In vivo biocompatibility of a new hydrophobic coated Al/Al2O3 nanowire surface on stents.

BACKGROUND: Intima proliferation and in-stent restenosis is a challenging situation in interventional treatment of small vessel obstruction. Al/Al2O3 nanowires have been shown to accelerate vascular endothelial cell proliferation and migration in vitro, while suppressing vascular smooth muscle cell growth. Moreover, surface modification of Al/Al2O3 nanowires with poly[bis(2,2,2-trifluoromethoxy)phosphazene (PTFEP) coating enables further advantages such as reduced platelet adhesion. Therefore, the study's goal was to compare the biocompatibility of novel Al/Al2O3 + PTFEP coated nanowire bare-metal stents to uncoated control stents in vivo using optical coherence tomography (OCT), quantitative angiography and histomorphometric assessment. METHODS: 15 Al/Al2O3 + PTFEP coated and 19 control stents were implanted in the cervical arteries of 9 Aachen minipigs. After 90 days, in-stent stenosis, thrombogenicity, and inflammatory response were assessed. Scanning electron microscopy was used to analyse the stent surface. RESULTS: OCT analysis revealed that neointimal proliferation in Al/Al2O3 + PTFEP coated stents was significantly reduced compared to control stents. The neointimal area was 1.16 ± 0.77 mm2 in Al/Al2O3 + PTFEP coated stents vs. 1.98 ± 1.04 mm2 in control stents (p = 0.004), and the neointimal thickness was 0.28 ± 0.20 vs. 0.47 ± 0.10 (p = 0.003). Quantitative angiography showed a tendency to less neointimal growth in coated stents. Histomorphometry showed no significant difference between the two groups and revealed an apparent inflammatory reaction surrounding the stent struts. CONCLUSIONS: At long-term follow-up, Al/Al2O3 + PTFEP coated stents placed in peripheral arteries demonstrated good tolerance with no treatment-associated vascular obstruction and reduced in-stent restenosis in OCT. These preliminary in vivo findings indicate that Al/Al2O3 + PTFEP coated nanowire stents may have translational potential to be used for the prevention of in-stent restenosis.

Renal tumor segmentation, visualization, and segmentation confidence using ensembles of neural networks in patients undergoing surgical resection.

OBJECTIVES: To develop an automatic segmentation model for solid renal tumors on contrast-enhanced CTs and to visualize segmentation with associated confidence to promote clinical applicability. MATERIALS AND METHODS: The training dataset included solid renal tumor patients from two tertiary centers undergoing surgical resection and receiving CT in the corticomedullary or nephrogenic contrast media (CM) phase. Manual tumor segmentation was performed on all axial CT slices serving as reference standard for automatic segmentations. Independent testing was performed on the publicly available KiTS 2019 dataset. Ensembles of neural networks (ENN, DeepLabV3) were used for automatic renal tumor segmentation, and their performance was quantified with DICE score. ENN average foreground entropy measured segmentation confidence (binary: successful segmentation with DICE score > 0.8 versus inadequate segmentation ≤ 0.8). RESULTS: N = 639/n = 210 patients were included in the training and independent test dataset. Datasets were comparable regarding age and sex (p > 0.05), while renal tumors in the training dataset were larger and more frequently benign (p < 0.01). In the internal test dataset, the ENN model yielded a median DICE score = 0.84 (IQR: 0.62-0.97, corticomedullary) and 0.86 (IQR: 0.77-0.96, nephrogenic CM phase), and the segmentation confidence an AUC = 0.89 (sensitivity = 0.86; specificity = 0.77). In the independent test dataset, the ENN model achieved a median DICE score = 0.84 (IQR: 0.71-0.97, corticomedullary CM phase); and segmentation confidence an accuracy = 0.84 (sensitivity = 0.86 and specificity = 0.81). ENN segmentations were visualized with color-coded voxelwise tumor probabilities and thresholds superimposed on clinical CT images. CONCLUSIONS: ENN-based renal tumor segmentation robustly performs in external test data and might aid in renal tumor classification and treatment planning. CLINICAL RELEVANCE STATEMENT: Ensembles of neural networks (ENN) models could automatically segment renal tumors on routine CTs, enabling and standardizing downstream image analyses and treatment planning. Providing confidence measures and segmentation overlays on images can lower the threshold for clinical ENN implementation. KEY POINTS: Ensembles of neural networks (ENN) segmentation is visualized by color-coded voxelwise tumor probabilities and thresholds. ENN provided a high segmentation accuracy in internal testing and in an independent external test dataset. ENN models provide measures of segmentation confidence which can robustly discriminate between successful and inadequate segmentations.

