Artificial Intelligence in Interventional Radiology: A Literature Review and Future Perspectives.

The term "artificial intelligence" (AI) includes computational algorithms that can perform tasks considered typical of human intelligence, with partial to complete autonomy, to produce new beneficial outputs from specific inputs. The development of AI is largely based on the introduction of artificial neural networks (ANN) that allowed the introduction of the concepts of "computational learning models," machine learning (ML) and deep learning (DL). AI applications appear promising for radiology scenarios potentially improving lesion detection, segmentation, and interpretation with a recent application also for interventional radiology (IR) practice, including the ability of AI to offer prognostic information to both patients and physicians about interventional oncology procedures. This article integrates evidence-reported literature and experience-based perceptions to assist not only residents and fellows who are training in interventional radiology but also practicing colleagues who are approaching to locoregional mini-invasive treatments.

Immuno-oncology and interventional oncology: a winning combination. The latest scientific evidence.

OBJECTIVE: Interventional oncology (IO) is an emergent field in interventional radiology that can be considered the fourth pillar of oncology. Interventional oncology has the unique capability to treat malignancy in a loco-regional fashion enabling curative (percutaneous ablation), disease stabilization (intra-arterial chemo/radioembolization), and palliative treatment (such as biliary drainage or nephrostomy). The whole arsenal of IO acts by inducing necrosis and apoptosis, with interactions with the tumour's microenvironment potentially crucial for oncological outcomes. Considering that tumour's microenvironment is a pivotal target for both immuno-oncology and interventional-oncology, the interactions between these two anti-tumour weapons must be investigated to understand their synergy. Interestingly, substantial efforts have been directed to understand which technique combinations are best for specific tumours. This review article summarizes the latest scientific evidence highlighting the future prospective of this winning combination, integrating evidence-reported literature and experience-based perceptions.

The ten commandments of liver ablation: expert discussion and report from Mediterranean Interventional Oncology (MIOLive) congress 2017.

Percutaneous liver ablation has become a cornerstone of the recently developed subspecialty of radiology - that is, interventional oncology. Thermal ablation technology has evolved rapidly during the past decades, with substantial technical and procedural improvements that can help obtain better clinical outcomes and safety profiles. Due to the widespread use of percutaneous ablation, a comprehensive review of the methodologic and technical considerations seems to be mandatory. This article summarizes the expert discussion and report from Mediterranean Interventional Oncology Live Congress (MIOLive 2017) that was held in Rome, Italy, integrating evidence-reported literature and experience-based perceptions, to assist not only residents and fellows who are training in interventional radiology but also practicing colleagues who are approaching to this locoregional treatment.

The ten commandments of chemoembolization: expert discussion and report from Mediterranean Interventional Oncology (MIOLive) congress 2017.

Transarterial therapies in the setting of primary and secondary liver malignancies are becoming an essential part of the oncology landscape. The mechanism of action of c-TACE is the induction of tumor necrosis due to the high concentration of the chemotherapeutic that is delivered only locally and to the embolic effect that causes ischemia and increased dwell time of the chemotherapeutic in the tumor. Recently, DEB-TACE has emerged as a variation of c-TACE with the potential for the selective delivery of large amounts of drugs to the tumor for a prolonged period, thereby decreasing plasma levels of the chemotherapeutic agent and related systemic effects. There is an increasing consensus that compared with conventional lipiodol-based regimen, DEB-TACE offers standardized methodology, is more reproducible and is associated with improved response and significantly better safety profile. Using an easy to access point by point format, this manuscript summarizes the expert discussion from the Mediterranean Interventional Oncology Live Congress (MIOLive 2017) about the role of TACE in the treatment of liver tumors.

The ten commandments of hepatic radioembolization: expert discussion and report from Mediterranean Interventional Oncology (MIOLive) congress 2017.

Microsphere and particle technology represent the next-generation agents that have formed the basis of interventional oncology, an evolving subspecialty of interventional radiology. One of these platforms, yttrium-90 microspheres, is increasingly being used as a treatment modality for primary and secondary liver tumors. Due to the widespread use of radioembolization, a comprehensive review of the methodologic and technical considerations seems to be mandatory. This article summarizes the expert discussion and report from Mediterranean Interventional Oncology Live Congress (MIOLive 2017) that was held in Rome, Italy, integrating evidence-reported literature and experience-based perceptions, to assist not only residents and fellows who are training in interventional radiologists but also practicing colleagues who are approaching to this intra-arterial treatment.

