Osteoid osteoma: treatment outcome and long-term follow-up after MRI-guided laser ablation.

Background: Aim of this study was to investigate short-term and long-term treatment outcome, complication rates, and patient satisfaction after MRI-guided laser ablation (LA) of osteoid osteoma (OO). Methods: Thirty-five patients with OO in typical and atypical localizations were treated by MRI-guided LA with MRI thermometry in an open 1.0 T system. Twenty-nine patients underwent a standardized telephone interview including questions about recurrence, residual pain or functional symptoms, and satisfaction for short-term follow-up after a mean of 31 months. Twenty-one of these patients were available for long-term telephone follow-up after a mean of 116 months. Results: Technical success of MRI-guided LA was 100% without major complications. Two minor complications included transient local inflammation and transient damage of the peroneal nerve associated with improper patient positioning during the procedure. Primary clinical success was 92% (11/12) in typically located OO and 82% (14/17) in atypically located OO. Secondary clinical success after repeat ablation was 100% regardless of OO location. Patient satisfaction and acceptance of the intervention were very good at both short-term (97%) and long-term (100%) follow-up. Conclusions: MRI-guided LA of OO is a safe and effective treatment option resulting in high short-term and long-term patient satisfaction and acceptance rates. Recurrence and adverse events were more common in patients with atypically located OO. Level of Evidence: Level 3, non-randomized follow-up study.

25 years of experience with transjugular intrahepatic portosystemic shunt (TIPS): changes in patient selection and procedural aspects.

BACKGROUND: TIPS is an established treatment for portal hypertension. The aim was to analyze how patient selection for TIPS implantation and procedural aspects have changed over 25 years. Routinely collected demographic, clinical, laboratory, and procedural data of 835 patients treated with TIPS in a single center were used. Time trends over the observational period from 1993 to 2018 were retrospectively analyzed. Descriptive statistical analysis was performed. RESULTS: The most common indication for TIPS implantation has changed significantly from secondary prevention of variceal hemorrhage in the early years to treatment of recurrent ascites. During the observation period, increasingly more severely ill patients became TIPS candidates. There was little change in MELD scores over this period (in total median 13.00; IQR 10.00-18.00). The proportion of patients with Child-Pugh C cirrhosis increased. The most frequent underlying diseases in total were alcohol-related liver disease (66.5%) and viral hepatitis (11.9%). However, shares of cryptogenic liver cirrhosis, autoimmune hepatitis, and NASH increased over time. The proportion of patients post liver transplant also increased. While bare metal stents were standard in the past, use of covered stents increased. The success rate of TIPS (defined by successful implantation and a decrease in the portosystemic pressure gradient ≤ 12 mmHg) increased significantly over time. The total success rate according to this definition was 84.9%. CONCLUSION: The results of our analysis reflect technical developments in TIPS, especially in terms of stent material and gains in clinical experience, particularly regarding indications and patient selection for TIPS implantation.

Duodenal tropism of SARS-CoV-2 and clinical findings in critically ill COVID-19 patients.

PURPOSE: Duodenal involvement in COVID-19 is poorly studied. Aim was to describe clinical and histopathological characteristics of critically ill COVID-19 patients suffering from severe duodenitis that causes a significant bleeding and/or gastrointestinal dysmotility. METHODS: In 51 critically ill patients suffering from SARS-CoV-2 pneumonia, severe upper intestinal bleeding and/or gastric feeding intolerance were indications for upper gastrointestinal endoscopy. Duodenitis was diagnosed according to macroscopic signs and mucosal biopsies. Immunohistochemistry was performed to detect viral specific protein and ACE2. In situ hybridization was applied to confirm viral replication. RESULTS: Nine of 51 critically ill patients (18%) suffering from SARS-CoV-2 pneumonia had developed upper GI bleeding complications and/or high gastric reflux. Five of them presented with minor and four (44%) with severe duodenitis. In two patients, erosions had caused severe gastrointestinal bleeding requiring PRBC transfusions. Immunohistochemical staining for SARS-CoV-2 spike protein was positive inside duodenal enterocytes in three of four patients suffering from severe duodenitis. Viral replication could be confirmed by in situ hybridization. CONCLUSION: Our data suggest that about 8% of critically ill COVID-19 patients may develop a severe duodenitis presumably associated with a direct infection of the duodenal enterocytes by SARS-CoV-2. Clinical consequences from severe bleeding and/or upper gastrointestinal dysmotility seem to be underestimated.

