research should emphasize improving FI's technological capabilities and clinical applicability to a broader range of tumor types and ablation procedures.

An update on locoregional percutaneous treatment technologies in colorectal cancer liver metastatic disease

INTRODUCTION

Liver-dominant metastatic colorectal cancer is noted in approximately 20%-35% of the patients. Systemic chemotherapy remains the first-line treatment for mCRC, but the prognosis is poor due to liver failure. Novel minimally invasive technologies have enabled the optimization of locoregional treatment options.

AREAS COVERED

This is a comprehensive review of novel locoregional treatment technologies, both percutaneous ablation and transcatheter arterial treatments, which can be used to decrease hepatic disease progression in patients with mCRC. Trans-arterial radioembolization is the most recently developed locoregional treatment for metastatic liver disease, and robust evidence has been accumulated over the past years.

EXPERT OPINION

Image-guided techniques, endovascular and ablative, have gained wide acceptance for the treatment of liver malignancies, in selected patients with non-resectable disease. The optimization of dosimetry and microsphere technological advancement will certainly upgrade the role of liver radioembolization segmentectomy or lobectomy in the upcoming years, due to its curative intent. Also, ablative interventions provide local curative intent, offering significant and sustained local tumor control. Standardization protocols in terms of predictability and reliability using immediate treatment assessment and ablation zone software could further ameliorate clinical outcomes.

Prevention of major biliary complications by fusion imaging for thermal ablation of malignant liver tumors adjacent to the bile ducts: a preliminary comparative study

PURPOSE

Ultrasound (US)-guided thermal ablation (TA) may cause major biliary complications, particularly in patients with malignant liver tumors (MLTs) adjacent to the bile ducts. Fusion imaging (FI), is postulated to reduce complication rate; however, there is a lack of clinical data to support this theory. Thus, the aim of our study was to evaluate the safety and efficacy of FI for TA of MLTs proximal to the bile ducts.

METHODS

A retrospective single-center review was conducted on a total of 289 patients with 316 MLTs adjacent to the bile ducts. The patients were divided into two groups based on whether FI was used in the ablation procedures. The choice of the FI-assisted procedure always depends on different operation periods and whether registrations will succeed. The baseline demographics and outcomes of these patients were compared. The efficacy was determined at the 1-month follow-up using contrast-enhanced computed tomography/magnetic resonance. Biliary complications and local tumor progression were subsequently followed-up every 3-6 months. The last follow-up visit was before August 30, 2019.

RESULTS

Among the included tumors, the incidence rate of major biliary complications after ablation in the FI group was 1.6%, which was significantly lower than that in the non-FI group (7.9%, p = 0.005). There was no significant difference in the efficacy rates of the techniques [99.5% (185/186) versus 98.4% (123/125), p = 0.56] or local progression rates [3.8% (7/185) versus 5.7% (7/123), p = 0.61] between the FI and non-FI groups.

CONCLUSION

FI for US-guided TA could be a noninvasive means to decrease major biliary complications. Trial registration number and date of registration: retrospectively registered.

Contemporary evidence on colorectal liver metastases ablation: toward a paradigm shift in locoregional treatment

Image-guided percutaneous ablation techniques represent an attractive local therapy for the treatment of colorectal liver metastases (CLM) given its low risk of severe complications, which allows for early initiation of adjuvant therapies and spare functional liver parenchyma, allowing repeated treatments at the time of recurrence. However, ablation does not consistently achieve similar oncological outcomes to surgery, with the latter being currently considered the first-line local treatment modality in international guidelines. Recent application of computer-assisted ablation planning, guidance, and intra-procedural response assessment has improved percutaneous ablation outcomes. In addition, the evolving understanding of tumor molecular profiling has brought to light several biological factors associated with oncological outcomes following local therapies. The standardization of ablation procedures, the understanding of previously unknown biological factors affecting ablation outcomes, and the evidence by ongoing prospective clinical trials are poised to change the current perspective and indications on the use of ablation for CLM.

