Higher coronary artery calcium score is associated with increased risk of atrial fibrillation recurrence after catheter ablation

BackgroundCoronary artery calcium score (CACS) is associated with an increased risk of atrial fibrillation (AF) development, but scarce data are available regarding the impact on AF recurrence. This study aims to assess the impact of CACS on AF recurrence following catheter ablation.MethodsRetrospective study of patients with AF undergoing cardiac computed tomography (CCT) before ablation (2017–2019). Patients with coronary artery disease (CAD), significant valvular heart disease and previous catheter ablation were excluded. A cut-off of CACS ≥ 100 was used according to literature.ResultsA total of 311 patients were included (median age 57 [48, 64] years, 65% men and 21% with persistent AF). More than half of the patients had a CACS > 0 (52%) and 18% a CACS ≥ 100. Patients with CACS ≥ 100 were older (64 [59, 69] vs 55 [46, 63] years, p ?< ?0.001), had more frequently hypertension (68% vs 42%, p ?< ?0.001) and diabetes mellitus (21% vs 10%, p ?= ?0.020). During a median follow-up of 34 months (12–57 months), 98 patients (32%) had AF recurrence. CACS ≥ 100 was associated with increased risk of AF recurrence (unadjusted Cox regression: hazard ratio [HR] 2.0; 95% confidence interval [CI], 1.3–3.1, p ?= ?0.002). After covariate adjustment, CACS ≥ 100 and persistent AF remained independent predictors of AF recurrence (HR, 1.7; 95% CI, 1.0–2.8, p ?= ?0.039 and HR, 2.0; 95% CI, 1.3–3.2, p ?= ?0.004, respectively).ConclusionAn opportunistic evaluation of CACS could be an important tool to improve clinical care considering that CACS ≥ 100 was independently associated with a 69% increase in the risk of AF recurrence after first catheter ablation.     

CT assessment of the left atrial appendage post-transcatheter occlusion – A systematic review and meta analysis

BackgroundTransesophageal echocardiography (TEE) is the standard imaging modality used to assess the left atrial appendage (LAA) after transcatheter device occlusion. Cardiac computed tomography angiography (CCTA) offers an alternative non-invasive modality in these patients. We aimed to conduct a comparison of the two modalities.MethodsWe performed a comprehensive systematic review of the current literature pertaining to CCTA to establish its usefulness during follow-up for patients undergoing LAA device closure. Studies that reported the prevalence of inadequate LAA closure on both CCTA and TEE were further evaluated in a meta-analysis. 19 studies were used in the systematic review, and six studies were used in the meta-analysis.ResultsThe use of CCTA was associated with a higher likelihood of detecting LAA patency than the use of TEE (OR, 2.79, 95% CI 1.34–5.80, p ?= ?0.006, I² ?= ?70.4%). There was no significant difference in the prevalence of peridevice gap ≥5 ?mm (OR, 3.04, 95% CI 0.70–13.17, p ?= ?0.13, I² ?= ?0%) between the two modalities. Studies that reported LAA assessment in early and delayed phase techniques detected a 25%–50% higher prevalence of LAA patency on the delayed imaging.ConclusionCCTA can be used as an alternative to TEE for LAA assessment post occlusion. Standardized CCTA acquisition and interpretation protocols should be developed for clinical practice.     

Analysis of the anatomical features of pulmonary veins on pre-procedural cardiac CT images resulting in incomplete cryoballoon ablation for atrial fibrillation

