33 results on '"Doppler, Michael"'
Search Results
2. Effect of Hirtisation treatment on surface quality and mechanical properties of AlSi10Mg samples produced by laser powder bed fusion
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Beevers, Emilie, Neumayer, Dominic, Bonvoisin, Benoit, Brandão, Ana, Hansal, Selma, Doppler, Michael, Rohr, Thomas, and Van Hooreweder, Brecht
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- 2024
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3. Large Language Models for Simplified Interventional Radiology Reports: A Comparative Analysis
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Can, Elif, Uller, Wibke, Vogt, Katharina, Doppler, Michael C., Busch, Felix, Bayerl, Nadine, Ellmann, Stephan, Kader, Avan, Elkilany, Aboelyazid, Makowski, Marcus R., Bressem, Keno K., and Adams, Lisa C.
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- 2024
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4. Photon-counting computed tomography of coronary and peripheral artery stents: a phantom study
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Stein, Thomas, Taron, Jana, Verloh, Niklas, Doppler, Michael, Rau, Alexander, Hagar, Muhammad Taha, Faby, Sebastian, Baltas, Dimos, Westermann, Dirk, Ayx, Isabelle, Schönberg, Stefan O., Nikolaou, Konstantin, Schlett, Christopher L., Bamberg, Fabian, and Weiss, Jakob
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- 2023
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5. Influence of microstructure and surface topography on material removal by the Hirtisation® process.
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Gunnerek, Rasmus, Soundarapandiyan, Gowtham, Christoph Doppler, Michael, Hryha, Eduard, and Klement, Uta
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SURFACE topography ,CRYSTAL grain boundaries ,SURFACE roughness ,PROCESS capability ,LASER beams - Abstract
The Hirtisation® process is an electro-chemical process, wherein the electrolyte can easily access both external and internal surfaces. The process shows promising results in both support structure removal and reduction of surface roughness, and has the potential to solve the productivity and quality trade-off in powder bed fusion – laser beam (PBF-LB) processing. In this study, the role of the microstructure and surface topography on the capability of the Hirtisation® process to lower the PBF-LB produced surface roughness, has been investigated. A detailed microstructure analysis by SEM was used to determine the effect of the Hirtisation® process on removal of sintered powder, the effects on melt pool boundaries and grain boundaries, and thus the final surface quality. The Hirtisation® process significantly reduced surface roughness thanks to the complete removal of sintering powder from the as-built surface. Additionally, preferential material removal was detected along melt pool boundaries, leading to creation of notches of up to 10 µm in depth. [ABSTRACT FROM AUTHOR]
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- 2024
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6. Stent-PTA tumorbedingter venöser Obstruktionen.
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Fingerhut, Johannes Beat, Kulka, Charlotte, Doppler, Michael, Vogt, Katharina, Uller, Wibke, and Verloh, Niklas
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- 2024
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7. Comparison of sequential CT arterioportography-arteriosplenography with standard cross-sectional imaging and endoscopy in children with portal hypertension
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Hammer, Simone, Zeman, Florian, Schlitt, Hans Jürgen, Stroszczynski, Christian, Greiner, Barbara, Doppler, Michael Christian, and Uller, Wibke
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- 2022
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8. Red and Green Laser Powder Bed Fusion of Pure Copper in Combination with Chemical Post-Processing for RF Cavity Fabrication.
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Mayerhofer, Michael, Brenner, Stefan, Dickmann, Marcel, Doppler, Michael, Gruber, Samira, Helm, Ricardo, Lopez, Elena, Maier, Verena, Mitteneder, Johannes, Neukirchen, Carsten, Nedeljkovic-Groha, Vesna, Reinarz, Bernd, Schuch, Michael, Stepien, Lukas, and Dollinger, Günther
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LINEAR accelerators ,SELECTIVE laser melting ,LASER fusion ,ELECTRON spectroscopy ,QUALITY factor - Abstract
Linear particle accelerators (Linacs) are primarily composed of radio frequency cavities (cavities). Compared to traditional manufacturing, Laser Powder Bed Fusion (L-PBF) holds the potential to fabricate cavities in a single piece, enhancing Linac performance and significantly reducing investment costs. However, the question of whether red or green laser PBF yields superior results for pure copper remains a subject of ongoing debate. Eight 4.2 GHz single-cell cavities (SCs) were manufactured from pure copper using both red and green PBF (SCs R and SCs G). Subsequently, the surface roughness of the SCs was reduced through a chemical post-processing method (Hirtisation) and annealed at 460 °C to maximize their quality factor ( Q 0 ). The geometric accuracy of the printed SCs was evaluated using optical methods and resonant frequency ( f R ) measurements. Surface conductivity was determined by measuring the quality factor ( Q 0 ) of the SCs. Laser scanning microscopy was utilized for surface roughness characterization. The impact of annealing was quantified using Energy-Dispersive X-ray Spectroscopy and Electron Backscatter Diffraction to evaluate chemical surface properties and grain size. Both the SCs R and SCs G achieved the necessary geometric accuracy and thus f R precision. The SCs R achieved a 95% Q 0 after a material removal of 40 µm. The SCs G achieved an approximately 80% Q 0 after maximum material removal of 160 µm. Annealing increased the Q 0 by an average of about 5%. The additive manufacturing process is at least equivalent to conventional manufacturing for producing cavities in the low-gradient range. The presented cavities justify the first high-gradient tests. [ABSTRACT FROM AUTHOR]
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- 2024
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9. Differentiating Well-Differentiated from Poorly-Differentiated HCC: The Potential and the Limitation of Gd-EOB-DTPA in the Presence of Liver Cirrhosis.
