Quantitative Dual-Energy CT Image Guidance for Thermochemical Ablation: In Vivo Results in the Rabbit VX2 Model.

PURPOSE: To evaluate the feasibility of using dual-energy computed tomography (CT) and theranostic cesium hydroxide (CsOH) for image guidance of thermochemical ablation (TCA) in a rabbit VX2 tumor model. MATERIALS AND METHODS: In vivo experiments were performed on New Zealand white rabbits, where VX2 tumor fragments (0.3 mL) were inoculated into the right and left flanks (n = 16 rabbits, 32 tumors). Catheters were placed in the approximate center of 1- to 2-cm diameter tumors under ultrasound guidance. TCA was delivered in 1 of 3 treatment groups: untreated control, 5-M TCA, or 10-M TCA. The TCA base reagent was doped with 250-mM CsOH. Dual-energy CT was performed before and after TCA. Cesium (CS)-specific images were postprocessed on the basis of previous phantom calibrations to determine Cs concentration. Line profiles were drawn through the ablation center. Twenty-four hours after TCA, subjects were euthanized, and the resulting damage was evaluated with histopathology. RESULTS: Cs was detected in 100% of treated tumors (n = 21). Line profiles indicated highest concentrations at the injection site and decreased concentrations at the tumor margins, with no Cs detected beyond the ablation zone. The maximum detected Cs concentration ranged from 14.39 to 137.33 mM. A dose-dependent trend in tissue necrosis was demonstrated between the 10-M TCA and 5-M TCA treatment groups (P = .0005) and untreated controls (P = .0089). CONCLUSIONS: Dual-energy CT provided image guidance for delivery, localization, and quantification of TCA in the rabbit VX2 model.

Application of Trifluoroacetic Acid as a Theranostic Agent for Chemical Ablation of Solid Tissue.

PURPOSE: To evaluate trifluoroacetic acid (TFA) as a theranostic chemical ablation agent and determine the efficacy of TFA for both noninvasive imaging and tissue destruction. MATERIALS AND METHODS: Fluorine-19 magnetic resonance imaging (19F-MRI) was optimized at 7 T using a custom-built volume coil. Fluorine images were acquired with both rapid acquisition with relaxation enhancement and balanced steady-state free precession (bSSFP) sequences with varying parameters to determine the optimal sequence for TFA. The theranostic efficacy of chemical ablation was examined by injecting TFA (100 µL; 0.25, 0.5, 1.0, and 2.0M) into ex vivo porcine liver. 19F and proton MRI were acquired and superimposed to visualize distribution of TFA in tissue and quantify sensitivity. Tissue damage was evaluated with gross examination, histology, and fluorescence microscopy. RESULTS: The optimal 19F-MRI sequence was found to be bSSFP with a repetition time of 2.5 ms and flip angle of 70°. The minimum imageable TFA concentration was determined to be 6.7 ± 0.5 mM per minute of scan time (0.63×0.63×5.00 mm voxel), and real-time imaging (temporal resolution of at least 1 s-1) was achieved with 2M TFA both in vitro and in ex vivo tissue. TFA successfully coagulated tissue, and damage was locally confined. In addition to hepatic cord disruption, cytoskeletal collapse and chromatin clumping were observed in severely damaged areas in tissues treated with 0.5M or higher TFA concentrations. CONCLUSIONS: TFA was determined to be a theranostic agent for chemical ablation of solid tissue. Ablation was both efficacious and imageable in ex vivo healthy tissue, even at low concentrations or with high temporal resolution.

Heating technology for malignant tumors: a review.

The therapeutic application of heat is very effective in cancer treatment. Both hyperthermia, i.e., heating to 39-45 °C to induce sensitization to radiotherapy and chemotherapy, and thermal ablation, where temperatures beyond 50 °C destroy tumor cells directly are frequently applied in the clinic. Achievement of an effective treatment requires high quality heating equipment, precise thermal dosimetry, and adequate quality assurance. Several types of devices, antennas and heating or power delivery systems have been proposed and developed in recent decades. These vary considerably in technique, heating depth, ability to focus, and in the size of the heating focus. Clinically used heating techniques involve electromagnetic and ultrasonic heating, hyperthermic perfusion and conductive heating. Depending on clinical objectives and available technology, thermal therapies can be subdivided into three broad categories: local, locoregional, or whole body heating. Clinically used local heating techniques include interstitial hyperthermia and ablation, high intensity focused ultrasound (HIFU), scanned focused ultrasound (SFUS), electroporation, nanoparticle heating, intraluminal heating and superficial heating. Locoregional heating techniques include phased array systems, capacitive systems and isolated perfusion. Whole body techniques focus on prevention of heat loss supplemented with energy deposition in the body, e.g., by infrared radiation. This review presents an overview of clinical hyperthermia and ablation devices used for local, locoregional, and whole body therapy. Proven and experimental clinical applications of thermal ablation and hyperthermia are listed. Methods for temperature measurement and the role of treatment planning to control treatments are discussed briefly, as well as future perspectives for heating technology for the treatment of tumors.