Image-Guided Ablation for Colorectal Liver Metastasis: Principles, Current Evidence, and the Path Forward

Image-guided ablation can provide effective local tumor control in selected patients with CLM. A randomized controlled trial suggested that radiofrequency ablation combined with systemic chemotherapy resulted in a survival benefit for patients with unresectable CLM, compared to systemic chemotherapy alone. For small tumors, ablation with adequate margins can be considered as an alternative to resection. The improvement of ablation technologies can allow the treatment of tumors close to major vascular structures or bile ducts, on which the applicability of thermal ablation modalities is challenging. Several factors affect the outcomes of ablation, including but not limited to tumor size, number, location, minimal ablation margin, RAS mutation status, prior hepatectomy, and extrahepatic disease. Further understanding of the impact of tumor biology and advanced imaging guidance on overall patient outcomes might help to tailor its application, and improve outcomes of image-guided ablation.

Challenges Facing Percutaneous Ablation in the Treatment of Hepatocellular Carcinoma: Extension of Ablation Criteria

As an emerging minimally invasive treatment method, percutaneous ablation is more and more widely used in the treatment of liver tumors. It has been recommended by guidelines for diagnosis and treatment of hepatocellular carcinoma (HCC) as a curative treatment alongside surgical resection and liver transplantation. In recent years, with the continuous advancement and innovation of percutaneous ablation technologies, their clinical efficacy and safety have been significantly improved, which has led to the expanded application of percutaneous ablation in the treatment of HCC—more and more patients who were previously considered unsuitable for ablation therapies are now being treated with percutaneous ablation. Obviously, percutaneous ablation can reduce the risk of treatment changes from curative strategies to palliative strategies. Based on clinical practice experience, this review enumerates the advantages and disadvantages of different ablative modalities and summarizes the existing combinations of ablation techniques, thus will help clinicians choose the most appropriate ablative modality for each patient and will provide scientific guidance for improving prognosis and making evidence-based treatment decisions. In addition, we point out the challenges and future prospects of the ablation therapies, thereby providing direction for future research.

Additional Diagnostic Value of Fusion Imaging of CEUS and First CEUS of Invisible Hepatic Lesions ≤2 cm

OBJECTIVE

To explore the clinical value of image fusion of contrast-enhanced ultrasonography (CEUS) and contrast-enhanced computed tomography (CECT) in the diagnosis of invisible lesions with a size ≤2 cm on conventional ultrasound imaging, and compare it with the clinical value of "first CEUS" .

METHODS

A total of 132 patients with 147 lesions with abnormal blood supply with a size ≤2 cm on CECT were included in this study. "first CEUS" was performed for these lesions. Then "fusion CEUS," that is, CEUS administered after fusion of US and CECT images, was carried out. The detection rates of the "first CEUS" and "fusion CEUS" were compared. How "fusion CEUS" corrects the misdiagnosis of liver lesions on CECT was analyzed.

RESULTS

One hundred nine lesions considered as HCC and 38 lesions considered as benign lesions on CECT were included. The detection rates for the lesions of "first CEUS" and "fusion CEUS" were 71.4% and 96.6%, respectively (P < 0.001). Among the 147 lesions, 68 were with a diameter ≤ 1 cm. The detection rate of "first CEUS" and "fusion CEUS" were 55.9% and 95.6%, respectively (P < 0.001) for the lesions with a size ≤1 cm. "Fusion CEUS" and "first CEUS" corrected the misdiagnosis in 2 lesions on CECT.

CONCLUSION

The "first CEUS" and "fusion CEUS" can improve the lesion conspicuity. Compared with "first CEUS," "fusion CEUS" has a higher diagnostic ability and hence can detect most of the invisible lesions on the former.