BackgroundTo investigate the anatomical features related to the failure of cryoballoon (CB) ablation for atrial fibrillation (AF) on pre-procedural CT images.MethodsWe retrospectively analyzed CT images of 100 patients with AF who had undergone a first CB ablation at our institution between June 2016 and April 2017. We measured the angle, short- and long axis length, and the area and ovality of 4 major pulmonary vein (PV) ostium on CT images. We performed logistic regression analysis to analyze the anatomical features related to the failure (incomplete CB ablation) of PV isolation. We also performed a receiver-operating characteristic (ROC) curve analysis to identify an appropriate cut-off value for anatomical features significantly associated with incomplete CB ablation.ResultsWe analyzed 400 PVs in 100 patients [aged 64 (range, 27–82) years, 59% male]. The rate of incomplete CB ablation was significantly higher for right-than left-sided PVs (p < 0.001). The anatomical feature significantly associated with incomplete CB ablation was the angle at the right inferior PV (RIPV) (AOR: 1.17; 95% CI: 1.09–1.27, p < 0.001) and the right superior PV (RSPV) (AOR: 1.12; 95% CI: 1.01–1.23; p = 0.014). In the ROC analysis, the optimal cut-off value for RIPV and RSPV angle to discriminate an incomplete CB ablation were 40.1° and 79.7°, respectively.ConclusionOur findings may help to select the appropriate ablation strategy to treat patients with AF. We show that the angle is an anatomical feature significantly related to failed CB ablation.     

Quantification of extracellular volume with cardiac computed tomography in patients with dilated cardiomyopathy

BackgroundCardiac computed tomography (CCT) was recently validated to measure extracellular volume (ECV) in the setting of cardiac amyloidosis, showing good agreement with cardiovascular magnetic resonance (CMR). However, no evidence is available with a whole-heart single source, single energy CT scanner in the clinical context of newly diagnosed left ventricular dysfunction. Therefore, the aim of this study was to test the diagnostic accuracy of ECV_CCT in patients with a recent diagnosis of dilated cardiomyopathy, having ECV_CMR as the reference technique.Methods39 consecutive patients with newly diagnosed dilated cardiomyopathy (LVEF <50%) scheduled for clinically indicated CMR were prospectively enrolled. Myocardial segment evaluability assessment with each technique, agreement between ECV_CMR and ECV_CCT, regression analysis, Bland-Altman analysis and interclass correlation coefficient (ICC) were performed.ResultsMean age of enrolled patients was 62 ​± ​11 years, and mean LVEF at CMR was 35.4 ​± ​10.7%. Overall radiation exposure for ECV estimation was 2.1 ​± ​1.1 ​mSv. Out of 624 myocardial segments available for analysis, 624 (100%) segments were assessable by CCT while 608 (97.4%) were evaluable at CMR. ECV_CCT demonstrated slightly lower values compared to ECV_CMR (all segments, 31.8 ​± ​6.5% vs 33.9 ​± ​8.0%, p ​< ​0.001). At regression analysis, strong correlations were described (all segments, r ​= ​0.819, 95% CI: 0.791 to 0.844). On Bland-Altman analysis, bias between ECV_CMR and ECV_CCT for global analysis was 2.1 (95% CI: −6.8 to 11.1). ICC analysis showed both high intra-observer and inter-observer agreement for ECV_CCT calculation (0.986, 95%CI: 0.983 to 0.988 and 0.966, 95%CI: 0.960 to 0.971, respectively).ConclusionsECV estimation with a whole-heart single source, single energy CT scanner is feasible and accurate. Integration of ECV measurement in a comprehensive CCT evaluation of patients with newly diagnosed dilated cardiomyopathy can be performed with a small increase in overall radiation exposure.     

CT imaging with ultra-high-resolution: Opportunities for cardiovascular imaging in clinical practice

Cardiovascular computed tomography (CT) angiography has become an established alternative to invasive catheter angiography. However, imaging artifacts due to partial volume effects with current systems hinder accurate evaluation of calcified or stented segments. Increased spatial resolution may allow to overcome these barriers to precise delineation of vascular disease. Recent developments in CT hardware and reconstruction have enabled CT angiography with ultra-high spatial resolution (UHRCT). In this review we aim to describe the methods to achieve greater spatial resolution in CT that are either in clinical or preclinical stage. In addition, we provide an overview of the available clinical evidence including diagnostic accuracy studies supporting improved vascular assessment with this technology. The benefits that can be gleaned from the initial experiences with UHRCT are promising. Using UHRCT, more patients may receive non-invasive characterization of coronary atherosclerosis by overcoming the limitations of current CT spatial resolution in visualizing and quantifying calcified, stented or small diameter segments. UHRCT may potentially impact existing management pathways as well as contribute to better understanding of the underlying pathophysiology of both macro- and microvascular disease.     

