Evaluation of the ablation margin of hepatocellular carcinoma using CEUS-CT/MR image fusion in a phantom model and in patients

Microwave ablation for colorectal liver metastases with ultrasound fusion imaging assistance: a stratified analysis study based on tumor size and location

PURPOSE

To investigate the efficacy of ultrasound fusion imaging-assisted microwave ablation (MWA) for patients with colorectal liver metastases (CRLM) based on stratified analysis of tumor size and location.

METHODS

Patients with CRLM who underwent ultrasound fusion imaging-assisted MWA in our hospital between February 2020 and February 2023 were enrolled into this retrospective study. Ultrasound fusion imaging was used for detection, guidance, monitoring and immediate evaluation throughout the MWA procedures. Technical success, technique efficacy, local tumor progression (LTP), intrahepatic progression and overall survival (OS) were recorded and analyzed. The subgroup analysis of intrahepatic progression of MWA for CRLM was performed according to tumor size and location.

RESULTS

A total of 51 patients with 122 nodules were enrolled. Both technical success and technique efficacy were acquired in all nodules. In a median follow-up period of 19 months, 2.5% of the nodules (3/122) were observed LTP. The 1-year and 2-year cumulative intrahepatic progression rates were 38.7% and 52.1% respectively. Patients were divided into subgroups according to tumor size (≥ 30 mm, n = 13; < 30 mm, n = 38) and tumor location (perivascular, n = 20; non-perivascular, n = 31 and subcapsular, n = 36; non-subcapsular, n = 15). The cumulative intrahepatic progression rates were similar between the subgroups regarding tumor size and perivascular location, while significantly higher in the subcapsular group than in the non-subcapsular group (p = 0.021).

CONCLUSION

Ultrasound fusion imaging-assisted MWA exhibited satisfactory local efficacy for CRLM, especially for non-subcapsular tumors.

Precise localization of microvascular invasion in hepatocellular carcinoma based on three-dimensional histology-MR image fusion: an ex vivo experimental study

Background

Microvascular invasion (MVI) is an independent risk factor for postoperative recurrence of hepatocellular carcinoma (HCC). However, MVI cannot be detected by conventional imaging. To localize MVI precisely on magnetic resonance (MR) images, we evaluated the feasibility and accuracy of 3-dimensional (3D) histology-MR image fusion of the liver.

Methods

Animal models of VX2 liver tumors were established in 10 New Zealand white rabbits under ultrasonographic guidance. The whole liver lobe containing the VX2 tumor was extracted and divided into 4 specimens, for a total of 40 specimens. MR images were obtained with a T2-weighted sequence for each specimen, and then histological images were obtained by intermittent, serial pathological sections. 3D histology-MR image fusion was performed via landmark registration in 3D Slicer software. We calculated the success rate and registration errors of image fusion, and then we located the MVI on MR images. Regarding influencing factors, we evaluated the uniformity of tissue thickness after sampling and the uniformity of tissue shrinkage after dehydration.

Results

The VX2 liver tumor model was successfully established in the 10 rabbits. The incidence of MVI was 80% (8/10). 3D histology-MR image fusion was successfully performed in the 39 specimens, and the success rate was 97.5% (39/40). The average registration error was 0.44±0.15 mm. MVI was detected in 20 of the 39 successfully registered specimens, resulting in a total of 166 MVI lesions. The specific location of all MVI lesions was accurately identified on MR images using 3D histology-MR image fusion. All MVI lesions showed as slightly hyperintense on the high-resolution MR T2-weighted images. The results of the influencing factor assessment showed that the tissue thickness was uniform after sampling (P=0.38), but the rates of the tissue shrinkage was inconsistent after dehydration (P<0.001).

Conclusions

3D histology-MR image fusion of the isolated liver tumor model is feasible and accurate and allows for the successful identification of the specific location of MVI on MR images.

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 in silico assessment on the potential of using saline infusion to overcome non-confluent coagulation zone during two-probe, no-touch bipolar radiofrequency ablation of liver cancer

No-touch bipolar radiofrequency ablation (bRFA) is known to produce incomplete tumour ablation with a 'butterfly-shaped' coagulation zone when the interelectrode distance exceeds a certain threshold. Although non-confluent coagulation zone can be avoided by not implementing the no-touch mode, doing so exposes the patient to the risk of tumour track seeding. The present study investigates if prior infusion of saline into the tissue can overcome the issues of non-confluent or butterfly-shaped coagulation. A computational modelling approach based on the finite element method was carried out. A two-compartment model comprising the tumour that is surrounded by healthy liver tissue was developed. Three cases were considered; i) saline infusion into the tumour centre; ii) one-sided saline infusion outside the tumour; and iii) two-sided saline infusion outside the tumour. For each case, three different saline volumes were considered, i.e. 6, 14 and 22 ml. Saline concentration was set to 15% w/v. Numerical results showed that saline infusion into the tumour centre can overcome the butterfly-shaped coagulation only if the infusion volume is sufficient. On the other hand, one-sided infusion outside the tumour did not overcome this. Two-sided infusion outside the tumour produced confluent coagulation zone with the largest volume. Results obtained from the present study suggest that saline infusion, when carried out correctly, can be used to effectively eradicate liver cancer. This presents a practical solution to address non-confluent coagulation zone typical of that during two-probe bRFA treatment.