Dual-Energy CT: Lower Limits of Iodine Detection and Quantification.

Background Assessments of the quantitative limitations among the six commercially available dual-energy (DE) CT acquisition schemes used by major CT manufacturers could aid researchers looking to use iodine quantification as an imaging biomarker. Purpose To determine the limits of detection and quantification of DE CT in phantoms by comparing rapid peak kilovoltage switching, dual-source, split-filter, and dual-layer detector systems in six different scanners. Materials and Methods Seven 50-mL iohexol solutions were used, with concentrations of 0.03-2.0 mg iodine per milliliter. The solutions and water sample were scanned five times each in two phantoms (small, 20-cm diameter; large, 30 × 40-cm diameter) with six DE CT systems and a total of 10 peak kilovoltage settings or combinations. Iodine maps were created, and the mean iodine signal in each sample was recorded. The limit of blank (LOB) was defined as the upper limit of the 95% confidence interval of the water sample. The limit of detection (LOD) was defined as the concentration with a 95% chance of having a signal above the LOB. The limit of quantification (LOQ) was defined as the lowest concentration where the coefficient of variation was less than 20%. Results The LOD range was 0.021-0.26 mg/mL in the small phantom and 0.026-0.55 mg/mL in the large phantom. The LOQ range was 0.07-0.50 mg/mL in the small phantom and 0.20-1.0 mg/mL in the large phantom. The dual-source and rapid peak kilovoltage switching systems had the lowest LODs, and the dual-layer detector systems had the highest LODs. Conclusion The iodine limit of detection using dual-energy CT systems varied with scanner and phantom size, but all systems depicted iodine in the small and large phantoms at or below 0.3 and 0.5 mg/mL, respectively, and enabled quantification at concentrations of 0.5 and 1.0 mg/mL, respectively. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Hindman in this issue.

On the Need for a Taxonomy for Interventional Radiology: Initiating Dialogue for the Future.

OBJECTIVE: Interventional radiology (IR) needs comprehensive structure. The reactive structure of the past is strategically unwise for long-term growth of IR. CONCLUSION: IR needs a structured approach to move forward most effectively. A preliminary taxonomic scaffold is put forth and critically analyzed to illustrate new areas of research for the field, to identify new opportunities for growth, and to serve as a starting point for future discussion.

A molecular dynamics approach towards evaluating osmotic and thermal stress in the extracellular environment.

OBJECTIVE: A molecular dynamics approach to understanding fundamental mechanisms of combined thermal and osmotic stress induced by thermochemical ablation (TCA) is presented. METHODS: Structural models of fibronectin and fibronectin bound to its integrin receptor provide idealized models for the effects of thermal and osmotic stress in the extracellular matrix. Fibronectin binding to integrin is known to facilitate cell survival. The extracellular environment produced by TCA at the lesion boundary was modelled at 37 °C and 43 °C with added sodium chloride (NaCl) concentrations (0, 40, 80, 160, and 320 mM). Atomistic simulations of solvated proteins were performed using the GROMOS96 force field and TIP3P water model. Computational results were compared with the results of viability studies of human hepatocellular carcinoma (HCC) cell lines HepG2 and Hep3B under matching thermal and osmotic experimental conditions. RESULTS: Cell viability was inversely correlated with hyperthermal and hyperosmotic stresses. Added NaCl concentrations were correlated with a root mean square fluctuation increase of the fibronectin arginylglycylaspartic acid (RGD) binding domain. Computed interaction coefficients demonstrate preferential hydration of the protein model and are correlated with salt-induced strengthening of hydrophobic interactions. Under the combined hyperthermal and hyperosmotic stress conditions (43 °C and 320 mM added NaCl), the free energy change required for fibronectin binding to integrin was less favorable than that for binding under control conditions (37 °C and 0 mM added NaCl). CONCLUSION: Results quantify multiple measures of structural changes as a function of temperature increase and addition of NaCl to the solution. Correlations between cell viability and stability measures suggest that protein aggregates, non-functional proteins, and less favorable cell attachment conditions have a role in TCA-induced cell stress.

