Radiofrequency ablation of porcine liver in vivo: effects of blood flow and treatment time on lesion size

Effects of Anesthetic Fluid Injectates on Lesion Sizes in Cooled Radiofrequency Ablation

STUDY DESIGN

Nonrandomized trial.

OBJECTIVE

This is an ex vivo study using pork chops to simulate human vertebra to determine the effects of various anesthetic fluids injectates and concentrations on lesion size and shape created when using cooled radiofrequency ablation. Secondary objective is to determine the effects of various time durations of applied lesion on lesion size created. Our final objective is to determine the effects of fluid injectates on tissue temperature and impedance.

SUMMARY OF BACKGROUND DATA

Radiofrequency neurotomy is a therapeutic procedure involving ablation of sensory afferent nerves to the vertebral zygapophyseal joints. Larger lesions increase the likelihood the target nerve is ablated.

METHODS

Before cooled radiofrequency ablation, tissue was injected with either 0.9% normal saline, 1% lidocaine, 2% lidocaine, 0.25% bupivacaine, 0.5% bupivacaine, 0.75% bupivacaine, 0.2% ropivacaine, 0.5% ropivacaine, or 1% ropivacaine. Duration of cooled radiofrequency was either 45, 90, or 150 seconds.

RESULTS

There was no significant difference in the size of the lesion created when using different injectates and concentrations. There was no significant difference in the size of the lesion created when applying a 90 seconds duration lesion compared with a 150 seconds duration lesion.

CONCLUSION

Applying a 90 seconds duration lesion can be considered in clinical use for cooled radiofrequency ablation. The use of an injectate did not significantly alter the size or desired spherical shape of the lesion created, did not significantly alter the time required to create the lesion, and did not significantly lower the temperature threshold. The study is limited by the use of ex vivo tissue which does not account for the effects of tissue perfusion. The use of an injectate before cooled radiofrequency ablation can be made at the interventionalist's discretion.

LEVEL OF EVIDENCE

N/A.

Safety and effectiveness of endobiliary radiofrequency ablation according to the different power and target temperature in a swine model

BACKGROUND AND AIM

Endobiliary radiofrequency ablation (EB-RFA) is a new endoscopic palliation and adjunctive tool. Although EB-RFA is performed worldwide, a possibility of iatrogenic thermal injury leading to perforation or bleeding still remains. Therefore, we aimed to assess the effects of thermal and coagulation injury after in vivo EB-RFA using a new catheter with a temperature sensor in a swine model.

METHODS

Twelve mini pigs were divided into four groups according to power (33 mm 10 W electrode vs. 18 mm 7 W electrode) and RFA target temperature (75°C vs. 80°C). All mini pigs underwent endoscopic retrograde cholangiography and target temperature controlled EB-RFA for 120 s. Additional cholangiogram was taken immediately after RFA, and all pigs were sacrificed after 24 h to assess the macroscopic/microscopic RFA injury.

RESULTS

Microscopic maximal injury depth and ablation area of EB-RFA using a 33-mm 10 W RFA electrode were significantly deeper and larger than those of EB-RFA using an 18-mm 7 W electrode (median; 2.7 vs. 2.1 mm, P = 0.004, 48.9 vs. 36.2 mm² , P = 0.016). However, there were no significant differences in microscopic ablation parameters between two different RFA target temperatures (75°C vs. 80°C). In addition, a post-RFA cholangiogram and assessment of the resected specimen at 24 h after the RFA showed no adverse events such as perforation or bleeding.

CONCLUSIONS

EB-RFA using a temperature controlled RFA catheter successfully ablates the bile duct wall without adverse events in a swine model.

Consideration of different heating lengths of needles with induction heating and resistance system: A novel design of needle module for thermal ablation

Thermal ablation using alternating electromagnetic fields is a promising method to treat tissues including tumors. With this approach, an electromagnetic field is generated around an induction coil, which is supplied with high frequency current from a power source. Any electrically conducting object, which is placed in the electromagnetic field, is then heated due to eddy currents. Basic principles underlying this novel thermotherapy needle system are internal induction and resistance heating. This presents a new design of a standard gauge 18 percutaneous trans-hepatic cholangiography needle module combined with a compact power source. Three needle modules containing coils of different lengths were used to locally heat up different volumes of tissues in in vitro experiments on pig livers. Temperature on the inside surface of the needle was controlled and monitored through a K-type thermocouple. By using this needle module system, no two-section or ferromagnetic nanoparticle-coated needles were required; the system worked well with the SUS-304 stainless-steel needle. Successful results were demonstrated in the in vitro experiments on pig livers with different heating lengths of 10, 20, and 30 mm needles. With low power sources, needles could be heated up to a high temperature. The novel design of the needle module incorporated with a high frequency power source was thus shown to be a promising technology for tissue ablation. Bioelectromagnetics.38:220-226, 2017. © 2016 Wiley Periodicals, Inc.

Adverse effects of irreversible electroporation of malignant liver tumors under CT fluoroscopic guidance: a single-center experience

PURPOSE

We aimed to describe the frequency of adverse events after computed tomography (CT) fluoroscopy-guided irreversible electroporation (IRE) of malignant hepatic tumors and their risk factors.

METHODS

We retrospectively analyzed 85 IRE ablation procedures of 114 malignant liver tumors (52 primary and 62 secondary) not suitable for resection or thermal ablation in 56 patients (42 men and 14 women; median age, 61 years) with regard to mortality and treatment-related complications. Complications were evaluated according to the standardized grading system of the Society of Interventional Radiology. Factors influencing the occurrence of major and minor complications were investigated.

RESULTS

No IRE-related death occurred. Major complications occurred in 7.1% of IRE procedures (6/85), while minor complications occurred in 18.8% (16/85). The most frequent major complication was postablative abscess (4.7%, 4/85) which affected patients with bilioenteric anastomosis significantly more often than patients without this condition (43% vs. 1.3%, P = 0.010). Bilioenteric anastomosis was additionally identified as a risk factor for major complications in general (P = 0.002). Minor complications mainly consisted of hemorrhage and portal vein branch thrombosis.

CONCLUSION

The current study suggests that CT fluoroscopy-guided IRE ablation of malignant liver tumors may be a relatively low-risk procedure. However, patients with bilioenteric anastomosis seem to have an increased risk of postablative abscess formation.

The prediction of radiofrequency ablation zone volume using vascular indices of 3-dimensional volumetric colour Doppler ultrasound in an in vitro blood-perfused bovine liver model

OBJECTIVE

To determine the most reliable predictor of radiofrequency (RF) ablation zone volume among three-dimensional (3D) volumetric colour Doppler vascular indices in an in vitro blood-perfused bovine liver model.

METHODS

3D colour Doppler volume data of the local hepatic parenchyma were acquired from 37 areas of 13 bovine livers connected to an in vitro oxygenated blood perfusion system. Doppler vascular indices of vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were obtained from the volume data using 3D volume analysis software. 37 RF ablations were performed at the same locations where the ultrasound data were obtained from. The relationship of these vascular indices and the ablation zone volumes measured from gross specimens were analyzed using a general linear mixed model fit with random effect for liver and backward stepwise regression analysis.

RESULTS

FI was significantly associated with ablation zone volumes measured on gross specimens (p = 0.0047), but explained little of the variance (R_β² = 0.21). Ablation zone volume decreased by 0.23 cm³ (95% confidence interval: -0.38, -0.08) for every 1 increase in FI. Neither VI nor VFI was significantly associated with ablation zone volumes (p > 0.05).

