Incomplete Ablation Research Articles

A Review of Imaging Methods to Assess Ultrasound-Mediated Ablation.

Ultrasound ablation techniques are minimally invasive alternatives to surgical resection and have rapidly increased in use. The response of tissue to HIFU ablation differs based on the relative contributions of thermal and mechanical effects, which can be varied to achieve optimal ablation parameters for a given tissue type and location. In tumor ablation, similar to surgical resection, it is desirable to include a safety margin of ablated tissue around the entirety of the tumor. A factor in optimizing ablative techniques is minimizing the recurrence rate, which can be due to incomplete ablation of the target tissue. Further, combining focal ablation with immunotherapy is likely to be key for effective treatment of metastatic cancer, and therefore characterizing the impact of ablation on the tumor microenvironment will be important. Thus, visualization and quantification of the extent of ablation is an integral component of ablative procedures. The aim of this review article is to describe the radiological findings after ultrasound ablation across multiple imaging modalities. This review presents readers with a general overview of the current and emerging imaging methods to assess the efficacy of ultrasound ablative treatments.

Tailoring Chemoimmunostimulant Bioscaffolds for Inhibiting Tumor Growth and Metastasis after Incomplete Microwave Ablation.

Microwave ablation has attracted the most attention as a locoregional therapeutic method for solid neoplasms. However, the high incidence of incomplete ablation that could promote the rapid cancer progression still remains a challenge in clinic. Herein, we found that the high invasiveness of residual tumor following incomplete microwave ablation (iMWA) is mainly due to the myeloid cell-mediated immunosuppression. Accordingly, we develop a biohydrogel scaffold-enabled chemoimmunotherapeutic strategy by targeting myeloid cells with a phosphoinositide 3-kinase γ (PI3Kγ) inhibitor (IPI549) to synergize with immunostimulatory chemotherapy (Oxaliplatin, OX) for post-ablative cancer therapy. With several tumor mouse models, we reveal that OX&IPI549@Gel-based localized chemoimmunotherapy can substantially suppress the growth of tumor post-iMWA, simultaneously evoke robust systemic anticancer immunity to inhibit metastatic spread, and offer strong long-term immunological memory functions against tumor rechallenge. Besides, this work proposes a potential opportunity for precision medicine by utilizing a mechanism-based rationale to the adoption of our pre-existing arsenal of anticancer immunotherapeutic schedule.

Mathematical modeling of microwave liver ablation with a variable-porosity medium approach

Background and objectivesThermal ablation of tumors plays a key role to fight cancer, since it is a minimally invasive treatment which involves some advantages compared to surgery and chemotherapy, such as shorter hospital stays and consequently lower costs, along with minor side effects. In this context, computational modeling of heat transfer during thermal ablation is relevant to accurately predict the obtained ablation zone in order to avoid tumor recurrence risk caused by incomplete ablation, and the same time to save the surrounding healthy tissue. The aim of this work is to develop a more realistic porous media-based mathematical model to simulate a microwave thermal ablation (MWA) of an in vivo liver tumor surrounded by healthy tissue. MethodsThe domain is made up of a spherical tumor bounded by a cylindrical healthy liver tissue. The simulated microwave antenna is a 14 G HS Amica-Gen Probe, and the supplied power of 60 W is applied for 300 s and 600 s. The model consists in coupling modified Local Thermal Non Equilibrium (LTNE) equations with the electromagnetic equations. The LTNE equations include a variable porosity function which fits the porosity changing from the tumor core to the rim based on experimental measures in in vivo cases. Moreover, four different blood vessels’ uniform distributions are investigated to compare the effects of different vascularizations of the considered target tissue. ResultsThe results are shown in terms of temperature fields, ablation diameters and volumes based on the Arrhenius thermal damage model with 99% of cell death probability. The outcomes show a very good agreement with a clinical study on human patients with hepatocellular carcinoma using the same antenna and energy setting, when terminal arteries distribution is included. ConclusionsIn this work, an in vivo microwave ablation of liver tumor surrounded by healthy tissue is modeled with a variable-porosity medium approach based on experimental measures. The outcomes shown for distinct vascularizations underline the key relevance of modeling more and more accurately tumor MWA, by considering increasingly realistic features, avoiding tumor recurrence, and improving both medical protocols and devices.

Technical and safety performance of CT-guided percutaneous microwave ablation for lung tumors: an ablate and resect study.