Radiomics and machine learning for renal tumor subtype assessment using multiphase computed tomography in a multicenter setting.

OBJECTIVES: To distinguish histological subtypes of renal tumors using radiomic features and machine learning (ML) based on multiphase computed tomography (CT). MATERIAL AND METHODS: Patients who underwent surgical treatment for renal tumors at two tertiary centers from 2012 to 2022 were included retrospectively. Preoperative arterial (corticomedullary) and venous (nephrogenic) phase CT scans from these centers, as well as from external imaging facilities, were manually segmented, and standardized radiomic features were extracted. Following preprocessing and addressing the class imbalance, a ML algorithm based on extreme gradient boosting trees (XGB) was employed to predict renal tumor subtypes using 10-fold cross-validation. The evaluation was conducted using the multiclass area under the receiver operating characteristic curve (AUC). Algorithms were trained on data from one center and independently tested on data from the other center. RESULTS: The training cohort comprised n = 297 patients (64.3% clear cell renal cell cancer [RCC], 13.5% papillary renal cell carcinoma (pRCC), 7.4% chromophobe RCC, 9.4% oncocytomas, and 5.4% angiomyolipomas (AML)), and the testing cohort n = 121 patients (56.2%/16.5%/3.3%/21.5%/2.5%). The XGB algorithm demonstrated a diagnostic performance of AUC = 0.81/0.64/0.8 for venous/arterial/combined contrast phase CT in the training cohort, and AUC = 0.75/0.67/0.75 in the independent testing cohort. In pairwise comparisons, the lowest diagnostic accuracy was evident for the identification of oncocytomas (AUC = 0.57-0.69), and the highest for the identification of AMLs (AUC = 0.9-0.94) CONCLUSION: Radiomic feature analyses can distinguish renal tumor subtypes on routinely acquired CTs, with oncocytomas being the hardest subtype to identify. CLINICAL RELEVANCE STATEMENT: Radiomic feature analyses yield robust results for renal tumor assessment on routine CTs. Although radiologists routinely rely on arterial phase CT for renal tumor assessment and operative planning, radiomic features derived from arterial phase did not improve the accuracy of renal tumor subtype identification in our cohort.

The TOPOS study.

Background: We aimed to study the long-term safety and efficacy of oblique venous stents for post-thrombotic syndrome (PTS) with iliac vein compression. Patients and methods: In the multinational, prospective, single-arm TOPOS study, PTS patients scheduled for endovascular therapy with the sinus-Obliquus® stent and optional distal extension with the sinus-Venous® or sinus-XL Flex® stent were enrolled at eight European vascular centres between October 2016 and December 2020. The primary outcome was primary stent patency at 24 months, and secondary outcomes included the clinical course of PTS (Villalta score, revised Venous Clinical Severity Score [rVCSS], Visual Analog Scale [VAS] of pain), quality of life changes (Chronic Venous Insufficiency Quality of Life Questionnaire, CIVIQ-20), and device-related complications. Results: We enrolled 60 patients (mean age 46±15 years, 68% women, 13% active ulcers): 80% required stent extension (70% below the inguinal ligament). The primary patency rate at 24 months was 80.7% (95%CI 68.1-90.0%); it was higher in patients without vs. those with stent extension (90.9% vs. 78.3%, p=.01). Compared to baseline, the Villalta, rVCSS, pain VAS, and CIVIQ-20 decreased by a median of 8 (interquartile range (IQR): 4-11), 5 (IQR: 3-7), 3 (IQR: 2-5), and 17 (IQR: 6-22) points, respectively; p<.001 for all parameters. Overall, 9 events of acute stent occlusion, 4 symptomatic stent stenosis, and 1 pulmonary embolism occurred. We did not observe major bleeding events or contralateral thrombosis. Conclusions: Endovascular treatment with the oblique stent and optional stent extension was safe and resulted in high patency rates at 24 months. The reduction in PTS severity was substantial and persisted over 2-year follow-up.

