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Purpose: Radiological reporting is transitioning to quantitative analysis, requiring large-scale multi-center validation of biomarkers. A major prerequisite and bottleneck for this task is the voxelwise annotation of image data, which is time-consuming for large cohorts. In this study, we propose an iterative training workflow to support and facilitate such segmentation tasks, specifically for high-resolution thoracic CT data., Methods: Our study included 132 thoracic CT scans from clinical practice, annotated by 13 radiologists. In three iterative training experiments, we aimed to improve and accelerate segmentation of the heart and mediastinum. Each experiment started with manual segmentation of 5-25 CT scans, which served as training data for a nnU-Net. Further iterations incorporated AI pre-segmentation and human correction to improve accuracy, accelerate the annotation process, and reduce human involvement over time., Results: Results showed consistent improvement in AI model quality with each iteration. Resampled datasets improved the Dice similarity coefficients for both the heart (DCS 0.91 [0.88; 0.92]) and the mediastinum (DCS 0.95 [0.94; 0.95]). Our AI models reduced human interaction time by 50 % for heart and 70 % for mediastinum segmentation in the most potent iteration. A model trained on only five datasets achieved satisfactory results (DCS > 0.90)., Conclusions: The iterative training workflow provides an efficient method for training AI-based segmentation models in multi-center studies, improving accuracy over time and simultaneously reducing human intervention. Future work will explore the use of fewer initial datasets and additional pre-processing methods to enhance model quality., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Rationale and Objectives: The prognostic role of pericardial effusion (PE) in Covid 19 is unclear. The aim of the present study was to estimate the prognostic role of PE in patients with Covid 19 in a large multicentre setting., Materials and Methods: This retrospective study is a part of the German multicenter project RACOON (Radiological Cooperative Network of the Covid 19 pandemic). The acquired sample comprises 1197 patients, 363 (30.3%) women and 834 (69.7%) men. In every case, chest computed tomography was analyzed for PE. Data about 30-day mortality, need for mechanical ventilation and need for intensive care unit (ICU) admission were collected. Data were evaluated by means of descriptive statistics. Group differences were calculated with Mann-Whitney test and Fisher exact test. Uni-and multivariable regression analyses were performed., Results: Overall, 46.4% of the patients were admitted to ICU, mechanical lung ventilation was performed in 26.6% and 30-day mortality was 24%. PE was identified in 159 patients (13.3%). The presence of PE was associated with 30-day mortality: HR= 1.54, CI 95% (1.05; 2.23), p = 0.02 (univariable analysis), and HR= 1.60, CI 95% (1.03; 2.48), p = 0.03 (multivariable analysis). Furthermore, density of PE was associated with the need for intubation (OR=1.02, CI 95% (1.003; 1.05), p = 0.03) and the need for ICU admission (OR=1.03, CI 95% (1.005; 1.05), p = 0.01) in univariable regression analysis. The presence of PE was associated with 30-day mortality in male patients, HR= 1.56, CI 95%(1.01-2.43), p = 0.04 (multivariable analysis). In female patients, none of PE values predicted clinical outcomes., Conclusion: The prevalence of PE in Covid 19 is 13.3%. PE is an independent predictor of 30-day mortality in male patients with Covid 19. In female patients, PE plays no predictive role., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Association of University Radiologists. Published by Elsevier Inc. All rights reserved.)