State of the art paper: Cardiovascular CT for planning ventricular tachycardia ablation procedures

In the last 20 years coronary computed tomography angiography (CCTA) gained a pivotal role in the evaluation of patients with suspected coronary artery disease (CAD) as finally recognized by the ESC guidelines on stable CAD. Technological advances have progressively improved the temporal resolution of CT scanners, contemporary reducing acquisition time, radiation dose and contrast volume needed for the whole heart volume acquisition, further expanding the role of cardiac CT beyond coronary anatomy evaluation. Aim of the present review is to discuss use and benefit of cardiac CT for the planning and preparation of VT ablation.     

Ischemic ventricular tachycardia: Multimodality imaging in precision ablation guidance

Radiofrequency ablation is commonly performed in the management of incessant ventricular tachycardias. Pre-procedural planning using different imaging modalities including cardiac computed tomography and cardiac magnetic resonance plays an integral role in understanding the anatomy and potential origin of the arrhythmias to guide successful targeted ablation.     

Endobronchial Navigation Guided by Cone-Beam CT–Based Augmented Fluoroscopy without a Bronchoscope: Feasibility Study in Phantom and Swine

PurposeTo evaluate the accuracy of cone-beam computed tomography (CT)-based augmented fluoroscopy (AF) image guidance for endobronchial navigation to peripheral lung targets.MethodsPrototypic endobronchial navigation AF software that superimposed segmented airways, targets, and pathways based on cone-beam CT onto fluoroscopy images was evaluated ex vivo in fixed swine lungs and in vivo in healthy swine (n = 4) without a bronchoscope. Ex vivo and in vivo (n = 3) phase 1 experiments used guide catheters and AF software version 1, whereas in vivo phase 2 (n = 1) experiments also used an endovascular steerable guiding sheath, upgraded AF software version 2, and lung-specific low-radiation-dose protocols. First-pass navigation success was defined as catheter delivery into a targeted airway segment solely using AF, with second-pass success defined as reaching the targeted segment by using updated AF image guidance based on confirmatory cone-beam CT. Secondary outcomes were navigation error, navigation time, radiation exposure, and preliminary safety.ResultsFirst-pass success was 100% (10/10) ex vivo and 19/24 (79%) and 11/15 (73%) for in vivo phases 1 and 2, respectively. Phase 2 second-pass success was 4/4 (100%). Navigation errors were 2.2 ± 1.2 mm ex vivo and 4.9 ± 3.2 mm and 4.0 ± 2.6 mm for in vivo phases 1 and 2, respectively. No major device-related complications were observed in the in vivo experiments.ConclusionsEndobronchial navigation is feasible and accurate with cone-beam CT-based AF image guidance. AF can guide endobronchial navigation with endovascular catheters and steerable guiding sheaths to peripheral lung targets, potentially overcoming limitations associated with bronchoscopy.     

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

PurposeTo evaluate the safety and effectiveness of percutaneous image-guided thermal ablation (IGTA) for juxtacardiac lung tumors.Materials and MethodsThis 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.ResultsThe 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.ConclusionsIGTA 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.     

MR Imaging–Based In Vivo Macrophage Imaging to Monitor Immune Response after Radiofrequency Ablation of the Liver