Microwave ablation of hepatic tumors with a third generation system: loco­regional efficacy in a prospective cohort study with intermediate term follow-up.

PURPOSE: To evaluate the safety and intermediate-term efficacy of percutaneous microwave ablation (MWA) in primary and secondary liver tumors using a third generation MWA device, under ultrasound guidance. PATIENTS AND METHODS: Sixty-two patients (median age 74 years, 73 % males) with 69 liver tumors were enrolled in this prospective observational study. Forty-seven patients (76 %) had hepatocellular carcinoma (HCC) and 15 (24 %) metastases. Median follow-up was 3.6 years. RESULTS: Median tumor diameter at contrast enhanced computed tomography was 23 mm (I-III quartiles, 18 - 31 mm). All procedures were performed percutaneously using a 2.45 GHz generator. Median ablation time was 10 minutes (I-III quartiles, 10 - 14 minutes). A single percutaneous antenna insertion was performed for 56/69 (81 %) of the tumors. Technical success was obtained in all tumors. Primary efficacy at 24 hours was achieved in 68/69 (99 %) tumors. The overall one-year cumulative local tumor progression rate was 15.1 % (95 % CI, 7.7 - 24.8 %) with no significant difference between HCC and metastases (p = 0.26). There was one procedure-related mortality (1.6 %) and one major bleeding (1.6 %). CONCLUSION: Microwave ablation is a valid option for thermal ablation of HCC and liver metastases with comparable complication rate to other local ablative procedures.

Percutaneous laser ablation of metastatic lymph nodes in the neck from papillary thyroid carcinoma: preliminary results.

CONTEXT: Percutaneous laser ablation (PLA) may be useful in treating patients with metachronous metastatic lymph nodes in the neck. OBJECTIVE: Our objective was to assess PLA as a treatment of difficult-to-treat metachronous cervical lymph node metastases from papillary thyroid carcinoma. DESIGN AND SETTING: We conducted a retrospective analysis of prospectively collected data at a public hospital. PATIENTS: Fifteen patients with previous resection of papillary thyroid carcinoma with elevated serum levels of thyroglobulin (Tg) or anti-Tg antibodies (TgAbs) and 24 metachronous nodal metastases treated between September 2010 and April 2012 were followed with [¹8F]fluorodeoxyglucose (¹8FDG) positron emission tomography (PET)/computed tomography (CT) and contrast-enhanced ultrasound (CEUS). INTERVENTION: Intervention was PLA. OUTCOME MEASURES: Technique feasibility and technical success were evaluated. Tg/TgAb serum levels and ¹8FDG-PET/CT, and CEUS appearance were assessed at 6 and 12 months and compared with baseline. Complications were recorded. RESULTS: PLA was always feasible, and technical success was achieved in all patients. At 6 months, local control was achieved in 11 of 15 patients (73%), with 6 (40%) having serum Tg/TgAb normalized (P = .017 vs baseline). Whereas 20 of 24 (83%) nodes were negative at ¹8FDG-PET/CT and CEUS (P < .001 vs baseline), 4 were ¹8FDG-PET/CT-positive (3 also CEUS-positive). At the 12-month follow-up, local control was achieved in 10 of 14 patients (71.4%). Sixteen of 20 nodes (80%) were negative at ¹8FDG-PET/CT and CEUS (P < .001 vs baseline), 4 were ¹8FDG-PET/CT-positive (2 also CEUS-positive). Four of 10 (40%) patients had normalization of serum Tg/TgAb (P = .098 vs baseline). No major complications occurred. CONCLUSIONS: PLA is potentially feasible, safe, and effective for the treatment of metachronous cervical nodal metastases from papillary thyroid carcinoma. This procedure may reduce or delay a large number of highly invasive repeat neck dissections.

Cox-2 inhibition enhances the activity of sunitinib in human renal cell carcinoma xenografts.