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Goetz, Andrea, Verloh, Niklas, Utpatel, Kirsten, Fellner, Claudia, Rennert, Janine, Einspieler, Ingo, Doppler, Michael, Luerken, Lukas, Alizadeh, Leona S., Uller, Wibke, Stroszczynski, Christian, and Haimerl, Michael
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MAGNETIC resonance imaging ,CIRRHOSIS of the liver ,CONTRAST media ,HEPATOCELLULAR carcinoma ,GADOLINIUM - Abstract
This study uses magnetic resonance imaging (MRI) to investigate the potential of the hepatospecific contrast agent gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA) in distinguishing G1- from G2/G3-differentiated hepatocellular carcinoma (HCC). Our approach involved analyzing the dynamic behavior of the contrast agent in different phases of imaging by signal intensity (SI) and lesion contrast (C), to surrounding liver parenchyma, and comparing it across distinct groups of patients differentiated based on the histopathological grading of their HCC lesions and the presence of liver cirrhosis. Our results highlighted a significant contrast between well- and poorly-differentiated lesions regarding the lesion contrast in the arterial and late arterial phases. Furthermore, the hepatobiliary phase showed limited diagnostic value in cirrhotic liver parenchyma due to altered pharmacokinetics. Ultimately, our findings underscore the potential of Gd-EOB-DTPA-enhanced MRI as a tool for improving preoperative diagnosis and treatment selection for HCC while emphasizing the need for continued research to overcome the diagnostic complexities posed by the disease. [ABSTRACT FROM AUTHOR]
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- 2024
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10. Percutaneous transcatheter aspiration of pulmonary embolism leading to diagnosis of hepatocellular carcinoma tumor embolus and change in systemic chemotherapy.
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Verloh, Niklas, Vogt, Katharina, Bettinger, Dominik, Schultheiß, Michael, Kandilaris, Kosmas, Holzner, Philipp A., Doppler, Michael C., and Uller, Wibke
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CANCER chemotherapy ,RESPIRATORY aspiration ,HEPATOCELLULAR carcinoma ,PULMONARY embolism ,DIAGNOSIS ,PULMONARY artery - Abstract
The management of metastatic hepatocellular carcinoma (HCC) is complex, particularly when complicated by pulmonary embolism. In these cases, atezolizumab-bevacizumab therapy is contraindicated due to an elevated risk of thromboembolic events. Differentiating pulmonary tumor embolism from thromboembolic disease is diagnostically challenging. This report outlines the benefit of transcatheter aspiration to obtain pathological evidence of pulmonary artery tumor embolus in anHCC patient. The intervention enabled a significant shift in the management strategy, leading to an escalation of systemic HCC therapy. This case underscores the importance of precise diagnostic techniques such as transcatheter aspiration in guiding treatment decisions, particularly in cases where pulmonary embolism may signify an underlying malignancy-driven process. [ABSTRACT FROM AUTHOR]
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- 2024
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11. Deep learning-based differentiation of peripheral high-flow and low-flow vascular malformations in T2-weighted short tau inversion recovery MRI.
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Hammer, Simone, Nunes, Danilo Weber, Hammer, Michael, Zeman, Florian, Akers, Michael, Götz, Andrea, Balla, Annika, Doppler, Michael Christian, Fellner, Claudia, Platz Batista da Silva, Natascha, Thurn, Sylvia, Verloh, Niklas, Stroszczynski, Christian, Wohlgemuth, Walter Alexander, Palm, Christoph, and Uller, Wibke
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CONVOLUTIONAL neural networks ,HUMAN abnormalities ,MAGNETIC resonance imaging ,RARE diseases - Abstract
BACKGROUND: Differentiation of high-flow from low-flow vascular malformations (VMs) is crucial for therapeutic management of this orphan disease. OBJECTIVE: A convolutional neural network (CNN) was evaluated for differentiation of peripheral vascular malformations (VMs) on T2-weighted short tau inversion recovery (STIR) MRI. METHODS: 527 MRIs (386 low-flow and 141 high-flow VMs) were randomly divided into training, validation and test set for this single-center study. 1) Results of the CNN's diagnostic performance were compared with that of two expert and four junior radiologists. 2) The influence of CNN's prediction on the radiologists' performance and diagnostic certainty was evaluated. 3) Junior radiologists' performance after self-training was compared with that of the CNN. RESULTS: Compared with the expert radiologists the CNN achieved similar accuracy (92% vs. 97%, p = 0.11), sensitivity (80% vs. 93%, p = 0.16) and specificity (97% vs. 100%, p = 0.50). In comparison to the junior radiologists, the CNN had a higher specificity and accuracy (97% vs. 80%, p < 0.001; 92% vs. 77%, p < 0.001). CNN assistance had no significant influence on their diagnostic performance and certainty. After self-training, the junior radiologists' specificity and accuracy improved and were comparable to that of the CNN. CONCLUSIONS: Diagnostic performance of the CNN for differentiating high-flow from low-flow VM was comparable to that of expert radiologists. CNN did not significantly improve the simulated daily practice of junior radiologists, self-training was more effective. [ABSTRACT FROM AUTHOR]
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- 2024
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12. Solar wind sputtering of wollastonite as a lunar analogue material – Comparisons between experiments and simulations
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Szabo, Paul S., Chiba, Rimpei, Biber, Herbert, Stadlmayr, Reinhard, Berger, Bernhard M., Mayer, Daniel, Mutzke, Andreas, Doppler, Michael, Sauer, Markus, Appenroth, Julia, Fleig, Jürgen, Foelske-Schmitz, Annette, Hutter, Herbert, Mezger, Klaus, Lammer, Helmut, Galli, André, Wurz, Peter, and Aumayr, Friedrich
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- 2018
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13. Improving Fabrication and Performance of Additively Manufactured RF Cavities by Employing Co-Printed Support Structures and Their Subsequent Removal.
