Real-Time US-18FDG-PET/CT Image Fusion for Guidance of Thermal Ablation of 18FDG-PET-Positive Liver Metastases: The Added Value of Contrast Enhancement

Artificial intelligence in interventional radiology: state of the art

Artificial intelligence (AI) has demonstrated great potential in a wide variety of applications in interventional radiology (IR). Support for decision-making and outcome prediction, new functions and improvements in fluoroscopy, ultrasound, computed tomography, and magnetic resonance imaging, specifically in the field of IR, have all been investigated. Furthermore, AI represents a significant boost for fusion imaging and simulated reality, robotics, touchless software interactions, and virtual biopsy. The procedural nature, heterogeneity, and lack of standardisation slow down the process of adoption of AI in IR. Research in AI is in its early stages as current literature is based on pilot or proof of concept studies. The full range of possibilities is yet to be explored.Relevance statement Exploring AI's transformative potential, this article assesses its current applications and challenges in IR, offering insights into decision support and outcome prediction, imaging enhancements, robotics, and touchless interactions, shaping the future of patient care.Key points• AI adoption in IR is more complex compared to diagnostic radiology.• Current literature about AI in IR is in its early stages.• AI has the potential to revolutionise every aspect of IR.

Imaging Considerations before and after Liver-Directed Locoregional Treatments for Metastatic Colorectal Cancer

Colorectal cancer is a leading cause of cancer-related death. Liver metastases will develop in over one-third of patients with colorectal cancer and are a major cause of morbidity and mortality. Even though surgical resection has been considered the mainstay of treatment, only approximately 20% of the patients are surgical candidates. Liver-directed locoregional therapies such as thermal ablation, Yttrium-90 transarterial radioembolization, and stereotactic body radiation therapy are pivotal in managing colorectal liver metastatic disease. Comprehensive pre- and post-intervention imaging, encompassing both anatomic and metabolic assessments, is invaluable for precise treatment planning, staging, treatment response assessment, and the prompt identification of local or distant tumor progression. This review outlines the value of imaging for colorectal liver metastatic disease and offers insights into imaging follow-up after locoregional liver-directed therapy.

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.

Radiofrequency Ablation, Cryoablation, and Microwave Ablation for the Treatment of Small Renal Masses: Efficacy and Complications

Over the last two decades the detection rate of small renal masses has increased, due to improving diagnostic accuracy, and nephron-sparing treatments have become the first-choice curative option for small renal masses. As a minimally invasive alternative, thermal ablation has increased in popularity, offering a good clinical outcome and low recurrence rate. Radiofrequency ablation, Cryoablation, and Microwave ablation are the main ablative techniques. All of them are mostly overlapping in term of cancer specific free survival and outcomes. These techniques require imaging study to assess lesions features and to plan the procedure: US, CT, and both of them together are the leading guidance alternatives. Imaging findings guide the interventional radiologist in assessing the risk of complication and possible residual disease after procedure. The purpose of this review is to compare different ablative modalities and different imaging guides, underlining the effectiveness, outcomes, and complications related to each of them, in order to assist the interventional radiologist in choosing the best option for the patient.

Interventional oncology of liver tumors: how it all started and where are we now

Liver was the very first organ for which interventional procedures were applied for the local treatment of primary and secondary malignancies. In this paper, the history of Interventional Oncology of liver, from the very beginning to the current situation, is summarized, including both percutaneous and intravascular procedures, and together with the evolution of the techniques for image guidance. The main ongoing developments, such as new techniques, combined interventional treatments and association of local interventions with new drugs are briefly described, too.

Functional Investigation of the Tumoural Heterogeneity of Intrahepatic Cholangiocarcinoma by In Vivo PET-CT Navigation: A Proof-of-Concept Study

Intra-tumoural heterogeneity (IH) is a major determinant of resistance to therapy and outcomes but remains poorly translated into clinical practice. Intrahepatic cholangiocarcinoma (ICC) often presents as large heterogeneous masses at imaging. The present study proposed an innovative in vivo technique to functionally assess the IH of ICC. Preoperative 18F-FDG PET-CT and intraoperative ultrasonography were merged to perform the intraoperative navigation of functional tumour heterogeneity. The tumour areas with the highest and the lowest metabolism (SUV) at PET-CT were selected, identified during surgery, and sampled. Three consecutive patients underwent the procedure. The areas with the highest uptake at PET-CT had higher proliferation index (KI67) values and higher immune infiltration compared to areas with the lowest uptake. One of the patients showed a heterogeneous presence of FGFR2 translocation within the samples. Tumour heterogeneity at PET-CT may drive biopsy to sample the most informative ICC areas. Even more relevant, these preliminary data show the possibility of achieving a non-invasive evaluation of IH in ICC, paving the way for an imaging-based precision-medicine approach.

Technical Feasibility of Electromagnetic US/CT Fusion Imaging and Virtual Navigation in the Guidance of Spine Biopsies

PURPOSE

 To test the technical feasibility of electromagnetic computed tomography (CT) + ultrasound fusion (US)-guided bone biopsy of spinal lesions.

