Superparamagnetic iron oxide nanoparticle enhanced percutaneous microwave ablation: Ex-vivo characterization using magnetic resonance thermometry.

BACKGROUND: Percutaneous microwave ablation (pMWA) is a minimally invasive procedure that uses a microwave antenna placed at the tip of a needle to induce lethal tissue heating. It can treat cancer and other diseases with lower morbidity than conventional surgery, but one major limitation is the lack of control over the heating region around the ablation needle. Superparamagnetic iron oxide nanoparticles have the potential to enhance and control pMWA heating due to their ability to absorb microwave energy and their ease of local delivery. PURPOSE: The purpose of this study is to experimentally quantify the capabilities of FDA-approved superparamagnetic iron oxide Feraheme nanoparticles (FHNPs) to enhance and control pMWA heating. This study aims to determine the effectiveness of locally injected FHNPs in increasing the maximum temperature during pMWA and to investigate the ability of FHNPs to create a controlled ablation zone around the pMWA needle. METHODS: PMWA was performed using a clinical ablation system at 915 MHz in ex-vivo porcine liver tissues. Prior to ablation, 50 uL 5 mg/mL FHNP injections were made on one side of the pMWA needle via a 23-gauge needle. Local temperatures at the FHNP injection site were directly compared to equidistant control sites without FHNP. First, temperatures were compared using directly inserted thermocouples. Next, temperatures were measured non-invasively using magnetic resonance thermometry (MRT), which enabled comprehensive four-dimensional (volumetric and temporal) assessment of heating effects relative to nanoparticle distribution, which was quantified using dual-echo ultrashort echo time (UTE) subtraction MR imaging. Maximum heating within FHNP-exposed tissues versus control tissues were compared at multiple pMWA energy delivery settings. The ability to generate a controlled asymmetric ablation zone using multiple FHNP injections was also tested. Finally, intra-procedural MRT-derived heat maps were correlated with gold standard gross pathology using Dice similarity analysis. RESULTS: Maximum temperatures at the FHNP injection site were significantly higher than control (without FHNP) sites when measured using direct thermocouples (93.1 ± 6.0°C vs. 57.2 ± 8.1°C, p = 0.002) and using non-invasive MRT (115.6 ± 13.4°C vs. 49.0 ± 10.6°C, p = 0.02). Temperature difference between FHNP-exposed and control sites correlated with total energy deposition: 66.6 ± 17.6°C, 58.1 ± 8.5°C, and 20.8 ± 9.2°C at high (17.5 ± 2.2 kJ), medium (13.6 ± 1.8 kJ), and low (8.8 ± 1.1 kJ) energies, respectively (all pairwise p < 0.05). Each FHNP injection resulted in a nanoparticle distribution within 0.9 ± 0.2 cm radially of the injection site and a local lethal heating zone confined to within 1.1 ± 0.4 cm radially of the injection epicenter. Multiple injections enabled a controllable, asymmetric ablation zone to be generated around the ablation needle, with maximal ablation radius on the FHNP injection side of 1.6 ± 0.2 cm compared to 0.7 ± 0.2 cm on the non-FHNP side (p = 0.02). MRT intra-procedural predicted ablation zone correlated strongly with post procedure gold-standard gross pathology assessment (Dice similarity 0.9). CONCLUSIONS: Locally injected FHNPs significantly enhanced pMWA heating in liver tissues, and were able to control the ablation zone shape around a pMWA needle. MRI and MRT allowed volumetric real-time visualization of both FHNP distribution and FHNP-enhanced pMWA heating that was useful for intra-procedural monitoring. This work strongly supports further development of a FHNP-enhanced pMWA paradigm; as all individual components of this approach are approved for patient use, there is low barrier for clinical translation.

Image-guided percutaneous ablation of hepatic epithelioid hemangioendothelioma.

