Percutaneous image-guided ablation: From techniques to treatments

Percutaneous cryoablation in the management of spinal metastases: a comprehensive systematic review and meta-analysis

BACKGROUND

Minimally invasive techniques such as vertebroplasty, kyphoplasty, radiofrequency ablation, and stereotactic body radiotherapy have been widely used to manage spinal metastases. Among these, percutaneous cryoablation (PCA) has emerged as a promising option for local tumor control and pain management, offering targeted treatment with minimal damage to surrounding tissues. This systematic review and meta-analysis aimed to evaluate the efficacy and safety of PCA for spinal metastases.

METHODS

A systematic review was conducted using PubMed and Embase databases to identify studies that reported outcomes of PCA for spinal metastases. The reported radiologic, clinical, and complication outcomes were then combined and analyzed using meta-analytic methods including the calculation of pooled means and proportions, subgroup analysis, and meta-regression.

RESULTS

Eleven studies, including 229 patients, met inclusion criteria and were analyzed. Patients had a mean age of 61.8 years, with 60.6% being female. Breast (18.6%), lung (16.0%), and thyroid (8.0%) were the most common primary cancer sites. PCA was primarily conducted under general anesthesia (47.5%) and with CT/MRI guidance (93.9%). Local tumor control was achieved in 70.5% of cases over a mean follow-up of 12.6 months. Pain severity significantly decreased postoperatively, with a mean reduction of 4.5 points (P < 0.0001). Major and minor complication rates were 2.0% and 4.8%, respectively.

CONCLUSIONS

PCA is an effective alternative treatment for spinal metastases, offering pain relief and local tumor control with low complication rates in appropriately selected patients. However, tumor location and patient age may influence treatment outcomes, underscoring the need for individualized treatment planning.

Augmented Reality for Surgical Navigation: A Review of Advanced Needle Guidance Systems for Percutaneous Tumor Ablation

Percutaneous tumor ablation has become a widely accepted and used treatment option for both soft and hard tissue malignancies. The current standard-of-care techniques for performing these minimally invasive procedures require providers to navigate a needle to their intended target using two-dimensional (2D) US or CT to obtain complete local response. These traditional image-guidance systems require operators to mentally transpose what is visualized on a 2D screen into the inherent three-dimensional (3D) context of human anatomy. Advanced navigation systems designed specifically for percutaneous needle-based procedures often fuse multiple imaging modalities to provide greater awareness and planned needle trajectories for the avoidance of critical structures. However, even many of these advanced systems still require mental transposition of anatomy from a 2D screen to human anatomy. Augmented reality (AR)-based systems have the potential to provide a 3D view of the patient's anatomy, eliminating the need for mental transposition by the operator. The purpose of this article is to review commercially available advanced percutaneous surgical navigation platforms and discuss the current state of AR-based navigation systems, including their potential benefits, challenges for adoption, and future developments. Keywords: Computer Applications-Virtual Imaging, Technology Assessment, Augmented Reality, Surgical Navigation, Percutaneous Ablation, Interventional Radiology ©RSNA, 2025.

Technical Feasibility and Safety of Image-Guided Biphasic Monopolar Pulsed Electric Field Ablation of Metastatic and Primary Malignancies

PURPOSE

To assess the technical feasibility and safety of image-guided percutaneous biphasic monopolar pulsed electric field (PEF) ablation of primary and metastatic tumors.

MATERIALS AND METHODS

With institutional review board (IRB) approval and Health Insurance Portability and Accountability Act (HIPAA) compliance, this retrospective, single-institution study cohort of 17 patients (mean age, 53.5 years; range, 20-94 years) with overall progressive disease underwent 26 PEF ablation procedures for 30 metastatic (90%) and primary (10%) target lesions in the thorax (n = 20), abdomen (n = 7), and head and neck (n = 3). Concurrent systemic therapy was used in 14 of the 17 patients (82%). Follow-up imaging was scheduled for 1, 3, and 6 months after PEF ablation, and target and off-target lesion sizes were recorded. The overall response was assessed by the Response Evaluation Criteria in Solid Tumors (RECIST) 1.1 criteria with imaging immediately before PEF serving as baseline. Adverse events (AEs) were determined by the Society of Interventional Radiology (SIR) classification.

RESULTS

PEF ablation procedures were well tolerated and technically feasible for all 17 patients. The mean initial sizes of the target and off-target tumors were 2.6 cm (standard deviation [SD] ± 1.5; range, 0.4-6.9 cm) and 2.2 cm (SD ± 1.1; range, 1.0-5.2 cm), respectively. Overall, 15 of the 30 (50%) target lesions and 12 of the 24 (50%) off-target lesions were unchanged or decreased in size at the patient's last follow-up. Eight patients had overall stable disease (47%) at the last follow-up. Of the 26 AEs, there were 9 mild (35%) and 1 moderate (4%) AE.