Objectives: Non-contrast computed tomography (NCCT) markers are robust predictors of parenchymal hematoma expansion in intracerebral hemorrhage (ICH). We investigated whether NCCT features can also identify ICH patients at risk of intraventricular hemorrhage (IVH) growth., Methods: Patients with acute spontaneous ICH admitted at four tertiary centers in Germany and Italy were retrospectively included from January 2017 to June 2020. NCCT markers were rated by two investigators for heterogeneous density, hypodensity, black hole sign, swirl sign, blend sign, fluid level, island sign, satellite sign, and irregular shape. ICH and IVH volumes were semi-manually segmented. IVH growth was defined as IVH expansion > 1 mL (eIVH) or any delayed IVH (dIVH) on follow-up imaging. Predictors of eIVH and dIVH were explored with multivariable logistic regression. Hypothesized moderators and mediators were independently assessed in PROCESS macro models., Results: A total of 731 patients were included, of whom 185 (25.31%) suffered from IVH growth, 130 (17.78%) had eIVH, and 55 (7.52%) had dIVH. Irregular shape was significantly associated with IVH growth (OR 1.68; 95%CI [1.16-2.44]; p = 0.006). In the subgroup analysis stratified by the IVH growth type, hypodensities were significantly associated with eIVH (OR 2.06; 95%CI [1.48-2.64]; p = 0.015), whereas irregular shape (OR 2.72; 95%CI [1.91-3.53]; p = 0.016) in dIVH. The association between NCCT markers and IVH growth was not mediated by parenchymal hematoma expansion., Conclusions: NCCT features identified ICH patients at a high risk of IVH growth. Our findings suggest the possibility to stratify the risk of IVH growth with baseline NCCT and might inform ongoing and future studies., Clinical Relevance Statement: Non-contrast CT features identified ICH patients at a high risk of intraventricular hemorrhage growth with subtype-specific differences. Our findings may assist in the risk stratification of intraventricular hemorrhage growth with baseline CT and might inform ongoing and future clinical studies., Key Points: • NCCT features identified ICH patients at a high risk of IVH growth with subtype-specific differences. • The effect of NCCT features was not moderated by time and location or indirectly mediated by hematoma expansion. • Our findings may assist in the risk stratification of IVH growth with baseline NCCT and might inform ongoing and future studies., (© 2023. The Author(s).)

Background: Noncontrast Computed Tomography (NCCT) features are promising markers for acute hematoma expansion (HE) in patients with intracerebral hemorrhage (ICH). It remains unclear whether accurate identification of these markers is also reliable in raters with different levels of experience., Methods: Patients with acute spontaneous ICH admitted at four tertiary centers in Germany and Italy were retrospectively included from January 2017 to June 2020. In total, nine NCCT markers were rated by one radiology resident, one radiology fellow, and one neuroradiology fellow with different levels experience in ICH imaging. Interrater reliabilities of the resident and radiology fellow were evaluated by calculated Cohen's kappa (κ) statistics in reference to the neuroradiology fellow who was referred as the gold standard. Gold-standard ratings were evaluated by calculated interrater κ statistics. Global interrater reliabilities were evaluated by calculated Fleiss kappa statistics across all three readers. A comparison of receiver operating characteristics (ROCs) was used to evaluate differences in the diagnostic accuracy for predicting acute hematoma expansion (HE) among the raters., Results: Substantial-to-almost-perfect interrater concordance was found for the resident with interrater Cohen's kappa from 0.70 (95% CI 0.65-0.81) to 0.96 (95% CI 0.94-0.98). The interrater Cohen's kappa for the radiology fellow was moderate to almost perfect and ranged from 0.58 (95% CI 0.52-0.65) to 94 (95% CI 92-0.97). The intrarater gold-standard Cohen's kappa was almost perfect and ranged from 0.79 (95% CI 0.78-0.90) to 0.98 (95% CI 0.78-0.90). The global interrater Fleiss kappa ranged from 0.62 (95%CI 0.57-0.66) to 0.93 (95%CI 0.89-0.97). The diagnostic accuracy for the prediction of acute hematoma expansion (HE) was different for the island sign and fluid sign, with p -values < 0.05., Conclusion: The NCCT markers had a substantial-to-almost-perfect interrater agreement among raters with different levels of experience. Differences in the diagnostic accuracy for the prediction of acute HE were found in two out of nine NCCT markers. The study highlights the promising utility of NCCT markers for acute HE prediction.

