Voxel-based dosimetry predicting treatment response and related toxicity in HCC patients treated with resin-based Y90 radioembolization: a prospective, single-arm study.

BACKGROUND: There is an increasing body of evidence indicating Y90 dose thresholds for tumor response and treatment-related toxicity. These thresholds are poorly studied in resin Y90, particularly in hepatocellular carcinoma (HCC). PURPOSE: To evaluate the efficacy of prospective voxel-based dosimetry for predicting treatment response and adverse events (AEs) in patients with HCC undergoing resin-based Y90 radioembolization. MATERIALS AND METHODS: This correlative study was based on a prospective single-arm clinical trial (NCT04172714), which evaluated the efficacy of low/scout (555 MBq) activity of resin-based Y90 for treatment planning. Partition model was used with goal of tumor dose (TD) > 200 Gy and non-tumoral liver dose (NTLD) < 70 Gy for non-segmental therapies. Single compartment dose of 200 Gy was used for segmentectomies. Prescribed Y90 activity minus scout activity was administered for therapeutic Y90 followed by Y90-PET/CT. Sureplan® (MIM Software, Cleveland, OH) was used for dosimetry analysis. Treatment response was evaluated at 3 and 6 months. Receiver operating characteristic curve determined TD response threshold for objective response (OR) and complete response (CR) as well as non-tumor liver dose (NTLD) threshold that predicted AEs. RESULTS: N = 30 patients were treated with 33 tumors (19 segmental and 14 non-segmental). One patient died before the first imaging, and clinical follow-up was excluded from this analysis. Overall, 26 (81%) of the tumors had an OR and 23 (72%) had a CR. A mean TD of 253 Gy predicted an OR with 92% sensitivity and 83% specificity (area under the curve (AUC = 0.929, p < 0.001). A mean TD of 337 Gy predicted a CR with 83% sensitivity and 89% specificity (AUC = 0.845, p < 0.001). A mean NTLD of 81 and 87 Gy predicted grade 3 AEs with 100% sensitivity and 100% specificity in the non-segmental cohort at 3- and 6-month post Y90, respectively. CONCLUSION: In patients with HCC undergoing resin-based Y90, there are dose response and dose toxicity thresholds directly affecting outcomes. CLINICAL TRIAL NUMBER: NCT04172714.

Accuracy and Safety of Scout Dose Resin Yttrium-90 Microspheres for Radioembolization Therapy Treatment Planning: A Prospective Single-Arm Clinical Trial.

PURPOSE: To compare the accuracy and safety of 0.56 GBq resin yttrium-90 (90Y) (scout90Y) microspheres with those of technetium-99m macroaggregated albumin (MAA) in predicting the therapeutic 90Y (Rx90Y) dose for patients with hepatocellular carcinoma (HCC). MATERIALS AND METHODS: This prospective single-arm clinical trial (Clinicaltrials.gov: NCT04172714) recruited patients with HCC. Patients underwent same-day mapping with MAA and scout90Y. Rx90Y activity was administered 3 days after mapping. Using paired t test and Pearson correlation, the tumor-to-normal ratio (TNR), lung shunt fraction (LSF), predicted mean tumor dose (TD), and nontumoral liver dose (NTLD) by MAA and scout90Y were compared with those by Rx90Y. Bland-Altman plots compared the level of agreement between the TNR and LSF of scout90Y and MAA with that of Rx90Y. The safety of scout90Y was evaluated by examining the discrepancy in extrahepatic activity between MAA and scout90Y. RESULTS: Thirty patients were treated using 19 segmental and 14 nonsegmental (ie, 2 contiguous segments or nonsegmental) therapies. MAA had weak LSF, moderate TNR, and moderate TD linear correlation with Rx90Y. Scout90Y had a moderate LSF, strong TNR, strong TD, and very strong NTLD in correlation with those of Rx90Y. Furthermore, the TNR and LSF of scout90Y had a stronger agreement with those of Rx90Y than with those of MAA. In the nonsegmental subgroup, MAA had no significant correlation with the TD and NTLD of Rx90Y, whereas scout90Y had a very strong correlation with both of these factors. In the segmental subgroup, both MAA and scout90Y had a strong linear correlation with the TD and NTLD of Rx90Y. CONCLUSIONS: Compared with MAA, scout90Y is a more accurate surrogate for Rx90Y biodistribution for nonsegmental therapies.