PurposeTo establish molecular magnetic resonance (MR) imaging instruments for in vivo characterization of the immune response to hepatic radiofrequency (RF) ablation using cell-specific immunoprobes.Materials and MethodsSeventy-two C57BL/6 wild-type mice underwent standardized hepatic RF ablation (70 °C for 5 minutes) to generate a coagulation area measuring 6–7 mm in diameter. CD68⁺ macrophage periablational infiltration was characterized with immunohistochemistry 24 hours, 72 hours, 7 days, and 14 days after ablation (n = 24). Twenty-one mice were subjected to a dose-escalation study with either 10, 15, 30, or 60 mg/kg of rhodamine-labeled superparamagnetic iron oxide nanoparticles (SPIONs) or 2.4, 1.2, or 0.6 mg/kg of gadolinium-160 (¹⁶⁰Gd)-labeled CD68 antibody for assessment of the optimal in vivo dose of contrast agent. MR imaging experiments included 9 mice, each receiving 10-mg/kg SPIONs to visualize phagocytes using T2¹-weighted imaging in a horizontal-bore 9.4-T MR imaging scanner, ¹⁶⁰Gd-CD68 for T1-weighted MR imaging of macrophages, or 0.1-mmol/kg intravenous gadoterate (control group). Radiological-pathological correlation included Prussian blue staining, rhodamine immunofluorescence, imaging mass cytometry, and immunohistochemistry.ResultsRF ablation–induced periablational infiltration (206.92 μm ± 12.2) of CD68⁺ macrophages peaked at 7 days after ablation (P < .01) compared with the untreated lobe. T2¹-weighted MR imaging with SPION contrast demonstrated curvilinear T2¹ signal in the transitional zone (TZ) (186 μm ± 16.9), corresponsing to Iron Prussian blue staining. T1-weighted MR imaging with ¹⁶⁰Gd-CD68 antibody showed curvilinear signal in the TZ (164 μm ± 3.6) corresponding to imaging mass cytometry.ConclusionsBoth SPION-enhanced T2¹-weighted and ¹⁶⁰Gd-enhanced T1-weighted MR imaging allow for in vivo monitoring of macrophages after RF ablation, demonstrating the feasibility of this model to investigate local immune responses.     

Robotically-Assisted Sonic Therapy for Renal Ablation in a Live Porcine Model: Initial Preclinical Results

PurposeTo demonstrate the feasibility of Robotically Assisted Sonic Therapy (RAST)—a noninvasive and nonthermal focused ultrasound therapy based on histotripsy—for renal ablation in a live porcine model.Materials and MethodsRAST ablations (n = 11) were performed in 7 female swine: 3 evaluated at 1 week (acute) and 4 evaluated at 4 weeks (chronic). Treatment groups were acute bilateral (3 swine, 6 ablations with immediate computed tomography [CT] and sacrifice); chronic single kidney (3 swine, 3 ablations; CT at day 0, week 1, and week 4 after treatment, followed by sacrifice); and chronic bilateral (1 swine, 2 ablations). Treatments were performed using a prototype system (VortxRx; HistoSonics, Inc) and targeted a 2.5-cm-diameter sphere in the lower pole of each kidney, intentionally including the central collecting system.ResultsMean treatment time was 26.4 minutes. Ablations had a mean diameter of 2.4 ± 0.3 cm, volume of 8.5 ± 2.4 cm³_, and sphericity index of 1.00. Median ablation volume decreased by 96.1% over 4 weeks. Histology demonstrated complete lysis with residual blood products inside the ablation zone. Temporary collecting system obstruction by thrombus was observed in 4/11 kidneys (2 acute and 2 chronic) and resolved by 1 week. There were no urinary leaks, main vessel thromboses, or adjacent organ injuries on imaging or necropsy.ConclusionsIn this normal porcine model, renal RAST demonstrated complete histologic destruction of the target renal tissue while sparing the urothelium.     

Percutaneous Radiofrequency Ablation to Occlude the Thoracic Duct: Preclinical Studies in Swine for a Potential Alternative to Embolization