PURPOSE: Disease control and survival following percutaneous ablation of hepatic epithelioid hemangioendothelioma (EHE) was studied retrospectively. METHODS: Six patients underwent 16 image-guided ablation procedures to treat 35 liver tumors from 2015 to 2022 (17 microwave ablation, 9 irreversible electroporation, 8 cryoablation, and 1 radiofrequency ablation). Technical success, local progression, intrahepatic progression, distant progression, overall survival, and adverse events were assessed. RESULTS: Four of six (67%) patients were treatment naïve prior to ablation. The mean length of imaging follow-up from first ablation procedure was 43.0 ± 31.2 months. Thirty-three of 35 (94.3%) ablated tumors did not progress locally. Three of 6 patients (50%) had new intrahepatic progression and underwent repeat ablation or systemic treatment. No extrahepatic progression was observed. One patient died from EHE 2.7 years after initial diagnosis. No severe adverse events occurred. CONCLUSION: Percutaneous ablation is feasible, often in a staged fashion, and may provide favorable intermediate to long-term disease control for patients with hepatic EHE.

Motorized template for MRI-guided focal cryoablation of prostate cancer.

MR-guided focal cryoablation of prostate cancer has often been selected as a minimally-invasive treatment option. Placing multiple cryo-needles accurately to form an ablation volume that adequately covers the target volume is crucial for better oncological/functional outcomes. This paper presents an MRI-compatible system combining a motorized tilting grid template with insertion depth sensing capabilities, enabling the physician to precisely place the cryo-needles into the desired location. In vivo animal study in a swine model (3 animals) was performed to test the device performance including targeting accuracy and the procedure workflow. The study showed that the insertion depth feedback improved the 3D targeting accuracy when compared to the conventional insertion technique (7.4 mm vs. 11.2 mm, p=0.04). All three cases achieved full iceball coverage without repositioning the cryo-needles. The results demonstrate the advantages of the motorized tilting mechanism and real-time insertion depth feedback, as well as the feasibility of the proposed workflow for MRI-guided focal cryoablation of prostate cancer.

PET/CT Fluoroscopy during PET/CT-Guided Interventions: Initial Experience.

This study assessed the feasibility and functionality of the use of a high-speed image fusion technology to generate and display positron emission tomography (PET)/computed tomography (CT) fluoroscopic images during PET/CT-guided tumor ablation procedures. Thirteen patients underwent 14 PET/CT-guided ablations for the treatment of 20 tumors. A Food and Drug Administration-cleared multimodal image fusion platform received images pushed from a scanner, followed by near-real-time, nonrigid image registration. The most recent intraprocedural PET dataset was fused to each single-rotation CT fluoroscopy dataset as it arrived, and the fused images were displayed on an in-room monitor. PET/CT fluoroscopic images were generated and displayed in all procedures and enabled more confident targeting in 3 procedures. The mean lag time from CT fluoroscopic image acquisition to the in-room display of the fused PET/CT fluoroscopic image was 21 seconds ± 8. The registration accuracy was visually satisfactory in 13 of 14 procedures. In conclusion, PET/CT fluoroscopy was feasible and may have the potential to facilitate PET/CT-guided procedures.

Tumor and Ablation Margin Visibility during Cryoablation of Musculoskeletal Tumors: Comparing Intraprocedural PET/CT Images with CT-Only Images.

PURPOSE: To compare tumor and ice-ball margin visibility on intraprocedural positron emission tomography (PET)/computed tomography (CT) and CT-only images and report technical success, local tumor progression, and adverse event rates for PET/CT-guided cryoablation procedures for musculoskeletal tumors. MATERIALS AND METHODS: This Health Insurance Portability and Accountability Act (HIPAA)-compliant and institutional review board-approved retrospective study evaluated 20 PET/CT-guided cryoablation procedures performed with palliative and/or curative intent to treat 15 musculoskeletal tumors in 15 patients from 2012 to 2021. Cryoablation was performed using general anesthesia and PET/CT guidance. Procedural images were reviewed to determine the following: (a) whether the tumor borders could be fully assessed on PET/CT or CT-only images; and (b) whether tumor ice-ball margins could be fully assessed on PET/CT or CT-only images. The ability to visualize tumor borders and ice-ball margins on PET/CT images was compared with that on CT-only images. RESULTS: Tumor borders were fully assessable for 100% (20 of 20; 95% CI, 0.83-1) of procedures on PET/CT versus 20% (4 of 20; 95 CI, 0.057-0.44) of procedures on CT only (P < .001). The tumor ice-ball margin was fully assessable in 80% (16 of 20; 95% CI, 0.56-0.94) of procedures using PET/CT versus 5% (1 of 20; 95% CI, 0.0013-0.25) of procedures using CT only (P < .001). Primary technical success was achieved in 75% (15 of 20; 95% CI, 0.51-0.91) of procedures. There was local tumor progression in 23% (3/13; 95% CI, 0.050-0.54) of the treated tumors with at least 6 months of follow-up. There were 3 adverse events (1 Grade 3, 1 Grade 2, and 1 Grade 1). CONCLUSIONS: PET/CT-guided cryoablation of musculoskeletal tumors can provide superior intraprocedural visualization of the tumor and ice-ball margins compared with that provided by CT alone. Further studies are warranted to confirm the long-term efficacy and safety of this approach.