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Mayerhofer, Michael, Brenner, Stefan, Doppler, Michael, Catarino, Luis, Girst, Stefanie, Nedeljkovic-Groha, Vesna, and Dollinger, Günther
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COPPER ,SURFACE roughness ,SELECTIVE laser melting ,RADIO frequency ,QUALITY factor - Abstract
The enormous potential of additive manufacturing (AM), particularly laser powder bed fusion (L-PBF), to produce radiofrequency cavities (cavities) has already been demonstrated. However, the required geometrical accuracy for GHz T M 010 cavities is currently only achieved by (a) avoiding downskin angles < 40 ∘ , which in turn leads to a cavity geometry with reduced performance, or (b) co-printed support structures, which are difficult to remove for small GHz cavities. We have developed an L-PBF-based manufacturing routine to overcome this limitation. To enable arbitrary geometries, co-printed support structures are used that are designed in such a way that they can be removed after printing by electrochemical post-processing, which simultaneously reduces the surface roughness and thus maximizes the quality factor Q 0 . The manufacturing approach is evaluated on two T M 010 single cavities printed entirely from high-purity copper. Both cavities achieve the desired resonance frequency and a Q 0 of approximately 8300. [ABSTRACT FROM AUTHOR]
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- 2024
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14. Biliary Leak after Pediatric Liver Transplantation Treated by Percutaneous Transhepatic Biliary Drainage—A Case Series.
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Doppler, Michael, Fürnstahl, Christin, Hammer, Simone, Melter, Michael, Verloh, Niklas, Schlitt, Hans Jürgen, and Uller, Wibke
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LIVER transplantation ,BILE ,LEUKOCYTE count ,LIVER enzymes ,BILE ducts ,SURVIVAL rate - Abstract
Background: Biliary leaks are a severe complication after pediatric liver transplantation (pLT), and successful management is challenging. Objectives: The aim of this case series was to assess the outcome of percutaneous transhepatic biliary drainage (PTBD) in children with bile leaks following pLT. The necessity of additional percutaneous bilioma drainage and laboratory changes during therapy and follow-up was documented. Material and Methods: All children who underwent PTBD for biliary leak following pLT were included in this consecutive retrospective single-center study and analyzed regarding site of leak, management of additional bilioma, treatment response, and patient and transplant survival. The courses of inflammation, cholestasis parameters, and liver enzymes were retrospectively reviewed. Results: Ten children underwent PTBD treatment for biliary leak after pLT. Seven patients presented with leakage at the hepaticojejunostomy, two with leakage at the choledocho-choledochostomy and one with a bile leak because of an overlooked segmental bile duct. In terms of the mean, the PTBD treatment started 40.3 ± 31.7 days after pLT. The mean duration of PTBD treatment was 109.7 ± 103.6 days. Additional percutaneous bilioma drainage was required in eight cases. Bile leak treatment was successful in all cases, and no complications occurred. The patient and transplant survival rate was 100%. CRP serum level, leukocyte count, gamma-glutamyl transferase (GGT), and total and direct bilirubin level decreased significantly during treatment with a very strong effect size. Additionally, the gamma-glutamyl transferase level showed a statistically significant reduction during follow-up. Conclusions: PTBD is a very successful strategy for bile leak therapy after pLT. [ABSTRACT FROM AUTHOR]
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- 2023
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15. Diagnostic Accuracy of Indocyanine Green Clearance Test for Different Stages of Liver Fibrosis and Cirrhosis.