PurposeTo investigate the feasibility of percutaneous radiofrequency (RF) ablation to occlude the thoracic duct (TD) in a swine model with imaging and histologic correlation.Materials and MethodsSix swine underwent TD RF ablation. Two terminal (4 hours, 1 open and 1 percutaneous) and 4 survival (30 days, all percutaneous) studies were performed. Two 20-gauge needles were placed adjacent to the TD under direct visualization after right thoracotomy or under fluoroscopic guidance using a percutaneous transabdominal approach after intranodal lymphangiography. RF electrodes were advanced through the needles, and ablation was performed at 90°C for 90 seconds. Lymphangiography was performed, and the TD and adjacent structures were resected and examined microscopically at the end of each study period.ResultsFour of 6 subjects survived the planned study period and underwent follow-up lymphangiography. Two subjects in the survival group were euthanized early—1 after developing an acute chylothorax and 1 because of gastric volvulus 14 days after ablation. Occlusion of the targeted TD segment was noted on lymphangiography in 3 of the 4 remaining subjects (2 acute and 1 survival). Histology 4 hours after RF ablation demonstrated necrosis of the TD wall and hemorrhage within the lumen. Histology at 14 and 30 days revealed fibrosis with hemosiderin-laden macrophages replacing the ablated TD. Collagen degeneration within the aortic wall involving a maximum of 60% thickness was noted in 5 of the 6 subjects.ConclusionsPercutaneous RF ablation can achieve short-segment TD occlusion. Further study is needed to improve safety and demonstrate clinical efficacy in treating TD leaks.     

A Single-Institutional Comparative Analysis of Advanced Versus Standard Snare Removal of Inferior Vena Cava Filters

PurposeTo investigate differences in procedure time, radiation exposure, and periprocedural complications associated with advanced inferior vena cava (IVC) filter retrieval compared with standard snare retrieval.Materials and MethodsA total of 378 patients underwent standard or advanced IVC filter retrieval over a 5-year period. Technical success, retrieval techniques, fluoroscopy time, radiation dose, and complications were analyzed. All retrieval procedures with techniques other than a “snare-and-sheath” method were categorized as advanced, including failed standard attempts requiring intraprocedural conversion to advanced techniques.ResultsA total of 462 filter retrieval attempts were made in 378 patients (57% female). Success rates for standard and advanced retrieval attempts were 86.8% (317 of 365) and 91.8% (89 of 97), respectively. The rate of periprocedural complications was significantly higher in the advanced retrieval group (P = .006). Complication rates for standard and advanced retrievals were 0.6% (2 of 318; all minor) and 5.2% (5 of 97; 3 minor [3.1%] and 2 major [2.1%]), respectively. The 2 major complications during advanced retrievals included filter fracture and embolization. Average fluoroscopy time for advanced retrievals was significantly higher than for standard retrievals (23.1 min vs 4.3 min; P < .001). Average radiation dose for advanced retrievals was also significantly higher than for standard retrievals (557.2 mGy vs 156.9 mGy; P < .001). Use of general anesthesia was also significantly more common in advanced retrievals compared with standard retrievals (6.2% vs 0.9%; P = .002).ConclusionsAdvanced filter retrieval results in a similarly high rate of technical success compared with standard snare retrieval but is associated with greater fluoroscopy time, anesthesia requirements, and radiation exposure.     

Correlation between Post-Procedure Residual Thrombus and Clinical Outcome in Deep Vein Thrombosis Patients Receiving Pharmacomechanical Thrombolysis in a Multicenter Randomized Trial

PurposeTo evaluate relationships between immediate venographic results and clinical outcomes of pharmacomechanical catheter-directed thrombolysis (PCDT).Materials and MethodsVenograms from 317 patients with acute proximal deep vein thrombosis (DVT) who received PCDT in a multicenter randomized trial were reviewed. Quantitative thrombus resolution was assessed by independent readers using a modified Marder scale. The physician operators recorded their visual assessments of thrombus regression and venous flow. These immediate post-procedure results were correlated with patient outcomes at 1, 12, and 24 months.ResultsPCDT produced substantial thrombus removal (P < .001 for pre-PCDT vs. post-PCDT thrombus scores in all segments). At procedure end, spontaneous venous flow was present in 99% of iliofemoral venous segments and in 89% of femoral–popliteal venous segments. For the overall proximal DVT population, and for the femoral–popliteal DVT subgroup, post-PCDT thrombus volume did not correlate with 1-month or 24-month outcomes. For the iliofemoral DVT subgroup, over 1 and 24 months, symptom severity scores were higher (worse), and venous disease-specific quality of life (QOL) scores were lower (worse) in patients with greater post-PCDT thrombus volume, with the difference reaching statistical significance for the 24-month Villalta post-thrombotic syndrome (PTS) severity score (P = .0098). Post-PCDT thrombus volume did not correlate with 12-month valvular reflux.ConclusionsPCDT successfully removes thrombus in acute proximal DVT. However, the residual thrombus burden at procedure end does not correlate with the occurrence of PTS during the subsequent 24 months. In iliofemoral DVT, lower residual thrombus burden correlates with reduced PTS severity and possibly also with improved venous QOL and fewer early symptoms.     