Image-Guided Ablation of Recurrent or Unresectable Intrahepatic Cholangiocarcinoma.

PURPOSE: To assess the safety and effectiveness of image-guided ablation of recurrent or unresectable intrahepatic cholangiocarcinoma (ICC). MATERIALS AND METHODS: In this retrospective study, 25 patients (14 women; age, 36-84 years) underwent 37 image-guided liver tumor ablation procedures to treat 47 ICCs (May 2004 to January 2022). At initial diagnosis, 20 patients had Stage 1 or 2 disease and 5 had Stage 3 or 4 disease. Before ablation, 19 (76.0%) of the 25 patients had progressed through prior treatments, including resection (n = 11), chemotherapy (n = 11), transarterial embolization (n = 3), or radiotherapy (n = 1); 6 (24.0%) of the 25 patients were treatment naïve. Ablation modality selection was based on patient and tumor characteristics and operator preference. Primary outcomes included local progression-free survival (LPFS) and overall survival (OS) after ablation. Statistical analysis included Kaplan-Meier (KM) survival analyses and Cox proportional hazards models. RESULTS: The mean ablated tumor size was 2.0 cm ± 1.2 (range, 0.5-5.0 cm). The 1-, 2-, and 5-year LPFS rates were 84.0% (95% CI, 72.9-96.8), 73.0% (95% CI, 59.0-90.4), and 59.5% (95% CI, 41.6-85.1), respectively. The 1-, 2-, and 5-year secondary LPFS rates were 89.5% (95% CI, 80.2-99.9), 81.9% (95% CI, 69.4-96.6), and 75.6% (95% CI, 60.2-94.9). The 1-, 2-, and 5-year LPFS rates for tumors ≤2 cm in size were all 95.8% (95% CI, 88.2-100.0). The 1-, 2-, and 5-year OS rates were 78.5% (95% CI, 63.5-97.2), 68.4% (95% CI, 51.3-91.1), and 43.5% (95% CI, 23.5-80.5). Larger tumor size was associated with decreased time to local progression (hazard ratio, 1.93; P = .012). CONCLUSIONS: Percutaneous ablation provided favorable intermediate to long-term disease control for patients with recurrent or inoperable cholangiocarcinoma.

Safety and Effectiveness of Percutaneous Image-Guided Thermal Ablation of Juxtacardiac Lung Tumors.

PURPOSE: To evaluate the safety and effectiveness of percutaneous image-guided thermal ablation (IGTA) for juxtacardiac lung tumors. MATERIALS AND METHODS: This bi-institutional retrospective cohort study included 23 consecutive patients (13 [57%] male; mean age, 55 years ± 18) with 30 juxtacardiac lung tumors located ≤10 mm from the pericardium treated in 28 IGTA sessions (25 sessions of cryoablation and 3 sessions of microwave ablation) between April 2008 and August 2022. The primary outcome was any adverse cardiac event within 90 days after ablation. Secondary outcomes included noncardiac adverse events, local tumor progression-free survival (LT-PFS), and the cumulative incidence of local tumor progression with death as a competing risk. Two tumors treated without curative intent or follow-up imaging were considered in the safety analysis but not in the progression analysis. RESULTS: The median imaging follow-up duration was 22 months (interquartile range [IQR], 10-53 months). Primary technical success was achieved in 25 (89%) ablations. No adverse cardiac events attributable to IGTA occurred. One patient experienced a phrenic nerve injury. The median LT-PFS duration was 59 months (IQR, 32-73 months). At 1, 3, and 5 years, LT-PFS was 90% (95% CI, 78%-100%), 74% (CI, 53%-100%), and 45% (CI, 20%-97%), respectively, and the cumulative incidence of local tumor progression was 4.3% (CI, 0.29%-19%), 11% (CI, 1.6%-30%), and 26% (CI, 3.3%-58%), respectively. CONCLUSIONS: IGTA is safe and effective for lung tumors located ≤10 mm from the pericardium. No adverse cardiac events were not observed within 90 days after ablation.