Dual mode single agent thermochemical ablation by simultaneous release of heat energy and acid: hydrolysis of electrophiles.

PURPOSE: This study aimed to investigate two readily available electrophilic reagents, acetyl chloride (AcCl), and acetic anhydride (Ac(2)O), for their potential in tissue ablation. MATERIALS AND METHODS: Reagents were diluted in diglyme as solutions up to 8 mol/L and tested in a gel phantom with NaOH solutions and ex vivo in porcine liver. Temperature, pH, and volume measurements were obtained. Infrared and gross pathological images were obtained in bisected specimens immediately after injection. RESULTS: AcCl was much more reactive than Ac(2)O and AcCl was therefore used in the tissue studies. Temperature increases of up to 37°C were noted in vitro and 30°C in ex vivo tissues using 4 mol/L AcCl solutions. Experiments at 8 mol/L were abandoned due to the extreme reactivity at this higher concentration. A change in pH of up to 4 log units was noted with 4 mol/L solutions of AcCl with slight recovery over time. Ablated volumes were consistently higher than injected volumes. CONCLUSIONS: Reaction of electrophiles in tissues shows promise as a new thermochemical ablation technique by means of only a single reagent. Further studies in this area are warranted.

Cellular and molecular mechanisms of hepatocellular carcinoma: an update.

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor that accounts for ~80 % of all liver cancer cases worldwide. It is a multifactorial disease caused by a variety of risk factors and often develops in the background of underlying cirrhosis. A number of cellular phenomena, such as tumor microenvironment, inflammation, oxidative stress, and hypoxia act in concert with various molecular events to facilitate tumor initiation, progression, and metastasis. The emergence of microRNAs and molecular-targeted therapies adds a new dimension in our efforts to combat this deadly disease. Intense research in this multitude of areas has led to significant progress in our understanding of cellular processes and molecular mechanisms that occur during multistage events that lead to hepatocarcinogenesis. In this review, we discuss the current knowledge of HCC, focusing mainly on advances that have occurred during the past 5 years and on the development of novel therapeutics for liver cancer.

Quantitative dual-energy computed tomography with cesium as a novel contrast agent for localization of thermochemical ablation in phantoms and ex vivo models.

BACKGROUND: Thermochemical ablation (TCA) is a minimally invasive therapy under development for hepatocellular carcinoma. TCA simultaneously delivers an acid (acetic acid, AcOH) and base (sodium hydroxide, NaOH) directly into the tumor, where the acid/base chemical reaction produces an exotherm that induces local ablation. However, AcOH and NaOH are not radiopaque, making monitoring TCA delivery difficult. PURPOSE: We address the issue of image guidance for TCA by utilizing cesium hydroxide (CsOH) as a novel theranostic component of TCA that is detectable and quantifiable with dual-energy CT (DECT). MATERIALS AND METHODS: To quantify the minimum concentration of CsOH that can be positively identified by DECT, the limit of detection (LOD) was established in an elliptical phantom (Multi-Energy CT Quality Assurance Phantom, Kyoto Kagaku, Kyoto, Japan) with two DECT technologies: a dual-source system (SOMATOM Force, Siemens Healthineers, Forchheim, Germany) and a split-filter, single-source system (SOMATOM Edge, Siemens Healthineers). The dual-energy ratio (DER) and LOD of CsOH were determined for each system. Cesium concentration quantification accuracy was evaluated in a gelatin phantom before quantitative mapping was performed in ex vivo models. RESULTS: On the dual-source system, the DER and LOD were 2.94 and 1.36-mM CsOH, respectively. For the split-filter system, the DER and LOD were 1.41- and 6.11-mM CsOH, respectively. The signal on cesium maps in phantoms tracked linearly with concentration (R2  = 0.99) on both systems with an RMSE of 2.56 and 6.72 on the dual-source and split-filter system, respectively. In ex vivo models, CsOH was detected following delivery of TCA at all concentrations. CONCLUSIONS: DECT can be used to detect and quantify the concentration of cesium in phantom and ex vivo tissue models. When incorporated in TCA, CsOH performs as a theranostic agent for quantitative DECT image-guidance.