BackgroundPercutaneous image-guided thermal ablation has an increasing role in the treatment of primary and metastatic lung tumors. Achieving acceptable clinical outcomes requires better tools for pre-procedure prediction of ablation zone size and shape.MethodsThis was a prospective, non-randomized, single-arm, multicenter study conducted by Medtronic (ClinicalTrials.gov ID: NCT02323854). Subjects scheduled for resection of metastatic or primary lung nodules underwent preoperative percutaneous microwave ablation. Ablation zones as measured via CT imaging following ablation immediately and before resection surgically versus predicted ablation zones as prescribed by the investigational system software were compared. This CT scan occurred after the ablation was finished but the antenna still in position. Time (minutes) from antenna placement to removal was 23.7±13.1 (n=14); median: 21.0 (range, 6.0 to 48.0). The definition of the secondary endpoint of complete ablation was 100% non-viable tumor cells based on nicotinamide adenine dinucleotide hydrogen (NADH) staining. Safety endpoints were type, incidence, and severity of adverse events.ResultsFifteen patients (mean age 58.9 years; 67% male; 33% female) were enrolled in the study, 33.3% (5/15) with previous thoracic surgery, 73% (11/15) with metastasis, and 27% (4/15) with primary lung tumors. All underwent percutaneous microwave ablation followed by surgical resection the same day. Complete ablation was detected in 54.4% (6/11), incomplete ablation in 36.4% (4/11), and delayed necrosis in 9.1% (1/11). There were no device-related adverse events. Ablation zone volume was overestimated in all patients.ConclusionsHistological complete ablation was observed in 55% of subjects. CT scanning less than an hour after ablation and tissue shrinkage may account for the smaller zone of ablation observed compared to predicted by the investigational system software.

Incomplete radiofrequency ablation induced chemoresistance by up-regulating heat shock protein 70 in hepatocellular carcinoma

Radiofrequency ablation (RFA) is a common minimally invasive treatment for hepatocellular carcinoma (HCC). Incomplete RFA (iRFA) due to the sub-lethal heat shock challenge of some cell populations leads to the generation of transformed survivor cells with enhanced chemoresistance. However, the underlying mechanism of iRFA on HCCs chemoresistance remains unknown. In the present study, we investigated the effect of iRFA on HCCs sensitivity to cisplatin. Cells treated with the sub-lethal heat shock challenge were used to mimic iRFA treatment in vitro. An orthotopic implantation HCC model was established and also performed iRFA treatment. Flow cytometry, transwell assay, and cell counting kit-8 assay were used to determine the effect of iRFA treatment on cisplatin-induced HCC cell apoptosis, invasion, and cell viability. ELISA and Western blot were used to detect the effect of iRFA treatment on cisplatin-induced HCC cell pyroptosis. We found that iRFA treatment increased the HCC cell proliferation and invasion ability, and inhibited cisplatin-induced pyroptosis. Further experiments showed that iRFA treatment induced upregulation of HSP70, which inhibited the cisplatin-induced NLRP3 inflammasome activation, leading to inhibition of pyroptosis. HSP70 knockdown or NLRP3 overexpression could reverse the effect of iRFA treatment in vitro. In vivo, HSP70 knockdown reversed the chemosensitivity of HCC to cisplatin, which was decreased by iRFA. In conclusion, we demonstrated that iRFA induced drug resistance by HSP70-mediated inhibition of cell pyroptosis in HCC.

Detectability of Target Lesion During CT-Guided Tumor Ablations: Impact on Ablation Outcome.