Machine learning assisted feature identification and prediction of hemodynamic endpoints using computed tomography in patients with CTEPH.

Chronic thromboembolic pulmonary hypertension (CTEPH) is a rare but potentially curable cause of pulmonary hypertension (PH). Currently PH is diagnosed by right heart catheterisation. Computed tomography (CT) is used for ruling out other causes and operative planning. This study aims to evaluate importance of different quantitative/qualitative imaging features and develop a supervised machine learning (ML) model to predict hemodynamic risk groups. 127 Patients with diagnosed CTEPH who received preoperative right heart catheterization and thoracic CTA examinations (39 ECG-gated; 88 non-ECG gated) were included. 19 qualitative/quantitative imaging features and 3 hemodynamic parameters [mean pulmonary artery pressure, right atrial pressure (RAP), pulmonary artery oxygen saturation (PA SaO2)] were gathered. Diameter-based CT features were measured in axial and adjusted multiplane reconstructions (MPR). Univariate analysis was performed for qualitative and quantitative features. A random forest algorithm was trained on imaging features to predict hemodynamic risk groups. Feature importance was calculated for all models. Qualitative and quantitative parameters showed no significant differences between ECG and non-ECG gated CTs. Depending on reconstruction plane, five quantitative features were significantly different, but mean absolute difference between parameters (MPR vs. axial) was 0.3 mm with no difference in correlation with hemodynamic parameters. Univariate analysis showed moderate to strong correlation for multiple imaging features with hemodynamic parameters. The model achieved an AUC score of 0.82 for the mPAP based risk stratification and 0.74 for the PA SaO2 risk stratification. Contrast agent retention in hepatic vein, mosaic attenuation pattern and the ratio right atrium/left ventricle were the most important features among other parameters. Quantitative and qualitative imaging features of reconstructions correlate with hemodynamic parameters in preoperative CTEPH patients-regardless of MPR adaption. Machine learning based analysis of preoperative imaging features can be used for non-invasive risk stratification. Qualitative features seem to be more important than previously anticipated.

Feasibility of aortic aneurysm sac embolization using a novel shape memory polymer embolic device.

BACKGROUND: We investigated the feasibility of aneurysm sac embolization using a novel self-expanding porous shape memory polymer (SMP) device during endovascular aortic abdominal or thoracic aneurysm repair (EVAR). METHODS: Retrospective analysis of consecutive patients treated at 2 centers in Germany. Patients were treated from January 2019 to July 2021 with follow-up at 7 days and 3, 6, and 12 months. Aneurysm sacs were implanted with SMP devices immediately following endograft placement during the same procedure. Primary endpoint was technically successful SMP-device deployment into the aneurysm sac outside the endograft. Secondary endpoints were changes in aneurysm volume and associated complications (e.g., endoleaks). RESULTS: We included 18 patients (16 males), aged 72 ± 9 years, achieving 100% technical success. Mean preprocedure aortic aneurysm sac volume was 195 ± 117 mL with a perfused aneurysm volume of 97 ± 60 mL. A mean of 24 ± 12 SMP devices per patient were used (range 5-45, corresponding to 6.25-56.25 mL expanded embolic material volume). All evaluable patients exhibited sac regression except 2 patients yet to reach 3-month follow-up. At mean 11 ± 7 months (range 3-24), change in aneurysm volume from baseline was -30 ± 21 mL (p < 0.001). In 8 patients, aneurysm regression was observed despite type 2 endoleaks in 6 and type 1A endoleaks in 2, none of them requiring further intervention to date. No morbidity or mortality related to this treatment occurred. CONCLUSIONS: SMP devices for aortic aneurysm sac embolization during endovascular repair appear feasible and safe in this small case series. Prospective studies are needed. KEY POINTS: • Shape memory polymer is a novel, self-expanding, porous, and radiolucent embolic device material. • Aortic aneurysm sacs were treated with polymer devices immediately following endograft placement. • Aortic aneurysm sac regression was observed in all patients with over 3-month follow-up. • Aortic aneurysm sac regression was observed even in the presence of endoleaks.

[Acute interventions-dialysis shunt recanalization]. / Akute Interventionen ­ Rekanalisation von Dialyseshunts.