Image Fusion Involving Real-Time Transabdominal or Endoscopic Ultrasound for Gastrointestinal Malignancies: Review of Current and Future Applications

Image fusion of CT, MRI, and PET with endoscopic ultrasound and transabdominal ultrasound can be promising for GI malignancies as it has the potential to allow for a more precise lesion characterization with higher accuracy in tumor detection, staging, and interventional/image guidance. We conducted a literature review to identify the current possibilities of real-time image fusion involving US with a focus on clinical applications in the management of GI malignancies. Liver applications have been the most extensively investigated, either in experimental or commercially available systems. Real-time US fusion imaging of the liver is gaining more acceptance as it enables further diagnosis and interventional therapy of focal liver lesions that are difficult to visualize using conventional B-mode ultrasound. Clinical studies on EUS guided image fusion, to date, are limited. EUS-CT image fusion allowed for easier navigation and profiling of the target tumor and/or surrounding anatomical structure. Image fusion techniques encompassing multiple imaging modalities appear to be feasible and have been observed to increase visualization accuracy during interventional and diagnostic applications.

3.0-T closed MR-guided microwave ablation for HCC located under the hepatic dome: a single-center experience

PURPOSE

To analyze the clinical safety and efficacy of 3.0-T closed MR-guided microwave ablation (MWA) for the treatment of HCC located under the hepatic dome.

METHODS

From May 2018 to October 2020, 49 patients with 74 HCCs located under the hepatic dome underwent MWA using 3.0-T closed MR guidance. The technical success rate, operative time, complete ablation (CA) rate, complications, local tumor progression (LTP), tumor-free survival (TFS) and overall survival (OS) were examined. Routine blood analysis, liver/kidney function and alpha fetoprotein (AFP) and protein induced by vitamin k absent or antagonist (PIVKA) levels were compared before and 2 months after MWA.

RESULTS

All patients underwent MWA successfully, including 10 patients who underwent general anesthesia. The technical success rate was 100% without major complications. The CA rate was 95.9% (71/74) at the 2-month evaluation. The LTP rate was 2.7% during the median follow-up of 17.8 months (range: 4-43 months); the 6-, 12-, 18-month TFS rates were 97.8, 90.6, 68.1%, respectively, and the 6-, 12-, 18-month OS rates were 100, 97.6, 92.1%, respectively. There were no significant changes in routine blood tests and liver/kidney function (p > 0.05), while the AFP and PIVKA level decreased significantly at 2 months (p < 0.05).

CONCLUSION

3.0-T MR-guided MWA is safe and feasible for HCC lesions located under the hepatic dome.

Thermochromic Tissue-Mimicking Phantoms for Thermal Ablation Based on Polyacrylamide Gel

In recent years, thermal ablation has played an increasingly important role in treating various tumors in the clinic. A practical thermochromic phantom model can provide a favorable platform for clinical thermotherapy training of young physicians or calibration and optimization of thermal devices without risk to animals or human participants. To date, many tissue-mimicking thermal phantoms have been developed and are well liked, especially the polyacrylamide gel (PAG)-based phantoms. This review summarizes the PAG-based phantoms in the field of thermotherapy, details their advantages and disadvantages and provides a direction for further optimization. The relevant physical parameters (such as electrical, acoustic, and thermal properties) of these phantoms are also presented in this review, which can assist operators in a deeper understanding of these phantoms and selection of the proper recipes for phantom fabrication.

Loco-regional treatment of hepatocellular carcinoma: Role of contrast-enhanced ultrasonography

Hepatocellular carcinoma (HCC) is one of the few cancers for which locoregional treatments (LRTs) are included in international guidelines and are considered as a valid alternative to conventional surgery. According to Barcelona Clinic Liver Cancer classification, percutaneous treatments such as percutaneous ethanol injection, radiofrequency ablation and microwave ablation are the therapy of choice among curative treatments in patients categorized as very early and early stage, while transcatheter arterial chemoembolization is considered the better option for intermediate stage HCC. A precise assessment of treatment efficacy and surveillance is essential to optimize survival rate, whereas residual tumor requires additional treatment. Imaging modalities play a key role in this task. Currently, contrast-enhanced computed tomography/magnetic resonance imaging are considered the standard imaging modalities for this purpose. Contrast enhanced ultrasound (CEUS), using second generation contrast agents, plays an increasingly important role in detecting residual disease after LRTs. CEUS is a straightforward to perform, repeatable and cost-effective imaging modality for patients with renal failure or iodine allergies. Due to the ability to focus on single regions, CEUS can also provide high temporal resolution. Moreover, several studies have reported the same or better diagnostic accuracy as contrast-enhanced computed tomography for assessing tumor vascularity 1 mo after LRTs, and recently three-dimensional (3D)-CEUS has been reported as a promising technique to improve the evaluation of tumor response to therapy. Furthermore, CEUS could be used early after procedures in monitoring HCC treatments, but nowadays this indication is still debated, and data from literature are conflicting, especially after transcatheter arterial chemoembolization procedure.

A novel tissue-mimicking phantom for US/CT/MR-guided tumor puncture and thermal ablation

AIM

This study aimed to develop a novel tumor-bearing tissue phantom model that can be used for US/CT/MR-guided tumor puncture and thermal ablation.

METHODS

The phantom model comprised two parts: a normal tissue-mimicking phantom and a tumor-mimicking phantom. A normal tissue phantom was prepared based on a polyacrylamide gel mixed with thermochromic ink. Moreover, a spherical phantom containing contrast agents was constructed and embedded in the tissue phantom to mimic a tumor lesion. US/CT/MR imaging features and thermochromic property of the phantom model were characterized. Finally, the utility of the phantom model for imaging-guided microwave ablation training was examined.