Small hepatic malignancies scheduled for CT-guided percutaneous ablation may have been identified in the hepatobiliary phase of liver MRI or in a specific phase of multi-phase CT but may be occult on unenhanced CT used to guide the ablation. We investigated whether the detectability of the target lesion would impact the efficacy of CT-guided hepatic tumor ablations. We included 69 patients with 99malignant liver lesions (25 primary, 44 metastases) who underwent IRE (n = 35), RFA (n = 41), or MWA (n = 23) between 01/2015 and 06/2018. All procedures were performed under CT guidance. Lesions not detectable on CT (NDL) were targeted through identification of anatomical landmarks on preinterventional contrast-enhanced CT or MRI. Rates of incomplete ablation, size of ablation zone, local tumor recurrence, intrahepatic progression-free survival (ihPFS), and adverse event rates were compared for detectable lesions (DL) vs. NDL. 40 lesions were NDL, and 59 lesions were DL on unenhanced CT. The mean follow-up was 16.2 months (14.8for DL and 18.2 for NDL). The mean diameter of NDL and DL was similar (12.9 mm vs. 14.9 mm). The mean ablation zone size was similar (37.1 mm vs. 38.8 mm). Incomplete ablation did not differ between NDL vs. DL (5.0 % [2/40; 0.6-16.9 %] vs. 3.4 % [2/59; 0.4-11.7 %]), nor did local tumor recurrence (15.4 % [6/39; 5.7 %-30.5 %] vs. 16.9 % [10/59; 8.4-29.0 %]), or median ihPFS (15.5 months vs. 14.3 months). Target lesion detectability on interventional CT does not have a significant impact on outcome after percutaneous liver ablation when anatomical landmarks are used to guide needle placement. · Liver tumors can be successfully ablated even if they are not detectable on the navigational CT scan.. · Anatomical landmarks should be used and compared to preinterventional imaging.. · Barzakova E, Senthilvel N, Bruners P et al. Detectability of Target Lesion During CT-Guided Tumor Ablations: Impact on Ablation Outcome . Fortschr Röntgenstr 2022; 194: 515 - 520.

Initial Incomplete Thermal Ablation Is Associated With a High Risk of Tumor Progression in Patients With Hepatocellular Carcinoma.

PurposeTo investigate whether incomplete thermal ablation is associated with a high risk of tumor progression in patients with hepatocellular carcinoma (HCC), and to compare the efficacy of repeated thermal ablation and transarterial chemoembolization (TACE) for residual tumor after incomplete ablation.MethodsThis retrospective study included 284 patients with unresectable HCC who underwent thermal ablation from June 2014 to September 2020. The response of the initially attempted ablation was classified into complete (n=236) and incomplete (n=48). The progression-free survival (PFS) and overall survival (OS) were compared between patients with complete and incomplete responses, before and after a one-to-one propensity score-matching (PSM), and between patients in whom repeated ablation or TACE was performed after a first attempt incomplete ablation.ResultsAfter PSM of the 284 patients, 46 pairs of patients were matched. The PFS was significantly higher in the complete response group than in the incomplete response group (P<0.001). No difference in OS was noted between two groups (P=0.181). After a first attempt incomplete ablation, 29 and 19 patients underwent repeated ablation and TACE, respectively. There were no significant differences in PFS (P=0.424) and OS (P=0.178) between patients who underwent repeated ablation and TACE. In multivariate Cox regression analysis, incomplete response (P<0.001) and Child-Pugh class B (P=0.017) were independent risk factors for tumor progression, while higher AFP level (P=0.011) and Child-Pugh class B (P=0.026) were independent risk factors for poor OS.ConclusionAlthough patients with incomplete ablation are associated with tumor progression compared with those with complete ablation, their OS is not affected by incomplete ablation. When patients present with residual tumors, TACE may be an alternative if repeated ablation is infeasible.

Value of 18F-FDG PET/MR Imaging in the Early Evaluation of Treatment Response following Radiofrequency Ablation of Liver Cancer in a Rabbit Model

PurposeTo test the hypothesis that 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) and magnetic resonance (MR) imaging can detect early residual tumor following radiofrequency (RF) ablation of liver cancer using a VX2 tumor model. Materials and MethodsTwenty-four rabbits with VX2 liver tumors were randomly divided into 3 groups (n = 8/group): Group 1 without RF ablation treatment, Group 2 with complete ablation, and Group 3 with partial ablation. An 18F-FDG PET/MR imaging scan was obtained within 2 hours after RF ablation. The maximum standardized uptake values (SUV) of the nontreated liver tumor, benign periablational enhancement (BPE), residual tumor, ablated tumor, and adjacent liver parenchyma and mean SUV of the normal liver were measured. The ratios of maximum SUV for these targets to the mean SUV of the normal liver (TNR) were calculated and compared. ResultsThe mean TNR of the nontreated liver tumors in Group 1 was significantly greater than that of the adjacent liver parenchyma (8.68 ± 0.71 vs 1.89 ± 0.26, P < .001). In Group 2, the mean TNR of BPE was significantly greater than that of the adjacent liver parenchyma (2.85 ± 0.20 vs 1.86 ± 0.25, P < .001). In Group 3, the mean TNR of the residual tumor was significantly greater than that of BPE (8.64 ± 0.59 vs 2.78 ± 0.23, P < .001), which was significantly greater than that of completely ablated tumor (2.78 ± 0.23 vs 0.50 ± 0.06, P < .001). Conclusions18F-FDG PET/MR imaging may serve as a promising imaging tool for the early detection of viable residual tumors due to incomplete tumor ablation.