Vascularized Hepatocellular Carcinoma on a Chip to Control Chemoresistance through Cirrhosis, Inflammation and Metabolic Activity.

Understanding the effects of inflammation and cirrhosis on the regulation of drug metabolism during the progression of hepatocellular carcinoma (HCC) is critical for developing patient-specific treatment strategies. In this work, we created novel three-dimensional vascularized HCC-on-a-chips (HCCoC), composed of HCC, endothelial, stellate, and Kupffer cells tuned to mimic normal or cirrhotic liver stiffness. HCC inflammation was controlled by tuning Kupffer macrophage numbers, and the impact of cytochrome P450-3A4 (CYP3A4) was investigated by culturing HepG2 HCC cells transfected with CYP3A4 to upregulate expression from baseline. This model allowed for the simulation of chemotherapeutic delivery methods such as intravenous injection and transcatheter arterial chemoembolization (TACE). We showed that upregulation of metabolic activity, incorporation of cirrhosis and inflammation, increase vascular permeability due to upregulated inflammatory cytokines leading to significant variability in chemotherapeutic treatment efficacy. Specifically, we show that further modulation of CYP3A4 activity of HCC cells by TACE delivery of doxorubicin provides an additional improvement to treatment response and reduces chemotherapy-associated endothelial porosity increase. The HCCoCs were shown to have utility in uncovering the impact of the tumor microenvironment (TME) during cancer progression on vascular properties, tumor response to therapeutics, and drug delivery strategies.

Concentration and volume effects in thermochemical ablation in vivo: results in a porcine model.

PURPOSE: To explore the effects of volume and concentration in thermochemical ablation using an in vivo porcine model. METHODS: Twelve swine 60-75 kg were used in this institutionally approved study. A needle design prototype coaxial device for reagent injections and a thermocouple were inserted into surgically exposed liver. Simultaneously, an acid and base (acetic acid and NaOH) were injected at 4 mL/min based on a 3 × 3 matrix with concentration (5, 10, and 15 mol/L) and volume on the axes (total volumes of 1, 2, and 4 mL). Three animals (centre grid position) strengthened the statistical analysis. Each animal received four identical injections (total 48). Temperatures and heart rate were recorded. Livers were formalin-fixed after sacrifice. After sectioning, coagulation zones were analysed by two observers. Area and slice thickness were used to calculate the volume, surface area, and sphericity for each treatment. RESULTS: Coagulation volumes ranged from 2.95 ± 0.29 to 14.72 ± 1.42 mL with a maximum of 18.3 mL. Highest peak temperature was 105°C with temperatures ranging 43.5 ± 2.6°C to 91.0 ± 6.5°C. There was no association between conditions and sphericity or heart rate. CONCLUSIONS: The method can be used successfully to ablate tissue in vivo. By neutralising acid in situ and releasing heat and a salt, this technique improves considerably upon the use of acetic acid used alone. Peak temperatures exceeded accepted coagulation thresholds even if the only mechanism operating was hyperthermia. Reagent concentrations and volumes increased the amount of the coagulum but not in a linear fashion.

In vivo comparison of simultaneous versus sequential injection technique for thermochemical ablation in a porcine model.

PURPOSE: To investigate simultaneous and sequential injection thermochemical ablation in a porcine model, and compare them to sham and acid-only ablation. MATERIALS AND METHODS: This IACUC-approved study involved 11 pigs in an acute setting. Ultrasound was used to guide placement of a thermocouple probe and coaxial device designed for thermochemical ablation. Solutions of 10 M acetic acid and NaOH were used in the study. Four injections per pig were performed in identical order at a total rate of 4 mL/min: saline sham, simultaneous, sequential, and acid only. Volume and sphericity of zones of coagulation were measured. Fixed specimens were examined by H&E stain. RESULTS: Average coagulation volumes were 11.2 mL (simultaneous), 19.0 mL (sequential) and 4.4 mL (acid). The highest temperature, 81.3°C, was obtained with simultaneous injection. Average temperatures were 61.1°C (simultaneous), 47.7°C (sequential) and 39.5°C (acid only). Sphericity coefficients (0.83-0.89) had no statistically significant difference among conditions. CONCLUSIONS: Thermochemical ablation produced substantial volumes of coagulated tissues relative to the amounts of reagents injected, considerably greater than acid alone in either technique employed. The largest volumes were obtained with sequential injection, yet this came at a price in one case of cardiac arrest. Simultaneous injection yielded the highest recorded temperatures and may be tolerated as well as or better than acid injection alone. Although this pilot study did not show a clear advantage for either sequential or simultaneous methods, the results indicate that thermochemical ablation is attractive for further investigation with regard to both safety and efficacy.