RESULTS

The tumor phantom containing contrast agents showed hyper-echogenicity, higher CT numbers, and lower T2 signal intensity compared with the normal tissue phantom in US/CT/MR images. Consequently, we could locate the position of the tumor in US/CT/MR imaging and perform an imaging-guided tumor puncture. When the temperature reached the threshold of 60 °C, the phantom exhibited a permanent color change from cream white to magenta. Based on this obvious color change, our phantom model could clearly map the thermal ablation region after thermotherapy.

CONCLUSIONS

We developed a novel US/CT/MR-imageable tumor-bearing tissue model that can be used for imaging-guided tumor puncture and thermal ablation. Furthermore, it allows visual assessment of the ablation region by analyzing the obvious color change. Overall, this phantom model could be a good training tool in the field of thermal ablation.

Efficacy and Safety of Fusion Imaging in Radiofrequency Ablation of Hepatocellular Carcinoma Compared to Ultrasound: A Meta-Analysis

Background: Radiofrequency ablation (RFA), generally performed under real-time guidance of ultrasound which is safe and effective, is a common minimally invasive therapy for treating hepatocellular carcinoma. Fusion imaging (FI) is a newly developed imaging method, which integrates CT/MRI accurate imaging and matches the characteristics of real-time ultrasound imaging, thereby providing a new approach to guide tumor ablation therapy. However, the efficacy and safety of FI as opposed to ultrasound in tumor ablation remains unclear.

Objective: The present study sought to evaluate the difference in the efficacy and safety between FI and ultrasound in radiofrequency surgery for the treatment of hepatocellular carcinoma through a metaanalysis.

Materials and Methods: Searching for studies comparing the efficacy and safety of FI and ultrasound in radiofrequency of hepatocellular carcinoma in PubMed, Embase, and Cochrane Library databases for articles published until April 2021. Random or fixed effect models were used for statistical analysis. Metaanalysis and sensitivity analysis were used on the included studies.

Results: A total of six studies met predefined inclusion criteria, and were finally included in the analysis. Sensitivity and subgroup analyses, based on predetermined patient characteristics, allowed minimization of bias. In the RFA of hepatocellular carcinoma, FI decreased 1-year overall survival (OS) when compared with ultrasound. But FI was not significantly different from ultrasound in terms of technical efficiency, 1-, 2-, and 3-year local tumor progression (LTP), complications, as well as 2-year OS. Subgroup analysis, based on tumor mean diameter, showed that FI reduced the rate of 1- and 2-year LTP in patients with tumors of mean diameter ≥15 mm when compared with ultrasound. Moreover, operative complications could be reduced in patients with tumor mean diameter <15 mm using FI, compared with ultrasound.

Conclusion: Overall, these results showed that FI may have some effects on improving efficacy and safety of thermal ablation in HCC patients, relative to ultrasound. However, it may be a more effective method for managing large lesions, as well as those that are difficult to ablate. Further large-scale and well-designed randomized controlled trials are needed to validate these findings.

Review of clinical tumor ablation advance in Asia

Tumor ablation has been widely applied in Asia, accounting for 44.65% of clinical studies worldwide. We reviewed 5853 clinical studies to provide insight on the advance of tumor ablation in Asia chronologically and geographically among different techniques and organs. Since 1998, tumor ablation application has dramatically evolved in Asia. All kinds of ablation techniques, including percutaneous ethanol injection (PEI), radiofrequency ablation (RFA), microwave ablation (MWA), laser ablation (LA), cryoablation (CA), high-intensity focused ultrasound (HIFU), and irreversible electroporation (IRE), have been applied, with the first application of PEI and the most popular application of RFA. Twenty-five countries and one district in Asia have applied tumor ablation in various organs, including liver, lung, uterus, thyroid, kidney, pancreas, bone, prostate, breast, adrenal gland, lymph node parathyroid, esophagus, etc. Due to the high incidence of tumors as well as advanced economy and technology, East Asia accounted for 93.87% of studies, led by China (45.00%), Japan (32.72%), South Korea (12.10%), and Taiwan (4.03%). With the enrichment of evidence from large-scale multicenter and randomized control studies, China and South Korea have issued several guidelines on tumor ablation for liver, lung, and thyroid, which provided recommendations for global standardization of tumor ablation techniques. Therefore, Asia has made active contribution to global tumor ablation therapy.KeypointsKey point 1: Asia accounted for 44.65% of clinical studies worldwide on tumor ablation.Key point 2: Twenty-five countries and one district in Asia have used tumor ablation in various organs, and East Asia accounted for 93.87% of studies, led by China (45.00%), Japan (32.72%), South Korea (12.10%), and Taiwan (4.03%).Key point 3: China and South Korea have issued several guidelines on tumor ablation for liver, lung, and thyroid, which provided recommendations for global standardization of tumor ablation techniques.

Feasibility and Efficacy of Fusion Imaging Systems for Immediate Post Ablation Assessment of Liver Neoplasms: Protocol for a Rapid Systematic Review

Introduction:

Percutaneous thermal ablation is widely adopted as a curative treatment approach for unresectable liver neoplasms. Accurate immediate assessment of therapeutic response post-ablation is critical to achieve favourable outcomes. The conventional technique of side-by-side comparison of pre- and post-ablation scans is challenging and hence there is a need for improved methods, which will accurately evaluate the immediate post-therapeutic response.

Objectives and Significance:

This review summarizes the findings of studies investigating the feasibility and efficacy of the fusion imaging systems in the immediate post-operative assessment of the therapeutic response to thermal ablation in liver neoplasms. The findings could potentially empower the clinicians with updated knowledge of the state-of-the-art in the assessment of treatment response for unresectable liver neoplasms.