Research on the feasibility and machining experiment of the laser-milling combination machining for Kevlar fiber reinforced composite

The Kevlar fiber-reinforced plastic (KFRP) had been received much attention and wide application in the field of weapon armor protection. There were many problems in mechanical processing, such as furry, difficult to chip removal, severe tool wear and so on. Many processing difficulties still remained. In order to avoid these defects of mechanical processing and these drawbacks, the laser-milling combination machining for KFRP was presented in this paper. The feasibility of the machining laser-milling combination machining was analyzed. The results show that the fiber carbonization zone and resin melting zone are observed after KFRP laser processing. In resin melting zone, the fibers are basically intact. The maximum kerf width is no more than 0.5 mm, and the kerf depth is less than 2 mm. The effects of the laser parameters on the kerf width a are relatively small, but that on the kerf depth h, fiber carbonization zone width A and resin melting zone width Am are significant. During milling of the laser-milling processing, the shape of the chip is big blocked and flocculent. If the fibers are incomplete ablation, the burrs are easy to occur. The burrs not only can be effectively avoided, but also the cutting forces and cutting temperature can be greatly reduced. Therefore, the processing quality can be improved and the degree of the processing difficulty can be reduced by using the laser-milling combination machining for KFRP.

SIMULTANEOUS HYBRID ABLATION WITH EPI-ENDOCARDIAL MAPPING FOR THE TREATMENT OF LONG STANDING PERSISTENT ATRIAL FIBRILLATION