[Chest X-rays in children and adolescents : Indications and limitations]. / Röntgenuntersuchungen des Thorax bei Kindern und Jugendlichen : Indikationen und Limitationen.

CLINICAL ISSUE: Chest X­ray is the most commonly performed X­ray examination in children and adolescents. The aim of this review is to present the benefit of this radiologic modality, but also its limitations. METHODS: Compared with older children, most X­ray examinations of the chest were performed in newborns. After the neonatal period, this review focusses on the diagnosis of inflammatory pulmonary changes, foreign body aspiration, detection of pulmonary nodules, and cystic fibrosis. METHODOLOGICAL INNOVATIONS: The radiation exposure of X­ray examinations is continuously decreasing due to technical innovations. However, other imaging modalities were also continuously being optimized; therefore, alternatives without radiation exposure, i.e., magnetic resonance imaging [MRI] and ultrasound, should be considered in case of specific clinical indications. PRACTICAL RECOMMENDATION: Even if the diagnostic performance of chest X­ray examinations is often minor compared to computed tomography or MRI, chest X­ray still has a high value in children and adolescents, due to its ubiquitous availability and the relatively simple acquisition.

Interventional Radiology Options after Visceral Surgery.

Background: Postoperative management of patients undergoing visceral surgery can present challenging clinical situations with significant morbidity and mortality. Interventional radiological techniques offer quick, safe, and effective minimally invasive treatment options in the postoperative management of visceral surgery. Summary: Most commonly done procedures include - but are not limited to - fluid or abscess drainage, biliary diversion, bleeding embolization, and re-canalization of a thrombosed vessel. While bleeding from side branches after hepatobiliary and pancreatic surgeries can be managed by coil embolization, the hepatic arterial injury should be managed by stent-graft placement. Hepatic venous complications can require a transhepatic or transjugular approach, whereas the transjugular intrahepatic portosystemic shunt approach has a higher clinical success rate in patients with portal vein thrombosis. Biliary leakages require multidisciplinary management, and interventional radiology can offer an efficient treatment, especially in patients with biliodigestive anastomosis. Key Messages: Interventional radiology provides a broad spectrum of procedures in the management of patients with recent visceral surgery.

Ultrashort echo time MRI of the lung in children and adolescents: comparison with non-enhanced computed tomography and standard post-contrast T1w MRI sequences.

OBJECTIVES: To compare the diagnostic value of ultrashort echo time (UTE) magnetic resonance imaging (MRI) for the lung versus the gold standard computed tomography (CT) and two T1-weighted MRI sequences in children. METHODS: Twenty-three patients with proven oncologic disease (14 male, 9 female; mean age 9.0 + / - 5.4 years) received 35 low-dose CT and MRI examinations of the lung. The MRI protocol (1.5-T) included the following post-contrast sequences: two-dimensional (2D) incoherent gradient echo (GRE; acquisition with breath-hold), 3D volume interpolated GRE (breath-hold), and 3D high-resolution radial UTE sequences (performed during free-breathing). Images were evaluated by considering image quality as well as distinct diagnosis of pulmonary nodules and parenchymal areal opacities with consideration of sizes and characterisations. RESULTS: The UTE technique showed significantly higher overall image quality, better sharpness, and fewer artefacts than both other sequences. On CT, 110 pulmonary nodules with a mean diameter of 4.9 + / - 2.9 mm were detected. UTE imaging resulted in a significantly higher detection rate compared to both other sequences (p < 0.01): 76.4% (84 of 110 nodules) for UTE versus 60.9% (67 of 110) for incoherent GRE and 62.7% (69 of 110) for volume interpolated GRE sequences. The detection of parenchymal areal opacities by the UTE technique was also significantly higher with a rate of 93.3% (42 of 45 opacities) versus 77.8% (35 of 45) for 2D GRE and 80.0% (36 of 45) for 3D GRE sequences (p < 0.05). CONCLUSION: The UTE technique for lung MRI is favourable in children with generally high diagnostic performance compared to standard T1-weighted sequences as well as CT. Key Points • Due to the possible acquisition during free-breathing of the patients, the UTE MRI sequence for the lung is favourable in children. • The UTE technique reaches higher overall image quality, better sharpness, and lower artefacts, but not higher contrast compared to standard post-contrast T1-weighted sequences. • In comparison to the gold standard chest CT, the detection rate of small pulmonary nodules small nodules ≤ 4 mm and subtle parenchymal areal opacities is higher with the UTE imaging than standard T1-weighted sequences.