Methods and Analysis:

A rapid review will be performed on publicly available major electronic databases to identify articles reporting the feasibility and efficacy of the fusion imaging systems in the immediate assessment of the therapeutic response to thermal ablation in liver neoplasms. The risk of bias and quality of articles will be assessed using the Cochrane risk of bias tool 2.0 and Newcastle Ottawa tool.

Ethics and Dissemination:

Being a review, we do not anticipate the need for any approval from the Institutional Review Board. The outcomes of this study will be published in a peer-reviewed journal.

Highlights

Evaluation of the therapeutic response in liver neoplasms immediately post-ablation is critical to achieve favourable patient outcomes. We will examine the feasibility and technical efficacy of different fusion imaging systems in assessing the immediate treatment response post-ablation. The findings are expected to guide the clinicians with updated knowledge on the state-of-the-art when assessing the immediate treatment response for unresectable liver neoplasms.

An Unsupervised Learning-Based Multi-Organ Registration Method for 3D Abdominal CT Images

Medical image registration is an essential technique to achieve spatial consistency geometric positions of different medical images obtained from single- or multi-sensor, such as computed tomography (CT), magnetic resonance (MR), and ultrasound (US) images. In this paper, an improved unsupervised learning-based framework is proposed for multi-organ registration on 3D abdominal CT images. First, the explored coarse-to-fine recursive cascaded network (RCN) modules are embedded into a basic U-net framework to achieve more accurate multi-organ registration results from 3D abdominal CT images. Then, a topology-preserving loss is added in the total loss function to avoid a distortion of the predicted transformation field. Four public databases are selected to validate the registration performances of the proposed method. The experimental results show that the proposed method is superior to some existing traditional and deep learning-based methods and is promising to meet the real-time and high-precision clinical registration requirements of 3D abdominal CT images.

Unidirectional ablation minimizes unwanted thermal damage and promotes better thermal ablation efficacy in time-based switching bipolar radiofrequency ablation

Switching bipolar radiofrequency ablation (bRFA) is a thermal treatment modality used for liver cancer treatment that is capable of producing larger, more confluent and more regular thermal coagulation. When implemented in the no-touch mode, switching bRFA can prevent tumour track seeding; a medical phenomenon defined by the deposition of cancer cells along the insertion track. Nevertheless, the no-touch mode was found to yield significant unwanted thermal damage as a result of the electrodes' position outside the tumour. It is postulated that the unwanted thermal damage can be minimized if ablation can be directed such that it focuses only within the tumour domain. As it turns out, this can be achieved by partially insulating the active tip of the RF electrodes such that electric current flows in and out of the tissue only through the non-insulated section of the electrode. This concept is known as unidirectional ablation and has been shown to produce the desired effect in monopolar RFA. In this paper, computational models based on a well-established mathematical framework for modelling RFA was developed to investigate if unidirectional ablation can minimize unwanted thermal damage during time-based switching bRFA. From the numerical results, unidirectional ablation was shown to produce treatment efficacy of nearly 100%, while at the same time, minimizing the amount of unwanted thermal damage. Nevertheless, this effect was observed only when the switch interval of the time-based protocol was set to 50 s. An extended switch interval negated the benefits of unidirectional ablation.

Comparisons between impedance-based and time-based switching bipolar radiofrequency ablation for the treatment of liver cancer

Switching bipolar radiofrequency ablation (bRFA) is a cancer treatment technique that activates multiple pairs of electrodes alternately based on a predefined criterion. Various criteria can be used to trigger the switch, such as time (ablation duration) and tissue impedance. In a recent study on time-based switching bRFA, it was determined that a shorter switch interval could produce better treatment outcome than when a longer switch interval was used, which reduces tissue charring and roll-off induced cooling. In this study, it was hypothesized that a more efficacious bRFA treatment can be attained by employing impedance-based switching. This is because ablation per pair can be maximized since there will be no interruption to RF energy delivery until roll-off occurs. This was investigated using a two-compartment 3D computational model. Results showed that impedance-based switching bRFA outperformed time-based switching when the switch interval of the latter is 100 s or higher. When compared to the time-based switching with switch interval of 50 s, the impedance-based model is inferior. It remains to be investigated whether the impedance-based protocol is better than the time-based protocol for a switch interval of 50 s due to the inverse relationship between ablation and treatment efficacies. It was suggested that the choice of impedance-based or time-based switching could ultimately be patient-dependent.

Role of Machine Learning and Artificial Intelligence in Interventional Oncology

PURPOSE OF REVIEW

The purpose of this review is to highlight the current role of machine learning and artificial intelligence and in the field of interventional oncology.

RECENT FINDINGS

With advancements in technology, there is a significant amount of research regarding the application of artificial intelligence and machine learning in medicine. Interventional oncology is a field that can benefit greatly from this research through enhanced image analysis and intraprocedural guidance. These software developments can increase detection of cancers through routine screening and improve diagnostic accuracy in classifying tumors. They may also aid in selecting the most effective treatment for the patient by predicting outcomes based on a combination of both clinical and radiologic factors. Furthermore, machine learning and artificial intelligence can advance intraprocedural guidance for the interventional oncologist through more accurate needle tracking and image fusion technology. This minimizes damage to nearby healthy tissue and maximizes treatment of the tumor. While there are several exciting developments, this review also discusses limitations before incorporating machine learning and artificial intelligence in the field of interventional oncology. These include data capture and processing, lack of transparency among developers, validating models, integrating workflow, and ethical challenged. In summary, machine learning and artificial intelligence have the potential to positively impact interventional oncologists and how they provide cancer care treatments.