Benefits of contrast-enhanced ultrasonography for interventional procedures

For evaluating unclear tumorous lesions, contrast-enhanced ultrasonography (CEUS) is an important imaging modality in addition to contrast-enhanced computed tomography and magnetic resonance imaging, and may provide valuable insights into the microvascularization of tumors in dynamic examinations. In interventional procedures, CEUS can make a valuable contribution in pre-, peri-, and post-interventional settings, reduce radiation exposure and, under certain circumstances, decrease the number of interventions needed for patients.

Contrast-enhanced ultrasound imaging of the liver: a review of the clinical evidence for SonoVue and Sonazoid

Contrast-enhanced ultrasound (CEUS) has become an established modality in various clinical indications for liver diseases. SonoVue®, a pure blood pure agent, and Sonazoid®, which exhibits an additional Kupffer phase, are contrast agents approved for liver imaging. This review discusses and compares the current clinical evidence for these two ultrasound contrast agents in the characterization and detection of focal liver lesions in the non-cirrhotic and cirrhotic liver, as well as for the use in interventional procedures such as liver biopsy guidance, and local ablation treatment monitoring. Reference is made to clinical studies which evaluated the accuracy of CEUS using a standard of reference, its safety, or to comparative studies of these two agents.

Advanced Fusion Imaging and Contrast-Enhanced Imaging (CT/MRI-CEUS) in Oncology

Fusion imaging depicts an innovative technique that facilitates combining assets and reducing restrictions of advanced ultrasound and cross-sectional imaging. The purpose of the present retrospective study was to evaluate the role of fusion imaging for assessing hepatic and renal lesions. Between 02/2011-08/2020, 92 patients in total were included in the study, of which 32 patients had hepatic lesions, 60 patients had renal lesions. Fusion imaging was technically successful in all patients. No adverse side effects upon intravenous (i.v.) application of SonoVue® (Bracco, Milan, Italy) were registered. Fusion imaging could clarify all 11 (100%) initially as indeterminate described hepatic lesions by computed tomography/magnetic resonance imaging (CT/MRI). Moreover, 5/14 (36%) initially suspicious hepatic lesions could be validated by fusion imaging, whereas in 8/14 (57%), malignant morphology was disproved. Moreover, fusion imaging allowed for the clarification of 29/30 (97%) renal lesions initially characterized as suspicious by CT/MRI, of which 19/30 (63%) underwent renal surgery, histopathology revealed malignancy in 16/19 (84%), and benignity in 3/19 (16%). Indeterminate findings could be elucidated by fusion imaging in 20/20 (100%) renal lesions. Its accessibility and repeatability, even during pregnancy and in childhood, its cost-effectiveness, and its excellent safety profile, make fusion imaging a promising instrument for the thorough evaluation of hepatic and renal lesions in the future.

Fusion imaging techniques and contrast-enhanced ultrasound for thermal ablation of hepatocellular carcinoma - A prospective randomized controlled trial

Objectives: This randomized controlled trial (RCT) aims to compare the clinical application values of contrast-enhanced ultrasound (CEUS), computed tomography/magnetic resonance-CEUS (CT/MR-CEUS), and three-dimensional ultrasound-CEUS (3DUS-CEUS) Fusion imaging (FI) techniques in the assistance of thermal ablation for hepatocellular carcinoma (HCC).Methods: A RCT was conducted on 374 patients with 456 HCCs between January 2016 and September 2017. CEUS, CT/MR-CEUS, and 3DUS-CEUS FI techniques were randomly used to assist HCC ablation. All lesions were ablated according to a previously determined plan, and FI groups required a 5-mm ablative margin. The primary endpoints were technical efficacy of thermal ablation and local tumor progression (LTP).Results: According to randomization, 153 (18.8 ± 8.0 cm), 153 (18.3 ± 6.6 cm) and 150 (19.1 ± 6.9 cm) HCCs were assigned to CT/MR-CEUS, 3DUS-CEUS and CEUS groups respectively. Technical efficacy rates (99.3% vs. 100% vs. 100%) were achieved in the three groups, showing no statistical differences (p = 1.000). The median follow-up time was 24 (1-37) months. LTP rates at 1 and 2 years were 3.4%, 12.2% for CT/MR-CEUS FI, 4.8%, 9.0% for 3DUS-CEUS FI, and 8.6%, 19.9% for CEUS, respectively (p = .105). The results of subgroup analysis for LTP were statistically significant when patients with albumin-bilirubin (ALBI) grade 2 and 3 (p = .000), and tumor located at risky positions (p = .042). In addition, the p value in group of multiple tumors was close to .05 (p = .052).Conclusions: All the three techniques are feasible for intraoperative HCC thermal ablation. Compared with CEUS, FI techniques are more suitable in patients with ALBI grade 2 and 3, multiple tumors, and in tumors at risky locations.

