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

C-Arm Computed Tomographic Image Fusion for Repetitive Transarterial Chemoembolization of Hepatocellular Carcinoma

OBJECTIVE

The aim of this study was to evaluate the potential implications of fusion imaging with C-arm computed tomography (CACT) scans for repetitive conventional transarterial chemoembolization (cTACE) for hepatocellular carcinoma.

MATERIALS AND METHODS

Fifty-six cTACE sessions were performed using fusion CACT images from September 2020 to June 2021 in a tertiary referral center, and the data were retrospectively analyzed. Fusion of unenhanced and enhanced CACT images was considered when previously accumulated iodized oil hampered the identification of local tumor progression or intrahepatic distant metastasis (indication A), when a tumor was supplied by multiple arteries with different origins from the aorta and missing tumor enhancement was suspected (indication B), or when iodized oil distribution on immediate post-cTACE CACT images needed to be precisely compared with the pre-cTACE images (indication C). Fusion image quality, initial tumor response, time to local progression (TTLP) of index tumors, and time to progression (TTP) were evaluated.

RESULTS

The fusion quality was satisfactory with a mean misregistration distance of 1.4 mm. For the 40 patients with indication A, the initial tumor responses at 3 months were nonviable, equivocal, and viable in 27 (67.5%), 4 (10.0%), and 9 (22.5%) index tumors, respectively. The median TTLP and TTP were 14.8 months and 4.5 months, respectively. For 10 patients with indication B, the median TTLP and TTP were 8.3 months and 2.6 months, respectively. Among the 6 patients with indication C, 2 patients were additionally treated at the same cTACE session after confirming incomplete iodized oil uptake on fusion imaging.

CONCLUSIONS

Fusion CACT images are useful in patients with hepatocellular carcinoma undergoing repetitive cTACE.

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.

Virtual Treatment Zone From Cone Beam CT Commonly Alters Treatment Plan and Identifies Tumor at Risk for Under-Treatment in US or US Fusion-Guided Microwave Ablation of Liver Tumors

Tumor ablation is included in several major cancer therapy guidelines. One technical challenge of percutaneous ablation is targeting and verification of complete treatment, which is prone to operator variabilities and human imperfections and are directly related to successful outcomes, risk for residual unablated tumor and local progression. The use of "Prediction Ablation Volume Software" may help the operating Interventional Radiologist to better plan, deliver, and verify before the ablation, via virtual treatment zones fused to target tumor. Fused and superimposed images provide 3-dimensional information from different timepoints, just when that information is most useful. The aim of this study is to evaluate the technical success and efficacy of an ablation treatment flowchart provided by a cone beam computed tomography (CBCT) "Prediction Ablation Volume Software." This is a single-center retrospective study. From April 2021 to January 2022, 29 nonconsecutive evaluable patients with 32 lesions underwent liver ablation with Prediction Ablation Volume Software. Each patient was discussed in a multidisciplinary tumor board and underwent an enhanced computed tomography or magnetic resonance imaging approximately 1 month before the procedure, as well as ∼1 month after. Technical success was defined as treatment of the tumor according to the protocol, covered completely by the Prediction Ablation Volume. Technical efficacy was defined as assessment of complete ablation of the target tumor at imaging follow up (∼1 month). Technical success, technical efficacy, and procedural factors were studied. Technical success was achieved in 30 of 32 liver lesions (94%), measuring 20 mm mean maximum diameter. The antenna was repositioned in 16 of 30 (53%) evaluable target lesions. Residual tumor was detected at 1 month imaging follow up in only 4 of 30 (13%) of the treated lesion. Technical efficacy was of 87% in this retrospective description of our process. The implementation of a CBCT Prediction Ablation Volume Software and flowchart for the treatment of liver malignancies altered the procedure, and demonstrated high technical success and efficacy. Such tools are potentially useful for procedural prediction and verification of ablation.

Precision Imaging Guidance in the Era of Precision Oncology: An Update of Imaging Tools for Interventional Procedures

Interventional oncology (IO) procedures have become extremely popular in interventional radiology (IR) and play an essential role in the diagnosis, treatment, and supportive care of oncologic patients through new and safe procedures. IR procedures can be divided into two main groups: vascular and non-vascular. Vascular approaches are mainly based on embolization and concomitant injection of chemotherapeutics directly into the tumor-feeding vessels. Percutaneous approaches are a type of non-vascular procedures and include percutaneous image-guided biopsies and different ablation techniques with radiofrequency, microwaves, cryoablation, and focused ultrasound. The use of these techniques requires precise imaging pretreatment planning and guidance that can be provided through different imaging techniques: ultrasound, computed tomography, cone-beam computed tomography, and magnetic resonance. These imaging modalities can be used alone or in combination, thanks to fusion imaging, to further improve the confidence of the operators and the efficacy and safety of the procedures. This article aims is to provide an overview of the available IO procedures based on clinical imaging guidance to develop a targeted and optimal approach to cancer patients.