Positron Emission Tomography and Computed Tomography Contributions to Patient Dose and Personnel Exposure to Radiation during PET/CT-Guided Tumor Ablations.

This study sought to quantify the positron emission tomography (PET) and computed tomography (CT) components of patient radiation doses and personnel exposure to radiations during PET/CT-guided tumor ablations and assess the utility of a rolling lead shield for operator protection. Two operators performed 21 PET/CT-guided ablations behind a customized, 25-mm-thick lead shield with midchest-to-midthigh coverage. The mean patient radiation dose per procedure was 3.90 mSv ± 1.13 (11.3%) from PET and 30.51 mSv ± 19.05 (88.7%) from CT. The mean primary and secondary operator exposure outside neck-level thyroid shields was 0.05 and 0.02 mSv per procedure, respectively. The radiation exposure levels behind the rolling lead shield, inside the primary operator's thyroid shield, and on the other personnel were below the measurable threshold cumulatively over 21 procedures. The mean PET exposure level at continuous close proximity to patients was 0.02 mSv per procedure. The PET radiation doses to the patients and personnel were small. Thus, the rolling lead shield provided limited benefit.

Comparison of Percutaneous Image-Guided Microwave Ablation and Cryoablation for Sarcoma Lung Metastases: A 10-Year Experience.

BACKGROUND. To our knowledge, outcomes between percutaneous microwave ablation (MWA) and cryoablation of sarcoma lung metastases have not been compared. OBJECTIVE. The purpose of this study was to compare technical success, complications, local tumor control, and overall survival (OS) after MWA versus cryoablation of sarcoma lung metastases. METHODS. This retrospective cohort study included 27 patients (16 women, 11 men; median age, 64 years; Eastern Cooperative Oncology Group performance score, 0-2) who, from 2009 to 2021, underwent 39 percutaneous CT-guided ablation sessions (21 MWA and 18 cryoablation sessions; one to four sessions per patient) to treat 65 sarcoma lung metastases (median number of tumors per patient, one [range, one to 12]; median tumor diameter, 11.0 mm [range, 5-33 mm]; 25% of tumors were nonperipheral). We compared complications according to ablation modality by use of generalized estimating equations. We evaluated ablation modality, tumor size, and location (peripheral vs nonperipheral) in relation to local tumor progression by use of proportional Cox hazard models, with death as the competing risk. We estimated OS using the Kaplan-Meier method. RESULTS. Primary technical success was 97% for both modalities. Median follow-up was 23 months (range, one to 102 months; interquartile range, 12-44 months). A total of seven of 61 tumors (11%) showed local progression. Estimated 1-year and 2-year local control rates were, for tumors 1 cm or smaller, 97% and 95% after MWA versus 99% and 98% after cryoablation, and for tumors larger than 1 cm, 74% and 62% after MWA versus 86% and 79% after cryoablation. Tumor size of 1 cm or smaller was associated with a decreased cumulative incidence of local progression (p = .048); ablation modality and tumor location were not associated with progression (p = .86 and p = .54, respectively). Complications (Common Terminology Criteria for Adverse Events [CTCAE] grade, ≤ 3) occurred in 17 of 39 sessions (44%), prompting chest tube placement in nine (23%). There were no CTCAE grade 4 or 5 complications. OS at 1, 2, and 3 years was 100%, 89%, and 82%, respectively. CONCLUSION. High primary technical success, local control, and OS support the use of MWA and cryoablation for treating sarcoma lung metastases. Ablation modality and tumor location did not affect local progression. The rate of local tumor progression was low, especially for small tumors. No life-threatening complications occurred. CLINICAL IMPACT. Percutaneous MWA and cryoablation are both suited for the treatment of sarcoma lung metastases, especially for tumors 1 cm or smaller, whether peripheral or nonperipheral. Complications, if they occur, are not life-threatening.

Periprocedural factors associated with overall patient survival following percutaneous image-guided liver tumor cryoablation.