Intra-Procedural CT/MR-Ultrasound Fusion Imaging Helps to Improve Outcomes of Thermal Ablation for Hepatocellular Carcinoma: Results in 502 Nodules

PURPOSE

 The aim was to assess the value of intra-procedural CT/MR-ultrasound (CT/MR-US) fusion imaging in the management of thermal ablation for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

 This retrospective study was approved by the institutional review board. From May 2010 to October 2016, 543 HCC nodules in 440 patients (387 men and 53 women; age range: 25-84 years) that met the Milan Criteria were treated by percutaneous thermal ablation using intra-procedural CT/MR-US fusion imaging. The HCC nodules were divided into subgroups and compared (≤ 3 cm and > 3 cm, or high-risk and low-risk location, or inconspicuous and conspicuous, respectively). Technique efficacy and major complication were calculated. Cumulative local tumor progression (LTP), tumor-free and overall survival rates were estimated with the Kaplan-Meier method.

RESULTS

 CT/MR-US fusion imaging was successfully registered in 419 patients with 502 nodules. The technique efficacy rate of thermal ablation was 99.4 %. The major complication rate was 1.9 %. The cumulative LTP rates were 3.2 %, 5.6 % and 7.2 % at 1, 3, and 5 years, respectively. There were no significant differences for the comparisons of cumulative LTP rates between different subgroups (P = 0.541, 0.314, 0.329). The cumulative tumor-free survival rates were 74.8 %, 54.0 % and 37.5 % at 1, 3, and 5 years, respectively. The cumulative overall survival rates were 97.8 %, 87.1 % and 81.7 % at 1, 3, and 5 years, respectively.

CONCLUSION

 Intra-procedural CT/MR-ultrasound fusion imaging is a useful technique for percutaneous liver thermal ablation. It could help to achieve satisfying survival outcomes for HCC patients who meet the Milan Criteria.

Bipolar radiofrequency ablation treatment of liver cancer employing monopolar needles: A comprehensive investigation on the efficacy of time-based switching

Radiofrequency ablation (RFA) is a thermal ablative treatment method that is commonly used to treat liver cancer. However, the thermal coagulation zone generated using the conventional RFA system can only successfully treat tumours up to 3 cm in diameter. Switching bipolar RFA has been proposed as a way to increase the thermal coagulation zone. Presently, the understanding of the underlying thermal processes that takes place during switching bipolar RFA remains limited. Hence, the objective of this study is to provide a comprehensive understanding on the thermal ablative effects of time-based switching bipolar RFA on liver tissue. Five switch intervals, namely 50, 100, 150, 200 and 300 s were investigated using a two-compartment 3D finite element model. The study was performed using two pairs of RF electrodes in a four-probe configuration, where the electrodes were alternated based on their respective switch interval. The physics employed in the present study were verified against experimental data from the literature. Results obtained show that using a shorter switch interval can improve the homogeneity of temperature distribution within the tissue and increase the rate of temperature rise by delaying the occurrence of roll-off. The coagulation volume obtained was the largest using switch interval of 50 s, followed by 100, 150, 200 and 300 s. The present study demonstrated that the transient thermal response of switching bipolar RFA can be improved by using shorter switch intervals.

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.

Integration of Real-Time Image Fusion in the Robotic-Assisted Treatment of Hepatocellular Carcinoma

Simple Summary

Hepatocellular carcinoma is one of the leading causes of cancer-related deaths worldwide. An image fusion system is developed for the robotic-assisted treatment of hepatocellular carcinoma, which is not only capable of imaging data interpretation and reconstruction, but also automatic tumor detection. The optimization and integration of the image fusion system within a novel robotic system has the potential to demonstrate the feasibility of the robotic-assisted targeted treatment of hepatocellular carcinoma by showing benefits such as precision, patients safety and procedure ergonomics.

Abstract

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths worldwide, with its mortality rate correlated with the tumor staging; i.e., early detection and treatment are important factors for the survival rate of patients. This paper presents the development of a novel visualization and detection system for HCC, which is a composing module of a robotic system for the targeted treatment of HCC. The system has two modules, one for the tumor visualization that uses image fusion (IF) between computerized tomography (CT) obtained preoperatively and real-time ultrasound (US), and the second module for HCC automatic detection from CT images. Convolutional neural networks (CNN) are used for the tumor segmentation which were trained using 152 contrast-enhanced CT images. Probabilistic maps are shown as well as 3D representation of HCC within the liver tissue. The development of the visualization and detection system represents a milestone in testing the feasibility of a novel robotic system in the targeted treatment of HCC. Further optimizations are planned for the tumor visualization and detection system with the aim of introducing more relevant functions and increase its accuracy.

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.

Intra-procedural real-time ultrasound fusion imaging improves the therapeutic effect and safety of liver tumor ablation in difficult cases

In certain difficult cases involving tumors unclear in B-mode ultrasound or tumors in a high-risk location, image-guided liver tumor thermal ablation was previously contraindicated. The aim of this retrospective study was to investigate the value of intra-procedural ultrasound fusion imaging in improving the therapeutic effect and safety of liver tumor ablation in difficult cases. A total of 502 patients (441 males and 61 females, aged 52 ± 11 years) with 805 liver tumors (16 ± 6 mm; range, 4-29 mm) who underwent thermal ablation with intra-procedural fusion imaging from October 2010 to June 2018 in our hospital were enrolled. Fusion imaging was employed for targeting, puncture guidance and immediate evaluation of the therapeutic response. Contrast-enhanced computed tomography (CT)/magnetic resonance imaging (MRI) was performed one month after ablation and every 3~6 months in the follow-up period. 511 and 294 liver tumors were in classified in the difficult case group and the non-difficult case group, respectively. The technical efficacy rate was 99.4% (800/805), and no difference was found between the two groups (P=0.658). No significant difference in the local tumor progression rate was found between the difficult case group (1 year: 3.2%; 3 years: 7.6%; 5 years: 7.6%) and non-difficult case group (1 year: 2.1%; 3 years: 5.5%; 5 years: 11.6%) (P=0.874). The major complication rate was 1.8% (11/608). Injury to adjacent organs occurred in only 1 patient who sustained a bile duct injury. We conclude that intra-procedural fusion imaging can improve the therapeutic efficacy and safety of thermal ablation in difficult cases and may expand the indications for thermal ablation.