Software-based assessment of tumor margins after percutaneous thermal ablation of liver tumors: A systematic review

PURPOSE

The purpose of this study was to make a systematic review of clinical studies evaluating software-based tumor margin assessment after percutaneous thermoablation (PTA) of liver tumors.

MATERIALS AND METHODS

A systematic literature search was performed through Pubmed/MEDLINE, Embase and the Cochrane Library. Original studies published in English that reported on software-based assessment of ablation margins (AM) following PTA of liver tumors were selected. Studies were analyzed with respect to design, number of patients and tumors, tumor type, PTA technique, tumor size, target registration error, study outcome(s) (subtypes: feasibility, comparative, clinical impact, predictive or survival), and follow-up period.

RESULTS

Twenty-nine articles (one multi-center and two prospective studies) were included. The majority were feasibility (26/29, 89.7%) or predictive (23/29, 79.3%) studies. AM was a risk factor of local tumor progression (LTP) in 25 studies (25/29, 86.2%). In nine studies (9/29, 31%) visual assessment overestimated AM compared with software-aided assessment. LTP occurred at the location of the thinnest margin in nine studies (9/29, 31%). Time for registration and analysis was heterogeneously reported, ranging between 5-30 min. Mean target registration error was reported in seven studies (7/29, 24.1%) at 1.62 mm (range: 1.20-2.23 mm). Inter-operator reproducibility was high (kappa range: 0.686-1). Ascites, liver deformation and inconspicuous tumor were major factors of co-registration error.

CONCLUSION

Available studies present a low level of evidence overall, since most of them are feasibility, retrospective and single-center studies.

Quantitative Automated Segmentation of Lipiodol Deposits on Cone Beam CT Imaging acquired during Transarterial Chemoembolization for Liver Tumors: A Deep Learning Approach

PURPOSE

The purpose of this study was to show that a deep learning-based, automated model for Lipiodol segmentation on CBCT after cTACE performs closer to the "ground truth segmentation" than a conventional thresholding-based model.

MATERIALS & METHODS

This post-hoc analysis included 36 patients with a diagnosis of HCC or other solid liver tumor who underwent cTACE with an intra-procedural CBCT. Semi-automatic segmentation of Lipiodol were obtained. Then, a convolutional U-net model was used to output a binary mask that predicts Lipiodol deposition. A threshold value of signal intensity on CBCT was used to obtain a Lipiodol mask for comparison. Dice similarity coefficient (DSC), Mean-squared error (MSE), and Center of Mass (CM), and fractional volume ratios for both masks were obtained by comparing them to the ground truth (radiologist segmented Lipiodol deposits) to obtain accuracy metrics for the two masks. These results were used to compare the model vs. the threshold technique.

RESULTS

For all metrics, the U-net outperformed the threshold technique: DSC (0.65±0.17 vs. 0.45±0.22,p<0.001) and MSE (125.53±107.36 vs. 185.98±93.82,p=0.005). Difference between the CM predicted, and the actual CM was (15.31±14.63mm vs. 31.34±30.24mm,p<0.001), with lesser distance indicating higher accuracy. The fraction of volume present ([predicted Lipiodol volume]/[ground truth Lipiodol volume]) was 1.22±0.84vs.2.58±3.52,p=0.048 for our model's prediction and threshold technique, respectively.

CONCLUSION

This study showed that a deep learning framework could detect Lipiodol in CBCT imaging and was capable of outperforming the conventionally used thresholding technique over several metrics. Further optimization will allow for more accurate, quantitative predictions of Lipiodol depositions intra-procedurally.

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.

Percutaneous Therapies for Hepatocellular Carcinoma: Evolution of Liver Directed Therapies

Percutaneous ablation is a mainstay of treatment for early stage, unresectable hepatocellular carcinoma (HCC). Recent advances in technology have created multiple ablative modalities for treatment of this common malignancy. The purpose of this review is to familiarize readers with the technical and clinical aspects of both existing and emerging percutaneous treatment options for HCC.

Anatomy-guided multimodal registration by learning segmentation without ground truth: Application to intraprocedural CBCT/MR liver segmentation and registration

Multimodal image registration has many applications in diagnostic medical imaging and image-guided interventions, such as Transcatheter Arterial Chemoembolization (TACE) of liver cancer guided by intraprocedural CBCT and pre-operative MR. The ability to register peri-procedurally acquired diagnostic images into the intraprocedural environment can potentially improve the intra-procedural tumor targeting, which will significantly improve therapeutic outcomes. However, the intra-procedural CBCT often suffers from suboptimal image quality due to lack of signal calibration for Hounsfield unit, limited FOV, and motion/metal artifacts. These non-ideal conditions make standard intensity-based multimodal registration methods infeasible to generate correct transformation across modalities. While registration based on anatomic structures, such as segmentation or landmarks, provides an efficient alternative, such anatomic structure information is not always available. One can train a deep learning-based anatomy extractor, but it requires large-scale manual annotations on specific modalities, which are often extremely time-consuming to obtain and require expert radiological readers. To tackle these issues, we leverage annotated datasets already existing in a source modality and propose an anatomy-preserving domain adaptation to segmentation network (APA2Seg-Net) for learning segmentation without target modality ground truth. The segmenters are then integrated into our anatomy-guided multimodal registration based on the robust point matching machine. Our experimental results on in-house TACE patient data demonstrated that our APA2Seg-Net can generate robust CBCT and MR liver segmentation, and the anatomy-guided registration framework with these segmenters can provide high-quality multimodal registrations.

