Objective: To evaluate the success and complications of thermal ablation (TA) based on the voluntary, prospective registry of the German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) with 303 participating centers from Germany, Austria, and Switzerland. Materials and methods: Registry data from 2018 until 2023 of 1102 patients with small renal tumors (age: 72.5 ± 11.6 years; female: 33.6%, 370/1102) were analyzed. Hospitals with ≥ 20 TAs were considered high-volume centers. Technical success and complication rates between different parameters were compared using the chi-square or Fisher’s exact test, p < 0.05 was considered statistically significant. Results: Patients were most frequently treated with radiofrequency ablation (RFA, 43.6%, 481/1102), then microwave ablation (MWA, 41.9%, 462/1102) or cryoablation (13.3%, 147/1102). Technical success for heat-based TA (RFA&MWA) was 94.3% (893/947), for cryoablation 97.3% (143/147). RFA&MWA was significantly more successful in lesions ≤ 3 cm (96.1%, 567/590) compared to 3–4 cm lesions (89.8%, 97/108; p = 0.005). In patients treated with cryoablation, no significant differences between sizes could be found (≤ 3 cm: 97.9%, 94/96; 3–4 cm: 85.7%, 12/14; p = 0.078). Complication rate was significantly higher in RFA&MWA of lesions 3–4 cm compared to ≤ 3 cm (≤ 3 cm: 3.9%, 23/590; 3–4 cm: 11.1%, 12/108, p = 0.002), while no significant differences were seen regarding cryoablation (≤ 3 cm: 1.0%, 1/96; 3–4 cm: 0.0%, 0/14; p = 1.000). Conclusions: In this exploratory analysis of the DeGIR registry, percutaneous TA of small renal masses is technically feasible with low complication rates. Heat-based TAs seem to have lower success rates and higher complication rates in larger tumors. Cryoablation could potentially be a safe alternative for 3- to 4-cm-sized tumors. Key Points: Question How effective is renal thermal ablation (TA) in terms of treatment success and complication rates? Findings In contrast to cryoablation, heat-based thermal ablation has lower success and higher complication rates in tumors measuring 3–4 cm compared to tumors < 3 cm . Clinical relevance Thermal ablation is not influenced by the need for additional techniques such as cooling, protective organ displacement, or temporary vessel occlusion. For small renal tumors, TA is an effective and safe treatment option. Cryoablation could be beneficial in larger tumors. Graphical

Purpose: In emergency diagnostics, head CT and CT angiography (CTA) of craniocervical vasculature are indispensable for children, despite their increased radiation sensitivity. This study assesses the radiation dose metrics of head CT and CTA in pediatric patients managed in the trauma resuscitation unit (TRU). Methods: All patients aged 0–<15 years who underwent head CT and CTA in the TRU between April 2020 and August 2023 were included. CT dose index volume (CTDIvol) and dose-length product (DLP) were extracted from the Radimetrics Enterprise Platform, which also provided organ doses estimated via Monte Carlo simulations and effective doses (ED) derived from these estimates. Dose metrics were compared with national diagnostic reference levels (DRLs), defined for three pediatric age groups: I (0–<5 years), II (5–<10 years), and III (10–<15 years). Results: Of 212 pediatric TRU patients, 62.7% (133/212) underwent CT and 72.2% (96/133) received combined CT and CTA. Median CTDIvol and DLP increased with age, whereas ED decreased. For head CT, CTDIvol ranged from 18.9 mGy to 29.4 mGy, DLP from 282 to 460 mGycm, and ED from 1.6 to 1.3 mSv. For CTA, CTDIvol ranged from 1.4 to 2.2 mGy, DLP from 40 to 83 mGycm, and ED from 1.0 to 0.8 mSv. All doses remained below national DRLs. Conclusion: Head CT and CTA in pediatric trauma can be performed with radiation doses well below national DRLs. Careful dose management is important to reduce potential long-term cancer risks and deterministic effects such as lens cataract formation.