BACKGROUND: An arteriovenous fistula is vital for patients who need regular hemodialysis. Continuous patency and sufficient functionality determine quality of life and associated morbidity and mortality of patients. PROBLEM: Following successful hemodialysis shunt creation, intimal hyperplasia and consecutive thrombosis or complete occlusion may cause different types of shunt dysfunctionality or even critical failure. OBJECTIVE: Immediate shunt recanalization and revision by using an endovascular-first approach is crucial for long-term survival of hemodialysis fistula. There are several mechanisms available for catheter-based thrombus removal to unmask the typically underlying shunt stenosis. METHODS: Primary technical recanalization success rates are very similar for clot cleaning. Treatment of intimal hyperplasia is preferably addressed by using drug-coated balloon angioplasty to allow for increased shunt patency compared to plain old balloon angioplasty. Stents and stent grafts are only used for resistant or repeated short-term recurrence of severe stenosis. Finally, surgical revision has a classical role in case of repeated failure of endovascular measures.

Endovascular Rescue Aortic Fenestration After Accidental False Lumen TEVAR in Type B Dissection.

PURPOSE: Unintended false-lumen thoracic endovascular aortic repair (TEVAR) is under-reported and often fatal. We present percutaneous endovascular rescue techniques for true-lumen reperfusion with strategies to address the peripheral artery perfusion needs unique to each case. CASE REPORT: Two patients deteriorated 24 hours after uncomplicated and complicated acute aortic type-B dissection TEVAR treatment at a tertiary community hospital. Reevaluation of index and repeated imaging studies revealed inadvertent false-lumen TEVAR with severe visceral and peripheral ischemia. Stepwise subtraction angiography was used to confirm continuous true-lumen catheterization from femoral puncture into the thoracic aorta. Retrograde fenestration distal to the misplaced TEVAR from the true- into the false-lumen allowed for snorkeling by distal stent-extension across the dissection membrane. In one case, TEVAR stent graft extension resulted in true-lumen re-expansion and in the other case, bare-metal stent-extension for stabilization of the dissection membrane resulted in true-lumen re-expansion in addition to preservation of visceral and peripheral perfusion via the false-lumen. Despite excellent acute hemodynamic results and initial signs of recovery, both patients eventually died (multiorgan failure; cerebral hemorrhagic infarction). CONCLUSION: Correct indication and prompt recognition of potential inadvertent false-lumen stenting is critical to avoid disastrous sequelae, for example, malperfusion. Endovascular salvage is feasible for restoration of correct perfusion and must be performed in a timely manner. CLINICAL IMPACT: Clinically apparent, complicated type-B dissection necessitates instantaneous treatment. Prerequisite for an endovascular approach is a true-lumen guidewire continuously from access to the ascending aorta. DSA after TEVAR and prompt clinical re-evaluation are to verify effective visceral and peripheral restoration of blood flow. Despite these measures, inadvertent false-lumen TEVAR may occur rarely. Immediate recognition may allow for timely true-lumen re-expansion using percutaneous endovascular salvage techniques e.g. retrograde fenestration from the true- into the false-lumen for distal snorkeling of the misplaced TEVAR across the dissection membrane. However, morbidity and mortality are very high, if erroneous stent graft placement is not identified early.

Iatrogenic arterio-biliary fistula and peripheral hepatic artery pseudoaneurysm after transjugular liver biopsy: complication management using a microvascular plug.

This study aimed to report on complication management in a 58-year-old woman referred for transjugular biopsy for the evaluation of unknown liver disease. After an initial uneventful biopsy procedure, the patient complained of severe upper abdominal pain. Laboratory tests revealed increasing liver enzymes. Imaging studies depicted an iatrogenic pseudoaneurysm associated with an arterio-biliary fistula originating from the right peripheral hepatic artery. Angiography and percutaneous transarterial superselective embolotherapy was performed by means of a microcatheter and microvascular plug. Precise device positioning allowed for successful closure of the bleeding site without compromising the hepatic vasculature.

DeGIR Quality Report 2019: Report on the treatment quality of minimally invasive methods - Interventional therapy (EVAR) of abdominal aortic aneurysms. / DeGIR-Qualitätsreport 2019: Bericht über die Behandlungsqualität minimalinvasiver Methoden ­ interventionelle Therapie (EVAR) von abdominellen Aortenaneurysmen.