CONCLUSION

Although FI was associated with ablation zone volumes, it could not sufficiently explain their variability, limiting its clinical applicability. VI, FI and VFI are not clinically useful in the prediction of RF ablation zone volume in the liver. Advances in knowledge: Despite a significant association of FI with ablation zone volumes, VI, FI and VFI cannot be used for their prediction. Different Doppler vascular indices need to be investigated for clinical use.

Non-Invasive Ultrasound Liver Ablation Using Histotripsy: Chronic Study in an In Vivo Rodent Model

Hepatocellular carcinoma, or liver cancer, has the fastest growing incidence among cancers in the United States. Current liver ablation methods are thermal-based and share limitations due to the heat sink effect from the blood flow through the highly vascular liver. Recently, our group has investigated histotripsy as a non-invasive liver cancer ablation method. Histotripsy is a non-thermal ultrasonic ablation method that fractionates tissue through the control of acoustic cavitation. Previous experiments in an in vivo porcine model show that histotripsy can create well-confined lesions in the liver through ribcage obstruction without damaging the overlying ribs and other tissues. Histotripsy can also completely fractionate liver tissue surrounding major vessels while preserving the vessels. In this study, we investigate the long-term effects of histotripsy liver ablation in a rodent model. We hypothesize that the fractionated histotripsy lesion will be resorbed by the liver, resulting in effective tissue healing. To test this hypothesis, the livers of 20 healthy rats were treated with histotripsy using an 8-element 1-MHz histotripsy transducer. Rats were euthanized after 0, 3, 7, 14 and 28 days (n = 4). In vivo and post mortem results showed histotripsy lesions were successfully generated through the intact abdomen in all 20 rats. Magnetic resonance imaging found primarily negative contrast on day 0, positive contrast on day 3 and rapid normalization of signal intensity thereafter (i.e., signal amplitude returned to baseline levels seen in healthy liver tissue). Histologically, lesions were completely fractionated into an acellular homogenate. The lesions had a maximum cross-sectional area of 17.2 ± 1.9 mm(2) and sharp boundaries between the lesion and the healthy surrounding tissue after treatment. As the animals recovered after treatment, the histotripsy tissue homogenate was almost completely replaced by regenerated liver parenchyma, resulting in a small fibrous lesion (<1 mm(2) maximum cross-section) remaining after 28 d. The results of this study suggest that histotripsy has potential as a non-invasive liver ablation method for effective tissue removal.

Analysis of iodinated contrast delivered during thermal ablation: is material trapped in the ablation zone?

Intra-procedural contrast-enhanced CT (CECT) has been proposed to evaluate treatment efficacy of thermal ablation. We hypothesized that contrast material delivered concurrently with thermal ablation may become trapped in the ablation zone, and set out to determine whether such an effect would impact ablation visualization. CECT images were acquired during microwave ablation in normal porcine liver with: (A) normal blood perfusion and no iodinated contrast, (B) normal perfusion and iodinated contrast infusion or (C) no blood perfusion and residual iodinated contrast. Changes in CT attenuation were analyzed from before, during and after ablation to evaluate whether contrast was trapped inside of the ablation zone. Visualization was compared between groups using post-ablation contrast-to-noise ratio (CNR). Attenuation gradients were calculated at the ablation boundary and background to quantitate ablation conspicuity. In Group A, attenuation decreased during ablation due to thermal expansion of tissue water and water vaporization. The ablation zone was difficult to visualize (CNR  =  1.57  ±  0.73, boundary gradient  =  0.7  ±  0.4 HU mm(-1)), leading to ablation diameter underestimation compared to gross pathology. Group B ablations saw attenuation increase, suggesting that iodine was trapped inside the ablation zone. However, because the normally perfused liver increased even more, Group B ablations were more visible than Group A (CNR  =  2.04  ±  0.84, boundary gradient  =  6.3  ±  1.1 HU mm(-1)) and allowed accurate estimation of the ablation zone dimensions compared to gross pathology. Substantial water vaporization led to substantial attenuation changes in Group C, though the ablation zone boundary was not highly visible (boundary gradient  =  3.9  ±  1.1 HU mm(-1)). Our results demonstrate that despite iodinated contrast being trapped in the ablation zone, ablation visibility was highest when contrast is delivered intra-procedurally. Therefore, CECT may be feasible for real-time thermal ablation monitoring.

Irreversible electroporation in the treatment of locally advanced pancreas and liver metastases of colorectal carcinoma

AIM OF THE STUDY

Irreversible electroporation is a new, non-thermal ablation technique in the treatment of parenchymal organ tumors which uses short high voltage pulses of electricity in order to induce apoptosis of targeted cells. In this paper the application of this method of treatment in locally advanced pancreatic cancer (LAPC) and liver cancer is analyzed.

MATERIAL AND METHODS

Between 04.2014 and 09.2014 two patients with LAPC and one with colorectal liver metastasis (CRLM) were qualified for treatment with irreversible electroporation. Both patients remained under constant observation and control. PubMed/Medline, Embase and Google Scholar databases were searched and eight original reports on irreversible electroporation of pancreatic and liver tumors based on the biggest groups of patients were found.

RESULTS

Two patients with LAPC and one with CRLM were qualified for ablation with irreversible electroporation. In all three patients a successful irreversible electroporation (IRE) procedure of the whole tumor was conducted. In the minimum seven-month follow-up 100% local control was achieved - without progression. In the literature review the local response to treatment ranged from 41% to 100%. The event-free survival rate in six-month observation was 94%.

CONCLUSIONS

Ablation with irreversible electroporation is a new non-thermal ablation technique which has been demonstrated, both in the previously published studies and in the cases described in this paper, as a safe and efficient therapeutic method for patients with LAPC and CRLM.

Liver Ablation: Best Practice

Tumor ablation in the liver has evolved to become a well-accepted tool in the management of increasing complex oncologic patients. At present, percutaneous ablation is considered first-line therapy for very early and early hepatocellular carcinoma and second-line therapy for colorectal carcinoma liver metastasis. Because thermal ablation is a treatment option for other primary and secondary liver tumors, an understanding of the underlying tumor biology is important when weighing the potential benefits of ablation. This article reviews ablation modalities, indications, patient selection, and imaging surveillance, and emphasizes technique-specific considerations for the performance of percutaneous ablation.

The Research of Feasibility and Efficacy of Radiofrequency Ablation in Treating Uterine Fibroids

To explore the feasibility and efficacy of radiofrequency ablation in treating uterine fibroids.Ninety patients with multiple uterine fibroids, who had undergone hysterectomy were included in the study. After the uterus was resected, the temperature of 60, 80, 100°C were adopted to ablate the in vitro fibroid with each temperature dealing with 30 patients. Simultaneously, 5 patients were included, whose in vivo fibroid were ablated with the temperature of 100°C before the fibroids were removed after laparotomy. After the fibroids were ablated, the smooth muscle in the ablated center (group A), the ablated edge (group B) and 1 cm away from the ablated edge (group C) were taken. Then, the samples were stained with hematoxylin and eosin (HE) to examine the histopathological changes, and immunohistochemistry was performed to detect the expression of estrogen receptor (ER) and progesterone receptor (PR).After radiofrequency ablation, the ablated lesions were round, toast tan, and dry on gross appearance. There were no obvious tissue carbonization and there were distinct boundary from periphery tissue. In vitro: On automated analysis, the average optical density of ER and PR in group A, B, and C was lower than the control group (P < 0.05), and which were gradually raised with the increased distance to electrode. In the same treatment group, ER optical density was gradually decreased with the increased temperature among 3 different groups. The PR optical density was decreased with the increased temperature under different temperatures in group A and group B, there was significant difference among groups (P < 0.05). But in group C, there was no difference in PR expression among the temperature of 60, 80, and 100°C (P > 0.05). In vivo: Compared with the control group, the average optical density of ER and PR were significantly different among group A, B, and C (P < 0.05), what's more, it was gradually raised with the increased distance to electrode.After radiofrequency ablation, the tissues displayed coagulative necrosis, and decreased ER and PR expression. Radiofrequency ablation may be considered a minimally invasive alternative for those women who wish to retain their reproductive potential. Eighty degree Celsius was expected to be the optimum temperature in radiofrequency ablation treatment of uterine fibroid.