BACKGROUND: Sunitinib (Su), a tyrosine kinase inhibitor of VEGFR, is effective at producing tumour response in clear cell renal cell carcinoma (cRCC), but resistance to therapy is inevitable. As COX-2 is a known mediator of tumour growth, we explored the potential benefit of COX-2 inhibition in combination with VEGFR inhibition in attempts at delaying tumour progression on Su. METHODS: COX-2 expression was compared with areas of hypoxia in tumours that progressed on Su vs untreated tumours. Mice bearing human cRCC xenografts were treated with Su and the COX-2 inhibitor, celecoxib, and the effects on tumour growth were assessed. Sequential vs concurrent regimens were compared. RESULTS: COX-2 expression was increased in cRCC xenografts in areas of tumour hypoxia. The combination of Su and celecoxib achieved longer times to tumour progression compared to treatment with either agent alone or to untreated control animals in four models. This effect was seen with concurrent but not with sequential therapy. CONCLUSION: COX-2 inhibition can extend the effectiveness of VEGFR inhibition. This effect is dependent on the timing of therapy. Clinical trials combining Su and COX-2 inhibitors should be considered as a means delaying time to progression on sunitinib in patients with metastatic cRCC.

Computer modeling of the effect of perfusion on heating patterns in radiofrequency tumor ablation.

PURPOSE: To use an established computer simulation model of radiofrequency (RF) ablation to further characterize the effect of varied perfusion on RF heating for commonly used RF durations and electrode types, and different tumor sizes. METHODS: Computer simulation of RF heating using 2-D and 3-D finite element analysis (Etherm) was performed. Simulated RF application was systematically modeled on clinically relevant application parameters for a range of inner tumor perfusion (0-5 kg/m3-s) and outer normal surrounding tissue perfusion (0-5 kg/m3-s) for internally cooled 3-cm single and 2.5-cm cluster electrodes over a range of tumor diameters (2-5 cm), and RF application times (5-60 min; n = 4618 simulations). Tissue heating patterns and the time required to heat the entire tumor +/- a 5-mm margin to > 50 degrees C were assessed. Three-dimensional surface response contours were generated, and linear and higher order curve-fitting was performed. RESULTS: For both electrodes, increasing overall tissue perfusion exponentially decreased the overall distance of the 50 degrees C isotherm (R2 = 0.94). Simultaneously, increasing overall perfusion exponentially decreased the time required to achieve thermal equilibrium (R2 = 0.94). Furthermore, the relative effect of inner and outer perfusion varied with increasing tumor size. For smaller tumors (2 cm diameter, 3-cm single; 2-3 cm diameter, cluster), the ability and time to achieve tumor ablation was largely determined by the outer tissue perfusion value. However, for larger tumors (4-5 cm diameter single; 5 cm diameter cluster), inner tumor perfusion had the predominant effect. CONCLUSION: Computer modeling demonstrates that perfusion reduces both RF coagulation and the time to achieve thermal equilibrium. These results further show the importance of considering not only tumor perfusion, but also size (in addition to background tissue perfusion) when attempting to predict the effect of perfusion on RF heating and ablation times.

RF tumour ablation: computer simulation and mathematical modelling of the effects of electrical and thermal conductivity.

This study determined the effects of thermal conductivity on RF ablation tissue heating using mathematical modelling and computer simulations of RF heating coupled to thermal transport. Computer simulation of the Bio-Heat equation coupled with temperature-dependent solutions for RF electric fields (ETherm) was used to generate temperature profiles 2 cm away from a 3 cm internally-cooled electrode. Multiple conditions of clinically relevant electrical conductivities (0.07-12 S m-1) and 'tumour' radius (5-30 mm) at a given background electrical conductivity (0.12 S m-1) were studied. Temperature response surfaces were plotted for six thermal conductivities, ranging from 0.3-2 W m-1 degrees C (the range of anticipated clinical and experimental systems). A temperature response surface was obtained for each thermal conductivity at 25 electrical conductivities and 17 radii (n=425 temperature data points). The simulated temperature response was fit to a mathematical model derived from prior phantom data. This mathematical model is of the form (T=a+bRc exp(dR) s(f) exp(g)(s)) for RF generator-energy dependent situations and (T=h+k exp(mR)+n?exp(p)(s)) for RF generator-current limited situations, where T is the temperature (degrees C) 2 cm from the electrode and a, b, c, d, f, g, h, k, m, n and p are fitting parameters. For each of the thermal conductivity temperature profiles generated, the mathematical model fit the response surface to an r2 of 0.97-0.99. Parameters a, b, c, d, f, k and m were highly correlated to thermal conductivity (r2=0.96-0.99). The monotonic progression of fitting parameters permitted their mathematical expression using simple functions. Additionally, the effect of thermal conductivity simplified the above equation to the extent that g, h, n and p were found to be invariant. Thus, representation of the temperature response surface could be accurately expressed as a function of electrical conductivity, radius and thermal conductivity. As a result, the non-linear temperature response of RF induced heating can be adequately expressed mathematically as a function of electrical conductivity, radius and thermal conductivity. Hence, thermal conductivity accounts for some of the previously unexplained variance. Furthermore, the addition of this variable into the mathematical model substantially simplifies the equations and, as such, it is expected that this will permit improved prediction of RF ablation induced temperatures in clinical practice.