PURPOSE: To assess the impact of periprocedural factors, including adverse events, on overall patient survival following image-guided liver tumor cryoablation procedures. METHODS: In this retrospective single-institution study, 143 patients (73 male, 70 female, ages 29-88) underwent 169 image-guided liver tumor cryoablation procedures between October 1998 and August 2014. Patient, tumor and procedural variables were recorded. The primary outcome was overall survival post-procedure (Kaplan-Meier analysis). Secondary outcomes were the impact of 15 variables on patient survival, which were assessed with multivariate cox regression and log-rank tests. RESULTS: Mean tumor diameter was 2.5 ± 1.2 cm. 26 of 143 (18.2%) patients had primary hepatic malignancies; 117 of 143 (81.8%) had liver metastases. Survival analysis revealed survivor functions at 3, 5, 7, 10 and 12 years post-ablation of 0.54, 0.37, 0.30, 0.17 and 0.06, with mean survival time of 40.8 ± 4.9 months. Tumor size ≥4 cm (p = .018), pre-procedural platelet count <100 × 103/µL (p = .023), and prior local radiation therapy (p = .014) were associated with worse overall patient survival. Grade 3 or higher adverse events were not associated with reduced survival (p = .49). CONCLUSIONS: All variables associated with overall survival were patient-related and none were associated with the cryoablation procedure. Pre-procedural thrombocytopenia, larger tumor size and history of prior local radiation therapy were independent risk factors for reduced overall survival in patients undergoing hepatic cryoablation. Adverse events related to hepatic cryoablation were not associated with decreased survival.

Outcomes Following Percutaneous Microwave and Cryoablation of Lung Metastases from Adenoid Cystic Carcinoma of the Head and Neck: A Bi-Institutional Retrospective Cohort Study.

OBECTIVE: The aim of this study was to report outcomes following percutaneous microwave and cryoablation of lung metastases from adenoid cystic carcinoma (ACC) of the head and neck. MATERIAL AND METHODS: This bi-institutional retrospective cohort study included 10 patients (6 females, median age 59 years [range 28-81]) who underwent 32 percutaneous ablation sessions (21 cryoablation, 11 microwave) of 60 lung metastases (median 3.5 tumors per patient [range 1-16]) from 2007 to 2019. Median tumor diameter was 16 mm [range 7-40], significantly larger for cryoablation (22 mm, p = 0.002). A median of two tumors were treated per session [range 1-7]. Technical success, local control, complications, and overall survival were assessed. RESULTS: Primary technical success was achieved for 55/60 tumors (91.7%). Median follow-up was 40.6 months (clinical) and 32.5 months (imaging, per tumor). Local control at 1, 2, and 3 years was 94.7%, 80.8%, and 76.4%, respectively, and did not differ between ablation modalities. Five of fifteen recurrent tumors underwent repeat ablation, and secondary technical success was achieved in four (80%). Assisted local tumor control at 1, 2, and 3 years was 96.2%, 89.8%, and 84.9%, respectively. Complications occurred following 24/32 sessions (75.0%) and 57.2% Common Terminology Criteria for Adverse Events (CTCAE) lower than grade 3. Of 13 pneumothoraces, 7 required chest tube placements. Hemoptysis occurred after 7/21 cryoablation sessions, and bronchopleural fistula developed more frequently with microwave (p = 0.037). Median length of hospital stay was 1 day [range 0-10], and median overall survival was 81.5 months (IQR 40.4-93.1). CONCLUSION: Percutaneous computed tomography-guided microwave and cryoablation can treat lung metastases from ACC of the head and neck. Complications are common but manageable, with full recovery expected.

F-18 FDG perfusion PET: intraprocedural assessment of the liver tumor ablation margin.