PURPOSE: To analyze the quality of endovascular aortic aneurysm repair using the data of the DeGIR quality management system. Comparison of data between 2011 and 2019. MATERIALS AND METHODS: A retrospective analysis of all data registered in the DeGIR quality management system of the year 2019 was performed regarding the treatment quality for endovascular aortic aneurysm repair. Registration of data was voluntary. As quality parameters indication, treatment process data and quality of results were examined. The latter was judged by treatment success, complication rates and radiation exposure. RESULTS: Out of 189 590 data sets overall 1639 cases of EVAR were registered; compared to 2011 this was an increase of 472 cases. 5.9 % of these cases encompassed emergency treatments. The most frequent indication was an abdominal aneurysm with 72 % of cases. In 54 % of cases, the aortic diameter ranged 50-70 mm. The rates for technical success, over all complications and major complications were 92.8 %, 6.7 % and 6.0 % respectively for all EVAR including emergency indications. In general, EVAR yielded a mortality rate of 1.2 % while emergency procedures had a mortality rate of 7.3 %. Median dose area product and fluoroscopy time were 10 503 cGy × cm2 and 20 minutes respectively at a mean procedure time of 114 minutes. CONCLUSION: Data analysis of the DeGIR quality management system persistently showed a very high technical success rate for endovascular aortic aneurysm repair performed by interventional radiologists accompanied by a low complication rate. KEY POINTS: · The voluntary DeGIR quality assurance-system has reached high acceptance among interventional radiologists.. · The database has nearly 200 000 submissions on record for 2019.. · EVAR by interventional radiologists has shown very high technical success as well as a low complication rate.. CITATION FORMAT: · Frenzel F, Bücker A, Paprottka P et al. DeGIR Quality Report 2019: Report on the treatment quality of minimally invasive methods - Interventional therapy (EVAR) of abdominal aortic aneurysms. Fortschr Röntgenstr 2022; 194: 49 - 61.

Acute Respiratory Distress Syndrome due to Mycoplasma pneumoniae Misinterpreted as SARS-CoV-2 Infection.

BACKGROUND: In 2020, a novel coronavirus caused a global pandemic with a clinical picture termed COVID-19, accounting for numerous cases of ARDS. However, there are still other infectious causes of ARDS that should be considered, especially as the majority of these pathogens are specifically treatable. Case Presentation. We present the case of a 36-year-old gentleman who was admitted to the hospital with flu-like symptoms, after completing a half-marathon one week before admission. As infection with SARS-CoV-2 was suspected based on radiologic imaging, the hypoxemic patient was immediately transferred to the ICU, where he developed ARDS. Empiric antimicrobial chemotherapy was initiated, the patient deteriorated further, therapy was changed, and the patient was transferred to a tertiary care ARDS center. As cold agglutinins were present, the hypothesis of an infection with SARS-CoV-2 was then questioned. Bronchoscopic sampling revealed Mycoplasma (M.) pneumoniae. When antimicrobial chemotherapy was adjusted, the patient recovered quickly. CONCLUSION: Usually, M. pneumoniae causes mild disease. When antimicrobial chemotherapy was adjusted, the patient recovered quickly. The case underlines the importance to adhere to established treatment guidelines, scrutinize treatment modalities, and not to forget other potential causes of severe pneumonia or ARDS.

Artifact quantification of venous stents in the MRI environment: Differences between braided and laser-cut designs.

PURPOSE: To quantify B0- and B1-induced imaging artifacts of braided venous stents and to compare the artifacts to a set of laser-cut stents used in venous interventions. METHODS: Three prototypes of braided venous stents with different geometries were tested in vitro. B0 field distortion maps were measured via the frequency shift Δf using multi-echo imaging. B1 distortions were quantified using the double angle method. The relative amplitudes B1rel were calculated to compare the intraluminal alteration of B1. Measurements were repeated with the stents in three different orientations: parallel, diagonal and orthogonal to B0. RESULTS: At 1.5 T, the braided stents induced a maximum frequency shift of Δfx<100Hz. Signal voids were limited to a distance of 2 mm to the stent walls at an echo time of 3 ms. No substantial difference in the B0 field distortions was seen between laser-cut and braided venous stents. B1rel maps showed strongly varying distortion patterns in the braided stents with the mean intraluminal B1rel ranging from 63±18% in prototype 1 to 98±38% in prototype 2. Compared to laser-cut stents the braided stents showed a 5 to 9 times higher coefficient of variation of the intraluminal B1rel. CONCLUSION: Braided venous stent prototypes allow for MR imaging of the intraluminal area without substantial signal voids due to B0-induced artifacts. Whereas B1 is attenuated homogeneously in laser-cut stents, the B1 distortion in braided stents is more inhomogeneous and shows areas with enhanced amplitude. This could potentially be used in braided stent designs for intraluminal signal amplification.