Hemostasis Plug for an Electromagnetic Thermotherapy and Its Application for Liver Laceration

Accident-induced liver trauma is a significant human health concern, as this organ is readily injured during periods at which the abdominal region is compromised. In this work, electromagnetic thermotherapy was successfully developed and employed in vitro and in vivo to treat livers that had been lacerated. Briefly, a new hemostasis plug was integrated with an electromagnetic thermotherapy system (ETS) to perform surgery on lacerated livers. The high-frequency, alternating electromagnetic field (EMF) was generated by the ETS and was shown to induce a pre-set temperature increase within the hemostasis plug embedded in the target tissue. In order to prevent overheating and maintain a constant hemostasis temperature, a temperature feedback control system was utilized. The effect of the intensity of the EMF on the heating capacity of the ETS-hemostasis system was first explored. Furthermore, the relationship between the coagulation zone and operating temperature were investigated in vitro. By utilizing the temperature feedback control system, the hemostasis plug could be heated to a specific temperature for efficient hemostasis. With this approach, the optimal treatment temperature and time were investigated for liver laceration. Lacerated livers from New Zealand white rabbits were successfully treated with the hemostasis plug and ETS within a short period of time. When compared with the traditional perihepatic packing approach, the volume of blood loss from liver laceration surgeries treated by ETS has been dramatically reduced by 83%, suggesting a high therapeutic potential for this system.

Irreversible electroporation of the pancreas is feasible and safe in a porcine survival model

OBJECTIVES

Use of thermal tumor ablation in the pancreatic parenchyma is limited because of the risk of pancreatitis, pancreatic fistula, or hemorrhage. This study aimed to evaluate the feasibility and safety of irreversible electroporation (IRE) in a porcine model.

METHODS

Ten pigs were divided into 2 study groups. In the first group, animals received IRE of the pancreatic tail and were killed after 60 minutes. In the second group, animals received IRE at the head of the pancreas and were followed up for 7 days. Clinical parameters, computed tomography imaging, laboratory results, and histology were obtained.

RESULTS

All animals survived IRE ablation, and no cardiac adverse effects were noted. Sixty minutes after IRE, a hypodense lesion on computed tomography imaging indicated the ablation zone. None of the animals developed clinical signs of acute pancreatitis. Only small amounts of ascites fluid, with a transient increase in amylase and lipase levels, were observed, indicating that no pancreatic fistula occurred.

CONCLUSIONS

This porcine model shows that IRE is feasible and safe in the pancreatic parenchyma. Computed tomography imaging reveals significant changes at 60 minutes after IRE and therefore might serve as an early indicator of therapeutic success. Clinical studies are needed to evaluate the efficacy of IRE in pancreatic cancer.

Effect of Change in Portal Venous Blood Flow Rates on the Performance of a 2.45-GHz Microwave Ablation Device

PURPOSE

To investigate the effect of change in portal venous blood flow rates on the size and shape of ablations created by a 2.45-GHz microwave ablation device.

MATERIALS AND METHODS

This study was exempt from review by the institutional animal care and use committee. An in vitro bovine liver model perfused with autologous blood via the portal vein at five flow rates (60, 70, 80, 90, and 100 mL/min per 100 g of liver) was used to evaluate the effect of change in flow rates on the size and shape of coagulation created by a 2.45-GHz, 140-W microwave ablation device operated for 5 and 10 minutes. Three ablations per ablation time were conducted in each of 10 livers, with two livers perfused at each flow rate. Short- and long-axis diameters were measured from gross specimens, and volume and sphericity index were calculated. General linear mixed models that accounted for correlations within the liver were used to evaluate the effects of lobe, flow, and ablation time on size and sphericity index of ablations.

RESULTS

Flow did not have a significant effect on the size or shape of coagulation created at 5 or 10 minutes (P > .05 for all tests). The mean short- and long-axis diameters and volume were 3.2 cm (95% confidence interval [CI]: 3.1, 3.3), 5.6 cm (95% CI: 5.4, 5.8), and 30.2 cm(3) (95% CI: 28.4, 32.1) for the 5-minute ablations and 3.8 cm (95% CI: 3.7, 3.9), 6.5 cm (95% CI: 6.3, 6.7), and 49.3 cm(3) (95% CI: 47.5, 51.2), for the 10-minute ablations, respectively. The mean sphericity index for both 5- and 10-minute ablations was 34.4% (95% CI: 32%, 36.7%).

CONCLUSION

Change in portal venous blood flow rates did not have an effect on the size and shape of ablations created by a 2.45-GHz microwave ablation device.

Factors associated with short-term local recurrence of liver cancer after percutaneous ablation using irreversible electroporation: a prospective single-center study

PURPOSE

To evaluate the risk factors associated with short-term local recurrence of malignant liver lesions after irreversible electroporation (IRE).

MATERIALS AND METHODS

Thirty-nine consecutive patients (79 malignant liver lesions) were treated with IRE, of whom 14 were excluded from the analysis (including 12 without 6 mo of follow-up and two with incomplete ablation). The remaining 25 patients (aged 59.4 y ± 11.2) had 48 malignant liver lesions, including 22 hepatocellular carcinomas (HCCs), six cholangiocellular carcinomas, and 20 metastatic liver cancers. Multivariate analyses were used to evaluate the associations of risk factors with early recurrence. The characteristics of patients, lesions, and IRE procedures were assessed by logistic regression.

RESULTS

Fourteen of the 48 treated lesions (29.2%) showed early local recurrence after 6 months. Tumor volume (< 5 cm(3) vs ≥ 5 cm(3); P = .022) and underlying disease type (HCC, cholangiocellular carcinoma, or metastatic disease; P = .023) were independently associated with early local recurrence. However, distances to the surrounding portal veins (< 0.5 cm vs ≥ 0.5 cm; P = .810), hepatic veins (P = .170), hepatic arteries (P = .761), and bile ducts (P = .226) were not significantly associated with local recurrence.

CONCLUSIONS

Because short distances to the surrounding vessels were not associated with early local recurrence, percutaneous IRE might provide an alternative treatment option for perivascular tumors. However, patients with larger tumor volumes appeared to be poor candidates for percutaneous IRE. Regarding the different types of treated lesions, patients with HCC had significantly better outcomes.

Safety assessment and therapeutic efficacy of percutaneous microwave ablation therapy combined with percutaneous ethanol injection for hepatocellular carcinoma adjacent to the gallbladder

OBJECTIVE

This study sought to evaluate the safety and efficacy of ultrasound-guided (US-guided) percutaneous microwave (MW) ablation combined with percutaneous ethanol injection (PEI) to treat liver tumours adjacent to the gallbladder.

MATERIALS AND METHODS

A total of 136 patients with hepatocellular carcinoma (HCC) adjacent to the gallbladder, who underwent ultra-sonographically-guided percutaneous MW ablation, which was combined with PEI in 132 patients, were retrospectively assessed. The patient population characteristics, tumour features, local tumour progression and treatment were compared and analysed. The safety and efficacy of the therapy were assessed by clinical data and imaging in follow-up examinations.