BACKGROUND While the paroxysmal form of atrial fibrillation (AF) can be managed pharmaceutically with antiarrhythmic drugs or by means of catheter ablation, persistent AF and longstanding persistent atrial fibrillation (LsP-AF) have presented more of a challenge. Hybrid ablation offers a minimally invasive tailored approach for these non-paroxysmal forms of AF which are associated with a more complex substrate. Moreover, given the recent evidence of endo-epicardial electrical asynchrony that can develop in patients with PAF and LsP-AF it is necessary to extensively validate lesion transmurality. Our hybrid technique employs high-density electrical mapping of both the epicardial and endocardial surfaces allowing the team to validate endpoints of ablation in an extensive manner during the procedure which mitigates the risk of incomplete ablation lines that could create re-entrant circuits and recurrence of AF (Fig.1 A-D). METHODS AND RESULTS We describe the outcomes of 15 consecutive patients who underwent simultaneous thoracoscopic hybrid ablation with epi-endocardial mapping for the treatment of LsPAF (Fig.1 E-H). Patient outcomes were recorded at 3 months, 6 months, 1 year and last follow-up greater than 1 year for each patient. Rhythm status was obtained primarily via a 24 hr Holter monitor and if that was not available, ECG measurements were used. Table 1 lists patient and procedure characteristics: age 62.7±11 yr; mean AF duration 51.6 months [range: 14-130]; previous transcatheter (TC) ablation 3/15 (20%); previous cardioversion 12/15 (80%); box lesion set 15/15 (100%); ablation time 20 ±4 mins; surgical gaps 8/15 (53%); adverse events (bleeding/stroke/pacemaker implantation) (0%). At discharge 13/15 (86.6%) of patients were in sinus rhythm (SR) with a mean post-op stay of 3.8 ± 1.1 days. SR restoration was as follows: 3 month 14/15(93.3%), 6 month 13/15 (86.7%) SR off anti-arrhythmic drugs (AAD), 1yr 11/15 (73.3%) SR off AAD. At last follow-up (22±7 month) 13/15 (86.7%) patients were in SR with 11/15 (73.3%) patients in SR off AAD; 4 patients underwent repeat TC ablation 18±3.6 month post hybrid ablation. The same areas that were endocardially targeted as surgical gaps during the index procedure were re-ablated (3/4) and areas that were not seen as surgical gaps in the first place were ablated during the repeat TC procedure (4/4). CONCLUSION Our hybrid approach is safe, feasible and has shown successful SR restoration off AAD in 73% (11/15) of our patients at 1 year follow-up and epicardial mapping before and after endocardial ablation provided an additional means of lesion validation. While the paroxysmal form of atrial fibrillation (AF) can be managed pharmaceutically with antiarrhythmic drugs or by means of catheter ablation, persistent AF and longstanding persistent atrial fibrillation (LsP-AF) have presented more of a challenge. Hybrid ablation offers a minimally invasive tailored approach for these non-paroxysmal forms of AF which are associated with a more complex substrate. Moreover, given the recent evidence of endo-epicardial electrical asynchrony that can develop in patients with PAF and LsP-AF it is necessary to extensively validate lesion transmurality. Our hybrid technique employs high-density electrical mapping of both the epicardial and endocardial surfaces allowing the team to validate endpoints of ablation in an extensive manner during the procedure which mitigates the risk of incomplete ablation lines that could create re-entrant circuits and recurrence of AF (Fig.1 A-D). We describe the outcomes of 15 consecutive patients who underwent simultaneous thoracoscopic hybrid ablation with epi-endocardial mapping for the treatment of LsPAF (Fig.1 E-H). Patient outcomes were recorded at 3 months, 6 months, 1 year and last follow-up greater than 1 year for each patient. Rhythm status was obtained primarily via a 24 hr Holter monitor and if that was not available, ECG measurements were used. Table 1 lists patient and procedure characteristics: age 62.7±11 yr; mean AF duration 51.6 months [range: 14-130]; previous transcatheter (TC) ablation 3/15 (20%); previous cardioversion 12/15 (80%); box lesion set 15/15 (100%); ablation time 20 ±4 mins; surgical gaps 8/15 (53%); adverse events (bleeding/stroke/pacemaker implantation) (0%). At discharge 13/15 (86.6%) of patients were in sinus rhythm (SR) with a mean post-op stay of 3.8 ± 1.1 days. SR restoration was as follows: 3 month 14/15(93.3%), 6 month 13/15 (86.7%) SR off anti-arrhythmic drugs (AAD), 1yr 11/15 (73.3%) SR off AAD. At last follow-up (22±7 month) 13/15 (86.7%) patients were in SR with 11/15 (73.3%) patients in SR off AAD; 4 patients underwent repeat TC ablation 18±3.6 month post hybrid ablation. The same areas that were endocardially targeted as surgical gaps during the index procedure were re-ablated (3/4) and areas that were not seen as surgical gaps in the first place were ablated during the repeat TC procedure (4/4). Our hybrid approach is safe, feasible and has shown successful SR restoration off AAD in 73% (11/15) of our patients at 1 year follow-up and epicardial mapping before and after endocardial ablation provided an additional means of lesion validation.

Evaluating the Role of Stereotactic Body Radiation Therapy With Respect to Androgen Receptor Signaling Inhibitors for Oligometastatic Prostate Cancer

PurposeOutcomes of stereotactic body radiation therapy (SBRT) with respect to androgen receptor signaling inhibitors (ARSI) have not been characterized for oligometastatic prostate cancer. We sought to characterize prostate specific antigen (PSA) response and progression-free survival (PFS) after SBRT among men who have progressed on ARSI therapy in the oligometastatic castration-resistant setting. Methods and MaterialsA single-institution retrospective analysis was performed for men with ARSI-resistant, oligometastatic, castrate-resistant prostate cancer (omCRPC). Intervention consisted of SBRT. PSA reduction greater than 50% and median PFS (PSA or radiographic progression) as determined by routine care comprised outcome measurements. Cox regression analysis was used to determine factors influencing PFS. ResultsThirty-five men with ARSI-resistant omCRPC and 65 lesions treated with SBRT were followed for a median of 17.2 months. In 63% of men PSA reduction greater than 50% was achieved. Median PFS was 9.0 months. Incomplete ablation (defined as the presence of untreated lesions after SBRT or receipt of prior palliative radiation therapy doses) was associated with worse PFS (hazard ratio 4.21 [1.74-10.19]; P < .01). For a subgroup of 22 men with complete ablation of metastatic sites with SBRT, the median PFS was 13.1 months. One-year overall survival was 93.1% (95% confidence interval, 84.4-100). ConclusionsSBRT may augment the efficacy of ARSI in omCRPC, provided that all lesions receive ablative radiation doses. Future prospective study of SBRT for men receiving ARSI is warranted.