Endoscopic lung volume reduction coils for patients with severe emphysema-a single-centre retrospective analysis.

OBJECTIVES: Patients with chronic obstructive pulmonary disease and lung emphysema may benefit from surgical or endoscopic lung volume reduction (ELVR). Previously reported outcomes of nitinol coil-based ELVR techniques have been ambiguous. The analysis was done to analyse outcomes of ELVR with nitinol coils in patients with severe pulmonary emphysema. METHODS: From September 2013 to November 2014, our centre performed a total of 41 coil implantations on 29 patients with severe emphysema. Coils were bronchoscopically placed during general anaesthesia. Twelve out of 29 patients received staged contralateral treatments up to 112 days later to avoid bilateral pneumothorax. Lung function and 6-min walking distance were assessed 1 week prior, 1 week after as well as 6-12 months after the procedure. Patients were followed up to 48 months after ELVR and overall mortality was compared to a historic cohort. RESULTS: While coil-based ELVR led to significant short-term improvement of vital capacity (VC, +0.14 ± 0.39 l, P = 0.032) and hyperinflation (Δ residual volume/total lung capacity -2.32% ± 6.24%, P = 0.022), no significant changes were observed in 6-min walking distance or forced expiratory volume in 1 s. Benefits were short-lived, with only 15.4% and 14.3% of patients showing sustained improvements in forced expiratory volume in 1 s or residual volume after 6 months. Adverse events included haemoptysis (40%) and pneumothorax (3.4%), major complications occurred in 6.9% of cases. Overall survival without lung transplant was 63.8% after 48 months following ELVR, differing insignificantly from what BODE indices of patients would have predicted as median 4-year survival (57%) at the time of ELVR treatment. CONCLUSIONS: ELVR with coils can achieve small and short-lived benefits in lung function at the cost of major complications in a highly morbid cohort. Treatment failed to improve 4-year overall survival. ELVR coils are not worthwhile the risk for most patients with severe emphysema.

Diagnostic Performance of a Lower-dose Contrast-Enhanced 4D Dynamic MR Angiography of the Lower Extremities at 3 T Using Multisegmental Time-Resolved Maximum Intensity Projections.

BACKGROUND: For peripheral artery disease (PAD), MR angiography (MRA) is a well-established diagnostic modality providing morphologic and dynamic information comparable to digital subtraction angiography (DSA). However, relatively large amounts of contrast agents are necessary to achieve this. PURPOSE: To evaluate the diagnostic accuracy of time-resolved 4D MR-angiography with interleaved stochastic trajectories (TWIST-MRA) by using maximum intensity projections (MIPs) of dynamic images acquired with reduced doses of contrast agent. STUDY TYPE: Retrospective. POPULATION: Forty adult PAD patients yielding 1088 artery segments. FIELD STRENGTH/SEQUENCE: A 3.0 T, time-resolved 4D MR-angiography with TWIST-MRA and MIP of dynamic images. ASSESSMENT: DSA was available in 14 patients (256 artery segments) and used as reference standard. Three-segmental MIP reconstructions of TWIST-images after administration of 3 mL of gadolinium-based contrast agent (Gadoteridol/Prohance®, 0.5 M) per anatomical level (pelvis, thighs, and lower legs) yielded 256 artery segments for correlation between MRA and DSA. Three independent observers rated image quality (scale: 1 [nondiagnostic] to 4 [excellent]) and the degree of venous overlay (scale: 0 [none] to 2 [significant]) for all segments. Diagnostic accuracy for the detection of >50% stenosis and artery occlusion was calculated for all observers. STATISTICAL TESTS: Binary classification test (sensitivity, specificity, positive/negative predictive values, diagnostic accuracy). Intraclass correlation coefficients (ICCs), logistic regression analysis with comparison of areas under the receiver-operating-characteristics (ROC) curves (AUCs) with the DeLong method. Bland-Altman-comparison. RESULTS: High diagnostic performance was achieved for the detection of >50% stenosis (sensitivity 92.9% [84.3-99.9% (95%-CI)] and specificity 98.5% [95.7-99.8% (95%-CI)]) and artery occlusion (sensitivity 93.1% [77.2-99.2% (95%-CI)] and specificity 99.1% [96.9-99.9% (95%-CI)]). Inter-reader agreement was excellent with ICC values ranging from 0.95 to 1.0 for >50% artery stenosis and occlusion. Image quality was good to excellent for both readers (3.41 ± 0.72, 3.33 ± 0.65, and 3.38 ± 0.61 [mean ± SD]) with good correlation between observer ratings (ICC 0.71-0.81). No significant venous overlay was observed (0.06 ± 0.24, 0.23 ± 0.43 and 0.11 ± 0.45 [mean ± SD]). DATA CONCLUSION: MIPs of dynamic TWIST-MRA offer a promising diagnostic alternative necessitating only reduced amounts (50%) of gadolinium-based contrast agents for the entire runoff vasculature. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 2.