MR-guided lumbar facet radiofrequency denervation for treatment of patients with chronic low back pain in an open 1.0 Tesla MRI system.

BACKGROUND: To evaluate the feasibility, safety and efficacy of magnetic resonance imaging (MRI)-guided lumbar facet joint radiofrequency denervation (FRD) in patients with chronic low back pain. METHODS: The study consisted of two parts. First, a preclinical analysis using an ex vivo animal model was performed to define optimal technical parameters for ablation. Then, 17 patients with chronic lumbar facet joint pain syndrome were prospectively included and underwent MRI-guided FRD in an open 1.0-Tesla MRI. We analyzed technical feasibility and complications as well as clinical outcome in terms of subjective pain assessed on a numerical visual analogue scale (VAS) before and after 1 week/6 months after FRD. Clinical assessment was complemented by measurement of paravertebral muscle volume and fat content before the intervention and at 6-month follow-up. RESULTS: All interventions were technically successful without major complications. Initial VAS scores (median: 8, IQR: 1, range: 6-9, CI: 7.14-8.04) decreased significantly both after one week (median: 4, IQR: 5, range: 0-7, CI: 1.9-4.69, P=0.003) and after 6 months (median: 1, IQR: 6, range: 0-7, CI: 1.06-4.23, P<0.001). Mean multifidus muscle volume increased significantly in the patient population (from 366.8±130.8 cm3 before to 435.4±146.7 cm3 after FRD, P=0.031). CONCLUSIONS: This proof of principle study shows MRI-guided FRD in an open 1.0-Tesla MRI system to be a potential therapy option for patients with chronic low back pain.

Comparison of liver exposure in CT-guided high-dose rate (HDR) interstitial brachytherapy versus SBRT in hepatocellular carcinoma.

BACKGROUND: In unresectable hepatocellular carcinoma several local ablative treatments are available. Among others, radiation based treatments such as stereotactic body radiotherapy (SBRT) and high-dose rate interstitial brachytherapy (HDR BT) have shown good local control rates. METHODS: We conducted a dose comparison between actually performed HDR BT versus virtually planned SBRT to evaluate the respective clinically relevant radiation exposure to uninvolved liver tissue. Moreover, dose coverage and conformity indices were assessed. RESULTS: Overall, 46 treatment sessions (71 lesions, 38 patients) were evaluated. HDR BT was applied in a single fraction with a dose prescription of 1 × 15 Gy. D98 was 17.9 ± 1.3 Gy, D50 was 41.8 ± 8.1 Gy. The SBRT was planned with a prescribed dose of 3 × 12.5 Gy (65%-Isodose), D98 was 50.7 ± 3.1 Gy, D2 was 57.0 ± 2.3 Gy, and D50 was 55.2 ± 2.3 Gy. Regarding liver exposure Vliver10GyBT was compared to Vliver15.9GySBRT, Vliver16.2GySBRT (EQD2 equivalent doses), and Vliver20GySBRT (clinically relevant dose), all results showed significant differences (p < .001). In a case by case analysis Vliver10GyBT was smaller than Vliver20GySBRT in 38/46 cases (83%). Dmean of the liver was significantly smaller in BT compared to SBRT (p < .001). GTV volume was correlated to the liver exposure and showed an advantage of HDR BT over SBRT in comparison of clinically relevant doses, and for EQD2 equivalent doses. The advantage was more pronounced for greater liver lesions The Conformity Index (CI) was significantly better for BT, while Healthy Tissue Conformity Index (HTCI) and Conformation Number (CN) showed an advantage for SBRT (p < .001). CONCLUSION: HDR BT can be advantageous in respect of sparing of normal liver tissue as compared to SBRT, while providing excellent target conformity.

Validation of the collapsed cone algorithm for HDR liver brachytherapy against Monte Carlo simulations.