MATERIALS AND METHODS

 This retrospective study included 14 patients referred for biopsy of spinal bone lesions without cortical disruption or intervertebral disc infection. Lesions were located in the sacrum (n = 4), lumbar vertebral body (n = 7) or intervertebral disc (n = 3). Fusion technology matched a pre-procedure CT scan with real-time ultrasound. The first six procedures were performed under both standard CT and CT + US fusion guidance (group 1). In the last eight procedures, the needle was positioned under fusion imaging guidance alone, and CT was only used at the end of needle placement to confirm correct positioning (group 2). Additionally, we retrieved 8 patients (controls) with location-matched lesions as group 2, which were biopsied in the past with the standard CT-guided technique. The procedure duration and number of CT passes were recorded.

RESULTS

 Mean procedure duration and median CT pass number were significantly higher in group 1 vs. group 2 (45 ± 5 vs. 26 ± 3 minutes, p = 0.002 and 7; 5.25-8.75 vs. 3; 3-3.25, p = 0.001). In controls, the mean procedure duration was 47 ± 4 minutes (p = 0.001 vs. group 2; p = 0.696 vs. group 1) and the number of CT passes was 6.5 (5-8) (p = 0.001 vs. group 2; p = 0.427 vs. group 1). No complications occurred and all specimens were adequate overall. In one case in group 2, the needle position was modified according to CT assessment before specimen withdrawal.

CONCLUSION

 Electromagnetic CT+US fusion-guided bone biopsy of spinal lesions is feasible and safe. Compared to conventional CT guidance, it may reduce procedural time and the number of CT passes.

PET/CT Ultrasound Fusion for Percutaneous Biopsy: A Retrospective Single-Center Study and Review of the Literature

PURPOSE

The aim of this study was to assess the diagnostic yield and complication rate of 18 F-FDG PET/CT ultrasound (US) fusion for percutaneous biopsy of FDG-avid lesions among patients with known or suspected malignancy.

PATIENTS AND METHODS

We describe the clinical, imaging, and histopathologic features of 36 patients who underwent percutaneous biopsy using real-time PET/CT US fusion. In addition, we review the literature on PET/CT US fusion. Using Medline, the following MeSH terms were searched and relevant citations assessed: "fusion imaging," "PET/CT fusion," "PET/CT-guided biopsy," "PET/US fusion," "ultrasound fusion," and "ultrasound fusion-guided biopsy."

RESULTS

A total of 36 patients (15 men, 21 women) with known or suspected malignancy and prior PET/CT imaging underwent percutaneous biopsy of FDG-avid lesions using PET/CT US fusion between October 2014 and July 2020. Coregistration was achieved using General Electric LOGIQ E9 software. Adequate tissue for analysis was obtained in all 36 patients. Histologic evaluation revealed malignancy in 14 patients (38.9%) and nonneoplastic tissue in 22 patients (61.1%). No intraprocedural or postprocedural complications were recorded.

CONCLUSIONS

Fusion of PET/CT and US for percutaneous biopsy of FDG-avid lesions can be used to achieve excellent diagnostic yield with a low risk of complications.

US-CT fusion-guided percutaneous radiofrequency ablation of large substernal benign thyroid nodules

The aim of the present study was to assess feasibility, safety and outcome of ultrasound (US) guided percutaneous radiofrequency (RF) ablation of large substernal benign thyroid nodules assisted by US-computed tomography (CT) fusion imaging and real-time virtual needle tracking (VT) system. Thirty patients (18 females, mean age 56 y, range 32-76 y) with 35 benign nonfunctioning thyroid nodules (mean volume ± SD 26.8 ± 7.6 mL; range 20-38mL) were selected for CT-US fusion guided RF ablation. Nodules' volume was evaluated before treatment and during 12-months follow-up. Complications' rate was also evaluated. US-CT fusion imaging with VT system was feasible in all cases (feasibility 100%) and it was always possible to complete the procedure as planned (technical success 100%). Minor complications occurred in 2/30 cases (6.6%). No major complications occurred. 50% volume reduction (technique efficacy) was achieved in 93% cases, with a significant mean volume reduction at 12 months follow-up (68.7 ± 10.8%), (p < .001). The VT system could be useful in thyroid nodules ablation procedures assistance being able to track the RF electrode tip even when this is obscured by the bubbles produced by the ablative process. The combination of fusion imaging with VT assisted RF ablation represents a safe, non-surgical treatment option for patients with large substernal benign thyroid nodules.

Data-driven, energy-based method for estimation of scattered events in positron emission tomography

Objective.Scattered events add bias in the reconstructed positron emission tomography (PET) images. Our objective is the accurate estimation of the scatter distribution, required for an effective scatter correction.Approach.In this paper, we propose a practical energy-based (EB) scatter estimation method that uses the marked difference between the energy distribution of the non-scattered and scattered events in the presence of randoms. In contrast to previous EB methods, we model the unscattered events using data obtained from measured point sources.Main results.We demonstrate feasibility using Monte Carlo simulated as well as experimental data acquired on the long axial field-of-view (FOV) PennPET EXPLORER scanner. Simulations show that the EB scatter estimated sinograms, for all phantoms, are in excellent agreement with the ground truth scatter distribution, known from the simulated data. Using the standard NEMA image quality (IQ) phantom we find that both the EB and single scatter simulation (SSS) provide good contrast recovery values. However, the EB correction gives better lung residuals.Significance.Application of the EB method on measured data showed, that the proposed method can be successfully translated to real-world PET scanners. When applied to a 20 cm diameter ×20 cm long cylindrical phantom the EB and SSS algorithms demonstrated very similar performance. However, on a larger 35 cm × 30 cm long cylinder the EB can better account for increased multiple scattering and out-of-FOV activity, providing more uniform images with 12%-36% reduced background variability. In typical PET ring sizes, the EB estimation can be performed in a matter of a few seconds compared to the several minutes needed for SSS, leading to efficiency advantages over the SSS implementation. as well.