Safety of Catheter Embolization of Pulmonary Arteriovenous Malformations-Evaluation of Possible Cerebrovascular Embolism after Catheter Embolization of Pulmonary Arteriovenous Malformations in Patients with Hereditary Hemorrhagic Telangiectasia/Osler Disease by Pre- and Post-Interventional DWI.

BACKGROUND: This paper aimed to prospectively evaluate the safety of embolization therapy of pulmonary arteriovenous malformations (PAVMs) for the detection of cerebral infarctions by pre- and post-interventional MRI. Method One hundred and five patients (male/female = 44/61; mean age 48.6+/-15.8; range 5-86) with pre-diagnosed PAVMs on contrast-enhanced MRA underwent embolization therapy. The number of PAVMs treated in each patient ranged from 1-8 PAVMs. Depending on the size and localization of the feeding arteries, either Nester-Coils or Amplatzer vascular plugs were used for embolization therapy. cMRI was performed immediately before, and at the 4 h and 3-month post-embolization therapy. Detection of peri-interventional cerebral emboli was performed via T2w and DWI sequences using three different b-values, with calculation of ADC maps. Results Embolization did not show any post-/peri-interventional, newly developed ischemic lesions in the brain. Only one patient who underwent re-embolization and was previously treated with tungsten coils that corroded over time showed newly developed, small, diffuse emboli in the post-interventional DWI sequence. This patient already had several episodes of brain emboli before re-treatment due to the corroded coils, and during treatment, when passing the corroded coils, experienced additional small, clinically inconspicuous brain emboli. However, this complication was anticipated but accepted, since the vessel had to be occluded distally. Conclusion Catheter-based embolization of PAVMs is a safe method for treatment and does not result in clinically inconspicuous cerebral ischemia, which was not demonstrated previously.

Volume-Function Analysis (LiMAx Test) in Patients with HCC and Cirrhosis Undergoing TACE-A Feasibility Study.

BACKGROUND: Transarterial chemoembolization (TACE) is an important therapy for hepatocellular carcinoma (HCC) in cirrhosis. In particular in advanced cirrhosis, post-TACE hepatic failure liver (PTHF) failure may develop. Currently, there is no standardization for the periinterventional risk assessment. The liver maximum capacity (LiMAx) test assesses the functional liver capacity, but has not been investigated in this setting. AIMS: The aim of this study was to prospectively evaluate periinterventional LiMAx and CT volumetry measurements in patients with cirrhosis and HCC undergoing repetitive TACE. METHODS: From 06/2016 to 11/2017, eleven patients with HCC and cirrhosis undergoing TACE were included. LiMAx measurements (n = 42) were conducted before and after each TACE. Laboratory parameters were correlated with the volume-function data. RESULTS: The median LiMAx levels before (276 ± 166 µg/kg/h) were slightly reduced after TACE (251 ± 122 µg/kg/h; p = 0.08). This corresponded to a median drop of 7.1%. Notably, there was a significant correlation between LiMAx levels before TACE and bilirubin (but not albumin nor albumin-bilirubin [ALBI] score) increase after TACE (p = 0.02, k = 0.56). Furthermore, a significantly higher increase in bilirubin in patients with LiMAx ≤ 150 µg/kg/h was observed (p = 0.011). LiMAx levels at different time points in single patients were similar (p = 0.2). CONCLUSION: In our prospective pilot study in patients with HCC and cirrhosis undergoing multiple TACE, robust and reliable LiMAx measurements were demonstrated. Lower LiMAx levels before TACE were associated with surrogate markers (bilirubin) of liver failure after TACE. Specific subgroups at high risk of PTHF should be investigated. This might facilitate the future development of strategies to prevent occurrence of PTHF.