Hyperthermia and Tumor Immunity.

Thermal ablation is a cornerstone in the management of cancer patients. Typically, ablation procedures are performed for patients with a solitary or oligometastatic disease with the intention of eradicating all sites of the disease. Ablation has traditionally played a less prominent role for patients with a widely metastatic disease. For such patients, attempting to treat numerous sites of disease compounds potential risks without a clear clinical benefit and, as such, a compelling justification for performing an intervention that is unlikely to alter a patient's clinical trajectory is uncommon. However, the discovery of immune checkpoints and the development of immune checkpoint inhibitors have brought a new perspective to the relevance of local cancer therapies such as ablation for patients with a metastatic disease. It is becoming increasingly apparent that local cancer therapies can have systemic immune effects. Thus, in the new perspective of cancer care centered upon immunologic principles, there is a strong interest in exploring the utility of ablation for patients with a metastatic disease for its immunologic implications. In this review, we summarize the unmet clinical need for adjuvant interventions such as ablation to broaden the impact of systemic immunotherapies. We additionally highlight the extant preclinical and clinical data for the immunogenicity of common thermal ablation modalities.

Tumor Microenvironment Alters Chemoresistance of Hepatocellular Carcinoma Through CYP3A4 Metabolic Activity.

Variations in tumor biology from patient to patient combined with the low overall survival rate of hepatocellular carcinoma (HCC) present significant clinical challenges. During the progression of chronic liver diseases from inflammation to the development of HCC, microenvironmental properties, including tissue stiffness and oxygen concentration, change over time. This can potentially impact drug metabolism and subsequent therapy response to commonly utilized therapeutics, such as doxorubicin, multi-kinase inhibitors (e.g., sorafenib), and other drugs, including immunotherapies. In this study, we utilized four common HCC cell lines embedded in 3D collagen type-I gels of varying stiffnesses to mimic normal and cirrhotic livers with environmental oxygen regulation to quantify the impact of these microenvironmental factors on HCC chemoresistance. In general, we found that HCC cells with higher baseline levels of cytochrome p450-3A4 (CYP3A4) enzyme expression, HepG2 and C3Asub28, exhibited a cirrhosis-dependent increase in doxorubicin chemoresistance. Under the same conditions, HCC cell lines with lower CYP3A4 expression, HuH-7 and Hep3B2, showed a decrease in doxorubicin chemoresistance in response to an increase in microenvironmental stiffness. This differential therapeutic response was correlated with the regulation of CYP3A4 expression levels under the influence of stiffness and oxygen variation. In all tested HCC cell lines, the addition of sorafenib lowered the required doxorubicin dose to induce significant levels of cell death, demonstrating its potential to help reduce systemic doxorubicin toxicity when used in combination. These results suggest that patient-specific tumor microenvironmental factors, including tissue stiffness, hypoxia, and CYP3A4 activity levels, may need to be considered for more effective use of chemotherapeutics in HCC patients.

Establishment and characterization of a unique 1 microm diameter liver-derived progenitor cell line.

Liver-derived progenitor cells (LDPCs) are recently identified novel stem/progenitor cells from healthy, unmanipulated adult rat livers. They are distinct from other known liver stem/progenitor cells such as the oval cells. In this study, we have generated a LDPC cell line RA1 by overexpressing the simian virus 40 (SV40) large T antigen (TAg) in primary LDPCs. This cell line was propagated continuously for 55 passages in culture, after which it became senescent. Interestingly, following transformation with SV40 TAg, LDPCs decreased in size significantly and the propagating cells measured 1 microm in diameter. RA1 cells proliferated in vitro with a doubling time of 5-7 days, and expressed cell surface markers of LDPCs. In this report, we describe the characterization of this novel progenitor cell line that might serve as a valuable model to study liver cell functions and stem cell origin of liver cancers.