PURPOSE: To validate the collapsed cone (CC) algorithm against Monte Carlo (MC) simulations for model-based dose calculations in high-dose-rate (HDR) liver brachytherapy. METHODS AND MATERIALS: Doses for liver brachytherapy treatment plans of 10 cases were retrospectively recalculated with a model-based approach using Monte Carlo n-Particle Code (MCNP) 6 (Dm,m-MC) and Oncentra Brachy ACE (Dm,m-ACE). Tissue segmentation consisted of assigning uniform compositions and mass densities to predefined Hounsfield Unit (HU) thresholds. Resulting doses were compared according to dose volume histogram parameters typical for clinical routine. These included the percentage liver volume receiving 5 Gy (V5Gy) or 10 Gy (V10Gy), the maximum dose to one cubic centimeter (D1cc) of organs at risk, the clinical target volume (CTV) fractions receiving 150% (V150), 100% (V100), 95% (V95) and 90% (V90) of the prescribed dose and the absolute doses to 95% (D95) and 90% (D90) of the CTV volumes. RESULTS: Doses from Oncentra Brachy ACE agreed well with MC simulations. Differences were seen far from the source, in low-density regions and bone structures. Median percentage deviations were 1.1% for the liver V5Gy and 0.4% for the liver V10Gy, with deviations of largest magnitude amounting to 2.2% and 1.0%, respectively. Organs at risk had median deviations ranging from 0.3% to 1.5% for D1cc, with outliers ranging up to 4.6%. CTV volume parameter deviations ranged between -1.5% and 0.5%, dose parameter deviations ranged mostly between -2% and 1%, with two outliers at -4.0% and -3.4% for a small CTV.

Time Requirement and Feasibility of a Systematic Quality Peer Review of Reporting in Radiology.

OBJECTIVE: To estimate the human resources required for a retrospective quality review of different percentages of all routine diagnostic procedures in the Department of Radiology at Bern University Hospital, Switzerland. MATERIALS AND METHODS: Three board-certified radiologists retrospectively evaluated the quality of the radiological reports of a total of 150 examinations (5 different examination types: abdominal CT, chest CT, mammography, conventional X-ray images and abdominal MRI). Each report was assigned a RADPEER score of 1 to 3 (score 1: concur with previous interpretation; score 2: discrepancy in interpretation/not ordinarily expected to be made; score 3: discrepancy in interpretation/should be made most of the time). The time (in seconds, s) required for each review was documented and compared. A sensitivity analysis was conducted to calculate the total workload for reviewing different percentages of the total annual reporting volume of the clinic. RESULTS: Among the total of 450 reviews analyzed, 91.1 % (410/450) were assigned a score of 1 and 8.9 % (40/450) were assigned scores of 2 or 3. The average time (in seconds) required for a peer review was 60.4 s (min. 5 s, max. 245 s). The reviewer with the greatest clinical experience needed significantly less time for reviewing the reports than the two reviewers with less clinical expertise (p < 0.05). Average review times were longer for discrepant ratings with a score of 2 or 3 (p < 0.05). The total time requirement calculated for reviewing all 5 types of examination for one year would be more than 1200 working hours. CONCLUSION: A retrospective peer review of reports of radiological examinations using the RADPEER system requires considerable human resources. However, to improve quality, it seems feasible to peer review at least a portion of the total yearly reporting volume. KEY POINTS: · A systematic retrospective assessment of the content of radiological reports using the RADPEER system involves high personnel costs.. · The retrospective assessment of all reports of a clinic or practice seems unrealistic due to the lack of highly specialized personnel.. · At least part of all reports should be reviewed with the aim of improving the quality of reports.. CITATION FORMAT: · Maurer MH, Brönnimann M, Schroeder C et al. Time Requirement and Feasibility of a Systematic Quality Peer Review of Reporting in Radiology. Fortschr Röntgenstr 2021; 193: 160 - 167.

Biodegradable Polydioxanone Microspheres for Transcatheter Arterial Embolization: Proof of Principle.