RESULTS

All patients were completely treated with two sessions; 120 patients underwent one session, 16 patients underwent two sessions. The primary technique was effective in 95.6% of the cases, according to the computed tomography (CT) or magnetic resonance imaging (MRI) in the one-month follow-up (132 of 138 sessions). PEI and other therapies were performed in the patients who had been incompletely treated (all six patients underwent PEI, and some underwent other therapies, including one transcatheter arterial chemoembolisation (TACE), one liver transplantation and two liver resections). There was a median follow-up period of 30.1 months and a range of 4 to 68 months. None of the patients had major complications. There were no treatment-related deaths. Twenty-six patients died of primary disease progression that was not directly attributable to MW ablation (19.1%, 26/136). Local tumour progression was noted in five patients (3.7%, 5/136), who had completely ablated tumours at follow-up. The patients with locally progressing tumours underwent additional therapy (three patients underwent PEI, one patient TACE, and one liver resection).

CONCLUSION

Ultrasound-guided percutaneous MW ablation, in combination with percutaneous ethanol injection and thermal monitoring, is a safe and effective treatment for HCC adjacent to the gallbladder.

Enhancement of radiofrequency ablation of the liver combined with transarterial embolization using various embolic agents

PURPOSE

Reducing blood flow in the liver during radiofrequency ablation causes enlargement of the ablation area. In this animal study, we evaluated the extended effects of radiofrequency ablation combined with transarterial embolization using various embolic agents.

METHODS

We treated 38 radiofrequency ablation lesions after embolization in 13 pigs using the following embolic agents: gelatin sponge (Group A); iodized oil followed by gelatin sponge (Group B); 700-900 µm calibrated microspheres (Group C); and 100-300 µm calibrated microspheres (Group D). Lesion size and pathological evaluations of these ablation lesions were compared with those receiving radiofrequency ablation alone (control).

RESULTS

Both the long- and short-axis diameters of the ablation lesions for Groups A, B, C, and D were significantly longer than those of controls (long axis/short axis for Groups A, B, C, D, and controls were 27.2/23.2, 30.2/26.0, 28.2/22.2, 32.0/24.4, and 23.2 mm/18.5 mm, respectively) (P < 0.05). The long-axis of the ablation lesion for Group D was significantly longer than those for both Groups A and C (P < 0.05). At pathological examination, the central ablation lesions showed coagulative necrosis with a surrounding hemorrhagic rim, and the microspheres were fitted to occlude the small arteries in peripheral liver parenchyma in Groups C and D.

CONCLUSIONS

The extended effects of embolization with small microspheres may be stronger than those with large microspheres and were equal to those with iodized oil followed by gelatin sponge.

Salvage treatment for local recurrence of hepatocellular carcinoma after local ablation therapy

AIM

Local recurrence of hepatocellular carcinoma (HCC) after local ablation therapy (LAT) is a serious problem; however, the optimal treatment strategy remains unclear.

METHODS

A retrospective analysis was conducted of 50 patients with local recurrence of HCC after LAT that underwent either salvage hepatectomy (n = 23) or radiofrequency ablation (RFA; n = 27). Their background characteristics, intraoperative data, and postoperative short- and long-term outcome were analyzed.

RESULTS

The RFA group was found to be significantly associated with an impaired liver functional reserve, smaller number and size of tumors. The hepatectomy group showed a significantly longer operation time, greater intraoperative blood loss and more frequent red blood cell transfusion. In-hospital stay mortality and morbidity rate did not significantly differ. The disease-free and overall survival showed no significant difference between the groups. Although local recurrence after salvage treatment was found in zero (0%) for hepatectomy and in seven (25.9%) for RFA, that did not affect the overall survival. The tumor size at the prior LAT was identified as an independent prognostic factor for disease-free survival and serum albumin for overall survival.

CONCLUSION

Whereas salvage hepatectomy for local recurrent HCC is recommended for selected patients in terms of its good local control effect, salvage RFA is also acceptable because it is less invasive and also has a reasonable long-term outcome.

Pain control in patients with hepatocellular carcinoma treated by percutaneous radiofrequency ablation: comparison of the efficacy of one-shot and continuous intravenous fentanyl delivery

BACKGROUND

Hepatic percutaneous radiofrequency ablation (RFA) is usually performed with the patient under deep intravenous (i.v.) sedation or general anesthesia. Nonetheless, many patients report pain during and/or after the procedure.

PURPOSE

To perform a prospective study of pain control obtained by the i.v. one-shot delivery and the continuous i.v. infusion of fentanyl in patients with hepatocellular carcinoma (HCC) treated by RFA.

MATERIAL AND METHODS

Between April 2007 and March 2010, 83 patients with 106 HCCs underwent percutaneous RFA. All HCCs were addressed by computed tomography (CT)-guided percutaneous RFA performed within 5 h of embolization of the tumor vessels with iodized oil and gelatin sponges. Standard anesthesia consisted of 10 mL of 1% lidocaine injected locally. For conscious sedation, group one patients (n = 41) were injected i.v. with 100 µg of fentanyl before and 100 µg of fentanyl 30 min after percutaneous RFA. In group two (n = 42) we delivered fentanyl by continuous i.v. infusion at 100 µg/h during RFA. Upon request, patients in both groups also received 5 mg of diazepam i.v. for pain during the RFA procedure. The severity of pain experienced by all patients was evaluated on a visual analogue scale (VAS) and complications elicited by the anesthesia regimens were recorded. We also assessed the effectiveness of the treatment on sequential follow-up CT and/or magnetic resonance imaging (MRI) at 3-month intervals.

RESULTS

Percutaneous RFA was technically successful in all 83 patients. Two patients in group one (4.8%) and one patient in group two (2.4%) manifested residual enhancement 3 months post RFA. There was no significant difference in the local recurrence rate between the two groups. At 4.0 ± 1.8 for group one and 3.4 ± 1.9 for group two, the VAS score was not significantly different. Major fentanyl or diazepam toxicity was recorded in 11 patients (24.4%) in group one and two patients (4.8%) in group two; the difference was statistically significant (P < 0.01).

CONCLUSION

The continuous infusion of fentanyl provided effective and safe analgesia in HCC patients undergoing percutaneous RFA.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes.

Various complications of percutaneous radiofrequency ablation for hepatic tumors: radiologic findings and technical tips

Radiofrequency ablation is a safe and effective treatment for primary and secondary liver malignancies and has a low complication rate; however, there are various radiofrequency ablation-related complications which can occur from the thorax to the pelvis. Although most of these complications are usually minor and self-limited, they may become fatal if diagnosis and treatment are delayed. It is important for radiologists performing radiofrequency ablation to have a perspective regarding the possible radiofrequency ablation-related complications and their risk factors as well as the radiologic findings for their timely detection and increase of the treatment efficacy, and thereby encouraging the use of the radiofrequency ablation technique. This article illustrates the various imaging features of common and rare radiofrequency ablation-related complications as well as offers technical tips in order to avoid these complications.

Radiofrequency ablation in the treatment of cartilaginous lesions in the long bones

Atypical cartilaginous tumours are usually treated by curettage. The purpose of this study was to show that radiofrequency ablation was an effective alternative treatment.

We enrolled 20 patients (two male, 18 female, mean age 56 years (36 to 72) in a proof-of-principle study. After inclusion, biopsy and radiofrequency ablation were performed, followed three months later by curettage and adjuvant phenolisation. The primary endpoint was the proportional necrosis in the retrieved material. Secondary endpoints were correlation with the findings on gadolinium enhanced MRI, functional outcome and complications.

Our results show that 95% to 100% necrosis was obtained in 14 of the 20 patients. MRI had a 91% sensitivity and 67% specificity for detecting residual tumour after curettage. The mean functional outcome (MSTS) score six weeks after radiofrequency ablation was 27.1 (23 to 30) compared with 18.1 (12 to 25) after curettage (p < 0.001). No complications occurred after ablation, while two patients developed a pathological fracture after curettage.