Immunofluorescence Assay of Ablated Colorectal Liver Metastases: The Frozen Section of Image-Guided Tumor Ablation?

PURPOSE

To validate an immunofluorescence assay (IFA) detecting residual viable tumor (VT) as intraprocedural thermal ablation (TA) zone assessment and demonstrate its prognostic value for local tumor progression (LTP) after colorectal liver metastasis (CLM) TA.

MATERIALS AND METHODS

This prospective study, approved by the institutional review board, included 99 patients with 155 CLMs ablated between November 2009 and January 2019. Tissue samples from the ablation zone (AZ) center and minimal margin underwent immunofluorescent microscopic examination interrogating cellular morphology and mitochondrial viability (IFA) within 30 minutes after ablation. The same tissue samples were subsequently evaluated with standard morphologic and immunohistochemical methods. The sensitivity, specificity, and overall accuracy of IFA versus standard morphologic and immunohistochemical examination were calculated. The LTP-free survival rates were evaluated for the 12-month follow-up period.

RESULTS

Of the 311 tissue samples stained, 304 (98%) were deemed evaluable. Of these specimens, 27% (81/304) were considered positive for the presence of VT. The accuracy of IFA was 94% (286/304). The sensitivity and specificity were 100% (63/63) and 93% (223/241), respectively. The 18 false-positive IFA assessments corresponded to samples that included viable cholangiocytes. The 12-month LTP-free survival was 59% versus 78% for IFA positive versus negative for VT AZs, respectively (P < .001). There was no difference in LTP between margin positive only and central AZ-positive tumors (25% vs 31%, P = 1).

CONCLUSIONS

The IFA assessment of the AZ can be completed intraprocedurally and serve as a valid real-time biomarker of complete tumor eradication or detect residual VT after TA. This method could improve tumor control by TA.

Biopsy and Margins Optimize Outcomes after Thermal Ablation of Colorectal Liver Metastases

Simple Summary

Thermal ablation (TA) is a non-surgical treatment of cancer that has been used with success in the treatment of colorectal liver metastases (CLM). TA consists of burning the cancer and a rim of surrounding tissue (margin) with a special needle placed in the tumor under image guidance. Despite the technological evolution of TA, tumor progression/recurrence rates remain higher than expected. We present a method that combines tissue and imaging tests performed immediately after ablation to determine whether there is complete tumor destruction or remaining live cancer cells that can cause tumor progression/recurrence. This information can provide guidance for additional treatments for patients with evidence of residual cancer, i.e.,: additional TA at the same or subsequent sitting, or additional chemotherapy and short-interval imaging follow-up to detect recurrence. The presented method proposes a clinical practice paradigm change that can improve clinical outcomes in a large population of patients with CLM treated by TA.

Abstract

Background: Thermal ablation is a definitive local treatment for selected colorectal liver metastases (CLM) that can be ablated with adequate margins. A critical limitation has been local tumor progression (LTP). Methods: This prospective, single-group, phase 2 study enrolled patients with CLM < 5 cm in maximum diameter, at a tertiary cancer center between November 2009 and February 2019. Biopsy of the ablation zone center and margin was performed immediately after ablation. Viable tumor in tissue biopsy and ablation margins < 5 mm were assessed as predictors of 12-month LTP. Results: We enrolled 107 patients with 182 CLMs. Mean tumor size was 2.0 (range, 0.6–4.6) cm. Microwave ablation was used in 51% and radiofrequency ablation in 49% of tumors. The 12- and 24-month cumulative incidence of LTP was 22% (95% confidence interval [CI]: 17, 29) and 29% (95% CI: 23, 36), respectively. LTP at 12 months was 7% (95% CI: 3, 14) for the biopsy tumor-negative ablation zone with margins ≥ 5 mm vs. 63% (95% CI: 35, 85) for the biopsy-positive ablation zone with margins < 5 mm (p < 0.001). Conclusions: Biopsy-proven complete tumor ablation with margins of at least 5 mm achieves optimal local tumor control for CLM, regardless of the ablation modality used.

Operator Evaluation of Ultrasound Fusion Imaging Usefulness in the Percutaneous Ablation of Hepatic Malignancies: A Prospective Study

The purpose of the work described here was to evaluate the use of ultrasound fusion imaging (US-FI) in percutaneous ablation of hepatic malignancies with respect to its global usefulness, improvement of conspicuity, confidence increment, needle route changes, and time savings. Thirty-four hepatic tumors (28 hepatocellular carcinomas, 6 metastases) were prospectively ablated in 16 consecutive patients (64 ± 11 y, 75% males), first simulating B-mode-only planning and then synchronizing computed tomography/magnetic resonance images with US and proceeding to needle insertion and tumor ablation under US-FI guidance. Surveys were administered to the operators to evaluate their perception of US-FI advantages. First treatment and local recurrence were also compared. US-FI was judged useful in 91% of cases and more useful when the tumor was not conspicuous in B-mode (p < 0.001), in particular for ablation of local recurrences (p = 0.021). Forty-one percent of tumors were undetectable at B-mode evaluation, and 93% of them were completely ablated under US-FI guidance. The confidence of the operator was highly increased by US-FI in 68% of cases. In 71% of cases, the radiologist saved time using US-FI, especially in treatment of local recurrences (p = 0.024). In conclusion, US-FI significantly increases the detection of target tumors, improves the confidence of the operator and is a time-saving method, especially in the treatment of local recurrences.