PURPOSE: To evaluate feasibility, embolization success, biodegradability, reperfusion, and biocompatibility of biodegradable microspheres (MS) made from polydioxanone (PDO) for transcatheter arterial embolization. MATERIALS AND METHODS: Unilateral selective renal embolization of a segmental artery was performed in 16 New Zealand White rabbits with PDO-MS (100-150 µm and 90-315 µm). Animals were randomly assigned to different observation periods and underwent control digital subtraction angiography (DSA) and MR imaging immediately (n = 3), 1 week (n = 2), 4 weeks (n = 2), 8 weeks (n = 2), 12 weeks (n = 5), and 16 weeks (n = 2) after embolization. Kidneys were harvested for macroscopic and histologic analysis of embolization success, biodegradability, and biocompatibility. RESULTS: Embolization was technically successful in 15 of 16 animals. One animal died of anesthesia-related circulatory failure. The 100-150 µm MS were injected easily through 3-F catheters; the 90-315 µm MS tended to clog with intermittent catheter obstruction. DSA and MR imaging showed successful target embolization in 13 of 15 animals. In 2 animals, the entire kidney was affected owing to catheter clogging, including a reflux of MS while flushing. Control DSA and MR imaging showed increasing vascular reperfusion with time. Macroscopic and histologic analysis revealed necrosis/infarction in areas in which embolization was achieved. MS were extensively degraded after 16 weeks, and overall inflammatory reaction was mild. CONCLUSIONS: Biodegradable PDO-MS induced effective embolization of target vessels while demonstrating good biocompatibility. MS increasingly dissolved at 16 weeks, partial reperfusion started at week 1, and complete reperfusion started at week 8, thus offering possible advantages as a temporary embolic agent.

Specific Management of Patients with Acute Abdomen during the COVID-19 Pandemic: A Surgical Perspective from Germany.

During the current COVID-19 pandemic, the triage, assessment, and management of patients presenting to the emergency department with critical conditions has become -challenging. The clinical features of COVID-19 are heterogeneous and subtle in many cases. They may easily be overlooked in the case of other acute diseases. Gastrointestinal symptoms are common in patients with COVID-19 as SARS-CoV-2 is able to enter gastrointestinal epithelial cells. However, these complaints can also be caused by a COVID-19-independent concomitant abdominal pathology. Therefore, patients with acute abdominal pain and fever need to be assessed very thoroughly. Based on a clinical case, we present our approach of managing emergency patients with acute abdomen and concomitant suspicion of -COVID-19.

Novel MR-Visible, Biodegradable Microspheres for Transcatheter Arterial Embolization: Experimental Study in a Rabbit Renal Model.

PURPOSE: To assess feasibility, embolization success, biodegradability, reperfusion, biocompatibility and in vivo visibility of novel temporary microspheres (MS) for transcatheter arterial embolization. MATERIAL AND METHODS: In 9 New Zealand white rabbits unilateral superselective embolization of the lower kidney pole was performed with biodegradable MS made of polydioxanone (PDO) (size range 90-300 and 200-500 µm) impregnated with super-paramagnetic iron oxide (SPIO). Magnetic resonance imaging (MRI) was performed post-interventionally to assess in vivo visibility. Embolization success was assessed on digital subtraction angiography, MRI and gross pathology. One animal was killed immediately after embolization to assess original particle appearance. 8 animals were randomly assigned to different observation periods (1, 4, 8, 12 and 16 weeks), after which control angiography and MRI were obtained to determine recanalization. Histopathological analysis was performed to determine biodegradability and biocompatibility by using dedicated quantitative assessment analysis. RESULTS: Ease of injection was moderate. Embolization was technically successful in 7 of 8 animals, one rabbit received non-selective embolization of the whole kidney and abdominal off-target embolization. Arterial occlusion was achieved in all kidneys, infarct areas in macro- and microscopic analysis confirmed embolization success. Control angiograms showed evidence of partial reperfusion. The microspheres showed extensive degradation over the course of time along with increasing inflammatory response and giant cell formation. SPIO-loaded MS were visible on MRI at all time points. CONCLUSIONS: SPIO-impregnated biodegradable PDO-MS achieved effective embolization with in vivo visibility on MRI and increasing biodegradation over time while demonstrating good biocompatibility, i.e., a physiologically immune response without transformation into chronic inflammation. Further studies are needed to provide clinical applicability.

Improvement of image quality and diagnostic confidence using Smart MAR - a projection-based CT protocol in patients with orthopedic metallic implants in hip, spine, and shoulder.