We have shown that radiofrequency ablation is capable of completely eradicating cartilaginous tumour cells in selective cases. MRI has a 91% sensitivity for detecting any residual tumour. Radiofrequency ablation can be performed on an outpatient basis allowing a rapid return to normal activities. If it can be made more effective, it has the potential to provide better local control, while improving functional outcome.

Cite this article: Bone Joint J 2014;96-B:1540–5.

Vessel patency post irreversible electroporation

PURPOSE

The purpose of the study was to evaluate the effect of Irreversible Electroporation (IRE) on vessel patency in close proximity to the ablation zone.

MATERIALS AND METHODS

Between January 2010 and November 2013, 101 patients underwent percutaneous IRE procedures using the NanoKnife for primary and metastatic tumors in different organs. Age ranged from 24 to 83 years. A total of 129 lesions were treated. [liver (100), pancreas (18), kidney (3), pelvis (1), aorto-caval lymph nodes (2), adrenal (2), lung (1), retroperitoneal (1), surgical bed of a prior Whipple procedure (1)]. Post treatment contrast-enhanced CT and MRI scans were reviewed to evaluate caliber, patency, and flow defects of vessels in close proximity to the ablation zone (defined as vessels within 0-1 cm from the treatment zone).

RESULTS

A total of 158 vessels were examined for patency on follow-up. The mean distance of the vessel from the treatment zone was 2.3 ± 2.5 mm. Ten vessels within the treatment zone were encased by tumor. Mean tumor size was 2.7 + 1.5 cm. Overall mean follow-up was 10.3 months. Abnormal vascular changes were noted in 7 of 158 (4.4%) vessels. No significant association was found between distances from the treatment zone and presence of narrowing/thrombosis at the follow-up imaging. (Mann-Whitney U, p = 0.772; logistic regression: p = 0.593; odds ratio: 0.908; CI 0.637-1.294).

CONCLUSION

This study demonstrates safety of IRE for the treatment of tumors near the large blood vessels and tumors already encasing the vessels. Further studies to substantiate these findings are essential to validate this crucial advantage of IRE.

Hepatocellular carcinoma: concomitant sorafenib promotes necrosis after radiofrequency ablation--propensity score matching analysis

PURPOSE

To retrospectively compare radiofrequency ablation (RFA) combined with the multikinase inhibitor sorafenib (hereafter, sorafenib-RFA) and RFA alone in the treatment of hepatocellular carcinoma (HCC).

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. Between January 2007 and December 2011, 16 patients (mean age, 72.8 years; age range 52-84 years; 10 men, six women) with HCC tumors less than 3 cm in diameter were included in the sorafenib-RFA group, and 136 patients (mean age, 72.1 years; age range, 51-86 years; 92 men, 44 women) with HCC tumors less than 3 cm in diameter were included in the RFA alone (control) group. Mean diameters of the greatest long-axis dimensions of HCC were 22.8 mm ± 4.6 (standard deviation) in the sorafenib-RFA group and 18.1 mm ± 4.4 in the control group. RFA was performed immediately after the 7-day administration of sorafenib. Propensity score matching analysis was used to adjust for potential biases.

RESULTS

Fifteen of the 16 patients in the sorafenib-RFA group and 30 of the 136 patients in the control group were selected during propensity score matching. No significant differences between the sorafenib-RFA group (n = 15) and the control group (n = 30) were observed with regard to age, sex, etiology, Child-Pugh class, tumor size, puncture number, needle size, location at the liver margin, or location adjacent to a main vessel. The respective mean diameters of the greatest long- and short-axis dimensions of the RFA-induced ablated area were 46.3 mm ± 10.3 and 33.0 mm ± 6.9 in the sorafenib-RFA group and 32.9 mm ± 7.6 and 25.6 mm ± 5.7 in the control group; both of these dimensions were significantly larger in the sorafenib-RFA group (both P < .001).

CONCLUSION

Sorafenib-RFA may be superior to standard RFA alone in the treatment of HCC tumors smaller than 3 cm in diameter.

Electromagnetic thermotherapy for deep organ ablation by using a needle array under a synchronized-coil system

Thermal ablation by using electromagnetic thermotherapy (EMT) has been a promising cancer modality in recent years. It has relatively few side effects and has therefore been extensively investigated for a variety of medical applications in internal medicine and surgery. The EMT system applies a high-frequency alternating electromagnetic field to heat up the needles which are inserted into the target tumor to cause tumor ablation. In this study, a new synchronized-coil EMT system was demonstrated, which was equipped with two synchronized coils and magnetic field generators to provide a long-range, penetrated electromagnetic field to effectively heat up the needles. The heating effect of the needles at the center of the two coils was first explored. The newly designed two-section needle array combined with the synchronized-coil EMT system was thus demonstrated in the in vitro and in vivo animal experiments. Experimental data showed that the developed system is promising for minimally invasive surgery since it might provide superior performance for thermotherapy in cancer treatment.

Evaluation of thermal injury to liver, pancreas and kidney during irreversible electroporation in an in vivo experimental model

BACKGROUND

Irreversible electroporation (IRE) is a new technique for tumour cell ablation that is reported to involve non-thermal-based energy using high voltage at short microsecond pulse lengths. In vivo assessment of the thermal energy generated during IRE has not been performed. Thermal injury can be predicted using a critical temperature model. The aim of this study was to assess the potential for thermal injury during IRE in an in vivo porcine model.

METHODS

In vivo continuous temperature assessments of 86 different IRE procedures were performed on porcine liver, pancreas, kidney and retroperitoneal tissue. Tissue temperature was measured continuously throughout IRE by means of two thermocouples placed at set distances (0·5 cm or less, and 1 cm) from the IRE probes within the treatment field. Thermal injury was defined as a tissue temperature of 54°C lasting at least 10 s. Tissue type, pulse length, probe exposure length, number of probes and retreatment were evaluated for associations with thermal injury. In addition, IRE ablation was performed with metal clips or metal stents within the ablation field to determine their effect on thermal injury.

RESULTS

An increase in tissue temperature above the animals' baseline temperature (median 36·0°C) was generated during IRE in all tissues studied, with the greatest increase found at the thermocouple placed within 0·5 cm in all instances. On univariable and multivariable analysis, ablation in kidney tissue (maximum temperature 62·8°C), ablation with a pulse length setting of 100 µs (maximum 54·7°C), probe exposure of at least 3·0 cm (maximum 52·0°C) and ablation with metal within the ablation field (maximum 65·3°C) were all associated with a significant risk of thermal injury.

CONCLUSION

IRE can generate thermal energy, and even thermal injury, based on tissue type, probe exposure lengths, pulse lengths and proximity to metal. Awareness of probe placement regarding proximity to critical structures as well as probe exposure length and pulse length are necessary to ensure safety and prevent thermal injury. A probe exposure of 2·5 cm or less for liver IRE, and 1·5 cm or less for pancreas, with maximum pulse length of 90 µs will result in safe and non-thermal energy delivery with spacing of 1·5-2·3 cm between probe pairs.