Evaluating the thermal performance of a balloon-based renal sympathetic denervation system with array electrodes: a finite element study

ABSTRACT Renal denervation transmits radiofrequency (RF) energy through an electrode to treat resistant hypertension (RH), applying ablation in the renal artery. Several experimental studies have shown that this treatment has been used effectively to treat RH. The aim of this paper is to investigate the effect of ablation parameters (i.e., electrode length, applied voltage, ablation time, and blood flow) on the temperature distribution using a balloon-based array electrodes system. A simplified three-dimensional model including four electrodes and a balloon was established. The balloon diameter was 3 mm and placed in a 5 mm diameter renal artery for forming intra-arterial occlusion. Four electrodes were mounted on the balloon and distributed in the same plane to mimic circumferential RF ablation. Computer simulations were conducted to investigate the thermal performances of the device by setting different electrode configurations, treatment protocols, and physiological factors. The thermal performances including the thermal distribution, maximum lesion depth, length, and area were analyzed. The lesion shape of the array RF electrodes was approximately a sphere with a 100% circumference coverage rate of the renal artery. The lesion depth and length increase with each factor except for blood velocity. Increasing the electrode length from 2 to 4 mm or 2 to 6 mm, the lesion depth increases by 1.15 mm and 0.54 mm at 60 s. The corresponding lesion length increases by 2.65 mm and 2.34 mm, respectively. The range of effective lesion depth is 1.90–4.90 mm, at a voltage of 15–30 V. But the peak temperature at the arterial outer wall exceeded 100 °C when the voltage is above 25 V. In tissue, the degree of thermal injury in the 2 mm area reached 100%, but in blood was not more than 5%. There was no significant difference at different flow conditions because the difference value in lesion depth was not exceeded 0.5 mm. The results showed that the balloon-based four electrodes system is expected to overcome the difficulty of incomplete ablation. In clinical application, 2 mm-electrode is recommended to avoid long wall damage as much as possible and control the voltage below 25 V. This treatment has little thermal injury on the blood, which means it may avoid coagulation formation. Moreover, the application of this device does not need to consider the difference in individual blood velocity.

B-PO02-216 MONOMORPHIC VENTRICULAR TACHYCARDIA FOLLOWING VENTRICULAR FIBRILLATION ABLATION IN BRUGADA SYNDROME

Radiofrequency (RF) epicardial RV/RV outflow tract (RVOT) substrate ablation can normalize Brugada pattern ECG & reduce Ventricular Fibrillation (VF) recurrence. There is no of literature about proarrhythmic effect of ablation and scar creation. Case of monomorphic Ventricular Tachycardia (MM VT) after VF ablation for Brugada Syndrome due to ablation induced scar related re-entry. NA 47-year-old male with Brugada syndrome diagnosed after sudden cardiac death & confirmed with SCN5A gene mutation had multiple ICD therapies for VF despite high dose oral Quinidine. Cardiac MRI showed structurally normal heart & absence of scar. He underwent VF ablation where epicardial surface & endocardial RV was mapped. RV endocardium was normal. Epicardial voltage map showed area of low voltage with late potentials over anterior RVOT. IV Procainamide resulted in expansion of low voltage area. RF ablation & homogenization of this area was performed. Post procedure normalization of ECG was noted at 3 months. He did not have ICD therapies for 1 year & quinidine was tapered with no anterior precordial ECG abnormalities. 1.5 years post ablation he had presyncope & sustained MM VT. ICD intracardiac electrograms showed MM VT, stable cycle length of 250ms. Anti-tachycardia pacing terminated VT. Far field EGM morphology suggested an inferiorly directed VT. Quinidine was restarted at low dose with no recurrent arrhythmias. Documented case of monomorphic VT post epicardial substrate modification for VF in Brugada syndrome. Scar created by RF ablation on epicardial RVOT may contribute to re-entrant VT via incomplete ablation or iatrogenic scar mediated reentry.

