Purpose: To assess suspected acute stroke, the computed tomography (CT) protocol contains a non-contrast CT (NCCT), a CT angiography (CTA), and a CT perfusion (CTP). Due to assumably high radiation doses of the complete protocol, the aim of this study is to examine radiation exposure and to establish diagnostic reference levels (DRLs). Methods: In this retrospective study, dose data of 921 patients with initial CT imaging for suspected acute stroke and dose monitoring with a DICOM header–based tracking and monitoring software were analyzed. Between June 2017 and January 2020, 1655 CT scans were included, which were performed on three different modern multi-slice CT scanners, including 921 NCCT, 465 CTA, and 269 CTP scans. Radiation exposure was reported for CT dose index (CTDI_vol) and dose-length product (DLP). DRLs were set at the 75th percentile of dose distribution. Results: DRLs were assessed for each step (CTDI_vol/DLP): NCCT 33.9 mGy/527.8 mGy cm and CTA 13.7 mGy/478.3 mGy cm. Radiation exposure of CTP was invariable and depended on CT device and its protocol settings with CTDI_vol 124.9–258.2 mGy and DLP 1852.6–3044.3 mGy cm. Conclusion: Performing complementary CT techniques such as CTA and CTP for the assessment of acute stroke increases total radiation exposure. Hence, the revised DRLs for the complete protocol are required, where our local DRLs may help as benchmarks.

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

Objectives: Percutaneous image-guided tumor ablation of liver malignancies has become an indispensable therapeutic procedure. The aim of this evaluation of the prospectively managed multinational registry of the voluntary German Society for Interventional Radiology and Minimally Invasive Therapy (DeGIR) was to analyze its use, technical success, and complications in clinical practice. Materials and methods: All liver tumor ablations from 2018 to 2022 were included. Technical success was defined as complete ablation of the tumor with an ablative margin. Results: A total of 7228 liver tumor ablations from 136 centers in Germany and Austria were analyzed. In total, 31.4% (2268/7228) of patients were female. Median age was 67 years (IQR 58–74 years). Microwave ablation (MWA) was performed in 65.1% (4703/7228), and radiofrequency ablation (RFA) in 32.7% (2361/7228). Of 5229 cases with reported tumor etiology, 60.3% (3152/5229) of ablations were performed for liver metastases and 37.3% (1950/5229) for hepatocellular carcinoma. The median lesion diameter was 19 mm (IQR 12–27 mm). In total, 91.8% (6636/7228) of ablations were technically successful. The rate of technically successful ablations was significantly higher in MWA (93.9%, 4417/4703) than in RFA (87.3%, 2061/2361) (p < 0.0001). The total complication rate was 3.0% (214/7228) and was significantly higher in MWA (4.0%, 189/4703) than in RFA (0.9%, 21/2361, p < 0.0001). Additional needle track ablation did not increase the rate of major complications significantly (24.8% (33/133) vs. 28.4% (23/81), p = 0.56)). Conclusion: MWA is the most frequent ablation method. Percutaneous image-guided liver tumor ablations have a high technical success rate, which is higher for MWA than RFA. The complication rate is generally low but is higher for MWA than RFA. Clinical relevance statement: Percutaneous image-guided liver ablation using microwave ablation and radiofrequency ablation are effective therapeutic procedures with low complication rates for the treatment of primary and secondary liver malignancies. Key Points: • Percutaneous image-guided liver tumor ablations have a high technical success rate, which is higher for microwave ablation than radiofrequency ablation. • Microwave ablation is the most frequent ablation method ahead of radiofrequency ablation. • The complication rate is generally low but is higher for microwave ablation than radiofrequency ablation.

Background: Cystic fibrosis bone disease (CFBD) is a common comorbidity in adult people with cystic fibrosis (pwCF), resulting in an increased risk of bone fractures. This study evaluated the capacity of artificial intelligence (AI)-assisted low-dose chest CT (LDCT) opportunistic screening for detecting low bone mineral density (BMD) in adult pwCF. Methods: In this retrospective single-center study, 65 adult pwCF (mean age 30.1 ± 7.5 years) underwent dual-energy X-ray absorptiometry (DXA) of the lumbar vertebrae L1 to L4 to determine BMD and corresponding z-scores and completed LDCTs of the chest within three months as part of routine clinical care. A fully automated CT-based AI algorithm measured the attenuation values (Hounsfield units [HU]) of the thoracic vertebrae Th9–Th12 and first lumbar vertebra L1. The ability of the algorithm to diagnose CFBD was assessed using receiver operating characteristic (ROC) curves. Results: HU values of Th9 to L1 and DXA-derived BMD and the corresponding z-scores of L1 to L4 showed a strong correlation (all p < 0.05). The area under the curve (AUC) for diagnosing low BMD was highest for L1 (0.796; p = 0.001) and Th11 (0.835; p < 0.001), resulting in a specificity of 84.9% at a sensitivity level of 75%. The HU threshold values for distinguishing normal from low BMD were <197 (L1) and <212 (Th11), respectively. Conclusions: Routine LDCT of the chest with the fully automated AI-guided determination of thoracic and lumbar vertebral attenuation values is a valuable tool for predicting low BMD in adult pwCF, with the best results for Th11 and L1. However, further studies are required to define clear threshold values.

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.

Background: In the assessment of diseases causing skeletal lesions such as multiple myeloma (MM), whole-body low-dose computed tomography (WBLDCT) is a sensitive diagnostic imaging modality, which has the potential to replace the conventional radiographic survey. Purpose: To optimize radiation protection and examine radiation exposure, and effective and organ doses of WBLDCT using different modern dual-source CT (DSCT) devices, and to establish local diagnostic reference levels (DRL). Material and Methods: In this retrospective study, 281 WBLDCT scans of 232 patients performed between January 2017 and April 2020 either on a second- (A) or third-generation (B) DSCT device could be included. Radiation exposure indices and organ and effective doses were calculated using a commercially available automated dose-tracking software based on Monte-Carlo simulation techniques. Results: The radiation exposure indices and effective doses were distributed as follows (median, interquartile range): (A) second-generation DSCT: volume-weighted CT dose index (CTDI_vol) 1.78 mGy (1.47–2.17 mGy); dose length product (DLP) 282.8 mGy·cm (224.6–319.4 mGy·cm), effective dose (ED) 1.87 mSv (1.61–2.17 mSv) and (B) third-generation DSCT: CTDI_vol 0.56 mGy (0.47–0.67 mGy), DLP 92.0 mGy·cm (73.7–107.6 mGy·cm), ED 0.61 mSv (0.52–0.69 mSv). Radiation exposure indices and effective and organ doses were significantly lower with third-generation DSCT ( P < 0.001). Local DRLs could be set for CTDI_vol at 0.75 mGy and DLP at 120 mGy·cm. Conclusion: Third-generation DSCT requires significantly lower radiation dose for WBLDCT than second-generation DSCT and has an effective dose below reported doses for radiographic skeletal surveys. To ensure radiation protection, DRLs regarding WBLDCT are required, where our locally determined values may help as benchmarks.