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Luerken, Lukas, Dollinger, Marco, Goetz, Andrea, Utpatel, Kirstin, Doppler, Michael Christian, Weiss, Jakob Benedikt, Uller, Wibke, Ignee, André, Verloh, Niklas, and Haimerl, Michael
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HEPATIC fibrosis ,CIRRHOSIS of the liver ,INDOCYANINE green ,NONINVASIVE diagnostic tests ,MANN Whitney U Test - Abstract
(1) Background: This study aimed to correlate the indocyanine green clearance (ICG) test with histopathological grades of liver fibrosis and liver cirrhosis to assess its diagnostic accuracy in differentiating normal liver parenchyma from liver fibrosis and liver cirrhosis. (2) Methods: A total of 82 patients who received a histopathological liver examination, imaging, and ICG test within three months were included in this retrospective study. The histopathological level of fibrosis was graded using the Ishak scoring system, and the patients were divided into five categories: no liver fibrosis (NLF), mild liver fibrosis (MLF), advanced liver fibrosis (ALF), severe liver fibrosis (SLF), and liver cirrhosis (LC). The non-parametric Kruskal–Wallis test with post hoc pairwise comparison utilizing Mann–Whitney U tests and Bonferroni adjustment was used to analyze differences in the ICG test results between the patient groups. Cross correlation between the individual fibrosis/cirrhosis stages and the score of the ICG test was performed, and the sensitivity, specificity, and positive and negative predictive values were calculated for each model predicting liver fibrosis/cirrhosis. (3) Results: A significant difference (p ≤ 0.001) between stages of NLF, LF, and LC was found for the ICG parameters (ICG plasma disappearance rate (ICG-PDR) and ICG retention percentage at 15 min (ICG-R15)). The post hoc analysis revealed that NLF significantly differed from SLF (ICG-PDR: p = 0.001; ICG-R15: p = 0.001) and LC (ICG-PDR: p = 0.001; ICG-R15: p = 0.001). ALF also significantly differed from SLF (ICG-PDR: p = 0.033; ICG-R15: p = 0.034) and LC (ICG-PDR: p = 0.014; ICG-R15: p = 0.014). The sensitivity for detection of an initial stage of liver fibrosis compared to no liver fibrosis (Ishak ≥ 1) was 0.40; the corresponding specificity was 0.80. The differentiation of advanced liver fibrosis or cirrhosis (Ishak ≥ 4) compared to other stages of liver fibrosis was 0.75, with a specificity of 0.81. (4) Conclusions: This study shows that the ICG test, as a non-invasive diagnostic test, is able to differentiate patients with no liver fibrosis from patients with advanced liver fibrosis and liver cirrhosis. The ICG test seems to be helpful in monitoring patients with liver fibrosis regarding compensation levels, thus potentially enabling physicians to both detect progression from compensated liver fibrosis to advanced liver fibrosis and cirrhosis and to initiate antifibrotic treatment at an earlier stage. [ABSTRACT FROM AUTHOR]
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- 2023
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16. Predictive Value of [ 99m Tc]-MAA-Based Dosimetry in Hepatocellular Carcinoma Patients Treated with [ 90 Y]-TARE: A Single-Center Experience.
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Doppler, Michael, Reincke, Marlene, Bettinger, Dominik, Vogt, Katharina, Weiss, Jakob, Schultheiss, Michael, Uller, Wibke, Verloh, Niklas, and Goetz, Christian
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MEDICAL dosimetry , *PATIENT portals , *PORTAL vein , *OVERALL survival , *LIVER tumors - Abstract
Transarterial radioembolization is a well-established method for the treatment of hepatocellular carcinoma. The tolerability and incidence of hepatic decompensation are related to the doses delivered to the tumor and healthy liver. This retrospective study was performed at our center to evaluate whether tumor- and healthy-liver-absorbed dose levels in TARE are predictive of tumor response according to the mRECIST 1.1 criteria and overall survival. One hundred and six patients with hepatocellular carcinoma were treated with [90Y]-loaded resin microspheres and completed the follow-up. The dose delivered to each compartment was calculated using a compartmental model. The model was based on [99mTc]-labelled albumin aggregate images obtained before the start of therapy. Tumor response was assessed after three months of treatment. Kaplan-Meier analysis was used to assess survival. The mean age of our population was 66 ± 13 years with a majority being BCLC B tumors. Forty-two patients presented with portal vein thrombosis. The response rate was 57% in the overall population and 59% in patients with thrombosis. Target-to-background (TBR) values measured on initial [99mTc]MAA-SPECT-imaging and tumor model dosimetric values were associated with tumor response (p < 0.001 and p = 0.009, respectively). A dosimetric threshold of 136.5 Gy was predictive of tumor response with a sensitivity of 84.2% and specificity of 89.4%. Overall survival was 24.1 months [IQR 13.1–36.4] for patients who responded to treatment compared to 10.4 months [IQR 6.3–15.9] for the remaining patients (p = 0.022). In this cohort, the initial [99mTc]MAA imaging is predictive of response and survival. The dosimetry prior to the application of TARE can be used for treatment planning and our results also suggest that the therapy is well-tolerated. In particular, hepatic decompensation can be predicted even in the presence of PVT. [ABSTRACT FROM AUTHOR]
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- 2023
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17. Interventional Management of Vascular Complications after Renal Transplantation.
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Verloh, Niklas, Doppler, Michael, Hagar, Muhammad Taha, Kulka, Charlotte, von Krüchten, Ricarda, Neubauer, Jakob, Weiß, Jakob, Röthele, Elvira, Schneider, Johanna, Jänigen, Bernd, and Uller, Wibke
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- 2023
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18. Stereotactic Microwave Ablation of Hepatocellular Carcinoma: The Impact of Tumor Size and Minimal Ablative Margin on Therapeutic Success.