Introduction: The aim of the study was to demonstrate the feasibility of a prototype for accelerometer-based guidance for percutaneous CT-guided punctures and compare it with free-hand punctures., Material and Methods: The prototype enabled alignment with the CT coordinate system and a wireless connectivity. Its feasibility was tested in a swine cadaver model: 20 out-of-plane device-assisted punctures performed without intermittent control scans (one-step punctures) were evaluated regarding deviation to target and difference between planned and obtained angle. Thereafter, 22 device-assisted punctures were compared with 20 free-hand punctures regarding distance to target, deviation from the planned angle, number of control scans and procedure time. Differences were compared with the Mann-Whitney U-test ( p  < .05)., Results: The one-step punctures revealed a deviation to target of 0.26 ± 0.37 cm (axial plane) and 0.21 ± 0.19 cm (sagittal plane) and differences between planned and performed puncture angles of 0.9 ± 1.09° (axial plane) and 1.15 ± 0.91° (sagittal planes). In the comparative study, device-assisted punctures showed a significantly higher accuracy, 0.20 ± 0.17 cm vs. 0.30 ± 0.21 cm ( p  < .05) and lower number of required control scans, 1.3 ± 1.1 vs. 3.7 ± 0.9 ( p  < .05) compared with free-hand punctures., Conclusion: The accelerometer-based device proved to be feasible and demonstrated significantly higher accuracy and required significantly less control scans compared to free-hand puncture.

Lymphatic spread determines treatment decisions in prostate cancer (PCa) patients. 68Ga-PSMA-PET/CT can be performed, although cost remains high and availability is limited. Therefore, computed tomography (CT) continues to be the most used modality for PCa staging. We assessed if convolutional neural networks (CNNs) can be trained to determine 68Ga-PSMA-PET/CT-lymph node status from CT alone. In 549 patients with 68Ga-PSMA PET/CT imaging, 2616 lymph nodes were segmented. Using PET as a reference standard, three CNNs were trained. Training sets balanced for infiltration status, lymph node location and additionally, masked images, were used for training. CNNs were evaluated using a separate test set and performance was compared to radiologists' assessments and random forest classifiers. Heatmaps maps were used to identify the performance determining image regions. The CNNs performed with an Area-Under-the-Curve of 0.95 (status balanced) and 0.86 (location balanced, masked), compared to an AUC of 0.81 of experienced radiologists. Interestingly, CNNs used anatomical surroundings to increase their performance, "learning" the infiltration probabilities of anatomical locations. In conclusion, CNNs have the potential to build a well performing CT-based biomarker for lymph node metastases in PCa, with different types of class balancing strongly affecting CNN performance.

Rationale and Objectives: To investigate the correlation between prevalence and degree of coronary artery calcification (CAC) and extracoronary calcifications (ECCs), scored quantitatively according to Agatston and semiquantitatively by visual analysis, in chest computed tomography (CT) studies obtained for lung cancer screening in asymptomatic subjects and in patients with known coronary heart disease (CHD), and to compare the association of ECC and CAC to established cardiovascular risk factors., Materials and Methods: Prospective study on 501 males (67 ± 8 years) with a history of working dust exposure who underwent nongated low-dose chest CT for lung cancer screening. Of these, 63 (12.6%) had a history of CHD, the remaining 438 subjects (87.4%) were clinically asymptomatic and without a history of CHD. On the day of the CT study, subjects underwent a thorough clinical examination including blood tests and completed a standardized questionnaire to establish a complete medical history. ECC and CAC scores were quantified according to Agatston and, in addition, by visual rating of calcium load of individual vessel territories on a five-point scale from "absent" to "extensive." Results were correlated with the respective subjects' cardiovascular risk factors and with the presence or absence of CHD., Results: ECC scores correlated significantly with CAC scores (two-sided Spearman 0.515; P < .001). ECC scores were associated significantly (P < .001) with cardiovascular risk factors (smoking history, hypertension, diabetes, and hypercholesterolemia) and with subjects' Framingham/prospective cardiovascular münster study scores, whereas CAC scores were associated only with the presence of hypercholesterolemia. CAC scores were strongly associated with CHD than ECC scores (area under the curve, 0.88 vs. 0.66 at receiver operating characteristic analysis). Visual scoring of ECC/CAC load correlated closely with the respective Agatston values (P < .001) and revealed the same association (or lack thereof) with cardiovascular risk factors/CHD., Conclusions: In nongated low-dose CT for lung cancer screening, CAC and ECC load can be accurately established by visual analysis. ECC and CAC scores correlate closely, but not perfectly. There is a strong association between established cardiovascular risk factors and ECC load, but not CAC load, providing further evidence that ECC scoring may complement CAC scoring for broader risk assessment, for example, regarding prediction of extracoronary vascular events., (Copyright © 2015 AUR. Published by Elsevier Inc. All rights reserved.)