PURPOSE: To evaluate 18F-fluorodeoxyglucose (FDG) perfusion PET during FDG PET/CT-guided liver tumor microwave ablation procedures for assessing the ablation margin and correlating minimum margin measurements with local progression. METHODS: This IRB-approved, HIPAA-compliant study included 20 adult patients (11 M, 9 F; mean age 65) undergoing FDG PET/CT-guided liver microwave ablation to treat 31 FDG-avid tumors. Intraprocedural FDG perfusion PET was performed to assess the ablation margin. Intraprocedural decisions regarding overlapping ablations were recorded. Two readers retrospectively interpreted intraprocedural perfusion PET and postprocedural contrast-enhanced MRI. Assessability of the ablation margin and minimum margin measurements were recorded. Imaging follow-up for local progression ranged from 30 to 574 days (mean 310). Regression modeling of minimum margin measurements was performed. Hazard ratios were calculated to correlate an ablation margin threshold of 5 mm with outcomes. RESULTS: Intraprocedural perfusion PET prompted additional overlapping ablations of two tumors, neither of which progressed. Incomplete ablation or local progression occurred in 8/31 (26%) tumors. With repeat ablation, secondary efficacy was 26 (84%) of 31. Both study readers deemed ablation margins fully assessable more often using perfusion PET than MRI (OR 69.7; CI 6.0, 806.6; p = 0.001). Minimum ablation margins ≥ 5 mm on perfusion PET correlated with a low risk of incomplete ablation/local progression by both study readers (HR 0.08 and 0.02, p < 0.001). CONCLUSION: Intraprocedural FDG perfusion PET consistently enabled complete liver tumor microwave ablation margin assessments, and the perfusion PET minimum ablation margin measurements correlated well with local outcomes. Clinical trial registration clinicaltrials.gov (NCT02018107).

Liver tumor F-18 FDG-PET before and immediately after microwave ablation enables imaging and quantification of tumor tissue contraction.

PURPOSE: Poor liver tumor visibility after microwave ablation (MWA) limits direct tumor ablation margin assessments using contrast-enhanced CT or ultrasound (US). Positron emission tomography (PET) or PET/CT may offer improved intraprocedural assessment of liver tumor ablation margins versus current imaging techniques, as 18F-fluorodeoxyglucose (18F-FDG)-avid tumors remain visible on PET immediately following ablation. The purpose of this study was to assess intraprocedural 18F-FDG PET scans before and immediately after PET/CT-guided MWA for visualization and quantification of metabolic liver tumor tissue contraction resulting from MWA. METHODS: This retrospective study, conducted at a large academic medical center after Institutional Review Board approval, included 36 patients (20 men; mean age 63 [range 37-85]) who underwent PET/CT-guided MWA of 42 18F-FDG-avid liver tumors from May 2013 to March 2018. Tumor metabolic diameters (short/long axes) were measured for each tumor on pre- and post-ablation PET images. Tumor metabolic volumes were calculated using tumor diameter measurements and compared with automated volumes using an SUV threshold algorithm. A two-tailed paired t test was used for the analyses. RESULTS: Comparing intraprocedural pre- and post-ablation PET images, mean metabolic tumor short- and long-axis diameters decreased from 21.4 to 14.9 mm [- 29%, p < 0.001, standard deviation (SD) 18%] and from 24.0 to 18.0 mm (- 24%, p < 0.001, SD 16%), respectively. The mean calculated tumor metabolic volume decreased from 10.5 to 4.6 mm3 (- 55%, p < 0.001, SD 26%). The mean automated tumor metabolic volume decreased from 10.6 to 5.8 mm3 (- 45%, p < 0.001, SD 30%). CONCLUSION: Intraprocedural PET images of 18F-FDG-avid liver tumors allow visualization and quantification of MWA-induced metabolic tumor tissue contraction during 18F-FDG PET/CT-guided procedures. The ability to visualize contracted tumor immediately post-MWA may facilitate emerging intraprocedural PET and PET/CT imaging techniques that address a clinical gap in directly assessing the ablation margin.

Aequorea's secrets revealed: New fluorescent proteins with unique properties for bioimaging and biosensing.

Using mRNA sequencing and de novo transcriptome assembly, we identified, cloned, and characterized 9 previously undiscovered fluorescent protein (FP) homologs from Aequorea victoria and a related Aequorea species, with most sequences highly divergent from A. victoria green fluorescent protein (avGFP). Among these FPs are the brightest green fluorescent protein (GFP) homolog yet characterized and a reversibly photochromic FP that responds to UV and blue light. Beyond green emitters, Aequorea species express purple- and blue-pigmented chromoproteins (CPs) with absorbances ranging from green to far-red, including 2 that are photoconvertible. X-ray crystallography revealed that Aequorea CPs contain a chemically novel chromophore with an unexpected crosslink to the main polypeptide chain. Because of the unique attributes of several of these newly discovered FPs, we expect that Aequorea will, once again, give rise to an entirely new generation of useful probes for bioimaging and biosensing.

Percutaneous CT- and MRI-guided Cryoablation of cT1 Renal Cell Carcinoma: Intermediate- to Long-term Outcomes in 307 Patients.