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Pausch, Antonia-Maria, Ghali, Tamam, Wertheimer, Tobias, Zeman, Florian, Mueller, Karolina, Doppler, Michael Christian, Einspieler, Ingo, Beyer, Lukas Philipp, Schleder, Stephan, Stroszczynski, Christian, and Luerken, Lukas
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HEPATOCELLULAR carcinoma ,COSMIC background radiation ,MICROWAVES ,PROGRESSION-free survival - Abstract
Background: Microwave ablation (MWA) has gained relevance in the treatment of hepatic malignancies and especially in hepatocellular carcinoma (HCC), and it is an important alternative to surgery. The purpose of the study was to evaluate whether the minimal ablative margin (MAM) or the initial tumor size has a greater effect on the success of stereotactic MWA of HCC regarding the time to local tumor progression (LTP) and overall survival (OS). Methods: 88 patients, who received stereotactic MWA of 127 tumor lesions with a curative intention were included in this single-center, retrospective study. The MAM was evaluated in a side-by-side comparison of pre- and post-ablative, contrast-enhanced slice imaging. A Cox proportional hazard model with a frailty term was computed to assess the influence of the MAM and the maximum tumor diameter on the time to LTP and the OS. Results: The maximum tumor diameter was identified as a significant positive predictor for LTP (hazard ratio 1.04, 95% CI 1.00–1.08, p = 0.03), but it was not a significant positive predictor for the OS (p = 0.20). The MAM did not have a significant influence on LTP-free survival (p = 0.23) and OS (p = 0.67). Conclusion: For the successful stereotactic MWA of HCC, the MAM and maximum tumor diameter might not have an influence on the OS, but the maximum tumor diameter seems to be an independent predictor of the time to LTP. [ABSTRACT FROM AUTHOR]
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- 2023
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19. Aktueller Stand zu perkutanen lokalablativen Verfahren beim hepatozellulären Karzinom.
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Luerken, Lukas, Haimerl, Michael, Doppler, Michael, Uller, Wibke, Beyer, Lukas Philipp, Stroszczynski, Christian, and Einspieler, Ingo
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- 2023
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20. Hepatic decompensation after transarterial radioembolization: A retrospective analysis of risk factors and outcome in patients with hepatocellular carcinoma.
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Reincke, Marlene, Schultheiss, Michael, Doppler, Michael, Verloh, Niklas, Uller, Wibke, Sturm, Lukas, Thimme, Robert, Goetz, Christian, and Bettinger, Dominik
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DISEASE risk factors ,HEPATOCELLULAR carcinoma ,FACTOR analysis ,RISK assessment ,RADIOEMBOLIZATION - Abstract
Transarterial radioembolization (TARE) is a well‐established therapy for intermediate and advanced tumor stages of hepatocellular carcinoma (HCC). Treatment‐associated toxicities are rare. Previous studies have outlined that the prognosis after TARE is determined primarily by tumor stage and liver function. The subset of patients benefiting from TARE remains to be defined. Sixty‐one patients with HCC treated with TARE between 2015 and 2020 were retrospectively included in the study. Hepatic decompensation was defined as an increase of bilirubin or newly developed ascites that was not explained by tumor progression within 3 months after TARE. Predictive factors of hepatic decompensation and prognostic factors were assessed. Hepatic decompensation was observed in 27.9% (n = 17) of TARE‐treated patients during follow‐up. Albumin‐bilirubin (ALBI) score at baseline and radiation dose on nontumor liver proved to be independent risk factors for the development of hepatic decompensation in multivariable regression models (ALBI score: odds ratio [OR] 6.425 [1.735;23.797], p < 0.005; radiation dose: OR 1.072 [1.016;1.131], p < 0.011). The occurrence of hepatic decompensation markedly impaired the prognosis of the patients. Survival was significantly worsened. Hepatic decompensation has shown to be an independent negative prognostic factor for death, adjusted for Barcelona Clinic Liver Cancer stage, age and ALBI grade (hazard ratio 5.694 [2.713;11.952], p < 0.001). Conclusion: Hepatic decompensation after TARE for HCC treatment is a highly relevant complication with major effects on the prognosis of patients. Main risk factors are the pretreatment ALBI score and radiation dose. There is an urgent need to define safe cutoff values and exclusion criteria for TARE to limit complications and improve patient outcomes. [ABSTRACT FROM AUTHOR]
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- 2022
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21. Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma.
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Luerken, Lukas, Haimerl, Michael, Doppler, Michael, Uller, Wibke, Beyer, Lukas Philipp, Stroszczynski, Christian, and Einspieler, Ingo
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- 2022
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22. Application of A U-Net for Map-like Segmentation and Classification of Discontinuous Fibrosis Distribution in Gd-EOB-DTPA-Enhanced Liver MRI.