Curative effect analysis of ultrasound-guided percutaneous radiofrequency ablation for caudate lobe hepatocellular carcinoma

Objective: To investigate the safety and efficacy of ultrasound-guided percutaneous radiofrequency ablation (RFA) for caudate lobe hepatocellular carcinoma (HCC) and the failure factors of incomplete tumor ablation. Methods: Twenty-four cases with caudate lobe hepatocellular carcinoma who underwent ultrasound-guided percutaneous RFA in the Affiliated Tumor Hospital of Zhengzhou University from January 2017 to October 2019 were enrolled. The ablation effect and complications conditions were recorded, and the primary technical effectiveness and local tumor progression (LTP) were evaluated. Results: Among 24 cases, 20 cases had complete ablation at one session, 4 cases had incomplete ablation, and after supplementary radiofrequency ablation all cases had achieved complete ablation. There was no evidence of local tumor progression in 24 cases after one-month postoperative evaluation. The primary technical effectiveness rate was 100%. The postoperative follow-up was 2 to 29 months (median follow-up time was 18 months). Of the 24 cases after ablation, LTP were detected in 11 cases, of which only 3 cases had distant intrahepatic recurrence, 1 case had distant intrahepatic recurrence and distant metastasis, and 5 cases had only distant metastasis, 2 cases died, and 4 cases had SIR grade B complications related to ablation. Conclusion: Ultrasound-guided percutaneous radiofrequency ablation was safe and effective for caudate lobe hepatocellular carcinoma. In addition, the distance between the tumor and the inferior vena cava < 0.5cm is a suspected risk factor for incomplete ablation of caudate lobe hepatocellular carcinoma (P < 0.05).

Long-term outcomes of CT-guided percutaneous cryoablation of T1a and T1b renal cell carcinoma

PURPOSE We aimed to evaluate the long-term outcomes of computed tomography-guided percutaneous cryoablation (PCA) for biopsy-confirmed renal cell carcinoma (RCC). METHODS This was a single-center, retrospective study investigating all patients treated with PCA between January 2010 and February 2019 for RCC tumors. Primary outcome measures included overall survival (OS), disease-free survival (DFS), progression-free survival (PFS) and cancer-specific survival (CSS). Secondary outcome measures included kidney function, complications, technical success, hospital stay, procedural time, and the identification of factors affecting the primary outcomes. RESULTS Fifty-three consecutive patients with 54 lesions (T1a: 49/54; T1b: 5/54) were included. Mean tumor diameter was 28.0±8.5 mm and mean R.E.N.A.L. score was 7.2±2.0. Technical success was 100% (54/54 lesions) after two reinterventions for incomplete ablation. Mean follow-up time was 46.7±28.6 months (range, 3-122 months). Local recurrence was noted in 5 patients (9.2%). According to Kaplan-Meyer analysis, OS was 98.2%, 94.2%, 71.2%, and 58.2% at 1, 3, 5, and 8 years. One patient (1.9%) died of cancer and CSS was 95.8% at 8 years. DFS was 100.0%, 95.5%, and 88.6%, and PFS was 100%, 94.3%, and 91.0%, at 1, 2, and 5 years. Clavien-Dindo grade II complication rate was 7.8% (5/64 procedures). There were no complications classified as grade III or greater. Mean creatinine increase was 7.1±6.3 μm/L (p = 0.31). No patient advanced to dialysis during follow up. Mean procedural time was 163±45 min. Median hospital stay was 2.0 days (IQR, 1-2.5 days). Diabetes was the only independent predictor of decreased OS (hazard ratio 4.3, 95% CI 0.043-0.914; p = 0.038). CONCLUSION PCA for stage T1a and T1b RCC provides favorable long-term oncological and renal function preservation outcomes, with acceptable complication rates.

Perivascular vital cells in the ablation center after multibipolar radiofrequency ablation in an in vivo porcine model

Multibipolar radiofrequency ablation (RFA) is an advanced ablation technique for early stage hepatocellular carcinoma and liver metastases. Vessel cooling in multibipolar RFA has not been systematically investigated. The objective of this study was to evaluate the presence of perivascular vital cells within the ablation zone after multibipolar RFA. Multibipolar RFA were performed in domestic pigs in vivo. Three internally cooled bipolar RFA applicators were used simultaneously. Three experimental settings were planned: (1) inter-applicator-distance: 15 mm; (2) inter-applicator-distance: 20 mm; (3) inter-applicator-distance: 20 mm with hepatic inflow occlusion (Pringle maneuver). A vitality staining was used to analyze liver cell vitality around all vessels in the ablation center with a diameter > 0.5 mm histologically. 771 vessels were identified. No vital tissue was seen around 423 out of 429 vessels (98.6%) situated within the central white zone. Vital cells could be observed around major hepatic vessels situated adjacent to the ablation center. Vessel diameter (> 3.0 mm; p < 0.05) and low vessel-to-ablation-center distance (< 0.2 mm; p < 0.05) were identified as risk factors for incomplete ablation adjacent to hepatic vessels. The vast majority of vessels, which were localized in the clinically relevant white zone, showed no vital perivascular cells, regardless of vessel diameter and vessel type. However, there was a risk of incomplete ablation around major hepatic vessels situated directly within the ablation center. A Pringle maneuver could avoid incomplete ablations.