Background Percutaneous ablation for cT1 renal cell carcinoma (RCC) remains underused, partially because of heterogeneous and limited long-term outcomes data assessing recent cryoablation methods. Purpose To report intermediate- to long-term outcomes of image-guided percutaneous cryoablation of cT1 RCC and to compare outcomes for CT versus MRI guidance. Materials and Methods This HIPAA-compliant retrospective single-institution study assessed patients who underwent percutaneous cryoablation for solitary pathology-proven cT1 RCC between August 2000 and July 2017. Tumors (cT1a, n = 282; cT1b, n = 25; size range, 0.6-6.5 cm; median size, 2.5 cm) underwent cryoablation with CT (n = 155) or MRI (n = 152) guidance. Primary end points of overall survival (OS), disease-specific survival (DSS), imaging-confirmed disease-free survival (DFS), and local progression-free survival (LPFS) were calculated by using Kaplan-Meier analysis. Secondary end points of technique efficacy and adverse event rate were also calculated. Primary and secondary end points for CT and MRI guidance were compared by using univariable regression analysis. Results A total of 307 patients (mean age, 68 years ± 11 [standard deviation]; 192 men) were evaluated. Median clinical follow-up lasted 95 months (range, 8-219 months), and median imaging follow-up lasted 41 months (range, 0-189 months). Survival metrics at 3, 5, 10, and 15 years, respectively, included OS of 91% (95% confidence interval [CI]: 88%, 94%), 86% (95% CI: 82%, 90%), 78% (95% CI: 73%, 84%), and 76% (95% CI: 69%, 83%); DSS of 99.6% (95% CI: 99%, 100%), 99% (95% CI: 98%, 100%), 99% (95% CI: 98%, 100%), and 99% (95% CI: 98%, 100%); DFS of 94% (95% CI: 92%, 97%), 91% (95% CI: 88%, 96%), 88% (95% CI: 83%, 93%), and 88% (95% CI: 83%, 93%); and LPFS of 97% (95% CI: 94%, 99%), 95% (95% CI: 93%, 98%), 95% (95% CI: 93%, 98%), and 95% (95% CI: 93%, 98%). Survival did not significantly differ between CT and MRI guidance, with univariable Cox regression analysis hazard ratios of 0.97 (95% CI: 0.57, 1.67; P = .92) for OS, 0.63 (95% CI: 0.26, 1.52; P = .30) for DFS, and 0.83 (95% CI: 0.26, 2.74; P = .77) for LPFS. Primary and secondary technique efficacy were 96% and 99%, respectively. Overall adverse event rate was 14% (43 of 307), including 11 grade 3 events and three grade 4 events according to the Common Terminology Criteria for Adverse Events. Conclusion Percutaneous CT- and MRI-guided cryoablation of cT1 renal cell carcinoma had similar excellent intermediate- and long-term outcomes. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Georgiades in this issue.

Liver Tumor Ablation Procedure Duration and Estimated Patient Radiation Dose: Comparing Positron Emission Tomography/CT and CT Guidance.

PURPOSE: To compare procedure duration and patient radiation dose in positron emission tomography/computed tomography (PET/CT) and CT-guided liver tumor ablation procedures. MATERIALS AND METHODS: In this retrospective, case-control study, 275 patients underwent 368 image-guided ablation procedures to treat 537 tumors. Radiologists used PET/CT guidance for 117 procedures and CT guidance for 251 procedures. PET/CT-guided procedures were performed by one radiologist (C: P.B.S.). All 3 radiologists (A: J.G.S., B: a radiologist who is not an author on this article, and C: P.B.S.) performed CT-guided procedures. Potential confounders included patient demographics, clinical and tumor characteristics, and procedural variables. RESULTS: The mean duration and estimated patient radiation dose of PET/CT-guided procedures performed by radiologist C were 21.5 ± 4.9 minutes longer and 0.7 ± 2.8 mSv higher than CT-guided procedures performed by all radiologists in an unadjusted comparison. Adjusting for confounding, mean duration and estimated dose of PET/CT-guided procedures performed by radiologist C were 28.3 ± 3.8 minutes longer (P < .0001) and 6.2 ± 2.9 mSv higher (P = .03) than CT-guided procedures performed by the same radiologist. Comparing CT-guided procedures performed by all 3 radiologists, adjusted mean durations and estimated patient doses of procedures by the least experienced radiologist, radiologist A, and the second most experienced radiologist, radiologist B, were 24.2 ± 5.1 (P < .0001) and 18.1 ± 8.9 (P = .04) minutes longer and 13.1 ± 3.7 (P < .001) and 14.5 ± 6.4 (P = .02) mSv higher, respectively, than procedures performed by the most experienced radiologist, radiologist C. CONCLUSIONS: PET/CT-guided liver ablations had a slightly longer duration with slightly higher estimated patient radiation dose than similar CT-guided liver ablations. Procedure duration and patient dose do not appear to be major impediments to the emerging field of PET/CT-guided tumor ablation.