Advances in managing hepatocellular carcinoma

Multiple modalities for treatment of hepatocellular carcinoma are available, depending on tumor size and number. Surgical resection remains the gold standard, so long as the residual liver function reserve is sufficient. In patients with advanced cirrhosis, liver transplantation is the preferred option, as these patients may not have adequate hepatic reserve after resection. Salvage liver transplantation has also become an option for a select few patients who recur after surgical resection. Ablative techniques have been used for palliation as well as to either completely destroy the tumor, act as an adjunct to resection, or downstage the tumor to meet Milan criteria such that a patient may be a candidate for liver transplantation. Radiofrequency ablation, microwave ablation, chemoembolization, radioembolization, and irreversible electroporation have all been used in this capacity. Currently, sorafenib is the only US Food and Drug Administration-approved chemotherapeutic for hepatocellular carcinoma. The efficacy of sorafenib, in combination with other agents, transarterial chemoembolization, and surgical resection is currently being investigated. Sunitinib and brivanib, tyrosine kinase inhibitors, have failed as potential first- or second-line options for chemotherapy. Bevacizumab in combination with erlotinib is also currently being studied. Final analysis for ramucirumab and axitinib are pending. Tivantinib, a selective mesenchymal-epithelial transition factor (MET) inhibitor, is also undergoing clinical trials for efficacy in MET-high tumors. This review serves to emphasize the current and new technologies emerging in the treatment of hepatocellular carcinoma.

MRI-based finite element simulation on radiofrequency ablation of thyroid cancer

In order to provide a quantitative disclosure on the RFA (radiofrequency ablation)-induced thermal ablation effects within thyroid tissues, this paper has developed a three-dimensional finite element simulation strategy based on a MRI (magnetic resonance imaging)-reconstructed model. The thermal lesion's growth was predicted and interpreted under two treatment conditions, i.e. single-cooled-electrode modality and two-cooled-electrode system. The results show that the thermal lesion's growth is significantly affected by two factors including the position of RF electrode and thermal-physiological behavior of the breathing airflow. Additional parametric studies revealed several valuable phenomena, e.g. with the electrode's movement, thermal injury with varying severity would happen to the trachea wall. Besides, the changes in airflow mass produced evident effects on the total heat flux of thyroid surface, while the changes in breathing frequency only generated minor effects that can be ignored. The present study provided a better understanding on the thermal lesions of RFA within thyroid domain, which will help guide future treatment of the thyroid cancer.

Effects of tissue mechanical properties on susceptibility to histotripsy-induced tissue damage

Histotripsy is a non-invasive tissue ablation method capable of fractionating tissue by controlling acoustic cavitation. To determine the fractionation susceptibility of various tissues, we investigated histotripsy-induced damage on tissue phantoms and ex vivo tissues with different mechanical strengths. A histotripsy bubble cloud was formed at tissue phantom surfaces using 5-cycle long ultrasound pulses with peak negative pressure of 18 MPa and PRFs of 10, 100, and 1000 Hz. Results showed significantly smaller lesions were generated in tissue phantoms of higher mechanical strength. Histotripsy was also applied to 43 different ex vivo porcine tissues with a wide range of mechanical properties. Gross morphology demonstrated stronger tissues with higher ultimate stress, higher density, and lower water content were more resistant to histotripsy damage in comparison to weaker tissues. Based on these results, a self-limiting vessel-sparing treatment strategy was developed in an attempt to preserve major vessels while fractionating the surrounding target tissue. This strategy was tested in porcine liver in vivo. After treatment, major hepatic blood vessels and bile ducts remained intact within a completely fractionated liver volume. These results identify varying susceptibilities of tissues to histotripsy therapy and provide a rational basis to optimize histotripsy parameters for treatment of specific tissues.

Real-time monitoring of radiofrequency ablation and postablation assessment: accuracy of contrast-enhanced US in experimental rat liver model

PURPOSE

To examine the accuracy of the unenhanced zone at contrast material-enhanced ultrasonography (US) in predicting coagulative necrosis during and 21 days after radiofrequency (RF) ablation by using radiologic-pathologic comparison.

MATERIALS AND METHODS

Animal studies were approved by the Institutional Animal Care and Use Committee. The livers of 28 rats underwent US-guided RF ablation. In four animals, contrast-enhanced US was performed during ablation and 2 hours and 2, 7, 14, and 21 days after ablation. The unenhanced zone area on US images was measured. DiI-labeled microbubbles were administered during ablation at 2, 4, and 6 minutes or at 2 hours and 2, 7, 14, and 21 days after ablation in the remaining 24 animals (n = 3 at each time point). One minute later, the animal was euthanized, and the ablated liver was harvested. Tissue samples were imaged to quantify total fluorescence, and NADH staining was performed on the same slice. Hematoxylin-eosin staining was also performed. The findings on fluorescence images, NADH-stained images, and hematoxylin-eosin-stained images were compared. The areas of DiI bubble-negative zones, NADH-negative zones, and lightly NADH-staining zones were measured. Data were analyzed by using one-way analysis of variance.

RESULTS

The area of the unenhanced zone on contrast-enhanced US images increased during RF ablation and reached a maximum within 2 days after ablation. At histopathologic examination, a transition zone manifested adjacent to the coagulation zone until 2 days after ablation. The DiI-bubble negative zone on fluorescence images and the damaged zone (transition zone plus coagulation zone) on NADH-stained images increased rapidly within 2 hours after ablation, then slowly reached the maximum on day 2. The ratios of the mean areas of these two zones at hour 2 to those at day 2 were 94.6% and 95.6%, respectively. High uniformity between the damaged zone on NADH-stained images and the DiI bubble-negative zone on fluorescence images was noted at all time points.

CONCLUSION

The temporary transition zone in NADH staining is partially damaged and should transition to nonviability 2 days after ablation. These results demonstrate that contrast-enhanced US can help delineate the maximum area of cell damage (to within 5% of the maximum) as early as 2 hours after ablation. Contrast-enhanced US may be a simple and accurate tool for monitoring the effects of RF ablation and quantifying the size of thermal damage after treatment.

Electromagnetic thermotherapy system with needle arrays: a practical tool for the removal of cancerous tumors

Thermotherapy has been a promising method to treat tumor. In recent years, electromagnetic thermotherapy (EMT) has been extensively investigated and holds the potential for a variety of medical applications including for cancer treatment when combined with minimally invasive surgery approach. In this study, an alternating electromagnetic frequency was provided by an EMT system to heat up stainless steel needle arrays which were inserted into the target tumor to a high temperature, therefore leading to local ablation of the tumor. A new two-section needle-array apparatus was further demonstrated to encompass the tumor to prevent the tumor cells to spread after the treatment process. By using the needle-array insertion apparatus, there is no limitation of the treatment area; this method could, therefore, be applied for tumors that are larger than 6 cm. It was first successfully demonstrated in the in vitro experiments on porcine livers. Then an in vivo experiment was directly conducted on pigs. The two-section needle array incorporated with the needle-array apparatus and EMT was demonstrated to be promising for no-touch isolation treatment of cancerous tumors.

Liver metastases in close contact to hepatic veins ablated under vascular exclusion

BACKGROUND

Liver metastases (LM) in close contact to hepatic veins (HV) are a frequent cause of unresectability. Reconstruction of hepatic veins is technically difficult and outcomes are poor. Intra-operative radiofrequency ablation (IRFA) with vascular exclusion (VE) may be a useful approach.

METHODS

Out of 358 patients operated for LM, 22 with LM close to a HV treated by IRFA under VE with at least one year of follow-up were included in this retrospective study. Technical success was evaluated at four months by CT scan of the ablated lesion. Complications; local, hepatic and extra-hepatic recurrence rates, and overall survival are reported.

RESULTS

The median number of metastases was 4.5 [range: 1-12]. Seventeen patients had bilateral metastases. The median size of ablated lesions was 2 cm [range: 1-5.5]. Seven complications occurred (1 Grade 1, 2 Grade 3b and 4 Grade IVa), with no mortality. No recurrence of ablated lesions was detected at four months or during follow-up. Seventeen patients had new or extra-hepatic lesions. Median overall survival for colorectal patients was 40 months 95%CI[17.5-not reached].

CONCLUSIONS

IRFA plus VE for LM in close contact to a HV is a novel approach, appearing to be a safe and effective technique which can extend the applications of liver metastases surgery.