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Strotzer, Quirin David, Winther, Hinrich, Utpatel, Kirsten, Scheiter, Alexander, Fellner, Claudia, Doppler, Michael Christian, Ringe, Kristina Imeen, Raab, Florian, Haimerl, Michael, Uller, Wibke, Stroszczynski, Christian, Luerken, Lukas, and Verloh, Niklas
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CONTRAST-enhanced magnetic resonance imaging ,HEPATIC fibrosis ,RECEIVER operating characteristic curves ,CONVOLUTIONAL neural networks ,ARTIFICIAL neural networks - Abstract
Highlights: - First application of a U-net for the segmentation and classification of discontinuous liver fibrosis distribution. - Fully automated, scalable pipeline for data pre-processing, segmentation, and classification. - The present research could serve as a cornerstone of further applications for non-invasive determination of liver tissue properties, for instance, in planned parenchymal resection. We aimed to evaluate whether U-shaped convolutional neuronal networks can be used to segment liver parenchyma and indicate the degree of liver fibrosis/cirrhosis at the voxel level using contrast-enhanced magnetic resonance imaging. This retrospective study included 112 examinations with histologically determined liver fibrosis/cirrhosis grade (Ishak score) as the ground truth. The T1-weighted volume-interpolated breath-hold examination sequences of native, arterial, late arterial, portal venous, and hepatobiliary phases were semi-automatically segmented and co-registered. The segmentations were assigned the corresponding Ishak score. In a nested cross-validation procedure, five models of a convolutional neural network with U-Net architecture (nnU-Net) were trained, with the dataset being divided into stratified training/validation (n = 89/90) and holdout test datasets (n = 23/22). The trained models precisely segmented the test data (mean dice similarity coefficient = 0.938) and assigned separate fibrosis scores to each voxel, allowing localization-dependent determination of the degree of fibrosis. The per voxel results were evaluated by the histologically determined fibrosis score. The micro-average area under the receiver operating characteristic curve of this seven-class classification problem (Ishak score 0 to 6) was 0.752 for the test data. The top-three-accuracy-score was 0.750. We conclude that determining fibrosis grade or cirrhosis based on multiphase Gd-EOB-DTPA-enhanced liver MRI seems feasible using a 2D U-Net. Prospective studies with localized biopsies are needed to evaluate the reliability of this model in a clinical setting. [ABSTRACT FROM AUTHOR]
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- 2022
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23. Diagnostik und Therapie von Gefäßmalformationen.
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Doppler, Michael and Uller, Wibke
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- 2022
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24. Diagnostik und Therapie von Gefäßmalformationen.
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Doppler, Michael and Uller, Wibke
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- 2021
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25. Interventionelle Onkologie – was der Radiologe im Tumorboard wissen sollte.
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Beyer, Lukas Philipp, Lürken, Lukas, Doppler, Michael, and Stroszczynski, Christian
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- 2019
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26. Guidelines for Understanding Magnification in the Modern Digital Microscope Era.
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DeRose, James A. and Doppler, Michael
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For digital light microscopes, which have image sensors but no eyepieces, the image is displayed directly on an electronic monitor. This development brings a significant change to the usual way magnification of an object viewed via a microscope is determined. Over the years, there have been various standards that define magnification when viewing an image through a microscope’s eyepieces. Only recently have magnification standards been developed that apply to a digital microscope. This article offers guidelines for determining the range of useful magnification values for digital microscopy, particularly when monitors of various sizes are employed. [ABSTRACT FROM AUTHOR]
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- 2018
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27. Potential Sputtering Experiments on Mineral Targets Relevant for the Lunar Surface.
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Szabo, Paul Stefan, Biber, Herbert, Weichselbaum, David, Brenner, Matthias, Stadlmayr, Reinhard, Mayer, Daniel, Mutzke, Andreas, Nenning, Andreas, Doppler, Michael, Sauer, Markus, Galli, André, Fleig, Jürgen, Foelske-Schmitz, Annette, Lammer, Helmut, Mezger, Klaus, Wurz, Peter, and Aumayr, Friedrich
- Published
- 2019
28. [Stent-PTA of tumor-related venous obstructions].
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Fingerhut JB, Kulka C, Doppler M, Vogt K, Uller W, and Verloh N
- Abstract
Competing Interests: Diese Arbeit wurde durch das Projekt MRT-VS unterstützt, das vom Bundesministerium für Bildung und Forschung (BMBF) unter dem Aktenzeichen 13GW0366C gefördert wird. Prof. Dr. Niklas Verloh hat in den letzten 3 Jahren ein Vortragshonorar von der Bentley InnoMed GmbH erhalten.
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- 2024
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29. Resolving a sticky situation: A case report of mechanical thrombectomy of Histoacryl emboli in the right atrium and inferior vena cava.
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Can E, Doppler MC, Wintergerst C, Efinger N, Udi J, Sekandarzad A, Uller W, Vogt K, and Grundmann S
- Abstract
A 68-year-old male with liver cirrhosis presented with dizziness and dyspnea two days after endoscopic Histoacryl occlusion of gastric varicses. Imaging revealed a large endovascular embolization of Histoacryl glue, spanning from porto-caval collaterals via the inferior vena cava to the right atrium, partially occluding right atrial inflow. This case report describes the successful removal of this large net-like mass of Histoacryl glue using thrombectomy devices from the inferior vena cava and the right atrium. Postprocedure imaging showed near-complete clearance with residual fragments in the superior mesenteric vein and small emboli in the pulmonary arteries. The patient was discharged in stable condition. Histoacryl glue can cause severe complications if embolized. This case highlights the potential of advanced thrombectomy devices for managing embolic complications from endovascular treatments., (© 2024 The Authors. Published by Elsevier Inc. on behalf of University of Washington.)