Microwave Ablation as Bridging to Liver Transplant for Patients with Hepatocellular Carcinoma: A Single-Center Retrospective Analysis.

PURPOSE: To evaluate the efficacy and safety of microwave (MW) ablation as first-line locoregional therapy (LRT) for bridging patients with hepatocellular carcinoma (HCC) to liver transplant. MATERIALS AND METHODS: This retrospective study evaluated 88 patients who received percutaneous MW ablation for 141 tumors as first-line LRT for HCC and who were listed for liver transplantation at a single medical center between 2011 and 2019. The overall survival (OS) rate statuses after liver transplant, waitlist retention, and disease progression were evaluated using the Kaplan-Meier techniques. RESULTS: Among the 88 patients (72 men and 16 women; mean age, 60 years; Model for End-Stage Liver Disease score, 11.2) who were listed for transplant, the median waitlist time was 9.4 months (interquartile range, 5.5-18.9). Seventy-one (80.7%) patients received transplant after a median waitlist time of 8.5 months. Seventeen (19.3%) patients were removed from the waitlist; of these, 4 (4.5%) were removed because of tumors outside of the Milan criteria (HCC-specific dropout). No difference in tumor size or alpha-fetoprotein was observed in the transplanted versus nontransplanted patients at the time of ablation (2.1 vs 2.1 cm and 34.4 vs 34.7 ng/mL for transplanted vs nontransplanted, respectively; P > .05). Five (5.1%) of the 88 patients experienced adverse events after ablation; however, they all recovered. There were no cases of tract seeding. The local tumor progression (LTP) rate was 7.2%. The OS status after liver transplant at 5 years was 76.7%, and the disease-specific survival after LTP was 89.6%, with a median follow-up of 61 months for all patients. CONCLUSIONS: MW ablation appears to be safe and effective for bridging patients with HCC to liver transplant without waitlist removal from seeding, adverse events, or LTP.

Management of uncomplicated total knee arthroplasty chronic pain and stiffness utilizing cooled radiofrequency ablation: a single institution pilot study.

OBJECTIVE: The objective of this study is to introduce cooled radiofrequency ablation technical feasibility as an alternative percutaneous image-guided treatment of chronic pain and stiffness in the setting of uncomplicated total knee arthroplasty. MATERIAL AND METHOD: This retrospective pilot study includes a total of 19 consecutive patients experiencing persistent chronic pain after total knee arthroplasty, without underlying hardware complications who had failed conservative care. Patients initially underwent anesthetic blocks of the genicular nerve branches to determine C-RFA candidacy. After adequate response to the anesthetic blocks (> 50% immediate pain relief), patients were subjected to cooled radiofrequency ablations 2-3 weeks later. Treatment response was evaluated utilizing clinically validated questionnaires (KOOS, the Knee Injury and Osteoarthritis Outcome Score) and visual analog scale (VAS) to assess pain severity, stiffness, functional activities of daily living, and use of pain medication. Follow-up outcome scores were collected up to 1 year after C-RFA procedure. RESULT: A total of 21 knees were treated consecutively between 4/2019 and 1/2020 (mean age 70.5 years; 5 M:14F). The mean total KOOS score improved significantly from baseline at 35.0 ± 14.0 to 64.2 ± 14.7 at a mean of 10.2 months after treatment (p < 0.0001), with significant improvement in mean stiffness score from 44.8 ± 16.7 to 68.8 ± 20 (p < 0.0001). The mean VAS score improved significantly from baseline at 8.30 ± 1.1 to 2.45 ± 1.8 (p < 0.0001). No major complications were encountered. No patients went on to receive re-treatment, surgical revision, or other intervention. CONCLUSION: Image-guided genicular nerve cooled radiofrequency ablation offers a promising alternative in treating chronic pain/stiffness in the setting of uncomplicated TKA.

Review of Extraosseous Applications of Thermal Ablation in the Treatment of Moderate to Severe Large Joint Osteoarthritis.