Contrast-enhanced ultrasound (CEUS) in HCC diagnosis and assessment of tumor response to locoregional therapies

Hepatocellular carcinoma (HCC) is a global problem constituting the second leading cause of cancer deaths worldwide, thereby necessitating an accurate and cost-effective solution for managing care. Ultrasound is well poised to address this need due to its low cost, portability, safety, and excellent temporal resolution. The role of ultrasound for HCC screening has been well established and supported by multiple international guidelines. Similarly, contrast-enhanced ultrasound (CEUS) can be used for the characterization of focal liver lesions in high-risk populations, and standardized criteria for CEUS have been established by the American College of Radiology Liver Imaging Reporting & Data System (LI-RADS). Following HCC identification, CEUS can also be highly beneficial in treatment planning, delivery, and monitoring HCC response to locoregional therapies. Specific advantages of CEUS include providing real-time treatment guidance and improved diagnostic performance for the detection of residual tumor viability or recurrence, thereby identifying patients in need of retreatment substantially earlier than contrast-enhanced CT and MRI. This review provides a primer on ultrasound and CEUS for the screening and characterization of HCC, with an emphasis on assessing tumor response to locoregional therapies.

Percutaneous radiofrequency ablation of HCC: reduced ablation duration and increased ablation size using single, internally cooled electrodes with an optimized pulsing algorithm

PURPOSE

To assess the use of optimized radiofrequency (RF) to achieve larger, spherical ablation volumes with short application duration for hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Twenty-two patients (M:F = 17:5, median age 69.6 year, range 63-88) with 28 HCCs due to HCV + liver cirrhosis underwent RFA. 20/28 (71.4%) were tumors ≤3cm diameter, and 8/28 (28.6%) ranged from 3.2 to 4.2 cm. RF was applied using up to 2500mA via an optimized pulsing algorithm with real-time ultrasound monitoring to detect hyperechogenic changes. Single insertions of an internally cooled electrode were performed using exposed tips of 2 or 3 cm for 13 HCCs and 4 cm for 15 HCCs. All patients were followed-up for a minimum of 5 years with contrast-enhanced computed tomography (CECT).

RESULTS

Technical success was achieved without adverse events in all cases. The mean ablation time was 8.5 ± 2.6 min. In 21/28 (75%), ablation duration ranged from 3 to 9 min, with 12 min duration applied in only 7/28 (25%). Mean coagulation diameters were 2.4 ± 0.14, 3.3 ± 0.62, and 4.4 ± 1.0, for 2, 3 and 4 cm electrodes, respectively (p < 0.01). The sphericity index was 74.9 ± 12.8 for 4 cm electrodes and 81.9 ± 8.0 for shorter electrodes (p = 0.091). At 5-year follow-up, no tumor ≤3 cm had recurrence and only 2/8 (25%) >3 cm tumors developed local progression. One patient had multifocal disease with no local progression.

CONCLUSION

Efficient delivery of RF energy can considerably decrease the ablation time in many instances while achieving larger, relatively spherical, and reproducible areas of ablation with extremely low rates of local tumor progression and adverse events.

Real-time US/cone-beam CT fusion imaging for percutaneous ablation of small renal tumours: a technical note

INTRODUCTION

Fusion imaging is gaining attention as an imaging technique to assist minimally invasive tumour ablation. Ultrasound (US) and computed tomography (CT) are the most common imaging modalities to guide thermal ablation of renal tumours, yet cone-beam CT (CBCT) has recently been described to successfully assist percutaneous renal interventions. Our goal was to evaluate primary technical success and correct lesion targeting of US/CBCT fusion imaging to guide the ablation of kidney masses < 2 cm in a small group of patients.

MATERIAL AND METHODS

Six renal lesions (maximum diameter 11-17 mm) were treated with RFA in 5 different patients using real-time US/CBCT. Fusion imaging was used to identify and monitor tumour ablation. Demographics, tumour characteristics and mean serum creatinine levels were recorded before and after the procedure. Primary technical success and correct lesion targeting represented the main endpoints of the study. Primary technique efficacy was confirmed at 1-month and 3-month contrast-enhanced CT follow-ups.

RESULTS

In all cases, a confident US/CBCT synchronisation was reached and allowed for a correct targeting and a successful percutaneous ablation. Primary technique efficacy was 100%. No recurrence was observed at the follow-up that ranged from 8 to 26 months (mean 16 months).

CONCLUSIONS

US/CBCT fusion proved to be a viable method to precisely guide safe and effective percutaneous thermal ablation in patients with small renal tumours, especially when hardly detectable on US.

KEY POINTS

• US/CBCT fusion imaging for renal ablation is safe and feasible. • US/CBCT fusion imaging allows for an improved targeting and complete ablation of small RCC with poor US-conspicuity.