Non-contrast computed tomography (CT) is commonly used for the evaluation of various pathologies including pulmonary infections or urolithiasis but, especially in low-dose protocols, image quality is reduced. To improve this, deep learning-based post-processing approaches are being developed. Therefore, we aimed to compare the objective and subjective image quality of different reconstruction techniques and a deep learning-based software on non-contrast chest and low-dose abdominal CTs. In this retrospective study, non-contrast chest CTs of patients suspected of COVID-19 pneumonia and low-dose abdominal CTs suspected of urolithiasis were analysed. All images were reconstructed using filtered back-projection (FBP) and were post-processed using an artificial intelligence (AI)-based commercial software (PixelShine (PS)). Additional iterative reconstruction (IR) was performed for abdominal CTs. Objective and subjective image quality were evaluated. AI-based post-processing led to an overall significant noise reduction independent of the protocol (chest or abdomen) while maintaining image information (max. difference in SNR 2.59 ± 2.9 and CNR 15.92 ± 8.9, p < 0.001). Post-processing of FBP-reconstructed abdominal images was even superior to IR alone (max. difference in SNR 0.76 ± 0.5, p ≤ 0.001). Subjective assessments verified these results, partly suggesting benefits, especially in soft-tissue imaging (p < 0.001). All in all, the deep learning-based denoising—which was non-inferior to IR—offers an opportunity for image quality improvement especially in institutions using older scanners without IR availability. Further studies are necessary to evaluate potential effects on dose reduction benefits.

Objectives: Malignant triton tumours (MTTs) are rare but aggressive subtypes of malignant peripheral nerve sheath tumours (MPNSTs) with a high recurrence rate and 5-year survival of 14%. Systematic imaging data on MTTs are scarce and mainly based on single case reports. Therefore, we aimed to identify typical CT and MRI features to improve early diagnosis rates of this uncommon entity. Methods: A systematic review on literature published until December 2022 on imaging characteristics of MTTs was performed. Based on that, we conducted a retrospective, monocentric analysis of patients with histopathologically proven MTTs from our department. Explorative data analysis was performed. Results: Initially, 29 studies on 34 patients (31.42 ± 22.6 years, 12 female) were evaluated: Literature described primary MTTs as huge, lobulated tumours (108 ± 99.3 mm) with central necrosis (56% [19/34]), low T1w (81% [17/21]), high T2w signal (90% [19/21]) and inhomogeneous enhancement on MRI (54% [7/13]). Analysis of 16 patients (48.9 ± 13.8 years; 9 female) from our institution revealed comparable results: primary MTTs showed large, lobulated masses (118 mm ± 64.9) with necrotic areas (92% [11/12]). MRI revealed low T1w (100% [7/7]), high T2w signal (100% [7/7]) and inhomogeneous enhancement (86% [6/7]). Local recurrences and soft-tissue metastases mimicked these features, while nonsoft-tissue metastases appeared unspecific. Conclusions: MTTs show characteristic features on CT and MRI. However, these do not allow a reliable differentiation between MTTs and other MPNSTs based on imaging alone. Therefore, additional histopathological analysis is required. Advances in knowledge: This largest published systematic analysis on MTT imaging revealed typical but unspecific imaging features that do not allow a reliable, imaging-based differentiation between MTTs and other MPNSTs. Hence, additional histopathological analysis remains essential.

Purpose: The standard modality for the diagnosis of ventriculoperitoneal (VP) shunt failure is the radiographic shunt series (RSS). However, ultra-low dose computed tomography (ULD-CT) may replace RSS. The aim of this study was to compare the radiation doses of RSS and ULD-CT in the diagnosis of mechanical shunt failure in human phantoms including pediatric phantoms and to further reduce the total CT dose by reducing the topogram radiation. Methods: Mechanical VP shunt complications were placed on human phantoms representing ages of 1, 5, 10 and 30 years. RSS and ULD-CT were performed on each phantom with different radiation doses of the topogram with varying tube currents (10, 20, 30, 40 and 50 mAs). Effective doses of RSS and ULD-CT were estimated by using conversion factors. Results: ULD-CT demonstrated lower effective doses than RSS in phantoms representing ages 5, 10 and 30 years, while successfully depicting all mechanical shunt complications. However, higher effective doses were assessed for ULD-CT scans of the 1-year phantom than RSS. The effective doses for RSS and ULD-CT (utilizing 10 mAs topograms), respectively, were estimated as follows: 1-year: 0.056 vs. 0.133 mSv; 5-year: 0.186 vs. 0.123 mSv; 10-year: 0.240 vs. 0.107 mSv; 30-year: 0.641 vs. 0.076 mSv. Conclusion: This study demonstrated ULD-CT as an alternative to RSS for the detection of mechanical VP shunt complications, reducing radiation doses in phantoms equivalent to 5 years of age and older while demonstrating the complications equally to RSS. This may be of clinical interest, especially in children due to the reduction of radiation risks.