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.     

Application of Trifluoroacetic Acid as a Theranostic Agent for Chemical Ablation of Solid Tissue

PurposeTo evaluate trifluoroacetic acid (TFA) as a theranostic chemical ablation agent and determine the efficacy of TFA for both noninvasive imaging and tissue destruction.Materials and MethodsFluorine-19 magnetic resonance imaging (¹⁹F-MRI) was optimized at 7 T using a custom-built volume coil. Fluorine images were acquired with both rapid acquisition with relaxation enhancement and balanced steady-state free precession (bSSFP) sequences with varying parameters to determine the optimal sequence for TFA. The theranostic efficacy of chemical ablation was examined by injecting TFA (100 μL; 0.25, 0.5, 1.0, and 2.0M) into ex vivo porcine liver. ¹⁹F and proton MRI were acquired and superimposed to visualize distribution of TFA in tissue and quantify sensitivity. Tissue damage was evaluated with gross examination, histology, and fluorescence microscopy.ResultsThe optimal ¹⁹F-MRI sequence was found to be bSSFP with a repetition time of 2.5 ms and flip angle of 70°. The minimum imageable TFA concentration was determined to be 6.7 ± 0.5 mM per minute of scan time (0.63×0.63×5.00 mm voxel), and real-time imaging (temporal resolution of at least 1 s^-1) was achieved with 2M TFA both in vitro and in ex vivo tissue. TFA successfully coagulated tissue, and damage was locally confined. In addition to hepatic cord disruption, cytoskeletal collapse and chromatin clumping were observed in severely damaged areas in tissues treated with 0.5M or higher TFA concentrations.ConclusionsTFA was determined to be a theranostic agent for chemical ablation of solid tissue. Ablation was both efficacious and imageable in ex vivo healthy tissue, even at low concentrations or with high temporal resolution.     

Evolution of Personalized Dosimetry for Radioembolization of Hepatocellular Carcinoma

Yttrium-90 transarterial radioembolization (TARE) has progressed from a salvage or palliative lobar or sequential bilobar regional liver therapy for patients with advanced disease to a versatile, potentially curative, and often highly selective local treatment for patients across Barcelona Clinic Liver Cancer stages. With this shift, radiation dosimetry has evolved to become more tailored to patients and target lesion(s), with treatment dose and distributions adapted for specific clinical goals (ie, palliation, bridging or downstaging to liver transplantation, converting to surgical resection candidacy, or ablative/curative intent). Data have confirmed that “personalizing” dosimetry yields real-world improvements in tumor response and overall survival while maintaining a favorable adverse event profile. In this review, imaging techniques used before, during, and after TARE have been reviewed. Historical algorithms and contemporary image-based dosimetry methods have been reviewed and compared. Finally, recent and upcoming developments in TARE methodologies and tools have been discussed.     

Vertebral Body Bone Ablation with and without a Saline-Infused System in a Porcine Model

The purpose of this study was to evaluate the effect of bone radiofrequency (RF) ablation in the spine with and without controlled saline infusion. RF ablation with and without controlled saline infusion was performed in the vertebral bodies of 2 swine with real-time temperature and impedance recordings. Histology and magnetic resonance (MR) imaging results were reviewed to evaluate the ablation zone size, breach of spinal canal, and damage to the spinal cord and nerves. There was no difference in maximum and mean temperatures between controlled saline and noninfusion groups. The impedance and power output were not significantly different between the groups. MR imaging and histopathology demonstrated ablation zones confined within the vertebral bodies. Ablation zone size correlated on MR imaging and histopathology by groups. No ablation effect, breach of posterior cortex, spinal cord injury, or nerve or ganglion injury was observed at any level using MR imaging or histology. Controlled saline infusion does not appear to impact bone RF ablation and, specifically, does not increase the ablation zone size.     