Combination radiofrequency thermal ablation and adjuvant IV liposomal doxorubicin increases tissue coagulation and intratumoural drug accumulation.

There has been marked interest in minimally-invasive, image-guided radiofrequency (RF) tumour ablation (i.e. coagulating tumour using short duration heating ( < 15 min) by directly applying temperatures > 50 degrees C via needle electrodes) to treat focal liver, renal, breast, bone and lung tumours. In spite of advances in RF technology and improved understanding of tumour biophysiology that now enable experimental treatment of tumours up to 5cm, investigators have been unable to achieve complete ablation in many cases, particularly at the tumour margins and adjacent to blood vessels. One strategy for overcoming these limitations has been to take advantage of complementary interactions between RF thermal ablation and chemotherapy, particularly liposomal doxorubicin preparations, to attempt more complete tumour destruction. This paper will review published laboratory investigations demonstrating that this combined treatment paradigm has the unique potential both to potentiate preferential delivery of cytotoxic agents in liposome vehicles and to maximize the completeness of ablation of a treated tumour. New confirmatory data describing increased tumour destruction with RF ablation combined with different liposome preparations, documenting increased lipid peroxidation and expanding on previously published tumour growth studies is presented. Additionally, early clinical data including a randomized, pilot clinical study on 10 patients with primary and metastatic liver tumours, in which a non-optimized combination of RF ablation and IV liposomal doxorubicin (Doxil) increased the volume of tumour destruction 25-30% compared to RF alone, will also be described in detail.

Dynamic intrahepatic flow and cellular alterations during radiofrequency ablation of liver tissue in mice.

PURPOSE: The purpose of this study was to identify microvascular and other associated changes that occur in the liver during focal heating with monopolar radiofrequency (RF). MATERIALS AND METHODS: Intravital video microscopy was performed on exteriorized transilluminated livers of 15 live mice during RF-induced heating of liver parenchyma. Microvascular flow parameters, flow reversibility, microbubble formation, phagocytic activity, and endothelial permeability were recorded throughout a range of tip temperatures (40 degrees C-95 degrees C). RESULTS: During RF application, five discrete zones extended outward from the electrode surface: (i) tissue coagulation, (ii) cellular edema/necrosis, (iii) sinusoidal stasis, (iv) parenchymal shunting, and (v) normal liver tissue. Reversal of stasis in sinusoids and small (<25 microm) vessels occurred at tip temperatures below 50 degrees C. This zone of stasis corresponded to the hyperemic zone on histologic analysis. Although alterations in permeability and phagocytic activity were first identified at 43 degrees C, tip temperatures higher than 55 degrees C always produced local endothelial leakiness to carbon microparticles at the periphery and always inhibited phagocytic activity. At tip temperatures higher than 95 degrees C, microbubble formation occurred with bubbles ultimately tracking through necrotic tissue into patent sinusoids. Larger peripheral vessels (>30 microm) limited extension of coagulation. CONCLUSION: Although coagulation occurs at tip temperatures higher than 50 degrees C, RF heating induced reversible microvascular stasis at temperatures lower than 50 degrees C. Increased sinusoidal endothelial permeability occurs at near-coagulative temperatures. Therefore, targeted endovascular microparticle delivery through this leaky endothelium may provide an additional and complimentary adjunct for RF ablation therapy.

Essential techniques for successful radio-frequency thermal ablation of malignant hepatic tumors.