Role of Fusion Imaging in Image-Guided Thermal Ablations

Thermal ablation (TA) procedures are effective treatments for several kinds of cancers. In the recent years, several medical imaging advancements have improved the use of image-guided TA. Imaging technique plays a pivotal role in improving the ablation success, maximizing pre-procedure planning efficacy, intraprocedural targeting, post-procedure monitoring and assessing the achieved result. Fusion imaging (FI) techniques allow for information integration of different imaging modalities, improving all the ablation procedure steps. FI concedes exploitation of all imaging modalities’ strengths concurrently, eliminating or minimizing every single modality’s weaknesses. Our work aims to give an overview of FI, explain and analyze FI technical aspects and its clinical applications in ablation therapy and interventional oncology.

Computed Tomography- (CT-) Based Virtual Surgery Planning for Spinal Intervertebral Foraminal Assisted Clinical Treatment

With the development of minimally invasive spine concepts and the introduction of new minimally invasive instruments, minimally invasive spine technology, represented by foraminoscopy, has flourished, and percutaneous foraminoscopy has become one of the most reliable minimally invasive procedures for the treatment of lumbar disc herniation. Percutaneous foraminoscopy is a safe and effective minimally invasive spinal endoscopic surgical technique. It fully protects the paravertebral muscles and soft tissues as well as the posterior column structure of the spine, provides precise treatment of the target nucleus pulposus tissue, with the advantages of less surgical trauma, fewer postoperative complications, and rapid postoperative recovery, and is widely promoted and used in clinical practice. In this paper, we can view the location, morphology, structure, alignment, and adjacency relationships by performing coronary, CT, and diagonal reconstruction along the attachment of the yellow ligaments and performing 3D reconstruction or processing techniques after performing CT scans. This allows clinicians to observe the laminoplasty and the stenosis of the vertebral canal in a more intuitive and overall manner. It has clinical significance for the display of the sublaminar spine as well as the physician's judgment of the disease and the choice of surgery.

The Role of Percutaneous Ablation in the Management of Colorectal Cancer Liver Metastatic Disease

Approximately 50% of colorectal cancer patients will develop metastases during the course of the disease. Local or locoregional therapies for the treatment of liver metastases are used in the management of oligometastatic colorectal liver disease, especially in nonsurgical candidates. Thermal ablation (TA) is recommended in the treatment of limited liver metastases as free-standing therapy or in combination with surgery as long as all visible disease can be eradicated. Percutaneous TA has been proven as a safe and efficacious therapy offering sustained local tumor control and improved patient survival. Continuous technological advances in diagnostic imaging and guidance tools, the evolution of devices allowing for optimization of ablation parameters, as well as the ability to perform margin assessment have improved the efficacy of ablation. This allows resectable small volume diseases to be cured with percutaneous ablation. The ongoing detailed information and increasing understanding of tumor biology, genetics, and tissue biomarkers that impact oncologic outcomes as well as their implications on the results of ablation have further allowed for treatment customization and improved oncologic outcomes even in those with more aggressive tumor biology. The purpose of this review is to present the most common indications for image-guided percutaneous ablation in colorectal cancer liver metastases, to describe technical considerations, and to discuss relevant peer-reviewed evidence on this topic. The growing role of imaging and image-guidance as well as controversies regarding several devices are addressed.

CT-US fusion imaging increases the feasibility of early ultrasound-guided percutaneous intervention of local drug therapy in pancreatic contusion and laceration

Background

Multimodal fusion imaging (MMFI) was usually used to assist percutaneous procedures for difficult lesions, with most applications occurring with hepatic and prostatic interventions. This paper aimed to evaluate the precision and effectiveness of computed tomography-ultrasound (CT-US) fusion imaging (CUFI)-assisted US-guided percutaneous intervention (UGPI) in early local drug therapy for pancreatic contusion and laceration (PCL).

Methods

A total of 12 pigs with PCL were randomly divided into a CUFI-assisted UGPI (MU) group (n=6) and a single UGPI (SU) group (n=6). The MU group underwent CUFI-assisted UGPI of locally applied medical protein glue (1 mL) injection while the SU group received the same therapy using two-dimensional UGPI. The duration and accuracy of each procedure were observed in the 2 groups.

Results

In the MU group, the overall time of the procedure for locking the plane was 1.85±0.06 minutes. Less time was spent in the selection of the pathway and puncture site in the MU group compared with the SU group (6.56±0.42 vs. 7.61±0.44 minutes, P<0.01). The duration of puncturing and drug injection was also shorter in the MU group than in the SU group (3.41±0.30 vs. 4.20±0.20 minutes, P<0.01) and the MU group had a higher accuracy of medical protein glue injection than the SU group (100% vs. 50%, P<0.05).

Conclusions

CUFI could increase the precision and effectiveness of early UGPI in the delivery of local drug therapy in PCL.

Virtual navigation-guided radiofrequency ablation for recurrent hepatocellular carcinoma invisible on ultrasound after hepatic resection

BACKGROUND

No reports are available on the technical efficiency and therapeutic response of virtual navigation (VN)-guided radiofrequency ablation (RFA) for patients with recurrent hepatocellular carcinoma (HCC) after hepatic resection. The aim of this study was to investigate the overall technical performance and outcome of VN-guided RFA in recurrent HCC patients. In addition, a nomogram model was developed to predict the factors influencing the overall survival (OS).