Purpose: Percutaneous punctures are often performed under computed tomography (CT) guidance using a freehand method. Especially in challenging cases, initial accuracy of the needle placement is highly dependent on the radiologist's experience. Thus, a miniature lightweight guidance device was developed which is capable of assisting a radiologist during the needle placement process., Methods: The device utilizes an accelerometer to measure the needle's tilt by calculating a set of orientation angles. This set can be matched with the coordinate system of the CT imaging software during a simple alignment process. After that, the needle's orientation can be expressed in terms of projected angles in the axial and sagittal planes. The accuracy of the device was evaluated in a phantom study, and initial clinical trials were carried out performing facet joint punctures in a swine cadaver., Results: The sensor was embedded in a cube with dimensions of [Formula: see text] and a total weight of about 11 g which can be attached to the puncture needle at its rear end or handgrip. A graphical user interface (GUÌ) has been created offering visual real-time orientation guidance. Results of the phantom experiments showed differences between planned target and performed puncture angles of [Formula: see text] for in-plane and [Formula: see text] for out-of-plane punctures., Conclusion: The results of the phantom and ex vivo study suggest that the device is useful to assist a radiologist in CT-guided percutaneous punctures and helps navigating the needle with high precision.

Postmortem computed tomography (PMCT) is a modern tool that complements autopsy diagnostics. In clinical autopsies, a major cause of death is cardiovascular disease. To improve the performance of PMCT in cardiovascular disease, full body angiography was developed (PMCT angiography [PMCTA]). Twenty PMCTA scans generated before autopsy were compared with native PMCT and clinical autopsy. The objective of the study was to quantify the additional diagnostic value of adding angiography to native imaging and to compare PMCT and PMCTA findings to autopsy findings. The diagnosis of the cause of death was identical or overlapped in 80% of the cases that used PMCTA and 70% that used PMCT. The additional diagnostic yield given by PMCT and PMCTA in combination with autopsy was 55%. PMCT yielded additional diagnoses in the musculoskeletal system. The greatest additional diagnostic value of PMCTA was in association with cardiovascular diagnoses. The accuracy of PMCTA for cardiac causes of death was 80%, and the positive predictive value was 90%. The findings indicate that native PMCT cannot display the cardiovascular system sufficiently clearly for high-quality diagnostic assessment. However, PMCTA is a powerful tool in autopsy cases with a history of cardiovascular disease and/or a suspected cardiovascular cause of death. The combination of PMCTA and clinical autopsy enhances diagnostic quality and completeness of the autopsy report. Furthermore, in cases without consent or with a restricted consent for clinical autopsy, PMCTA has the potential to provide information on cardiovascular causes of death., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Objectives: To evaluate the diagnostic value of contrast enhanced post mortem computed tomography (PMCT) in comparison to non-enhanced post mortem CT in the detection of cardiovascular causes of death (COD)., Background: As autopsy rates decline, new methods to determine CODs are necessary. So contrast enhanced PMCT shall be evaluated in comparison to established non-enhanced PMCT in order to further improve the method., Methods: In a prospective study, 20 corpses were examined using a 64-row multisclice CT (MSCT) before and after intraarterial perfusion with a newly developed, barium-bearing contrast agent and ventilation of the lungs. The cause of death was determined in enhanced and unenhanced scans and a level of confidence (LOC) was given by three experienced radiologists on a scale between 0 and 4. Results were compared to autopsy results as gold standard. Autopsy was performed blinded to PMCT-findings., Results: The method allowed visualization of different types of cause of death. There was a significant improvement in LOC in enhanced scans compared to unenhanced scans as well as an improvement in the detection of COD. The cause of death could be determined in 19 out of 20 patients., Conclusions: PMCT is feasible and appears to be robust for diagnosing cardiovascular causes of death. When compared with unenhanced post-mortem CT intraarterial perfusion and pulmonary ventilation significantly improve visualization and diagnostic accuracy. These promising results warrant further studies.