4D Flow MR Imaging to Improve Microwave Ablation Prediction Models: A Feasibility Study in an In Vivo Porcine Liver

PurposeTo characterize the effect of hepatic vessel flow using 4-dimensional (4D) flow magnetic resonance (MR) imaging and correlate their effect on microwave ablation volumes in an in vivo non-cirrhotic porcine liver model.Materials and MethodsMicrowave ablation antennas were placed under ultrasound guidance in each liver lobe of swine (n = 3 in each animal) for a total of 9 ablations. Pre- and post-ablation 4D flow MR imaging was acquired to quantify flow changes in the hepatic vasculature. Flow measurements, along with encompassed vessel size and vessel-antenna spacing, were then correlated with final ablation volume from segmented MR images.ResultsThe linear regression model demonstrated that the preablation measurement of encompassed hepatic vein size (β = –0.80 ± 0.25, 95% confidence interval [CI] –1.15 to –0.22; P = .02) was significantly correlated to final ablation zone volume. The addition of hepatic vein flow rate found via 4D flow MRI (β = –0.83 ± 0.65, 95% CI –2.50 to 0.84; P = .26), and distance from antenna to hepatic vein (β = 0.26 ± 0.26, 95% CI –0.40 to 0.92; P = .36) improved the model accuracy but not significantly so (multivariate adjusted R² = 0.70 vs univariate (vessel size) adjusted R² = 0.63, P = .24).ConclusionsHepatic vein size in an encompassed ablation zone was found to be significantly correlated with final ablation zone volume. Although the univariate 4D flow MR imaging-acquired measurements alone were not found to be statistically significant, its addition to hepatic vein size improved the accuracy of the ablation volume regression model. Pre-ablation 4D flow MR imaging of the liver may assist in prospectively optimizing thermal ablation treatment.     

Dynamic Contrast-Enhanced MR Imaging Evaluation of Perfusional Changes and Ablation Zone Size after Combination Embolization and Ablation Therapy

PurposeThe objectives of this study were to assess the utility of dynamic contrast-enhanced magnetic resonance (MR) imaging in quantifying parenchymal perfusional changes after embolization and to characterize the association between pharmacokinetic (PK) parameters and final microwave ablation volume.Materials and MethodsPK parameters from dynamic contrast-enhanced MR imaging were used to quantify perfusional changes in the liver after transarterial embolization of the right or left lobe in a swine liver model (n = 5). Each animal subject subsequently underwent microwave ablation (60 W for 5 minutes) of the embolized and nonembolized liver lobes. Changes in PK parameters from dynamic contrast-enhanced MR imaging were correlated with their respective final microwave ablation volumes in each liver lobe.ResultsMicrowave ablation volumes of embolized liver lobes were significantly larger than those of nonembolized liver lobes (28.0 mL ± 6.2 vs 15.1 mL ± 5.2, P < .001). PK perfusion parameters were significantly lower in embolized liver lobes than in nonembolized liver lobes (K^trans = 0.69 min^?1 ± 0.15 vs 1.52 min^?1 ± 0.37, P < .001; k_ep = 0.69 min^?1 ± 0.19 vs 1.54 min^?1 ± 0.42, P < .001). There was a moderate but significant correlation between normalized k_ep and ablation volume, with each unit increase in normalized k_ep corresponding to a 9.8-mL decrease in ablation volume (P = .035).ConclusionsPK-derived parameters from dynamic contrast-enhanced MR imaging can be used to quantify perfusional changes after transarterial embolization and are directly inversely correlated with final ablation volume.