Osteoarthritis (OA) is the most common joint disease worldwide, leading to significant pain, restricted range of motion, and disability. A gap exists between short- and long-term symptom-relieving therapies. Although arthroplasty is an effective treatment for symptomatic end-stage disease, most patients ultimately do not receive a joint replacement due to suboptimal surgical qualifications, comorbidities, or an aversion to surgery. The lack of additional treatment options in this setting makes opioid agonists a commonly used pharmacologic agent, contributing to the addiction epidemic that greatly afflicts our communities. Cooled radiofrequency ablation (CRFA) has arisen as a treatment modality in the setting of moderate to severe OA among patients refractory to conservative management, generally showing greater efficacy compared with other existing strategies. This review focuses on the benefits of CRFA and its technical feasibility as a management option among patients experiencing debilitating large joint OA with limited clinical options.

Robotically Assisted Sonic Therapy as a Noninvasive Nonthermal Ablation Modality: Proof of Concept in a Porcine Liver Model.

Purpose To determine the feasibility of creating a clinically relevant hepatic ablation (ie, an ablation zone capable of treating a 2-cm liver tumor) by using robotically assisted sonic therapy (RAST), a noninvasive and nonthermal focused ultrasound therapy based on histotripsy. Materials and Methods This study was approved by the institutional animal use and care committee. Ten female pigs were treated with RAST in a single session with a prescribed 3-cm spherical treatment region and immediately underwent abdominal magnetic resonance (MR) imaging. Three pigs (acute group) were sacrificed immediately following MR imaging. Seven pigs (chronic group) were survived for approximately 4 weeks and were reimaged with MR imaging immediately before sacrifice. Animals underwent necropsy and harvesting of the liver for histologic evaluation of the ablation zone. RAST ablations were performed with a 700-kHz therapy transducer. Student t tests were performed to compare prescribed versus achieved ablation diameter, difference of sphericity from 1, and change in ablation zone volume from acute to chronic imaging. Results Ablation zones had a sphericity index of 0.99 ± 0.01 (standard deviation) (P < .001 vs sphericity index of 1). Anteroposterior and transverse dimensions were not significantly different from prescribed (3.4 ± 0.7; P = .08 and 3.2 ± 0.8; P = .29, respectively). The craniocaudal dimension was significantly larger than prescribed (3.8 ± 1.1; P = .04), likely because of respiratory motion. The central ablation zone demonstrated complete cell destruction and a zone of partial necrosis. A fibrous capsule surrounded the ablation zone by 4 weeks. On 4-week follow-up images, ablation zone volumes decreased by 64% (P < .001). Conclusion RAST is capable of producing clinically relevant ablation zones in a noninvasive manner in a porcine model. © RSNA, 2018.

Safety and Efficacy of Percutaneous Microwave Hepatic Ablation Near the Heart.

PURPOSE: To evaluate safety and efficacy of percutaneous hepatic microwave (MW) ablation performed near the heart. MATERIALS AND METHODS: This study reviewed 118 consecutive peripheral (ablation zone margins within 5 mm of liver capsule) percutaneous MW hepatic ablations performed between June 2010 and August 2015. Ablation zones of 27 tumors (22.8%) extended to ≤ 5 mm from myocardium, and these ablations comprised the study group; the remaining ablations formed the control group. The study cohort included 14 men and 10 women (mean age, 59 y) with 16 hepatocellular carcinomas, 9 metastases, and 2 hemangiomas. Periprocedural imaging was used to evaluate tumor size and distance from the heart, ablation zone size, and complications. Mean tumor size and distance to myocardium were 2.6 cm ± 1.7 and 1.1 cm ± 1.1, respectively. The electronic medical record was used to retrospectively assess local tumor progression (LTP) and electrocardiogram and hemodynamic alterations during and after ablation. Statistical analysis was performed with Fisher exact test and t test. RESULTS: Median follow-up was 13.6 months (range, 1.2-38.7 months). No arrhythmias occurred during or after ablation in the follow-up period (0/27). There was no difference between groups in frequency of alterations in periprocedural blood pressure (25.9% vs 29.6%, p=0.81) or heart rate (18.5% vs 24.2%, P = .61) or rate of LTP (12.0% vs 10.8%, P = 1.0). CONCLUSIONS: Percutaneous MW ablation near the heart may be safe and effective, without increased risk of cardiac complications and with similar rates of LTP, compared with a control group of peripheral liver ablations.