Purpose: This study was designed to evaluate CO2 computed tomography angiography (CO2-CTA) of the iliac and lower limb arteries in patients with contraindications for iodinated contrast agent (ICA)., Methods: Five patients with contraindications for ICA were examined using CO2-fluoroscopic enhanced angiography (CO2-FLA) and CO2-CTA using a high-pitch examination protocol. Objective (vessel diameter) and subjective (visual score) image quality parameters were evaluated. Pathological findings in both modalities were compared., Results: CO2-CTA was feasible in all patients without adverse side effects, except for CO2 injection-associated pain. Objective vessel analysis revealed no significant difference in diameters as determined by CO2-CTA and CO2-FLA (0.44 ± 0.4 and 0.46 ± 0.41 mm, p = 0.93). CO2-CTA had on average a higher image-quality score (2.6 ± 1.0 vs. 2.3 ± 1.0, p = 0.009). While for pelvic and upper leg CO2-CTA advantageous (3.1 ± 0.74 vs. 2.7 ± 0.9, p = 0.0014) at good quality scores, for calf vessels no significant improvement was visible (1.9 ± 1.0 vs. 1.7 ± 0.9, p = 0.49) and scores were poorer., Conclusions: CO2-CTA with high-pitch CT was feasible in a limited number of patients. Image-quality scores were on average higher for CO2-CTA than for CO2-FLA, while limited imaging quality in the vessels below the knee needs further work on the CT protocol. An added value of cross-sectional imaging was apparent but needs further quantification.

Purpose: The purpose of this study was to evaluate the efficacy of antegrade pyeloperfusion with cooled 5% of glucose solution to protect the renal collecting system during microwave ablation (MWA)., Materials and Methods: Computed tomographically guided nephrostomy was performed in 1 kidney in each of 14 female pigs by placing a 6F nephrostomy catheter. Pyeloperfusion was performed through infusion of cooled 5% of glucose solution via the nephrostomy catheter (4°C; 10 mL/min). Microwave ablation (915 MHz) was performed at 45 W for 10 minutes in the irrigated and the non-irrigated kidneys creating a central lesion and a peripheral lesion in each kidney. Maximum ablation diameters were measured and ablation volumes were calculated after the animals were killed. The extent of thermal injury of the renal pyelon was assessed histopathologically in the slice of maximal thermal injury on a 10-point scale ranging from 0 (none) to 10 (complete)., Results: Pyeloperfusion did not impact the ablation volume or the degree of thermal injury to the collecting system for the central or peripheral MWA procedures: The mean (SD) volume of the MWA zones was equivalent for the irrigated versus non-irrigated kidneys for the peripheral (3.07 [2.39] mL vs 3.87 [3.08] mL) and central MWA procedures (2.26 [1.55] mL vs 2.40 [1.60] mL). The mean (SD) histologic scores of the thermal damage of the pyelon were similar for the irrigated versus non-irrigated kidneys in the peripheral MWA (1.0 [2.7] vs 0.2 [0.6]) and in the central MWA (1.6 [2.7] vs 3.4 [3.4])., Conclusions: In MWA, cooled antegrade pyeloperfusion is not useful to modulate the ablation volume in peripheral or central locations. Accordingly, pyeloperfusion may not be useful as a protective measure to avoid thermal damage in MWA of the kidney. Therefore, MWA of central renal tumors does not seem advisable.

Purpose: To systematically investigate the impact of image acquisition and contrast injection parameters for CO2-enhanced CT angiography (CTA) of the aorto-iliac and peripheral arteries in a pig model using commercially available equipment. The aim was to establish an imaging protocol that is ready for use in human subjects., Materials and Methods: Three domestic swine underwent CO2-CTA with varying injection parameters: pitch (1.0, 3.0), injection pressure (0.7 bar, 1.0 bar, 1.3 bar) and scan delay (2 s, 4 s, 6 s). Objective (vessel diameter) and subjective (image quality) parameters and applied radiation doses were systematically evaluated. To ensure clinical applicability of the setting, only approved catheters/injectors and standard injection parameters were evaluated., Results: The image quality scores were superior and the vessel diameter was larger with high pitch in comparison to standard pitch (diameters: 4.7 ± 2.0 mm vs. 3.6 ± 2.1 mm, p = 0.0040, scores: 2.6 ± 1.1 vs. 2.0 ± 1.1, p = 0.0038). High injection pressure (1.3 bar) improved the image quality as assessed by subjective and objective ratings (diameters: 3.6 ± 2.0 mm, 4.0 ± 2.1 mm and 4.6 ± 2.1 mm, for 0.7, 1.0 and 1.3 bar, p-values ≤ 0.0052, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.2, p-values ≤ 0.0017), the same was observed for a shorter injection delay (diameters: 3.5 ± 2.0 mm, 4.2 ± 2.1 mm and 4.8 ± 2.1 mm, for 6 s, 4 s, and 2 s, p ≤ 0.0022, scores: 1.9 ± 1.1, 2.3 ± 1.1 and 2.7 ± 1.1, p-values ≤ 0.0013). The dose length products were 239 ± 47 mGycm (high pitch) and 565 ± 63 mGycm (standard pitch, p-values < 0.0001)., Conclusion: A higher pitch, shorter delay and higher injection pressure improve image quality in CO2-enhanced CTA. Since commercially available, clinically approved equipment was used. The protocol is now ready for use in human subjects., (© Georg Thieme Verlag KG Stuttgart · New York.)