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- 2024
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30. Biliary Leak after Pediatric Liver Transplantation Treated by Percutaneous Transhepatic Biliary Drainage-A Case Series.
- Author
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Doppler M, Fürnstahl C, Hammer S, Melter M, Verloh N, Schlitt HJ, and Uller W
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- Humans, Child, Retrospective Studies, Postoperative Complications diagnostic imaging, Postoperative Complications etiology, Postoperative Complications therapy, Treatment Outcome, Drainage adverse effects, Transferases, Liver Transplantation adverse effects
- Abstract
Background: Biliary leaks are a severe complication after pediatric liver transplantation (pLT), and successful management is challenging., Objectives: The aim of this case series was to assess the outcome of percutaneous transhepatic biliary drainage (PTBD) in children with bile leaks following pLT. The necessity of additional percutaneous bilioma drainage and laboratory changes during therapy and follow-up was documented., Material and Methods: All children who underwent PTBD for biliary leak following pLT were included in this consecutive retrospective single-center study and analyzed regarding site of leak, management of additional bilioma, treatment response, and patient and transplant survival. The courses of inflammation, cholestasis parameters, and liver enzymes were retrospectively reviewed., Results: Ten children underwent PTBD treatment for biliary leak after pLT. Seven patients presented with leakage at the hepaticojejunostomy, two with leakage at the choledocho-choledochostomy and one with a bile leak because of an overlooked segmental bile duct. In terms of the mean, the PTBD treatment started 40.3 ± 31.7 days after pLT. The mean duration of PTBD treatment was 109.7 ± 103.6 days. Additional percutaneous bilioma drainage was required in eight cases. Bile leak treatment was successful in all cases, and no complications occurred. The patient and transplant survival rate was 100%. CRP serum level, leukocyte count, gamma-glutamyl transferase (GGT), and total and direct bilirubin level decreased significantly during treatment with a very strong effect size. Additionally, the gamma-glutamyl transferase level showed a statistically significant reduction during follow-up., Conclusions: PTBD is a very successful strategy for bile leak therapy after pLT.
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- 2023
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31. Interventional Management of Vascular Complications after Renal Transplantation.
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Verloh N, Doppler M, Hagar MT, Kulka C, von Krüchten R, Neubauer J, Weiß J, Röthele E, Schneider J, Jänigen B, and Uller W
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- Humans, Postoperative Complications diagnostic imaging, Postoperative Complications therapy, Kidney Transplantation adverse effects, Arteriovenous Fistula therapy, Aneurysm, False
- Abstract
Background: Kidney transplantations are increasing due to demographic changes and are the treatment of choice for end-stage renal disease. Non-vascular and vascular complications may occur in the early phase after transplantation and at later stages. Overall postoperative complications after renal transplantations occur in approximately 12 % to 25 % of renal transplant patients. In these cases, minimally invasive therapeutic interventions are essential to ensure long-term graft function. This review article focuses on the most critical vascular complications after renal transplantation and highlights current recommendations for interventional treatment., Method: A literature search was performed in PubMed using the search terms "kidney transplantation", "complications", and "interventional treatment". Furthermore, the 2022 annual report of the German Foundation for Organ Donation and the EAU guidelines for kidney transplantation (European Association of Urology) were considered., Results and Conclusion: Image-guided interventional techniques are favorable compared with surgical revision and should be used primarily for the treatment of vascular complications. The most common vascular complications after renal transplantation are arterial stenoses (3 %-12.5 %), followed by arterial and venous thromboses (0.1 %-8.2 %) and dissection (0.1 %). Less frequently, arteriovenous fistulas or pseudoaneurysms occur. In these cases, minimally invasive interventions show a low complication rate and good technical and clinical results. Diagnosis, treatment, and follow-up should be performed in an interdisciplinary approach at highly specialized centers to ensure the preservation of graft function. Surgical revision should be considered only after exhausting minimally invasive therapeutic strategies., Key Points: · Vascular complications after renal transplantation occur in 3 % to 15 % of patients.. · Image-guided interventional procedures should be performed primarily to treat vascular complications of renal transplantation.. · Minimally invasive interventions have a low complication rate with good technical and clinical outcomes.., Citation Format: · Verloh N, Doppler M, Hagar MT et al. Interventional Management of Vascular Complications after Renal Transplantation. Fortschr Röntgenstr 2023; 195: 495 - 504., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)
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- 2023
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32. Stereotactic Microwave Ablation of Hepatocellular Carcinoma: The Impact of Tumor Size and Minimal Ablative Margin on Therapeutic Success.