Effects of Microwave Ablation on Arterial and Venous Vasculature after Treatment of Hepatocellular Carcinoma.

Purpose To characterize vessel occlusion rates and their role in local tumor progression in patients with hepatocellular carcinoma (HCC) who underwent microwave tumor ablation. Materials and Methods This institutional review board approved, HIPAA-compliant retrospective review included 95 patients (75 men and 20 women) with 124 primary HCCs who were treated at a single center between January 2011 and March 2014. Complete occlusion of the portal veins, hepatic veins, and hepatic arteries within and directly abutting the ablation zone was identified with postprocedure contrast material-enhanced computed tomography. For each vessel identified in the ablation zone, its size and antenna spacing were recorded and correlated with vascular occlusion with logistic regression analysis. Local tumor progression rates were then compared between patent and occluded vessels for each vessel type with Fisher exact test. Results Occlusion was identified in 39.7% of portal veins (29 of 73), 15.0% of hepatic veins (six of 40), and 14.2% of hepatic arteries (10 of 70) encompassed within the ablation zone. Hepatic vein occlusion was significantly correlated with a smaller vessel size (P = .036) and vessel-antenna spacing (P = .006). Portal vein occlusion was only significantly correlated with a smaller vessel size (P = .001), particularly in vessels that were less than 3 mm in diameter. Local tumor progression rates were significantly correlated with patent hepatic arteries within the ablation zone (P = .02) but not with patent hepatic (P = .57) or portal (P = .14) veins. Conclusion During microwave ablation of HCC, hepatic veins and arteries were resistant to vessel occlusion compared with portal veins, and only arterial patency within an ablation zone was related to local tumor progression. © RSNA, 2016.

Microwave Ablation for the Treatment of Hepatic Adenomas.

Microwave (MW) ablation was used to treat 12 hepatocellular adenomas in six patients (five women and one man; mean age, 39.6 y). Mean treated tumor size was 2.7 cm ± 2.0. Tumor response was evaluated with serial cross-sectional imaging for a mean follow-up of 12.6 months ± 7.1. Primary treatment effectiveness and local tumor control were 100%. There were no instances of hemorrhage, malignant transformation, new hepatic tumors, or extrahepatic metastases. This early experience of treatment of hepatic adenomas by MW ablation demonstrates it to be a safe and feasible treatment modality at short-term follow-up. Continued investigation, including comparison with other treatment modalities, is warranted.

Use of Metformin and Survival in Patients with Hepatocellular Carcinoma (HCC) Undergoing Liver Directed Therapy: Analysis of a Nationwide Cancer Registry.

BACKGROUND: Examine the association of metformin use and overall survival (OS) in patients with HCC undergoing image-guided liver-directed therapy (LDT): ablation, transarterial chemoembolization (TACE), or Yttrium-90 radioembolization (Y90 RE). METHODS: Using National Cancer Institute Surveillance, Epidemiology, and End Results registry and Medicare claims databases between 2007 and 2016, we identified patients ≥ 66 years who underwent LDT within 30 days of HCC diagnosis. Patients with liver transplant, surgical resection, and other malignancies were excluded. Metformin use was identified by at least two prescription claims within 6 months before LDT. OS was measured by time between first LDT and death or last Medicare observation. Comparisons were performed between both all and diabetic patients on and not on metformin. RESULTS: Of 2746 Medicare beneficiaries with HCC undergoing LDT, 1315 (47.9%) had diabetes or diabetes-related complications. Among all and diabetic patients, 433(15.8%) and 402 (30.6%) were on metformin respectively. Median OS was greater for patients on metformin (19.6 months, 95% CI 17.1-23.0) vs those not (16.0 months, 15.0-16.9; p = 0.0238). Patients on metformin had lower risk of death undergoing ablation (HR 0.70; 0.51-0.95; p = 0.0239) and TACE (HR 0.76, 0.66-0.87; p = 0.0001), but not Y90 RE (HR1.22, 0.89-1.69; p = 0.2231). Among diabetics, OS was greater for those on metformin vs those not (HR 0.77, 0.68-0.88; p < 0.0001). Diabetic patients on metformin had longer OS undergoing TACE (HR 0.71, 0.61-0.83; p < 0.0001), but not ablation (HR 0.74, 0.52-1.04; p = 0.0886) or Y90 RE (HR 1.26, 0.87-1.85; p = 0.2217). CONCLUSION: Metformin use is associated with improved survival in HCC patients undergoing TACE and ablation.