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.

Shape-shifting thermal coagulation zone during saline-infused radiofrequency ablation: A computational study on the effects of different infusion location

BACKGROUND AND OBJECTIVE

The majority of the studies on radiofrequency ablation (RFA) have focused on enlarging the size of the coagulation zone. An aspect that is crucial but often overlooked is the shape of the coagulation zone. The shape is crucial because the majority of tumours are irregularly-shaped. In this paper, the ability to manipulate the shape of the coagulation zone following saline-infused RFA by altering the location of saline infusion is explored.

METHODS

A 3D model of the liver tissue was developed. Saline infusion was described using the dual porosity model, while RFA was described using the electrostatic and bioheat transfer equations. Three infusion locations were investigated, namely at the proximal end, the middle and the distal end of the electrode. Investigations were carried out numerically using the finite element method.

RESULTS

Results indicated that greater thermal coagulation was found in the region of tissue occupied by the saline bolus. Infusion at the middle of the electrode led to the largest coagulation volume followed by infusion at the proximal and distal ends. It was also found that the ability to delay roll-off, as commonly associated with saline-infused RFA, was true only for the case when infusion is carried out at the middle. When infused at the proximal and distal ends, the occurrence of roll-off was advanced. This may be due to the rapid and more intense heating experienced by the tissue when infusion is carried out at the electrode ends where Joule heating is dominant.

CONCLUSION

Altering the location of saline infusion can influence the shape of the coagulation zone following saline-infused RFA. The ability to 'shift' the coagulation zone to a desired location opens up great opportunities for the development of more precise saline-infused RFA treatment that targets specific regions within the tissue.

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.

Chemical Characteristics, Motivation and Strategies in choice of Materials used as Liver Phantom: A Literature Review

Liver phantoms have been developed as an alternative to human tissue and have been used for different purposes. In this article, the items used for liver phantoms fabrication are mentioned same as in the previous literature reviews. Summary and characteristics of these materials are presented. The main factors that need to be available in the materials used for fabrication in computed tomography, ultrasound, magnetic resonance imaging, and nuclear medicine were analyzed. Finally, the discussion focuses on some purposes and aims of the liver phantom fabrication for use in several areas such as training, diagnoses of different diseases, and treatment planning for therapeutic strategies – for example, in selective internal radiation therapy, stereotactic body radiation therapy, laser-induced thermotherapy, radiofrequency ablation, and microwave coagulation therapy. It was found that different liver substitutes can be developed to fulfill the different requirements.

A novel nomogram to predict the local tumor progression after microwave ablation in patients with early-stage hepatocellular carcinoma: A tool in prediction of successful ablation

OBJECTIVES

To develop a nomogram for the local tumor progression (LTP) in patients with early-stage hepatocellular carcinoma (HCC) after computed tomography-guided percutaneous microwave ablation (CT-PMWA) and to assess clinical-pathologic risk factors for individual LTP estimation. Furthermore, we compared the prognostic predictive ability for LTP between the nomogram and the traditional staging systems.

METHODS

This retrospective study was approved by the institutional review board. Five hundred and forty treatment-naïve patients with HCC according to the Milan criteria, who subsequently underwent CT-PMWA were reviewed from 2009 to 2019. Baseline characteristics were collected to identify the risk factors for the determination of LTP after CT-PMWA. The multivariate Cox proportional-hazards model based on significant prognostic factors of LTP was used to construct the nomogram, which was then assessed for its predictive accuracy using mainly the Harrell's C-index and time-dependent area under the curve (tAUC).

RESULTS

After a median follow-up time of 28.7 months, 6.5% (35/540) patients had LTP. The nomogram was developed based on the tumor size, tumor number, Child-Turcotte-Pugh (CTP) grade, platelet, and alanine aminotransferase (ALT). The nomogram had good calibration and discriminatory abilities in the training set, with C-indexes of 0.799 (95% confidence interval (CI): 0.738, 0.860), and tAUCs of 0.844 (CI: 0.728, 0.895), that were greater than those of traditional staging systems. Internal validation with 1000 bootstrap resamples had a good C-index of 0.735 (CI: 0.648, 0.816).

CONCLUSIONS

The nomogram model can be used to predict accurately LTP after CT-PMWA for early-stage HCC, as well as to assist physicians during the therapeutic decision-making process.