Radio-frequency thermal ablation is one of the most promising minimally invasive techniques for the treatment of nonresectable hepatic tumors. Essential technical tips to successful radio-frequency ablation therapy were collected from five international experts. They were organized into five categories: understanding the mechanisms and principles of radio-frequency ablation, modulation of tissue physiologic characteristics to increase tumor destruction, strategies of overlapping ablations, strategies to improve ablation according to tumor location, and imaging strategies after ablation to ensure adequate therapy. Established factors for optimal ablation, as well as emerging technical tips, are addressed with illustrations in each section. These essential tips will be very helpful for physicians performing radio-frequency ablation of hepatic tumors.

Percutaneous radio-frequency ablation of hepatic metastases from colorectal cancer: long-term results in 117 patients.

PURPOSE: To describe the results of an ongoing radio-frequency (RF) ablation study in patients with hepatic metastases from colorectal carcinoma. MATERIALS AND METHODS: In 117 patients, 179 metachronous colorectal carcinoma hepatic metastases (0.9-9.6 cm in diameter) were treated with RF ablation by using 17-gauge internally cooled electrodes. Computed tomographic follow-up was performed every 4-6 months. Recurrent tumors were retreated when feasible. Time to new metastases and death for each patient and time to local recurrence for individual lesions were modeled with Kaplan-Meier analysis. Modeling determined the effect of number of metastases on the time to new metastases and death and effect of tumor size on local recurrence. RESULTS: Estimated median survival was 36 months (95% CI; 28, 52 months). Estimated 1, 2, and 3-year survival rates were 93%, 69%, and 46%, respectively. Survival was not significantly related to number of metastases treated. In 77 (66%) of 117 patients, new metastases were observed at follow-up. Estimated median time until new metastases was 12 months (95% CI; 10, 18 months). Percentages of patients with no new metastases after initial treatment at 1 and 2 years were 49% and 35%, respectively. Time to new metastases was not significantly related to number of metastases. Seventy (39%) of 179 lesions developed local recurrence after treatment. Of these, 54 were observed by 6 months and 67 by 1 year. No local recurrence was observed after 18 months. Frequency and time to local recurrence were related to lesion size (P < or =.001). CONCLUSION: RF ablation is an effective method to treat hepatic metastases from colorectal carcinoma.

Percutaneous tumor ablation: increased necrosis with combined radio-frequency ablation and intratumoral doxorubicin injection in a rat breast tumor model.

PURPOSE: To determine whether a combination of intratumoral doxorubicin injection and radio-frequency (RF) ablation increases tumor destruction compared with RF ablation alone in an animal tumor model. MATERIALS AND METHODS: R3230 mammary adenocarcinoma 1.2-1.5-cm- diameter nodules (n = 110) were implanted subcutaneously in 84 female Fischer rats. For initial experiments (n = 46), tumors were treated with (a) conventional, monopolar RF (250 mA +/- 25 [SD] at 70 degrees C +/- 1 for 5 minutes) ablation alone; (b) direct intratumoral doxorubicin injection (volume, 250 microL; total dose, 0.5 mg) alone; (c) combined therapy (doxorubicin injection immediately followed by RF ablation); (d) RF ablation and injection of 250 microL of distilled water; or (e) no treatment. In subsequent experiments, amount of doxorubicin (0.02-2.50 mg; n = 40 additional tumors) and timing of doxorubicin administration (2 days before to 2 days after RF ablation; n = 24 more tumors) were varied. Pathologic examination, including staining for mitochondrial enzyme activity and perfusion, was performed, and the resultant tumor destruction from each treatment was evaluated. RESULTS: Coagulation diameter was 6.7 mm +/- 0.6 for tumors treated with RF ablation alone and 6.9 mm +/- 0.7 for those treated with RF ablation and water (P =.52), while intratumoral doxorubicin injection alone produced only 2.0-3.0 mm of coagulation (P <.001). Increased coagulation was observed only with combined doxorubicin injection and RF therapy (P <.001). Coagulation was dependent on concentration and timing of doxorubicin administration, with greatest coagulation (11.5 mm +/- 1.1) observed for doxorubicin administered within 30 minutes of RF ablation. CONCLUSION: Adjuvant intratumoral doxorubicin injection increases coagulation in solid tumors compared with RF ablation alone. Increased tumor destruction is also seen when doxorubicin is administered after RF ablation, which suggests that RF ablation may sensitize tumors to chemotherapy. Such combination therapies may, therefore, offer improved methods for ablating solid tumors.