Irreversible electroporation of a hepatocellular carcinoma lesion adjacent to a transjugular intrahepatic portosystemic shunt stent graft

We report in a 65-year-old man hepatocellular carcinoma adjacent to a transjugular intrahepatic portosystemic shunt stent-graft which was successfully treated with irreversible electroporation (IRE). IRE is a new non-thermal tissue ablation technique which uses electrical pulses to induce cell necrosis by irreversible membrane poration. IRE proved to be more advantageous in the ablation of perivascular tumor with little injury to the surrounding structures.

Image-guided non-invasive ultrasound liver ablation using histotripsy: feasibility study in an in vivo porcine model

Hepatocellular carcinoma (HCC), or liver cancer, is one of the fastest growing cancers in the United States. Current liver ablation methods are thermal based and share limitations resulting from the heat sink effect of blood flow through the highly vascular liver. In this study, we explore the feasibility of using histotripsy for non-invasive liver ablation in the treatment of liver cancer. Histotripsy is a non-thermal ablation method that fractionates soft tissue through the control of acoustic cavitation. Twelve histotripsy lesions ∼1 cm(3) were created in the livers of six pigs through an intact abdomen and chest in vivo. Histotripsy pulses of 10 cycles, 500-Hz pulse repetition frequency (PRF), and 14- to 17-MPa estimated in situ peak negative pressure were applied to the liver using a 1-MHz therapy transducer. Treatments were performed through 4-6 cm of overlying tissue, with 30%-50% of the ultrasound pathway covered by the rib cage. Complete fractionation of liver parenchyma was observed, with sharp boundaries after 16.7-min treatments. In addition, two larger volumes of 18 and 60 cm(3) were generated within 60 min in two additional pigs. As major vessels and gallbladder have higher mechanical strength and are more resistant to histotripsy, these remained intact while the liver surrounding these structures was completely fractionated. This work shows that histotripsy is capable of non-invasively fractionating liver tissue while preserving critical anatomic structures within the liver. Results suggest histotripsy has potential for the non-invasive ablation of liver tumors.

Palliative treatment of presacral recurrence of endometrial cancer using irreversible electroporation: a case report

INTRODUCTION

Irreversible electroporation (IRE) is a new minimally invasive tumor ablation technique which induces irreversible disruption of cell membrane integrity by changing the transmembrane potential resulting in cell death. Irreversible electroporation is currently undergoing clinical investigation as local tumor therapy for malignant liver and lung lesions. This is the first case report to describe the successful palliative ablation of a presacral recurrence of an endometrial cancer to achieve locoregional tumor control and pain relief.

CASE PRESENTATION

A 56-year-old Caucasian woman was referred for interventional treatment of an advanced local recurrence of endometrial cancer (11.9 × 11.6 × 14.9cm) with infiltration of the sacral bone and nerve plexus. Due to the immediate proximity to the sacral plexus, the patient could neither undergo surgical therapy nor a second radiation therapy. Due to its ablation mechanism irreversible electroporation was deemed to be the best therapy option.

CONCLUSION

We showed in this case that a large tumor mass adjacent to a bundle of neural structures, the sacral plexus, can be widely ablated by irreversible electroporation with only minor temporary impairment of the neural function, even though a large infiltrating tissue volume (941cm3) was ablated.

Controlled swine bile duct ablation with a bipolar radiofrequency catheter

BACKGROUND

Radiofrequency (RF) power is capable of ablation of neoplastic tissue arising from Barrett's esophagus. Endoscopic catheter bipolar RF ablation is a new technique for ablation of neoplastic tissue in the bile duct.

OBJECTIVE

To determine the effect of RF power on bile duct and solid organ histology.

DESIGN

Nonsurvival animal study.

SETTING

Academic center.

PATIENTS

This study involved 4 Yorkshire farm swine.

INTERVENTION

After we made a midline laparotomy incision, a bipolar RF catheter was placed with 3 power (5, 7, 10 W) and voltage settings (66, 132, 190 V) in the bile duct and solid organs (liver, spleen, kidney, and pancreas). Gross and histologic examinations were performed.

MAIN OUTCOME MEASUREMENTS

Depth of ablation in the bile duct wall, characteristics of the ablation in the solid organs.

RESULTS

An endoscopic bipolar RF catheter produced incomplete (bile duct), patchy ablation (pancreas) with 5 watts, intramural (bile duct) or confluent ablation with 7 watts, and transmural (bile duct) ablation at 10 W. The depth of ablation in the bile duct was 0.9 ± 0.3, 1.5 ± 0.2, 2.3 ± 0.6 mm at 5, 7, and 10 W, respectively (analysis of variance; P = .02). Histologic ablation was not achieved in the liver, although gross changes were seen.

LIMITATIONS

Animal study, normal bile duct.

CONCLUSION

RF energy applied to the bile duct or solid organs resulted in controlled ablation with a linear relationship between the depth of ablation in the bile duct and RF power.

Operative microwave ablation for hepatocellular carcinoma: complications, recurrence, and long-term outcomes

BACKGROUND

Treatment of hepatocellular carcinoma (HCC) in the setting of cirrhosis is limited by tumor size/location and underlying liver disease. Radiofrequency ablation is utilized in selected patients; however, local recurrence remains a concern. Microwave ablation (MWA) delivers energy to tissue in a unique fashion, reducing local recurrence. A minimally invasive operative approach allows for mobilization/protection of adjacent structures, intra-operative ultrasound, and assessment of ablation progress.

STUDY DESIGN

Retrospective review of operative MWA performed for HCC in patients with cirrhosis over a 4-year period at a single center. Complications were stratified by Clavien-Dindo classification. Incomplete ablation and local, regional, and metastatic recurrence was assessed on follow-up imaging. Survival was assessed in months.

RESULTS

Fifty-four patients with 73 tumors underwent MWA. Median tumor size was 2.6 cm (range 0.5-8.5 cm). Cirrhosis was present in 92.6 % of patients, with a Child-Pugh score of B/C in 27.8 % and hepatitis C present in 59.3 %. A minimally invasive approach was used in 94.5 % of patients. There were no deaths within 30 days. Thirty-day morbidity was 28.9 %, with grade III complications present in 11.5 %. Delayed complications occurred in 7.8 % of patients, with a 5.6 % 90-day mortality. Incomplete ablation was identified in 5.9 % of tumors with local recurrence of 2.9 % at 9 months median follow-up. Regional and metastatic recurrence occurred in 27.5 and 11.8 % at 9 months median follow-up. Median survival was not reached at 11 months median follow-up. One- and 2-year survival was 72.3 and 58.8 %.

CONCLUSION

Operative, preferably minimally invasive, MWA can be performed in cirrhotic patients with HCC with acceptable morbidity and low recurrence rates. High regional and metastatic recurrence rates in these patients underscore the need for minimally invasive, low morbidity approaches to liver-directed therapy.

Radiofrequency ablation combined with chemoembolization for intermediate-sized (3-5 cm) hepatocellular carcinomas under dual guidance of biplane fluoroscopy and ultrasonography

OBJECTIVE

To assess the technical feasibility and local efficacy of percutaneous radiofrequency ablation (RFA) combined with transcatheter arterial chemoembolization (TACE) for an intermediate-sized (3-5 cm in diameter) hepatocellular carcinoma (HCC) under the dual guidance of biplane fluoroscopy and ultrasonography (US).

MATERIALS AND METHODS

Patients with intermediate-sized HCCs were treated with percutaneous RFA combined with TACE. RFA was performed under the dual guidance of biplane fluoroscopy and US within 14 days after TACE. We evaluated the rate of major complications on immediate post-RFA CT images. Primary technique effectiveness rate was determined on one month follow-up CT images. The cumulative rate of local tumor progression was estimated with the use of Kaplan-Meier method.