Intraprocedural contrast-enhanced ultrasound-CT/MR fusion imaging assessment in HCC thermal ablation to reduce local tumor progression: compared with routine contrast-enhanced ultrasound

Purpose: To evaluate whether local tumor progression (LTP) would be further reduced when contrast-enhanced ultrasound (CEUS)-CT/MR fusion imaging was used as intraprocedural assessment method in hepatocellular carcinoma (HCC) thermal ablation compared with routine CEUS. Materials and methods: This prospective non-randomized study was conducted from December 2010 to July 2012. CEUS-CT/MR fusion imaging and routine CEUS were used for treatment response assessment in the ablation procedure of 146 HCCs and 122 HCCs, respectively. Supplementary ablations were performed immediately if necessary. The primary technique efficacy rate, LTP rate and overall survival (OS) rate were calculated. Results: For CEUS-CT/MR fusion imaging and routine CEUS, the technical success rate, technique efficacy rate and supplementary ablation rate were 86.3% (126/146) and 98.4% (120/122) (p = .000), 99.2% (125/126) and 94.2% (113/120) (p = .032), and 14.3% (18/126) and 4.2% (5/120) (p = .006), respectively. The cumulative LTP rate and OS rate were not significantly different between fusion imaging group and routine CEUS group. However, for lesions that were larger than 3 cm or close to major vessels (41 lesions in fusion imaging group and 44 lesions in routine CEUS group, who received transcatheter arterial chemoembolization before ablation), the cumulative LTP rate was significantly lower in fusion imaging group than in routine CEUS group (p = .032). Conclusion: Although intraprocedural CEUS-CT/MR fusion imaging has certain limitations in application, it might provide a potential more efficient method compared with routine CEUS in reducing LTP in HCC thermal ablation, especially for difficult ablation lesions.

Percutaneous image-guided ablation: From techniques to treatments

Image-guided ablation is performed by percutaneously introducing ablation probes to deliver energy into a tumor to destroy it in a controlled and localized fashion. Ablation modalities can be broadly classified as thermal or non-thermal based on the mechanism of tumor destruction and are performed using different types of image guidance for planning, delivering and follow-up of the treatment. Ablation is performed in a minimally invasive fashion, providing greater residual organ preservation with minimal morbidity to the patient. Image-guided ablation is being used in the clinic for the treatment of primary and metastatic tumors, and this article reviews state of the art for the treatment of malignancies in the liver, lung, kidney and musculoskeletal tissue.

3-D Contrast-Enhanced Ultrasound Fusion Imaging: A New Technique to Evaluate the Ablative Margin of Radiofrequency Ablation for Hepatocellular Carcinoma