CONCLUSIONS

All PEF procedures were technically feasible with 1 moderate AE and stable disease for 47% of patients with a median follow-up period of 3 months.

Thermal/ultrasound-triggered release of liposomes loaded with Ganoderma applanatum polysaccharide from microbubbles for enhanced tumour ablation

The effectiveness of thermal ablation for the treatment of liver tumours is limited by the risk of incomplete ablation, which can result in residual tumours. Herein, an enhancement strategy is proposed based on the controlled release of Ganoderma applanatum polysaccharide (GAP) liposome-microbubble complexes (GLMCs) via ultrasound (US)-targeted microbubble destruction (UTMD) and sublethal hyperthermic (SH) field. GLMCs were prepared by conjugating GAP liposomes onto the surface of microbubbles via biotin-avidin linkage. In vitro, UTMD promotes the cellular uptake of liposomes and leads to apoptosis of M2-like macrophages. Secretion of arginase-1 (Arg-1) and transforming growth factor-beta (TGF-β) by M2-like macrophages decreased. In vivo, restriction of tumour volume was observed in rabbit VX2 liver tumours after treatment with GLMCs via UTMD in GLMCs + SH + US group. The expression levels of CD68 and CD163, as markers of tumour-associated macrophages (TAMs) in the GLMCs + SH + US group were reduced in liver tumour tissue. Decreased Arg-1, TGF-β, Ki67, and CD31 factors related to tumour cell proliferation and angiogenesis was evident on histological analysis. In conclusion, thermal/US-triggered drug release from GLMCs suppressed rabbit VX2 liver tumour growth in the SH field by inhibiting TAMs, which represents a potential approach to improve the effectiveness of thermal ablation.

Interventional Oncology and Immuno-Oncology: Current Challenges and Future Trends

Personalized cancer treatments help to deliver tailored and biologically driven therapies for cancer patients. Interventional oncology techniques are able to treat malignancies in a locoregional fashion, with a variety of mechanisms of action leading to tumor necrosis. Tumor destruction determines a great availability of tumor antigens that can be recognized by the immune system, potentially triggering an immune response. The advent of immunotherapy in cancer care, with the introduction of specific immune checkpoint inhibitors, has led to the investigation of the synergy of these drugs when used in combination with interventional oncology treatments. The aim of this paper is to review the most recent advances in the field of interventional oncology locoregional treatments and their interactions with immunotherapy.

Percutaneous Application of High Power Microwave Ablation With 150 W for the Treatment of Tumors in Lung, Liver, and Kidney: A Preliminary Experience

OBJECTIVE

The aim of this study is to evaluate the feasibility, safety, and short-term effectiveness of a high-power (150 W) microwave ablation (MWA) device for tumor ablation in the lung, liver, and kidney.

METHODS

Between December 2021 and June 2022, patients underwent high-power MWA for liver, lung, and kidney tumors. A retrospective observational study was conducted in accordance with the Declaration of Helsinki. The MWA system utilized a 150-W, 2.45-GHz microwave generator (Emprint™ HP Ablation System, Medtronic). The study assessed technical success, safety, and effectiveness, considering pre- and post-treatment diameter and volume, lesion location, biopsy and/or cone beam computed tomography (CBCT) usage, MWA ablation time, MWA power, and dose-area product (DAP).

RESULTS

From December 2021 to June 2022, 16 patients were enrolled for high-power MWA. Treated lesions included hepatocellular carcinoma (10), liver metastasis from colon cancer (1), liver metastasis from pancreatic cancer (1), squamous cell lung carcinoma (2), renal cell carcinoma (1), and renal oncocytoma (1). Technical success rate was 100%. One grade 1 complication (6.25%) was reported according to CIRSE classification. Overall effectiveness was 92.8%. Pre- and post-treatment mean diameters for liver lesions were 19.9 mm and 37.5 mm, respectively; for kidney lesions, 34 mm and 35 mm; for lung lesions, 29.5 mm and 31.5 mm. Pre- and post-treatment mean volumes for liver lesions were 3.4 ml and 24 ml, respectively; for kidney lesions, 8.2 ml and 20.5 ml; for lung lesions, 10.2 ml and 32.7 ml. The mean ablation time was 48 minutes for liver, 42.5 minutes for lung, and 42.5 minutes for renal ablation. The mean DAP for all procedures was 40.83 Gcm2.