RESULTS

Twenty-one consecutive patients with 21 HCCs (mean size: 3.6 cm; range: 3-4.5 cm) were included. After TACE (mean: 6.7 d; range: 1-14 d), 20 (95.2%) of 21 HCCs were visible on fluoroscopy and were ablated under dual guidance of biplane fluoroscopy and US. The other HCC that was poorly visible by fluoroscopy was ablated under US guidance alone. Major complications were observed in only one patient (pneumothorax). Primary technique effectiveness was achieved for all 21 HCCs in a single RFA session. Cumulative rates of local tumor progression were estimated as 9.5% and 19.0% at one and three years, respectively.

CONCLUSION

RFA combined with TACE under dual guidance of biplane fluoroscopy and US is technically feasible and effective for intermediate-sized HCC treatment.

Comparison of internally cooled wet electrode and hepatic vascular inflow occlusion method for hepatic radiofrequency ablation

Background/Aims

Various strategies to expand the ablation zone have been attempted using hepatic radiofrequency ablation (RFA). The optimal strategy, however, is unknown. We compared hepatic RFA with an internally cooled wet (ICW) electrode and vascular inflow occlusion.

Methods

Eight dogs were assigned to one of three groups: only RFA using an internally cooled electrode (group A), RFA using an ICW electrode (group B), and RFA using an internally cooled electrode with the Pringle maneuver (group C). The ablation zone diameters were measured on the gross specimens, and the volume of the ablation zone was calculated.

Results

The ablation zone volume was greatest in group B (1.82±1.23 cm³), followed by group C (1.22±0.47 cm³), and then group A (0.48±0.33 cm³). The volumes for group B were significantly larger than the volumes for group A (p=0.030). There was no significant difference in the volumes between groups A and C (p=0.079) and between groups B and C (p=0.827).

Conclusions

Both the usage of an ICW electrode and hepatic vascular occlusion effectively expanded the ablation zone. The use of an ICW electrode induced a larger ablation zone with easy handling compared with using hepatic vascular occlusion, although this difference was not statistically significant.

Combined Hepatic Arterial Embolization and Hepatic Ablation for Unresectable Colorectal Metastases to the Liver

Liver-directed therapy for hepatic metastases includes: intra-arterial techniques such as trans-arterial chemoembolization (TACE) and yttrium-90 resin (90Y) microsphere radioembolization and ablative technologies: cryoablation, radiofrequency ablation, and microwave ablation. Combining embolization techniques with liver ablation may enhance the therapeutic benefit of each and result in improved patient survival. We retrospectively reviewed our experience with combined intra-arterial therapies and ablation for unresectable hepatic colorectal metastases from 1996 to 2011. Patient demographics, tumor characteristics, specific liver-directed treatments, procedure-related morbidity and mortality, and overall survival were recorded. There were 17 (53%) males and 15 (47%) females. Average age for the group was 74.1 years (median, 75.5 years). Fifteen patients (46.9%) had a single hepatic metastasis. Eleven (34%) patients had bilobar tumor distribution and seven (22%) patients had vascular invasion of the portal vein or hepatic/caval venous structures. Seven (21%) tumors were greater than 5 cm in diameter. Twenty-seven (84.4%) patients received TACE and five (15.6%) received 90Y. Fourteen (43%) were embolized before any ablation. Fifty-three per cent of patients required multiple hepatic ablation sessions. Median length of hospital stay was 1 day. There were no procedure-related mortalities and complications occurred in six (18.8%) patients. Mean follow-up for the group was 33 months. Kaplan-Meier 1-, 3-, and 5-year estimated survival was 93.8, 50.0, and 10.1 per cent, respectively. Median survival for the group was 46 months. Hepatic ablation and embolization techniques can be combined safely with minimal morbidity. In our series, we observed 5-year survival in 10 per cent of patients.

Radiofrequency ablation of the liver: effect of variation of portal venous blood flow on lesion size in an in-vitro perfused bovine liver

RATIONALE AND OBJECTIVES

An in vitro perfused bovine liver model was used to evaluate the relationship between the sizes of radiofrequency ablation lesions and variation in portal venous blood flow.

MATERIALS AND METHODS

Fourteen bovine livers were perfused with autologous heparinized blood at 37°C and 40% to 50% oxygenation via the portal vein. Flow rates were adjusted from 10 to 50 mL/min/100 g tissue. A 480-kHz generator and a 3.0-cm monopolar internally cooled electrode were used to create 57 ablations. The long-axis diameter, short-axis diameter (SAD), and volume of each ablation zone were measured and calculated from the dissected livers. Correlations between SAD, long-axis diameter, and volume versus blood flow were assessed using linear regression analysis.

RESULTS

SAD and lesion volume demonstrated inverse linear correlations with blood flow (for SAD, y = -0.044x + 3.925, r = 0.836, P < .001; for volume, y = -0.556x + 31.574, r = 0.842, P < .001). A 10 mL/min/100 g change in flow rate produced an average 4.4 ± 0.4 mm change in SAD and an average 5.6 ± 0.5 cm(3) change in volume. Long-axis diameter was not correlated with blood flow (y = -0.7694x + 4.1899, r = 0.2173, P = .111).

CONCLUSIONS

The SAD and volume of radiofrequency ablation lesions have statistically significant inverse linear correlations with portal venous blood flow, with an average 4.4-mm change in SAD and an average 5.6-cm(3) change in volume for each 10 mL/min/100 g change in flow rate.

Image-based 3D modeling and validation of radiofrequency interstitial tumor ablation using a tissue-mimicking breast phantom

PURPOSE

Minimally invasive treatment of solid cancers, especially in the breast and liver, remains clinically challenging, despite a variety of treatment modalities, including radiofrequency ablation (RFA), microwave ablation or high-intensity focused ultrasound. Each treatment modality has advantages and disadvantages, but all are limited by placement of a probe or US beam in the target tissue for tumor ablation and monitoring. The placement is difficult when the tumor is surrounded by large blood vessels or organs. Patient-specific image-based 3D modeling for thermal ablation simulation was developed to optimize treatment protocols that improve treatment efficacy.

METHODS

A tissue-mimicking breast gel phantom was used to develop an image-based 3D computer-aided design (CAD) model for the evaluation of a planned RF ablation. First, the tissue-mimicking gel was cast in a breast mold to create a 3D breast phantom, which contained a simulated solid tumor. Second, the phantom was imaged in a medical MRI scanner using a standard breast imaging MR sequence. Third, the MR images were converted into a 3D CAD model using commercial software (ScanIP, Simpleware), which was input into another commercial package (COMSOL Multiphysics) for RFA simulation and treatment planning using a finite element method (FEM). For validation of the model, the breast phantom was experimentally ablated using a commercial (RITA) RFA electrode and a bipolar needle with an electrosurgical generator (DRE ASG-300). The RFA results obtained by pre-treatment simulation were compared with actual experimental ablation.

RESULTS

A 3D CAD model, created from MR images of the complex breast phantom, was successfully integrated with an RFA electrode to perform FEM ablation simulation. The ablation volumes achieved both in the FEM simulation and the experimental test were equivalent, indicating that patient-specific models can be implemented for pre-treatment planning of solid tumor ablation.

CONCLUSION

A tissue-mimicking breast gel phantom and its MR images were used to perform FEM 3D modeling and validation by experimental thermal ablation of the tumor. Similar patient-specific models can be created from preoperative images and used to perform finite element analysis to plan radiofrequency ablation. Clinically, the method can be implemented for pre-treatment planning to predict the effect of an individual's tissue environment on the ablation process, and this may improve the therapeutic efficacy.