Short-term outcomes of radiofrequency ablation for hepatocellular carcinoma using cone-beam computed tomography for planning and image guidance

BACKGROUND

Percutaneous radiofrequency ablation (RFA) is an effective treatment for unresectable hepatocellular carcinoma (HCC) and a minimally invasive alternative to hepatectomy for treating tumour recurrence. RFA is often performed using contrast-enhanced computed tomography (CECT) and/or ultrasonography. In recent years, angiographic systems with flat panel image detectors and advanced image reconstruction algorithms have broadened the clinical applications of cone-beam computed tomography (CBCT), including RFA. Several studies have shown the effectiveness of using CBCT for immediate treatment assessments and follow-ups.

AIM

To assess the treatment response to RFA for HCC using CBCT.

METHODS

Forty-eight patients (44 men; aged 37-89 years) with solitary HCC [median size: 3.2 (1.2-6.6) cm] underwent RFA and were followed for 25.6 (median; 13.5-35.2) mo. Image fusion of CBCT and pre-operative CECT or magnetic resonance imaging (MRI) was used for tumour segmentation and needle path and ablation zone planning. Real-time image guidance was provided by overlaying the three-dimensional image of the tumour and needle path on the fluoroscopy image. Treatment response was categorized as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Disease progression, death, time to progression (TTP), and overall survival (OS) were recorded. Kaplan-Meier and Cox regression analyses were performed.

RESULTS

Initial post-RFA CECT/MRI showed 38 cases of CR (79.2%), 10 of PR (20.8%), 0 of SD, and 0 of PD, which strongly correlated with the planning estimation (42 CR, 87.5%; 6 PR, 12.5%; 0 SD; and 0 PD; accuracy: 91.7%, P < 0.01). Ten (20.8%) patients died, and disease progression occurred in 31 (35.4%, median TTP: 12.8 mo) patients, resulting in 12-, 24-, and 35-mo OS rates of 100%, 81.2%, and 72.2%, respectively, and progression-free survival (PFS) rates of 54.2%, 37.1%, and 37.1%, respectively. The median dose-area product of the procedures was 79.05 Gy*cm² (range 40.95-146.24 Gy*cm²), and the median effective dose was 10.27 mSv (range 5.32-19.01 mSv). Tumour size < 2 cm (P = 0.008) was a significant factor for OS, while age (P = 0.001), tumour size < 2 cm (P < 0.001), tumour stage (P = 0.010), and initial treatment response (P = 0.003) were significant factors for PFS.

CONCLUSION

Reliable RFA treatment planning and satisfactory outcomes can be achieved with CBCT.

Open Liver Resection, Laparoscopic Liver Resection, and Percutaneous Thermal Ablation for Patients with Solitary Small Hepatocellular Carcinoma (≤30 mm): Review of the Literature and Proposal for a Therapeutic Strategy

BACKGROUND

Patients with a single hepatocellular carcinoma (HCC) ≤3 cm and preserved liver function have the highest likelihood to be cured if treated. The most adequate treatment methods are yet a matter that is debated.

METHODS

We reviewed the literature about open anatomic resection (AR), laparoscopic liver resection (LLR), and percutaneous thermal ablation (PTA).

RESULTS

PTA is effective as resection for HCC < 2 cm, when they are neither subcapsular nor perivascular. PTA in HCC of 2-3 cm is under evaluation. AR with the removal of the tumor-bearing portal territory is recommended for HCC > 2 cm, except for subcapsular ones. In comparison with open surgery, LRR has better short-term outcomes and non-inferior long-term outcomes. LLR is standardized for superficial limited resections and for left-sided AR.

CONCLUSIONS

According to the available evidences, the following therapeutic proposal can be advanced. Laparoscopic limited resection is the standard for any subcapsular HCC. PTA is the first-line treatment for deep-located HCC < 2 cm, except for those in contact with Glissonean pedicles. Laparoscopic AR is the standard for deep-located HCC of 2-3 cm of the left liver, while open AR is the standard for deep-located HCC of 2-3 cm in the right liver. HCC in contact with Glissonean pedicles should be scheduled for resection (open or laparoscopic) independent of their size. Liver transplantation is reserved to otherwise untreatable patients or as a salvage procedure at recurrence.