A Review of Surface Haptics: Enabling Tactile Effects on Touch Surfaces.

In this article, we review the current technology underlying surface haptics that converts passive touch surfaces to active ones (machine haptics), our perception of tactile stimuli displayed through active touch surfaces (human haptics), their potential applications (human-machine interaction), and finally, the challenges ahead of us in making them available through commercial systems. This article primarily covers the tactile interactions of human fingers or hands with surface-haptics displays by focusing on the three most popular actuation methods: vibrotactile, electrostatic, and ultrasonic.

Intraprocedural Ablation Margin Assessment by Using Ammonia Perfusion PET during FDG PET/CT-guided Liver Tumor Ablation: A Pilot Study.

Purpose To prospectively determine whether nitrogen 13 (13N) ammonia perfusion positron emission tomography (PET) during fluorine 18 fluorodeoxyglucose (FDG) PET/computed tomography (CT)-guided liver tumor ablation can be used to intraprocedurally assess ablation margins. Materials and Methods Eight patients (five women and three men; age range, 36-74 years; mean age, 57 years) were enrolled in this pilot study and underwent FDG PET/CT-guided microwave ablation of 11 FDG-avid liver metastases (mean diameter, 22 mm; range, 11-34 mm). All procedures were performed between March 2014 and December 2016. Complete ablation margin visibility and minimum ablation margin thickness were assessed by using intraprocedural 13N-ammonia perfusion PET compared with 24-hour postprocedural MR imaging by two independent blinded radiologists. Local tumor progression for each ablated tumor was assessed at follow-up imaging for 3-38 months (median, 17.6 months). Descriptive analysis was performed. Results Eleven of 11 (100%) ablation margins were fully assessable by using intraprocedural perfusion PET by both readers; six of eleven (55%) margins were fully assessable by both readers at postprocedural 24-hour MR imaging. By using perfusion PET, one tumor that had been judged by both readers to have a minimum margin of 0 mm progressed locally. No tumors judged to have a minimum margin greater than 0 mm at perfusion PET progressed locally. Conclusion 13N-ammonia perfusion PET during FDG PET/CT-guided liver tumor ablations can potentially be used to intraprocedurally assess the entire ablation margin, including the minimum margin. © RSNA, 2018.

Hepatobiliary phase MRI: impact on planning image-guided liver tumor ablations.

PURPOSE: To assess the impact of hepatobiliary phase images obtained during intravenous gadoxetate disodium-enhanced liver MRI in the planning of image-guided liver tumor ablations. METHODS: This institutional review board-approved retrospective study included 34 patients (21 men, 13 women, ages 25-80) who underwent 36 liver MRI examinations with gadoxetate disodium within 12 weeks prior to image-guided thermal ablation of 62 liver tumors during 36 procedures. Visibility of bile ducts, subdivided by branch order, on hepatobiliary phase images was compared to standard MRI sequence images by an attending abdominal radiologist and fellow. Interventional decision making (whether or not to ablate and technical plan) using hepatobiliary phase images was compared with standard MRI sequences by the ablationists. The technical success and adverse events of ablation procedures were noted. RESULTS: Bile duct visibility was significantly increased by at least one branch order in 18/36 (50%) examinations (p < 0.0001). Interventional decisions were significantly impacted in 15 (41.7%) of 36 ablation procedures (p < 0.0001), including changes to the technical plan in six (16.7%) of these procedures (p = 0.005). Technical success was achieved for 60/62 (97%) of tumors. Mild (grade 1) adverse events occurred in 4/36 (11%) procedures; no biliary complications occurred. CONCLUSIONS: Use of hepatobiliary phase images obtained during gadoxetate disodium-enhanced liver MRI impacted both when and how to perform image-guided liver tumor ablations in our practice.