METHODS

This was a prospective study on 76 recurrent HCC patients who underwent VN-guided RFA between June 2015 and February 2018. The technical feasibility, success, and efficiency, OS, local tumor progression, and complications were evaluated. A multivariate Cox regression analysis was conducted to predict the significant factors, and a nomogram including independent predictive factors was subsequently plotted to predict OS.

RESULTS

The technical feasibility, success, and efficiency rates of VN-guided RFA were 86.4%, 94.7%, and 97.4%, respectively. The cumulative OS rates at 1-, 2-, and 3-year were 88.1%, 79.7%, and 71.0%, respectively. The cumulative local tumor progression rates at 1-, 2-, and 3-year were 5.5%, 8.7%, and 14.0%, respectively. In addition, the minor and major complication rates were 5.3% and 3.9%, respectively. No intervention-related deaths occurred during the follow-up period. The C-index of the OS nomogram in this study was 0.737.

CONCLUSIONS

VN-guided RFA is an effective therapeutic option in recurrent HCC patients and improves the long-term outcomes especially for the lesions that cannot be detected in the two-dimensional ultrasound. Besides, the nomogram may be a useful supporting tool in predicting OS to estimate the individual survival probability, optimize treatment options, and facilitate decision-making.

Comparative analysis of radiofrequency ablation and resection for colorectal liver metastases in caudate lobe: a retrospective study

Objective: To assess the therapeutic efficiency of radiofrequency ablation (RFA) for colorectal liver metastases (CRLM) in the caudate lobe compared with that of surgical resection.Methods: After approved by institutional review board, we retrospectively reviewed 20 patients with caudate CRLM treated by RFA or resection between 2006 and 2017. Comparative analysis was performed based on the different therapies, including patient characteristics, therapeutic outcomes, recurrences, and survivals.Results: During the median follow-up of 7 years (range, 2 -11 years), no differences in complications and recurrences were found between RFA and surgery groups (p > .05). The median overall survival (OS) of patients after RFA and resection were 41 months (95% confidence interval (CI) 23.5-70.5) and 54 months (95% CI 31.1-77.7), respectively (p = .627, hazard radio (HR) 0.7, 95% CI 0.2-2.6). However, OS of resection group was better than that of RFA group for large caudate CRLMs (>3 cm) (p = .042, HR 4.4, 95% CI 0.6-32.6).Conclusions: RFA is a feasible, safe, and effective treatment for CRLM in the caudate. Surgical resection revealed superior outcomes in the treatment of caudate CRLMs, particularly in cases with a hepatic tumor size  >3 cm.

Ultrasound-guided percutaneous microwave ablation for hepatocellular carcinoma adjacent to large vessels: a propensity score matching analysis

PURPOSE

This study aimed to compare the efficacy and safety of ultrasound-guided percutaneous microwave ablation (MWA) for hepatocellular carcinoma (HCC) adjacent to large vessels with those far from large vessels.

METHODS

The clinical data of patients who underwent ultrasound-guided percutaneous MWA for HCC were retrospectively analyzed between January 2011 and December 2018 in Shengjing Hospital. Patients with HCC adjacent to large vessels were included in the Vessel group, the remaining patients were included in the Control group. Propensity score matching analysis was used to reduce confounding bias. The rates of complete ablation, local recurrence, recurrence-free survival (RFS), overall survival (OS) and complications were compared between the two groups.

RESULTS

A total of 134 patients with 157 nodules (size range, 0.6-3.8 cm) were enrolled in this study, 23 in the Vessel group and 111 in the Control group. A total of 21 patients in the Vessel group (91.3%) and 105 patients in the Control group (94.6%) achieved complete ablation (p = .902). Following 1:2 propensity score matching, 22 patients were included in the Vessel group and 40 patients were enrolled in the Control group. Local recurrence was observed in 2 (9.1%) patients in the Vessel group and 5 (12.5%) in the Control group (p = .86). No significant difference in local recurrence rate, RFS and OS were observed between the two groups.

CONCLUSIONS

Ultrasound-guided percutaneous MWA appears to be a safe procedure and can achieve comparable oncological efficacy for HCC abutting large vessels.

Value of MRI/CT Image Fusion for Targeting "invisible" Lesions in Stereotactic Microwave Ablation (SMWA) of Malignant Liver Lesions: A Retrospective Analysis

PURPOSE

To assess the technical feasibility of MRI/CT image fusion and completeness of ablation treatment for primary or metastatic liver lesions invisible on contrast-enhanced CT planning scans and outcome in patients treated with stereotactic microwave ablation (SMWA).

MATERIALS AND METHODS

The study was approved by the local ethics committee. Patients who underwent SMWA between January 2015 and December 2018 were retrospectively analyzed. All liver lesions for which MRI/CT fusion was performed due to invisibility on pre-interventional CT planning scans were included and reassessed. The outcome measurement was successful ablation of the lesion at first follow-up imaging.

RESULTS

During the study period, 236 patients underwent 312 SMWAs with ablation of 496 lesions. Twenty-four lesions in 15 patients (mean age, 62 years; range, 43-80 years) were included. Following MRI/CT image fusion, all 24 lesions could be sufficiently localized to perform SMWA. The first follow-up imaging showed complete ablation of 22 lesions. Two initially incompletely ablated lesions were hepatocellular carcinomas and were successfully re-ablated afterwards.