Correlation of Non-tumoral Liver Dose with Treatment-Related Adverse Events in Patients with Hepatocellular Carcinoma Treated with Glass-Based Yttrium-90 Radioembolization.

PURPOSE: To evaluate the relationship between non-tumor liver (NTL) dose and adverse events (AE) in patients with hepatocellular carcinoma (HCC) treated with glass-based Yttrium-90 radioembolization (Y90-RE). MATERIALS AND METHODS: A retrospective analysis of patients with HCC treated with Y90-RE between 2013 and 2018 was performed. Baseline characteristics including demographics and Y90-RE treatment approach were captured. Common Terminology Criteria for Adverse Events v5 was assessed at months 3 and 6 post-treatment. Using voxel-based dosimetry with MIM Software V. 6.9, dose-volume histograms of treated area of liver were created. Receiver operator characteristic curve was used to determine NTL dose threshold predicting AEs. Multivariate analysis was used to determine independent clinical factors of predicting severe AEs. Chi-square analysis was used to compare proportions. RESULTS: Two hundred and twenty-nine consecutive patients (115(50.2%) lobar and 114(49.8%) segmental) were included. At 3 months, there was a lower rate of any grade AE (55(46%) segmental and 36(31%) lobar, p = 0.009) and increased rate of severe AEs for lobar compared to segmental (2(2%) segmental and 9(8%) lobar, p = 0.029). At 6 months, severe AEs were greater for lobar than segmental (1(1%) segmental vs 10(9%) lobar, p = 0.005). For lobar Y90-RE, mean NTL dose of 112 Gy predicted severe AE (89% sensitivity and 91% specificity (AUC = 0.95, p = < 0.0001) at 3 and 6 months. For the segmental group, no significant association was found between NTL dose and severe treatment-related AE at 3 and 6 months. CONCLUSION: In patients with HCC undergoing glass-based lobar Y90-RE, NTL dose of > 112 Gy is associated with severe treatment-related AEs at 3-6 months.

Vertebral body osteolysis following the use of bone morphogenetic protein in spinal surgery: a mimicker of infection.

This report describes the imaging findings in three patients who developed lumbar spine osteolysis after posterior spinal fusion using rhBMP-2. These cases demonstrate the variable course of osteolysis, as well as the importance of recognizing its radiological appearances to prevent confusion with infection following spinal fusion.

Intraarterial Therapies for the Management of Hepatocellular Carcinoma.

Image-guided locoregional therapies play a crucial role in the management of patients with hepatocellular carcinoma (HCC). Transarterial therapies consist of a group of catheter-based treatments where embolic agents are delivered directly into the tumor via their supplying arteries. Some of the transarterial therapies available include bland embolization (TAE), transarterial chemoembolization (TACE), drug-eluting beads-transarterial chemoembolization (DEB-TACE), selective internal radioembolization therapy (SIRT), and hepatic artery infusion (HAI). This article provides a review of pre-procedural, intra-procedural, and post-procedural aspects of each therapy, along with a review of the literature. Newer embolotherapy options and future directions are also briefly discussed.

Evaluation of Medium-Term Efficacy of Y90 Radiation Segmentectomy vs Percutaneous Microwave Ablation in Patients with Solitary Surgically Unresectable < 4 cm Hepatocellular Carcinoma: A Propensity Score Matched Study.