To investigate the feasibility of assessing the ablative margin (AM) of radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC) with 3-D contrast-enhanced ultrasound fusion imaging (3-DCEUS-FI), pre- and post-RFA 3-DCEUS images of 84 patients with HCC were fused for two radiologists to independently assess the AMs. The success rate, duration and influencing factors for registration; inter-observer agreement for AM classification; and local tumor progression (LTP) rate were evaluated. The success rate of the automatic registration (AR), which was completed within 4-12 s, was 57.1% (48/84). The duration and success rate of the interactive registration (IR) were 4.2 ± 1.8 min and 91.7% (77/84) for radiologist A and 4.8 ± 2.1 min and 91.7% (77/84) for radiologist B, respectively. The multivariate analysis demonstrated that the pre-RFA image quality, number of vessels (≥3 mm) and presence of acoustic shadow were independent factors for AR (p < 0.05), while the number of vessels was an independent factor for IR (p = 0.001). The agreement between observers was excellent (kappa = 0.914). LTP rate was significantly higher for AMs <5 mm than for AMs ≥5 mm (p = 0.024). Quantitatively evaluating the AM immediately after RFA for HCC with 3-DCEUS-FI was feasible.

[Contrast-enhanced ultrasound (CEUS) and image fusion for procedures of liver interventions]

CLINICAL/METHODICAL ISSUE

Contrast-enhanced ultrasound (CEUS) is becoming increasingly important for the detection and characterization of malignant liver lesions and allows percutaneous treatment when surgery is not possible. Contrast-enhanced ultrasound image fusion with computed tomography (CT) and magnetic resonance imaging (MRI) opens up further options for the targeted investigation of a modified tumor treatment.

METHODICAL INNOVATIONS

Ultrasound image fusion offers the potential for real-time imaging and can be combined with other cross-sectional imaging techniques as well as CEUS.

PERFORMANCE

With the implementation of ultrasound contrast agents and image fusion, ultrasound has been improved in the detection and characterization of liver lesions in comparison to other cross-sectional imaging techniques. In addition, this method can also be used for intervention procedures. The success rate of fusion-guided biopsies or CEUS-guided tumor ablation lies between 80 and 100% in the literature.

ACHIEVEMENTS

Ultrasound-guided image fusion using CT or MRI data, in combination with CEUS, can facilitate diagnosis and therapy follow-up after liver interventions.

PRACTICAL RECOMMENDATIONS

In addition to the primary applications of image fusion in the diagnosis and treatment of liver lesions, further useful indications can be integrated into daily work. These include, for example, intraoperative and vascular applications as well applications in other organ systems.

A novel software platform for volumetric assessment of ablation completeness

PURPOSE

To retrospectively evaluate the accuracy of a novel software platform for assessing completeness of percutaneous thermal ablations.

MATERIALS & METHODS

Ninety hepatocellular carcinomas (HCCs) in 50 patients receiving percutaneous ultrasound-guided microwave ablation (MWA) that resulted in apparent technical success at 24-h post-ablation computed tomography (CT) and with ≥1-year imaging follow-up were randomly selected from a 320 HCC ablation database (2010-2016). Using a novel volumetric registration software, pre-ablation CT volumes of the HCCs without and with the addition of a 5 mm safety margin, and corresponding post-ablation necrosis volumes were segmented, co-registered and overlapped. These were compared to visual side-by-side inspection of axial images.

RESULTS

At 1-year follow-up, CT showed absence of local tumor progression (LTP) in 69/90 (76.7%) cases and LTP in 21/90 (23.3%). For HCCs classified by the software as "incomplete tumor treatments", LTP developed in 13/17 (76.5%) and all 13 (100%) of these LTPs occurred exactly where residual non-ablated tumor was identified by retrospective software analysis. HCCs classified as "complete ablation with <100% 5 mm ablative margins" had LTP in 8/49 (16.3%), while none of 24 HCCs with "complete ablation including 100% 5 mm ablative margins" had LTP. Differences in LTP between both partially ablated HCCs vs completely ablated HCCs, and ablated HCCs with <100% vs with 100% 5 mm margins were statistically significant (p < .0001 and p = .036, respectively). Thus, 13/21 (61.9%) incomplete tumor treatments could have been detected immediately, were the software available at the time of ablation.

CONCLUSIONS

A novel software platform for volumetric assessment of ablation completeness may increase the detection of incompletely ablated tumors, thereby holding the potential to avoid subsequent recurrences.