Investigating the Accuracy of Ultrasound-Ultrasound Fusion Imaging for Evaluating the Ablation Effect via Special Phantom-Simulated Liver Tumors

The goal of this study was to investigate the accuracy of ultrasound-ultrasound (US-US) fusion imaging for evaluating the ablation effect via phantom-simulated liver tumors. Twenty special phantom models were established, ablated and divided into a complete ablation group (n = 10) and an incomplete ablation group (n = 10). US-US fusion imaging was performed to evaluate the ablation effect. Gross specimens were observed as a standard reference. In this US-US fusion imaging study, the registration success rate was 100% (20/20), and the assessment time was 3.8 ± 0.9 min. The accuracy rate of the evaluation was 100% (20/20). There was no significant difference in the residual pseudo-tumoral area between the evaluation with US-US fusion imaging and gross specimen observation (p = 0.811), and the measurement error was 1.1 ± 0.6 mm. In conclusion, the feasibility and accuracy of US-US fusion imaging when evaluating the ablation effect can be investigated with this phantom-simulated liver tumor ablation model in an ideal state.

Comparative safety and effectiveness of ultrasound-guided radiofrequency ablation combined with preoperative three-dimensional reconstruction versus surgical resection for solitary hepatocellular carcinoma of 3-5 cm

OBJECTIVE

To investigate the safety and effectiveness of ultrasound-guided radiofrequency ablation (RFA) combined with preoperative three-dimensional (3D) reconstruction versus surgical resection for solitary hepatocellular carcinoma of 3-5 cm.

METHODS

The cohort of this retrospective study included 66 consecutive patients who underwent open hepatectomy (Surgery group) between January 2009 and December 2014, as well as 54 consecutive patients who underwent ultrasound-guided RFA combined with preoperative 3D reconstruction (RFA group) during the same period. Preoperative 3D reconstruction was performed using Myrian-XP-Liver software. The image fusion system was used to evaluate the RFA safety margin at 1 month after surgery. Kaplan-Meier analysis and the log-rank test were used to compare the recurrence and overall survival (OS) rates between the two treatment groups.

RESULTS

There were no significant differences in the baseline characteristics of the two groups. The complete ablation rate was 94.4% (51/53). As compared with surgical resection for solitary HCC of 3-5 cm, ultrasound-guided RFA combined with preoperative 3D reconstruction significantly reduced the morbidity of excessive pain, total complications, and infections (p < 0.001). A significant decrease in the duration of the hospital stay after treatment was also observed in the RFA group (t = 10.017, p < 0.001). There was no significant difference in the cumulative recurrence rate between the two groups. Kaplan-Meier analysis and the log-rank test revealed no significant difference in the OS rate between the two groups over a 3-year follow-up period.

CONCLUSION

Ultrasound-guided RFA combined with preoperative 3D reconstruction appears to be a safe and effective therapeutic option for patients with solitary HCC of 3-5 cm.

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.

Accuracy of a CT-Ultrasound Fusion Imaging Guidance System Used for Hepatic Percutaneous Procedures

PURPOSE

To evaluate the accuracy of a fusion imaging guidance system using ultrasound (US) and computerized tomography (CT) as a real-time imaging modality for the positioning of a 22-gauge needle in the liver.

MATERIALS AND METHODS

The spatial coordinates of 23 spinal needles placed at the border of hepatic tumors before radiofrequency thermal ablation were determined in 23 patients. Needles were inserted up to the border of the tumor with the use of CT-US fusion imaging. A control CT scan was carried out to compare real (x, y, z) and virtual (x', y', z') coordinates of the tip of the needle (D for distal) and of a point on the needle located 3 cm proximally to the tip (P for proximal).

RESULTS

The mean Euclidian distances were 8.5 ± 4.7 mm and 10.5 ± 5.3 mm for D and P, respectively. The absolute value of mean differences of the 3 coordinates (|x' - x|, |y' - y|, and |z' - z|) were 4.06 ± 0.9, 4.21 ± 0.84, and 4.89 ± 0.89 mm for D and 3.96 ± 0.60, 4.41 ± 0.86, and 7.66 ± 1.27 mm for P. X = |x' - x| and Y = |y' - y| coordinates were <7 mm with a probability close to 1. Z = |z' - z| coordinate was not considered to be larger nor smaller than 7 mm (probability >7 mm close to 50%).

CONCLUSIONS

Positioning errors with the use of US-CT fusion imaging used in this study are not negligible for the insertion of a 22-gauge needle in the liver. Physicians must be aware of such possible errors to adapt the treatment when used for thermal ablation.

Contrast-enhanced ultrasound to ultrasound fusion during microwave ablation: feasibility study in a perfused porcine liver model

PURPOSE

To obtain a complete response with thermal ablation, the margin and entire tumor volume must be treated. Real-time ultrasound visualization is limited during ablation due to gas production. This study assesses the feasibility of fusing volumetric contrast-enhanced ultrasound (CEUS), obtained immediately prior to microwave ablation, with real-time CEUS during and following ablation in a machine-perfused porcine liver.

METHODS

Ten, 3-4 cm microwave ablations were performed in five explanted perfused livers. Prior to ablation, microbubbles were injected into the vasculature while an ultrasound sweep across the liver captured a volumetric image during maximum enhancement. This volumetric image was then fused to overlay the real-time ultrasound imaging. Since the perfused livers did not have tumors, a spherical marker circumscribing a target volume was placed on the images. Approximatively, 75% of the total intended circumscribed spherical volume was ablated. Following ablation, a second bolus injection of ultrasound contrast was administered demonstrating continued enhancement of the intentionally non-ablated 25%. A second volumetric image of the post-ablation CEUS was then fused to overlay the real-time ultrasound images for guidance during ablation of the remaining enhancing volume.

RESULTS

Technical success was achieved in 100% of the cases. The pre- and then the post-ablation CEUS volume was fused with real-time imaging during antenna placement for initial and subsequent ablation.

CONCLUSION

CEUS-CEUS fusion during thermal ablation is feasible and greatly improves the workflow. The approach may augment the use of dynamic CEUS for guidance, improving antenna placement, and aiding in the identification and ablation of initial and residual enhancing tissue.