OBJECTIVE: To evaluate the efficacy and safety of Y90 radiation segmentectomy (RS) vs. percutaneous microwave ablation (MWA) in patients with solitary HCC ≤ 4 cm. METHODS: From 2014 to 2017, 68 consecutive treatment naïve patients were included (34 per treatment arm). Chi-square and t-test were used to evaluate differences in baseline demographics between groups. Objective response was evaluated using mRECIST and toxicity using CTCAE. Overall survival (OS) and progression free survival (PFS) in the targeted tumor and the remainder of liver from initial treatment was calculated using Kaplan-Meier estimation. Propensity score matching was then performed with n = 24 patients matched in each group. Similar outcome analysis was then pre-formed. RESULTS: In the overall study population, both groups had similar baseline characteristics with the exception of larger lesions in the RS group. There was no difference in toxicity, objective tumor response, OS and non-target liver PFS between the MWA and RS group (p's > 0.05). In the matched cohort, the objective tumor response was 82.6% in MWA vs. 90.9%% in RS (p = 0.548). The mean OS in the MWA group (44.3 months) vs RS (59.0 months; p = 0.203). The targeted tumor mean PFS for the MWA groups was 38.6 months vs. 57.8 months in RS group (p = 0.005). There was no difference overall PFS and toxicity between the 2 matched groups. CONCLUSIONS: Our data suggest Y90 RS achieves similar tumor response and OS with a similar safety compared to MWA in the management of HCC lesions ≤ 4 cm. Additionally, targeted tumor PFS appears to be prolonged in the RS group with similar non-target liver PFS between RS and MWA group.

Predictors of Successful Yttrium-90 Radioembolization Bridging or Downstaging in Patients with Hepatocellular Carcinoma.

Purpose: This study aims to identify clinical and imaging prognosticators associated with the successful bridging or downstaging to liver transplantation (LT) in patients undergoing Yttrium-90 radioembolization (Y90-RE) for hepatocellular carcinoma (HCC). Methods: Retrospectively, patients with Y90-RE naïve HCC who were candidates or potential candidates for LT and underwent Y90-RE were included. Patients were then divided into favorable (maintained or achieved Milan criteria (MC) eligibility) or unfavorable (lost eligibility or unchanged MC ineligibility) cohorts based on changes to their MC eligibility after Y90-RE. Penalized logistic regression analysis was performed to identify the significant baseline prognosticators. Results: Between 2013 and 2018, 135 patients underwent Y90-RE treatment. Among the 59 (42%) patients within MC, LT eligibility was maintained in 49 (83%) and lost in 10 (17%) patients. Within the 76 (56%) patients outside MC, eligibility was achieved in 32 (42%) and unchanged in 44 (58%). Among the 81 (60%) patients with a favorable response, 16 (20%) went on to receive LT. Analysis of the baseline characteristics revealed that lower Albumin-Bilirubin score, lower Child-Pugh class, lower Barcelona Clinic Liver Cancer stage, HCC diagnosis using dynamic contrast-enhanced imaging on CT or MRI, normal/higher albumin levels, decreased severity of tumor burden, left lobe HCC disease, and absence of HBV-associated cirrhosis, baseline abdominal pain, or fatigue were all associated with a higher likelihood of bridging or downstaging to LT eligibility (p's < 0.05). Conclusion: Certain baseline clinical and tumor characteristics are associated with the successful bridging or downstaging of potential LT candidates with HCC undergoing Y90-RE.

Combination transarterial chemoembolization and microwave ablation improves local tumor control for 3- to 5-cm hepatocellular carcinoma when compared with transarterial chemoembolization alone.

PURPOSE: To compare transarterial chemoembolization (TACE) monotherapy to combination TACE and microwave ablation (MWA) for local control of 3- to 5-cm hepatocellular carcinoma (HCC). METHODS: Patients with HCC between 3 and 5 cm treated with TACE monotherapy or combination TACE + MWA at a single institution between 2007 and 2016 were retrospectively reviewed. Twenty-four HCCs (median diameter 3.8 cm) in 16 patients (13 males; median age 64 years) were treated using TACE monotherapy. Combination TACE + MWA was used to treat 23 HCCs (median diameter 4.2 cm) in 22 patients (18 males; median age 61 years). Microwave ablation was performed at a target time of two weeks following TACE. Individual tumors were followed by serial contrast-enhanced CT or MR. Response to treatment was evaluated on a tumor-by-tumor basis using mRECIST criteria with the primary outcome being local tumor progression (LTP). Data were analyzed using Fisher's exact test for categorical variables and Wilcoxon rank sum test for continuous variables. Time to LTP was estimated with the Kaplan-Meier method. RESULTS: Relative to TACE monotherapy, TACE + MWA provided a trend toward both a lower rate of LTP (34.8% vs. 62.5%, p = 0.11) and a higher complete response rate (65.2% vs. 37.5%; p = 0.12). Time to LTP (22.3 months vs. 4.2 months; p = 0.001) was significantly longer in the TACE + MWA group compared to TACE monotherapy. CONCLUSIONS: Combination therapy with TACE and microwave ablation improves local control and increases time to LTP for 3-5 cm HCC.