CONCLUSION

This preliminary study demonstrates the feasibility, safety, and effectiveness of the new 150 W MWA device. Additionally, it shows reduced ablation times for large lesions.

Image-Guided Percutaneous Ablation for Primary and Metastatic Tumors

Image-guided percutaneous ablation methods have been further developed during the recent two decades and have transformed the minimally invasive and precision features of treatment options targeting primary and metastatic tumors. They work by percutaneously introducing applicators to precisely destroy a tumor and offer much lower risks than conventional methods. There are usually shorter recovery periods, less bleeding, and more preservation of organ parenchyma, expanding the treatment options of patients with cancer who may not be eligible for resection. Image-guided ablation techniques are currently utilized for the treatment of primary and metastatic tumors in various organs including the liver, pancreas, kidneys, thyroid and parathyroid, prostate, lung, bone, and soft tissue. This article provides a brief review of the various imaging modalities and available ablation techniques and discusses their applications and associated complications in various organs.

Radiologic-pathologic analysis of increased ethanol localization and ablative extent achieved by ethyl cellulose

Ethanol provides a rapid, low-cost ablative solution for liver tumors with a small technological footprint but suffers from uncontrolled diffusion in target tissue, limiting treatment precision and accuracy. Incorporating the gel-forming polymer ethyl cellulose to ethanol localizes the distribution. The purpose of this study was to establish a non-invasive methodology based on CT imaging to quantitatively determine the relationship between the delivery parameters of the EC-ethanol formulation, its distribution, and the corresponding necrotic volume. The relationship of radiodensity to ethanol concentration was characterized with water-ethanol surrogates. Ex vivo EC-ethanol ablations were performed to optimize the formulation (n = 6). In vivo ablations were performed to compare the optimal EC-ethanol formulation to pure ethanol (n = 6). Ablations were monitored with CT and ethanol distribution volume was quantified. Livers were removed, sectioned and stained with NADH-diaphorase to determine the ablative extent, and a detailed time-course histological study was performed to assess the wound healing process. CT imaging of ethanol-water surrogates demonstrated the ethanol concentration-radiodensity relationship is approximately linear. A concentration of 12% EC in ethanol created the largest distribution volume, more than eight-fold that of pure ethanol, ex vivo. In vivo, 12% EC-ethanol was superior to pure ethanol, yielding a distribution volume three-fold greater and an ablation zone six-fold greater than pure ethanol. Finally, a time course histological evaluation of the liver post-ablation with 12% EC-ethanol and pure ethanol revealed that while both induce coagulative necrosis and similar tissue responses at 1-4 weeks post-ablation, 12% EC-ethanol yielded a larger ablation zone. The current study demonstrates the suitability of CT imaging to determine distribution volume and concentration of ethanol in tissue. The distribution volume of EC-ethanol is nearly equivalent to the resultant necrotic volume and increases distribution and necrosis compared to pure ethanol.

Percutaneous Image-Guided Thermal Ablation of Adrenal Metastasis from Melanoma: A Single-Institution Experience

The outcomes of technically successful image-guided percutaneous thermal ablation of melanoma adrenal metastases involving 11 tumors in 9 consecutive patients over 12 years (2009-2020) were evaluated. All patients had multiple treated metastatic sites, and 44.4% (4/9) had greater than 5 metastatic sites. The mean maximal tumor diameter was 3.6 ± 1.6 cm. The local recurrence-free survival at 1 year was 85.7%. With a median survival of 19.4 months, 66.6% (6/9) of patients died from tumor progression. The 1- and 3-year overall survival rate was 60.0% and 30.0%, respectively. All patients were pretreated with alpha-adrenergic blockade, and 36% (4/11) developed a hypertensive crisis. The median hospital length of stay was 1 day (range, 1-2 days), without any major complications. Thermal ablation of adrenal metastasis from a melanoma provides acceptable local control and a good safety profile.

Numerical analysis of three-dimensional echo decorrelation imaging

A numerical model for three-dimensional echo decorrelation imaging, a pulse-echo ultrasound method applicable to thermal ablation monitoring, is presented. Beam patterns for steered transmit and receive array apertures are combined with a three-dimensional numerical tissue model to yield beamformed scan lines in a pyramidal configuration, volumetric B-mode images, and spatial maps of normalized decorrelation between sequential image volumes. Simulated three-dimensional echo decorrelation images of random media are analyzed as estimators of local tissue reflectivity decoherence, mimicking thermal ablation effects. The estimation error is analyzed as a function of correlation window size, scan line density, and ensemble averaging of decorrelation maps.