BACKGROUND: In computed tomography (CT) scans, artifacts caused by metallic orthopedic implants still hamper the visualization of important, periprosthetic tissues. Smart MAR metal artifact reduction tool is a promising three-stage, projection-based, post-processing algorithm. PURPOSE: To determine whether the Smart MAR tool improves subjective and objective image quality and diagnostic confidence in patients with orthopedic implants of the hip, spine, and shoulder. MATERIAL AND METHODS: Seventy-two patients with orthopedic screws, hip/shoulder replacement, or spine spondylodesis were included. CT scans were performed on a single-source multislice CT scanner, raw data were post-processed using Smart MAR. Image quality was evaluated both quantitatively (ROI-based) and qualitatively (rater-based) and compared to iterative reconstructions (ASIR V). As comparative standard for artificial prosthetic breaks or loosening, follow-up examinations were used. RESULTS: Smart MAR reconstructions of the hip (n = 23), spine (n = 26), and shoulder (n = 23) showed a significantly reduced attenuation and noise of regions adjacent to metallic implants (P<0.002). Subjective image quality (P<0.005, shoulder P = 0.038/P = 0.046) and overall diagnostic confidence were higher in Smart MAR (all regions P<0.002). Signal-to-noise ratio (SNR; P = 0.72/P = 0.96) was not improved. Compared to standard ASIR V new, artificial metal extinctions (up to 50%) or periprosthetic hem lines (48%-73%) were introduced by Smart MAR. CONCLUSION: Smart MAR improved image quality of the hip, spine, and shoulder CT scans resulting in higher diagnostic confidence in evaluation of periprosthetic soft tissues. As shown for spine implants, it should be used with caution and as a complementary tool for evaluation of periprosthetic loosening or integrity of metal implant, as in many cases it introduced new artifacts.

The dosimetric impact of replacing the TG-43 algorithm by model based dose calculation for liver brachytherapy.

PURPOSE: To compare treatment plans for interstitial high dose rate (HDR) liver brachytherapy with 192Ir calculated according to current-standard TG-43U1 protocol with model-based dose calculation following TG-186 protocol. METHODS: We retrospectively evaluated dose volume histogram (DVH) parameters for liver, organs at risk (OARs) and clinical target volumes (CTVs) of 20 patient cases diagnosed with hepatocellular carcinoma (HCC) or metastatic colorectal cancer (mCRC). Dose calculations on a homogeneous water geometry (TG-43U1 surrogate) and on a computed tomography (CT) based geometry (TG-186) were performed using Monte Carlo (MC) simulations. The CTs were segmented based on a combination of assigning TG-186 recommended tissues to fixed Hounsfield Unit (HU) ranges and using organ contours delineated by physicians. For the liver, V5Gy and V10Gy were analysed, and for OARs the dose to 1 cubic centimeter (D1cc). Target coverage was assessed by calculating V150, V100, V95 and V90 as well as D95 and D90. For every DVH parameter, median, minimum and maximum values of the deviations of TG-186 from TG-43U1 were analysed. RESULTS: TG-186-calculated dose was found to be on average lower than dose calculated with TG-43U1. The deviation of highest magnitude for liver parameters was -6.2% of the total liver volume. For OARs, the deviations were all smaller than or equal to -0.5 Gy. Target coverage deviations were as high as -1.5% of the total CTV volume and -3.5% of the prescribed dose. CONCLUSIONS: In this study we found that TG-43U1 overestimates dose to liver tissue compared to TG-186. This finding may be of clinical importance for cases where dose to the whole liver is the limiting factor.

Renal Sympathetic Denervation by Image-Guided Percutaneous Ethanol Injection - Histopathologic Characteristics, Efficacy and Safety.