Microwave Ablation of the Lung in a Porcine Model: Vessel Diameter Predicts Pulmonary Artery Occlusion.

PURPOSE: To determine the size of pulmonary artery (PA) at risk for occlusion during percutaneous microwave ablation and to assess the effect of vessel diameter, number, and patency, on ablation zone volume. MATERIALS AND METHODS: Computed tomography (CT) fluoroscopy-guided percutaneous microwave ablations were performed in 8 pigs under general anesthesia. All ablations were performed at 65 W for 5 min with a single 17-gauge antenna positioned in the central third of the lungs. A CT pulmonary angiogram was performed immediately after the ablations. The maximum diameter, number and patency of PA branches within each ablation zone were recorded. Ablation volumes were measured at gross dissection and with CT. Student's t test was used to compare ablation zone volumes among groups. RESULTS: Twenty-one pulmonary ablations were performed. Six of the ablation zones (29%) contained at least 1 occluded PA branch. The mean diameter of the occluded PA branches in the ablation zones (2.4 mm; range, 2.0-2.8 mm) was significantly smaller than non-occluded PA branches (3.7 mm; range: 2.1-6.9 mm; p = 0.009). No PA branches ≥3 mm in size were occluded. There was no significant difference in volume of gross ablation zones that contained occluded versus non-occluded PAs (p = 0.42), one versus multiple PAs (p = 0.71), or PAs <3 mm versus ≥3 mm in diameter (p = 0.44). CONCLUSIONS: PAs ≥3 mm in size have a low risk for iatrogenic occlusion during percutaneous microwave ablation. The presence of multiple adjacent PA branches, an occluded PA branch, and a vessel diameter ≥3 mm within the ablation zone had no observed effect on ablation zone volume.

Percutaneous Microwave Ablation of Renal Angiomyolipomas.

PURPOSE: To evaluate the safety and efficacy of US-guided percutaneous microwave (MW) ablation in the treatment of renal angiomyolipoma (AML). MATERIALS AND METHODS: From January 2011 to April 2014, seven patients (5 females and 2 males; mean age 51.4) with 11 renal AMLs (9 sporadic type and 2 tuberous sclerosis associated) with a mean size of 3.4 ± 0.7 cm (range 2.4-4.9 cm) were treated with high-powered, gas-cooled percutaneous MW ablation under US guidance. Tumoral diameter, volume, and CT/MR enhancement were measured on pre-treatment, immediate post-ablation, and delayed post-ablation imaging. Clinical symptoms and creatinine were assessed on follow-up visits. RESULTS: All ablations were technically successful and no major complications were encountered. Mean ablation parameters were ablation power of 65 W (range 60-70 W), using 456 mL of hydrodissection fluid per patient, over 4.7 min (range 3-8 min). Immediate post-ablation imaging demonstrated mean tumor diameter and volume decreases of 1.8% (3.4-3.3 cm) and 1.7% (27.5-26.3 cm(3)), respectively. Delayed imaging follow-up obtained at a mean interval of 23.1 months (median 17.6; range 9-47) demonstrated mean tumor diameter and volume decreases of 29% (3.4-2.4 cm) and 47% (27.5-12.1 cm(3)), respectively. Tumoral enhancement decreased on immediate post-procedure and delayed imaging by CT/MR parameters, indicating decreased tumor vascularity. No patients required additional intervention and no patients experienced spontaneous bleeding post-ablation. CONCLUSION: Our early experience with high-powered, gas-cooled percutaneous MW ablation demonstrates it to be a safe and effective modality to devascularize and decrease the size of renal AMLs.