A tumor map generated from three-dimensional visualization of image fusion for the assessment of microwave ablation of hepatocellular carcinoma: a preliminary study

PURPOSE

This study aimed to investigate the clinical value of a tumor map for assessing the ablative effect after ultrasound-guided percutaneous microwave ablation (US-PMWA) for hepatocellular carcinoma (HCC).

METHODS

The medical records of 68 patients (49 male and 19 female, 59.9±12.7 years) with HCC who underwent US-PMWA from May 2013 to May 2017 were reviewed. A tumor map was generated from the fusion of three-dimensional (3D) visualization images based on the preoperative target tumor and postoperative ablation area, to evaluate whether the ablation area covering the tumor has reached a 5 mm ablative margin (AM). The lesions were divided into two groups according to the tumor maps: group A (failed to achieve AM) and group B (achieved AM). The cumulative local tumor progression (LTP) rates of both groups were statistically analyzed using the log-rank test.

RESULTS

Success rate of tumor map generation was 100% (68/68), and no residual tumors were found. MWA-related 3D images, which included target tumor volume, ablation area volume, and residual liver ratio, were compared between groups A and B (P=0.295, P=0.772, and P=0.527, respectively). Technique effectiveness rate (91.7% vs 100%) was achieved in the two groups, showing no significant statistical differences (P=0.672). The 3-, 6-, 9-, and 12-month LTP rate was 8.3%, 16.7%, 20.8%, and 34%, respectively, for group A and 0%, 2.8%, 2.8%, and 2.8%, respectively, for group B, showing significant statistical differences (P<0.001) between the two groups.

CONCLUSION

The novel technology of tumor map generated from 3D visualization of image fusion is feasible and useful in evaluating the ablative effect of US-PMWA for HCC.

Potential application of ultrasound-guided thermal ablation in rare liver tumors

BACKGROUND

With the advances of imaging techniques, the detection rate of rare liver tumor is increased. However, the therapeutic strategies of the rare liver tumors remain limited.

METHODS

We analyzed twelve pathologically confirmed rare liver tumors in 8 patients. All of the patients underwent ultrasound (US) guided biopsy and subsequent thermal ablation. The tumors were ablated according to the preoperative plans and monitored by real-time US. CT/MRI fused with contrast enhanced US (CEUS) or three-dimensional (3D) US-CEUS images were used to guide and assess the ablation zone more accurately during thermal ablation. The rate of technical efficacy was assessed based on the contrast-enhance CT/MRI (CECT/MRI) results one month after ablation. Local tumor progression (LTP), recurrence and complications were followed up and recorded.

RESULTS

Among these twelve nodules, nine were subject to US-guided thermal ablation, whereas the other three inconspicuous nodules were subject to CEUS-guided thermal ablation. Intra-procedure CT/MRI-CEUS or 3D US-CEUS fusion imaging assessments demonstrated that the ablation zone sufficiently covered the original tumor, and no immediate supplementary ablation was required. Additionally, no major complications were observed during the follow-up period. The postoperative CECT/MRI confirmed that the technique success rate was 100%. Within the surveillance period of 13 months, no LTP or recurrence was noted.

CONCLUSIONS

US-guided thermal ablation was feasible and safe for rare liver tumors. The use of fusion imaging technique might make US-guided thermal ablation as effective as surgical resection, and this technique might serve as a potential therapeutic modality for rare liver tumors in the future.

A Novel CT to Cone-Beam CT Registration Method Enables Immediate Real-Time Intraprocedural Three-Dimensional Assessment of Ablative Treatments of Liver Malignancies

Aim

To evaluate a novel contrast-enhanced cone-beam computed tomography (CE-CBCT) registration method for accurate immediate assessment of ablation outcomes.

Materials and Methods

Contrast-enhanced computed tomography (CECT) was registered with CE-CBCT by applying semiautomatic landmark registration followed by automatic affine and non-rigid registration to correct for respiratory phase differences and liver deformation. This scheme was retrospectively applied to 30 patients who underwent 38 percutaneous microwave liver ablations. Three datasets were obtained for each case: (1) conventional CECT scans 24 h before ablation, (2) intraprocedural CE-CBCT scans, and (3) CECT scans 24 h post-ablation. Using a five-point scale, two experienced radiologists qualitatively assessed registration quality, equivalence of CE-CBCT assessment of ablation outcome to 24 h post-ablation CECT, and perceived increase of confidence using the fusion method to CBCT alone. Additionally, residual post-ablation tumor volumes were measured at both CE-CBCT and 24 h CECT and compared to the pre-CECT.

Results

Registration quality was high for both radiologists (R1: 4.3 ± 0.6, R2: 4.4 ± 0.5; p = 0.87). Comparisons between the registration of pre-ablation CECT with CE-CBCT versus post-ablation CECT regarding the position of the ablated area to the treated target (R1: 4.4 ± 0.6, R2: 4.6 ± 0.4) and treatment outcome (R1: 4.5 ± 0.5, R2: 4.6 ± 0.4) were equivalent (p > 0.35). Increased confidence was noted when using fusion (R1: 4.6 ± 0.4, R2: 4.6 ± 0.4; p = 0.84). Moreover, in 6 ablations (15.8%) the intraprocedural registered CBCT showed residual tumor precisely where identified on the 24 h post-ablation CECT.

Conclusions

Combined CE-CBCT holds the potential to change the current workflow of mini-invasive cancer local treatments. Given earlier visual identification of residual tumor post-ablation, this includes potentially eliminating the need for some additional treatments.