PURPOSE: Evaluation of the efficacy and safety of chemical renal denervation by image-guided periarterial ethanol injection in pigs with emphasis on histopathological characteristics. MATERIALS AND METHODS: Unilateral renal periarterial ethanol injection under general anesthesia was performed in 16 animals with the contralateral kidney serving as the control. All interventions were performed in an open MRI system under real-time multiplanar guidance. In 10 pigs an ethanol-carbostesin contrast agent mixture was injected with amounts of 5 ml (6 animals, group I) and 10 ml (4 animals, group II). 6 pigs (group III) were treated with 10 ml of an ethanol-polyacrylic (2 %) mixture. Four weeks after treatment, all animals underwent MRI including MRA. After euthanasia, macroscopic and histologic examination of the kidneys, renal arteries and periarterial tissue was performed to assess nerve injury and potential side effects. Furthermore, the norepinephrine concentration (RTNEC) in the renal tissue was determined as a surrogate parameter of efficacy. RESULTS: Histologic signs of nerval degeneration with various degrees of severity and circumferential distribution were found in all groups. Injury depths ranged up to 7.6 mm. In groups II and III the nerve count was significantly lower on the treated side. Renal artery stenosis was not observed in any pig. In all pigs of group II treatment resulted in neural degeneration with a mean RTNEC reduction of 53 % (p < 0.02). In groups I and III significant changes in RTNEC were not observed. CONCLUSION: Image-guided percutaneous periarterial ethanol injection was efficient and safe for renal denervation. The detected variations in histologic outcome underlined the importance of the preclinical optimization of the technique in order to maximize treatment effects in humans. KEY POINTS: · Renal denervation by percutaneous periarterial ethanol injection is an effective and potentially safe procedure.. · The percutaneous approach is less prone to anatomical and procedural limitations compared to catheter-based procedures.. · The achievable nerve injury depth lies beyond those of current RFA-probes.. · Efficacy depends on amount, concentration, viscosity and periarterial distribution of the ethanol-mixture.. · Establishing an optimal balance between these parameters is mandatory for a maximum treatment effect at minimum risk for sensitive adjacent structures.. CITATION FORMAT: · Freyhardt P, Haage P, Walter A et al. Renal Sympathetic Denervation by Image-Guided Percutaneous Ethanol Injection - Histopathologic Characteristics, Efficacy and Safety. Fortschr Röntgenstr 2020; 192: 549 - 560.

Atypically Located Osteoid Osteoma: Characteristics and Therapeutic Success After Image-Guided Thermal Ablation. / Das atypisch lokalisierte Osteoidosteom: Charakteristiken und Therapieerfolg nach bildgesteuerter Thermoablation.

PURPOSE: While ostoeid osteomas (OO) are typically located in long tubular bones, OO occurring elsewhere are referred to as "atypical". Aim of our study was to review the characteristics of atypically located OO, course of symptoms and therapy, as well as clinical outcome, safety, and patient satisfaction of radiofrequency ablation (RFA). MATERIALS AND METHODS: In the period from 04/01 to 07/13, 33 patients were treated using thermal ablation (RFA or laser), partly with low temperature and short duration technique. Clinical records were analyzed. Additionally, 23 patients were interviewed via telephone. Primary endpoints were technical success, clinical success (recurrence rates), and adverse events. Secondary endpoints were course of symptoms and therapy as well as patient satisfaction. RESULTS: Mean follow-up was 22.1 ±â€Š21.5 months. Average patient age was 31.7 ±â€Š16.3 years. Localization: Most atypical OO (61 %) were located in the lower extremity, followed by axial skeleton (26 %) and upper extremity (13 %). Pain anamnesis: 74 % of patients stated that their pain occured predominantly at night and responded to NSAID, as typical for OO. Diagnostics: Patients consulted on average 4 different doctors and in 52 % patients, ≥ 3 different radiologic imaging techniques where used before the diagnosis "OO" was made. OUTCOME: Technical success of thermal ablation was 100 %. Primary clinical success was 91 %. Patient satisfaction was 100 %. No major complications occurred. CONCLUSION: In » of cases, atypical OO did not show the typical pain characteristics of OO. Image-guided thermal ablation is a promising and safe therapy also for patients with atypical OO. KEY POINTS: · Atypical OO are challenging regarding diagnostics and therapy. · Image-guided thermal ablation is a safe and effective procedure also for patients with atypical OO. · Image-guided thermal ablation shows high patient satisfaction. CITATION FORMAT: · Seemann RJ, Märdian S, Schwabe P et al. Atypically Located Osteoid Osteoma: Characteristics and Therapeutic Success After Image-Guided Thermal Ablation. Fortschr Röntgenstr 2020; 192: 335 - 342.