Artifacts in Contrast-Enhanced Ultrasound during Follow-up after Endovascular Aortic Repair: Impact on Endoleak Detection in Comparison with Computed Tomography Angiography.

The study described here systematically analyzed how specific artifacts in contrast-enhanced ultrasound (CEUS) can affect the detection of endoleaks during follow-up after endovascular aortic repair (EVAR). Patients undergoing EVAR of atherosclerotic or mycotic abdominal aortic aneurysms using various standard and branched stent-graft material for visceral and iliac preservation were enrolled over 5 y and followed up with computed tomography angiography (CTA) and CEUS simultaneously. CEUS artifacts were frequently identified after EVAR procedures (59% of examinations) and were caused mainly by contrast agent, different prosthesis or embolization material and postinterventional changes in the aneurysm sac. This article describes how to identify important artifacts and how to avoid false-negative or false-positive interpretations of endoleaks. Despite artifacts, CEUS had higher sensitivity for endoleak detection after EVAR than CTA. CEUS was superior to CTA in the identification of late endoleaks type II and in follow-up examinations after embolization procedures, where beam-hardening artifacts limited CTA.

Magnetic Resonance Imaging of Venous Stents at 1.5 T: Susceptibility Artifacts and Radiofrequency Shielding.

PURPOSE: The aims of this study were to assess radiofrequency (RF) shielding and susceptibility-induced imaging artifacts of venous stents with different designs at 1.5 T and to analyze the relationship between stent designs, that is, cell geometry and RF shielding. METHODS: Twelve dedicated venous stents and 1 stent used for venous pathologies with 8 different designs from 5 different manufacturers were tested: Blueflow (plus medica, Düsseldorf, Germany), Sinus Obliquus, Sinus Venous, Sinus XL (Optimed, Ettlingen, Germany), Vici (Veniti, St. Louis, MO), Zilver Vena (Cook, Bjaeverskov, Denmark), and Venovo (Bard, Tempe, AZ). Two versions with different lengths were available from all stents except the Venovo. For each stent, B1 and frequency mapping was performed using the double angle method and gradient multiecho imaging. Each stent was measured in 3 different orientations: parallel, orthogonal, and at 45 degrees to B0. A correlation analysis was performed between the induced B1 field strength inside the stents and the geometries of the cells. RESULTS: Radiofrequency shielding was found to be strongly varying between different stent designs. The 120-mm-long Vici stent showed the lowest mean relative B1 amplitude of (38% ± 16%) when oriented parallel to B0. The highest mean B1 amplitude was measured inside the 100-mm-long Blueflow stent with diagonal orientation (90% ± 20%). Averaged over all stents, the shielding was 18% stronger when the stents are oriented orthogonal to B0 compared with a parallel orientation and the between-stent variation was lower for the orthogonal orientation (11%) compared with the parallel orientation (20%). For laser-cut stents, a linear correlation was found between the amount of RF shielding and the length of individual cells measured perpendicular to the stents' long axes. The woven stents showed a strongly inhomogeneous intraluminal RF shielding pattern, whereas the laser-cut stents provided a more homogeneous shielding pattern. No substantial susceptibility-induced frequency shifts were measured near all stents with a maximum shift of [INCREMENT]f = 96 Hz measured in the vicinity of the 150-mm-long Sinus Obliquus stent. CONCLUSION: Magnetic resonance imaging in the vicinity of commercially available venous stents is feasible at 1.5 T with no substantial susceptibility-induced artifacts but reduced transmit and receive B1 field strengths inside the stents. The strength and homogeneity of the intraluminal B1 depend on the stents' fabrication (woven or laser-cut) and cell geometry.