Thermochemical ablation in an ex-vivo porcine liver model using acetic acid and sodium hydroxide: proof of concept.

PURPOSE: To establish proof of concept in tissue, using the exothermic neutralization reaction of acetic acid and sodium hydroxide in ex vivo porcine liver and to conduct an initial probe into the relationships of volume and concentration of reagents to temperatures and the areas affected. MATERIALS AND METHODS: A total of 0.5 mL or 2 mL of either 5 mole/L or 10 mole/L acid and base solutions was injected simultaneously into the periphery of ex vivo porcine liver using a prototype injection device. Tissue temperature was recorded at the injection site for 5 minutes using a type T thermocouple temperature probe inserted parallel to and near the tip of the injection device. The injections were repeated for infrared thermography, and ablated tissues were sectioned quickly and imaged. A gross photograph was captured in each case to provide correlation. RESULTS: Maximum temperatures (17°C baseline) ranged from 42.1° ± α3.34°C to 61.7° ± α10°C (P<.05) when injecting 0.5 mL of 5 mole/L reactants and 2 mL of 10 mole/L reactants, respectively. The maximum temperature measured by infrared imaging ranged from 31°-47°C. Using an infrared viewing scale from 19°-40°C, the cross-sectional area of tissue heating above baseline measured from 1.07 cm(2)± 0.45 to 4.95 cm(2)± 0.28 (P <05). CONCLUSIONS: The reaction of acetic acid and sodium hydroxide releases significant heat energy at the site of injection, and histologic changes are consistent with coagulation necrosis. Increased reagent concentration and volume were associated with larger temperature changes and larger areas of hyperthermia at gross pathology and infrared imaging.

In vitro thermal profile suitability assessment of acids and bases for thermochemical ablation: underlying principles.

PURPOSE: To measure and compare temperature changes in a recently developed gel phantom for thermochemical ablation as a function of reagent strength and concentration with several acids and bases. MATERIALS AND METHODS: Aliquots (0.5-1 mL) of hydrochloric acid or acetic acid and sodium hydroxide or aqueous ammonia were injected for 5 seconds into a hydrophobic gel phantom. Stepwise increments in concentration were used to survey the temperature changes caused by these reactions. Injections were performed in triplicate, measured with a thermocouple probe, and plotted as functions of concentration and time. RESULTS: Maximum temperatures were reached almost immediately in all cases, reaching 75 degrees C-110 degrees C at the higher concentrations. The highest temperatures were seen with hydrochloric acid and either base. More concentrated solutions of sodium hydroxide tended to mix incompletely, such that experiments at 9 M and higher were difficult to perform consistently. CONCLUSIONS: Higher concentrations for any reagent resulted in higher temperatures. Stronger acid and base combinations resulted in higher temperatures versus weak acid and base combinations at the same concentration. Maximum temperatures obtained are in a range known to cause tissue coagulation, and all combinations tested therefore appeared suitable for further investigation in thermochemical ablation. Because of the loss of the reaction chamber shape at higher concentrations of stronger agents, the phantom does not allow complete characterization under these circumstances. Adequate mixing of reagents to maximize heating potential and avoid systemic exposure to unreacted acid and base must be addressed if the method is to be safely employed in tissues. In addition, understanding factors that control lesion shape in a more realistic tissue model will be critical.

Stem cell origins and animal models of hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is a common malignant tumor that almost always occurs within a preexisting background of chronic liver disease and cirrhosis. Currently, medical therapy is not effective in treating most HCC, and the only hope of cure is either resection or liver transplantation. A small minority of patients is eligible for these therapies, which entail major morbidity at the very least. In spite of immense scientific advances during the past 3 decades, patient survival has improved very little. In order to reduce morbidity and mortality from HCC, improvements in early diagnosis and development of novel local and systemic therapies for advanced disease are essential, in addition to efforts geared towards primary prevention. Studies with experimental animal models that closely mimic human disease are very valuable in understanding physiological, cellular and molecular mechanisms underlying the disease. Furthermore, appropriate animal models have the potential to increase our understanding of the effects of image-guided minimally invasive therapies and thereby help to improve such therapies. In this review, we examine the evidence for stem cell origins of such tumors, critically evaluate existing models and reflect on how to develop new models for minimally invasive, image-guided treatment of HCC.