CONCLUSION

SMWA with MRI/CT image fusion is an accurate and safe treatment option for patients with liver lesions not detectable on contrast-enhanced CT planning scans. MRI/CT image fusion may allow more patients with malignant liver lesions to benefit from local ablation treatment even if their lesions are not visible on CT planning examinations.

Image-guided thermal ablation of central renal tumors with retrograde cold pyeloperfusion technique: a monocentric experience

Purpose: To evaluate feasibility, safety and efficacy of image-guided thermal ablations associated with retrograde pyeloperfusion in patients with centrally located renal tumors.Materials and methods: 48 patients (15 women, 33 men, mean age 69.1 ± 11.8) were treated with image-guided thermal ablation associated with pyeloperfusion for 58 centrally located renal tumors (mean diameter 32.3 ± 7.32 mm). 7 patients had a single kidney. Microwave and radiofrequency ablation were used. All treatments were performed with ultrasound, CT, or fusion imaging guidance under general anesthesia and simultaneous retrograde cold pyeloperfusion technique.Results: Procedure was feasible in all cases. Technical success and primary technical efficacy were reached in 51/58 (88%) and 45/54 tumors (83%). With a second ablation performed in 5 tumors, secondary technical efficacy was achieved in 50/50 (100%) tumors. Minor and major complications occurred in 8/58 (13%) and 5/58 (8%) tumors. No significative change in renal function occurred after treatment.During follow-up, 5 recurrences occurred, that were retreated with a second ablation. At last follow up (mean 32.2 ± 22.0 months), 41/48 (85%) treated patients were free from disease. The median TTP and PFS were 27.0 (range, 2.3-80.0) and 26.5 months (range, 2.3-80.0), respectively.Conclusion: Image-guided thermal ablation associated with protective pyeloperfusion is a feasible, safe, and effective treatment option for patients with central renal tumors with a minimal impact on renal function and relevant potential to avoid nephrectomy.

Percutaneous ablation techniques for renal cell carcinoma: current status and future trends

Percutaneous ablation is an increasingly applied technique for the treatment of localized renal tumors, especially for elderly or co-morbid patients, where co-morbidities increase the risk of traditional nephrectomy. Ablative techniques are technically suited for the treatment of tumors generally not exceeding 4 cm, which has been set as general consensus cutoff and is described as the upper threshold of T1a kidney tumors. This threshold cutoff is being challenged, but with still limited evidence. Percutaneous ablation techniques for the treatment of renal cell carcinoma (RCC) include radiofrequency ablation, cryoablation, laser or microwave ablation; the main advantage of all these techniques over surgery is less invasiveness, lower complication rates and better patient tolerability. Currently, international guidelines recommend percutaneous ablation either as intervention for frail patients or as a first line tool, provided that the tumor can be radically ablated. The purpose of this article is to describe the basic concepts of percutaneous ablation in the treatment of RCC. Controversies concerning techniques and products and the need for patient-centered tailored approaches during selection among the different techniques available will be discussed.

Long-Term Follow-Up Outcomes after Percutaneous US/CT-Guided Radiofrequency Ablation for cT1a-b Renal Masses: Experience from Single High-Volume Referral Center

Image-guided thermal ablations are increasingly applied in the treatment of renal cancers, under the guidance of ultrasound (US) or computed tomography (CT). Sometimes, multiple ablations are needed. The aim of the present study was to evaluate the long-term results in patients with renal mass treated with radiofrequency ablation (RFA) with both US and CT, with a focus on the multiple ablations rate. 149 patients (median age 67 years) underwent RFA from January 2008 to June 2015. Median tumor diameter was 25 mm (IQR 17–32 mm). Median follow-up was 54 months (IQR 44–68). 27 (18.1%) patients received multiple successful ablations, due to incomplete ablation (10 patients), local tumor progression (8 patients), distant tumor progression (4 patients) or multiple tumor foci (5 patients), with a primary and secondary technical efficacy of 100%. Complications occurred in 13 (8.7%) patients (6 grade A, 5 grade C, 2 grade D). 24 patients died during follow-up, all for causes unrelated to renal cancer. In conclusion, thermal ablations with the guidance of US and CT are safe and effective in the treatment of renal tumors in the long-term period, with a low rate of patients requiring multiple treatments over the course of their disease.

68Ga-PSMA-PET/CT and Diffusion MRI Targeting for Cone-Beam CT-Guided Bone Biopsies of Castration-Resistant Prostate Cancer Patients

Introduction

Precision medicine expands the treatment options for metastatic castration-resistant prostate cancer (mCRPC) by targeting druggable genetic aberrations. Aberrations can be identified following molecular analysis of metastatic tissue. Bone metastases, commonly present in mCRPC, hinder precision medicine due to a high proportion of biopsies with insufficient tumor cells for next-generation DNA sequencing. We aimed to investigate the feasibility of incorporating advanced target planning and needle guidance in bone biopsies and whether this procedure increases biopsy tumor yield and success rate of molecular analysis as compared to the current standards, utilizing only CT guidance.