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Pausch AM, Ghali T, Wertheimer T, Zeman F, Mueller K, Doppler MC, Einspieler I, Beyer LP, Schleder S, Stroszczynski C, and Luerken L
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- Humans, Retrospective Studies, Microwaves therapeutic use, Treatment Outcome, Carcinoma, Hepatocellular diagnostic imaging, Carcinoma, Hepatocellular surgery, Carcinoma, Hepatocellular pathology, Liver Neoplasms diagnostic imaging, Liver Neoplasms surgery, Liver Neoplasms pathology
- Abstract
Background: Microwave ablation (MWA) has gained relevance in the treatment of hepatic malignancies and especially in hepatocellular carcinoma (HCC), and it is an important alternative to surgery. The purpose of the study was to evaluate whether the minimal ablative margin (MAM) or the initial tumor size has a greater effect on the success of stereotactic MWA of HCC regarding the time to local tumor progression (LTP) and overall survival (OS)., Methods: 88 patients, who received stereotactic MWA of 127 tumor lesions with a curative intention were included in this single-center, retrospective study. The MAM was evaluated in a side-by-side comparison of pre- and post-ablative, contrast-enhanced slice imaging. A Cox proportional hazard model with a frailty term was computed to assess the influence of the MAM and the maximum tumor diameter on the time to LTP and the OS., Results: The maximum tumor diameter was identified as a significant positive predictor for LTP (hazard ratio 1.04, 95% CI 1.00-1.08, p = 0.03), but it was not a significant positive predictor for the OS ( p = 0.20). The MAM did not have a significant influence on LTP-free survival ( p = 0.23) and OS ( p = 0.67)., Conclusion: For the successful stereotactic MWA of HCC, the MAM and maximum tumor diameter might not have an influence on the OS, but the maximum tumor diameter seems to be an independent predictor of the time to LTP.
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- 2022
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33. Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma.
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Luerken L, Haimerl M, Doppler M, Uller W, Beyer LP, Stroszczynski C, and Einspieler I
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- Humans, Retrospective Studies, Treatment Outcome, Carcinoma, Hepatocellular pathology, Carcinoma, Hepatocellular surgery, Catheter Ablation methods, Chemoembolization, Therapeutic, Liver Neoplasms pathology, Liver Neoplasms surgery, Radiofrequency Ablation
- Abstract
Background: Hepatocellular carcinoma (HCC) is the fifth most common tumor worldwide. Because many hepatocellular carcinomas are already unresectable at the time of initial diagnosis, percutaneous tumor ablation has become established in recent decades as a curative therapeutic approach for very early (BCLC 0) and early (BCLC A) HCC. The aim of this paper is to provide a concise overview of the percutaneous local ablative procedures currently in use, based on their technical characteristics as well as clinical relevance, taking into account the current body of studies., Materials and Methods: The literature search included all original papers, reviews, and meta-analyses available via MEDLINE and Pubmed on the respective percutaneous ablation procedures; the primary focus was on randomized controlled trials and publications from the last 10 years., Results and Conclusions: Radiofrequency ablation (RFA) and microwave ablation (MWA) are well-established procedures that are considered equal to surgical resection in the treatment of stage BCLC 0 and A HCC with a diameter up to 3 cm due to their strong evidence in international and national guidelines. For tumors with a diameter between 3 and 5 cm, the current S3 guidelines recommend a combination of transarterial chemoembolization (TACE) and thermal ablation using RFA or MWA as combination therapy is superior to thermal ablation alone in tumors of this size and shows comparable results to surgical resection in terms of overall survival. Alternative, less frequently employed thermal procedures include cryotherapy (CT) and laser ablation (LA). Non-thermal procedures include irreversible electroporation (IRE), interstitial brachytherapy (IBT), and most recently, electrochemotherapy (ECT). Due to insufficient evidence, these have only been used in individual cases and within the framework of studies. However, the nonthermal methods are a reasonable alternative for ablation of tumors adjacent to large blood vessels and bile ducts because they cause significantly less damage to these structures than thermal ablation methods. With advances in the technology of the respective procedures, increasingly good evidence, and advancements in supportive techniques such as navigation devices and fusion imaging, percutaneous ablation procedures may expand their indications for the treatment of larger and more advanced tumors in the coming years., Key Points: · RFA and MWA are considered equal to surgical resection as a first-line therapy for the curative treatment of stage BCLC 0 and A HCCs with a diameter of up to 3 cm.. · For HCCs with a diameter between 3 and 5 cm, a combination of TACE and RFA or MWA is recommended. This combination therapy yields results comparable to those of surgical resection in terms of overall survival.. · Due to insufficient evidence, alternative ablation methods have only been used in individual cases and within the framework of studies. However, nonthermal methods, such as IRE, IBT, and, most recently, ECT, are a reasonable alternative for ablation of HCCs adjacent to large blood vessels and bile ducts because they cause significantly less damage to these structures than thermal ablation methods.., Citation Format: · Luerken L, Haimerl M, Doppler M et al. Update on Percutaneous Local Ablative Procedures for the Treatment of Hepatocellular Carcinoma. Fortschr Röntgenstr 2022; 194: 1075 - 1086., Competing Interests: The authors declare that they have no conflict of interest., (Thieme. All rights reserved.)
- Published
- 2022
- Full Text
- View/download PDF
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