P-230 Is stereotactic microwave ablation of resectable colorectal liver metastasis an alternative for liver resection in the Covid-19 pandemic?

Liver resection for resectable colorectal liver metastasis is still considered the standard local therapy. Recent studies showed no difference in overall survival between microwave ablation and resection of liver metastasis with a diameter less than 3 cm. Ablation by percutaneous approach and under CT guidance is considered less invasive than open or laparoscopic resection or ablation. On the other hand, percutaneous ablation by “free-hand” puncture is considered less accurate, potentially resulting in higher incomplete ablation and local recurrence rates.

Annular Fiber Probe for Interstitial Illumination in Photoacoustic Guidance of Radiofrequency Ablation.

Unresectable liver tumors are commonly treated with percutaneous radiofrequency ablation (RFA). However, this technique is associated with high recurrence rates due to incomplete tumor ablation. Accurate image guidance of the RFA procedure contributes to successful ablation, but currently used imaging modalities have shortcomings in device guidance and treatment monitoring. We explore the potential of using photoacoustic (PA) imaging combined with conventional ultrasound (US) imaging for real-time RFA guidance. To overcome the low penetration depth of light in tissue, we have developed an annular fiber probe (AFP), which can be inserted into tissue enabling interstitial illumination of tissue. The AFP is a cannula with 72 optical fibers that allows an RFA device to slide through its lumen, thereby enabling PA imaging for RFA device guidance and ablation monitoring. We show that the PA signal from interstitial illumination is not affected by absorber-to-surface depth compared to extracorporeal illumination. We also demonstrate successful imaging of the RFA electrodes, a blood vessel mimic, a tumor-mimicking phantom, and ablated liver tissue boundaries in ex vivo chicken and bovine liver samples. PA-assisted needle guidance revealed clear needle tip visualization, a notable improvement to current US needle guidance. Our probe shows potential for RFA device guidance and ablation detection, which potentially aids in real-time monitoring.

Covering the Cover

Covering the Cover

Value of spectral detector computed tomography for the early assessment of technique efficacy after microwave ablation of hepatocellular carcinoma.

ObjectivesTo investigate whether virtual monoenergetic images (VMI) and iodine maps derived from spectral detector computed tomography (SDCT) improve early assessment of technique efficacy in patients who underwent microwave ablation (MWA) for hepatocellular carcinoma (HCC) in liver cirrhosis.MethodsThis retrospective study comprised 39 patients with 49 HCC lesions treated with MWA. Biphasic SDCT was performed 7.7±4.0 days after ablation. Conventional images (CI), VMI and IM were reconstructed. Signal- and contrast-to-noise ratio (SNR, CNR) in the ablation zone (AZ), hyperemic rim (HR) and liver parenchyma were calculated using regions-of-interest analysis and compared between CI and VMI between 40–100 keV. Iodine concentration and perfusion ratio of HR and residual tumor (RT) were measured. Two readers evaluated subjective contrast of AZ and HR, technique efficacy (complete vs. incomplete ablation) and diagnostic confidence at determining technique efficacy.ResultsAttenuation of liver parenchyma, HR and RT, SNR of liver parenchyma and HR, CNR of AZ and HR were significantly higher in low-keV VMI compared to CI (all p<0.05). Iodine concentration and perfusion ratio differed significantly between HR and RT (all p<0.05; e.g. iodine concentration, 1.6±0.5 vs. 2.7±1.3 mg/ml). VMI50keV improved subjective AZ-to-liver contrast, HR-to-liver contrast, visualization of AZ margin and vessels adjacent to AZ compared to CI (all p<0.05). Diagnostic accuracy for detection of incomplete ablation was slightly higher in VMI50keV compared to CI (0.92 vs. 0.89), while diagnostic confidence was significantly higher in VMI50keV (p<0.05).ConclusionsSpectral detector computed tomography derived low-keV virtual monoenergetic images and iodine maps provide superior early assessment of technique efficacy of MWA in HCC compared to CI.