Materials and Methods

In a pilot study, ten mCRPC patients received ⁶⁸Ga-prostate-specific membrane antigen (PSMA)-PET/CT and diffusion-weighted MRI as biopsy planning images. These datasets were fused for targeting metastatic lesions with high tumor densities. Biopsies were performed under cone-beam CT (CBCT) guidance. Feasibility of target planning and needle guidance was assessed, and success of molecular analysis and tumor yield were reported.

Results

Fusion target planning and CBCT needle guidance were feasible. Nine out of ten biopsies contained prostate cancer cells, with a median of 39% and 40% tumor cells by two different sequencing techniques. Molecular analysis was successful in eight of ten patients (80%). This exceeds previous reports on CT-guided biopsies that ranged from 33 to 44%. In two patients, important druggable aberrations were found.

Discussion

A biopsy procedure using advanced target planning and needle guidance is feasible and can increase the success rate of molecular analysis in bone metastases, thereby having the potential of improving treatment outcome for patients with mCRPC.

Level of Evidence

Level 4, case series.

Cone-Beam CT-Assisted Ablation of Renal Tumors: Preliminary Results

INTRODUCTION

Renal ablation is a recognized treatment modality for small renal masses. Cone-beam CT (CBCT) has been recently used in interventional oncology as a promising new guidance device, but this technology still needs to be validated for renal ablations. We aimed to assess the technical success of CBCT applications in renal ablative treatments.

MATERIALS AND METHODS

Between March 2016 and June 2018, 14 patients (mean age 69, range 54-83, 7F, 7M) underwent 21 renal ablations for histologically proven renal cell carcinoma (RCC). All treatments were performed with ultrasound (US) and CBCT guidance under general anesthesia in a dedicated angiography room setting. CBCT was mainly used to assess needle placement and to exclude complications at the end of the procedure. In two small lesions (< 1 cm), pre-acquired CBCT was co-registered with real-time US to obtain a US-CBCT fusion image guidance for tumor ablation.

RESULTS

Whether used alone or in combination with other imaging modalities, CBCT was proven to be technically successful in all 21 procedures to guide or assist tumor ablation. A primary technical efficacy of thermal ablation was achieved in 19/21 ablations (90.1%) at 1 month. Mean procedure duration was 100.2 min (range 160-64). Mean length of hospital stay was 2 days (range 1-10 days). All patients are still under active surveillance for a mean follow-up of 14.5 months (range 4-26 months).

CONCLUSIONS

CBCT for renal ablation guidance is a viable tool. Larger series are needed to compare it to MDCT.

Thermal ablation with fusion imaging guidance of hepatocellular carcinoma without conspicuity on conventional or contrast-enhanced US: surrounding anatomical landmarks matter

AIM

Evaluating clinical and technical factors affecting thermal ablation of B-Mode/CEUS inconspicuous HCC nodules, relying only on fusion imaging (FI) performed under conscious sedation and using previously acquired CT or MR.

MATERIALS AND METHODS

Among 367 HCC nodules treated in the study period, data of 37 B-mode/CEUS undetectable HCC nodules treated with FI-guided ablation were extracted from our prospectively collected institutional database. Analyzed variables included patients' sex, age, cirrhosis etiology, Child-Pugh status, size of the lesion, liver segment, subcapsular or central liver site, type of imaging used for fusion (MR/CT), and the presence of surrounding anatomical landmarks (SAL) < 3 cm from the index lesion.

RESULTS

The primary efficacy was 59.4% (22/37 nodules); nine lesions (24.3%) were partially ablated (PA), six lesions (16.7%) were mistargeted (MA). Eight nodules were retreated with a CA obtained in all cases (100% CA, secondary efficacy in 30/37-81.1%). LTP was observed in 2/30 cases (6.7%). Two minor complications were registered (Clavien-Dindo, Grade1, CIRSE Classification Grade 2). SAL were related to a better ablation outcome (37.5% vs 84.6% p = 0.01). No differences were observed between CA group and PA-MA group in terms of lesion size (15.4 mm vs 14.9 mm p = 0.63), liver segment (p = 0.58), subcapsular or central liver site (8/22 36% vs 4/15 26.7% p = 0.84), and imaging (MR vs CT, p = 0.72).

CONCLUSION

Even in the presence of potentially critical conditions (completely B-Mode/CEUS inconspicuous nodules, spontaneous breathing, and previously acquired CT or MRI), FI-only guidance is safe and allows having good primary, secondary efficacy and LTP rates. The outcome of the procedure is heavily affected by the presence of SAL.

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.

Ultrasound-guided percutaneous procedures in pancreatic diseases: new techniques and applications

Ultrasound (US) is not only an important diagnostic tool for the evaluation of the pancreas, but is also a fundamental imaging technique to guide percutaneous interventions for several pancreatic diseases (fluid aspiration and drainage; invasive diagnosis by means fine-needle aspiration and core-needle biopsy; tumour ablation by radiofrequency, microwaves, irreversible electroporation, cryoablation, and high-intensity focused US). Technical improvements, such as contrast media and fusion imaging, have recently increased precision and safety and reduced procedure-related complications. New treatment US techniques for the ablation of pancreatic tumours, such as contrast-enhanced US and multimodality fusion imaging, have been recently developed and have elicited a growing interest worldwide. The purpose of this article was to review the most up-to-date role of US in percutaneous procedures for pancreatic diseases.