For the past century, autopsy techniques in clinical pathology have not changed significantly, while autopsy rates are declining. Modern imaging techniques offer interesting prospects of supportive post-mortem diagnostic investigation. In a prospective study of 29 autopsy cases, complimentary virtual autopsy using unenhanced post-mortem computed tomography (pmCT) was performed. We analysed in a prospective cohort study 29 unenhanced pmCT scans, generated prior to autopsy. Clinical information regarding clinical history and circumstances of death were provided. The objective of the study was to find consistency and/or discrepancy between virtual autopsy and conventional autopsy findings regarding cause of death and death-related diagnoses, reconstruction of the pathogenetic mechanisms involved, side diagnoses and CPR (cardiopulmonary resuscitation)- or death-related post-mortem changes. Accuracy of pmCT for cause of death was 68 % and the positive predictive value (PPV) was 75 %. Regarding the pathogenetic mechanisms, accuracy of pmCT was 21 % and PPV was 29 %. The combined diagnostic yield of autopsy and pmCT was 133 % compared to autopsy only. Modern imaging techniques give an opportunity for post-mortem diagnostics to complete but not yet replace traditional autopsy. We could show that in two out of three cases, the cause of death found by pmCT matched the diagnosis from classical autopsy. While both disciplines, pathology and radiology, will profit from the mutual exchange of data, it seems a realistic aim to strive for virtual autopsy possibly further supported by biopsies and contrast-enhanced pmCT as an alternative to the classical clinical autopsy. A combination of both methods enhances diagnostic quality and completeness of the autopsy report.

Purpose: To evaluate the feasibility of computed tomography (CT)-guided placement of inferior vena cava (IVC) filters in a swine model., Materials and Methods: Five domestic pigs (60-70 kg) underwent transfemoral and transjugular IVC filter placement under real-time CT fluoroscopic guidance. Filter position was confirmed by contrast-enhanced CT and digital subtraction angiography. Filter tilt, distance to target position, and fluoroscopy time were analyzed., Results: A total of 10 filters were successfully implanted (five via transfemoral approach, five via transjugular approach) without complications. The mean distance to the target position was 0.3 cm ± 0.2. Mean filter tilt was 3.2° ± 2.3 (range, 0°-7°), without differences between deployment techniques (P = .8486). Average fluoroscopy time was 25.9 s ± 6.9 per procedure., Conclusions: CT fluoroscopy-guided placement of IVC filters is safely feasible. Use of this technique may avoid the need to move critically ill patients., (Copyright © 2011 SIR. Published by Elsevier Inc. All rights reserved.)

The purpose of this paper was to evaluate computed tomography (CT) based electromagnetically tip-tracked (EMT) interventions in various clinical applications. An EMT system was utilized to perform percutaneous interventions based on CT datasets. Procedure times and spatial accuracy of needle placement were analyzed using logging data in combination with periprocedurally acquired CT control scans. Dose estimations in comparison to a set of standard CT-guided interventions were carried out. Reasons for non-completion of planned interventions were analyzed. Twenty-five procedures scheduled for EMT were analyzed, 23 of which were successfully completed using EMT. The average time for performing the procedure was 23.7 ± 17.2 min. Time for preparation was 5.8 ± 7.3 min while the interventional (skin-to-target) time was 2.7 ± 2.4 min. The average puncture length was 7.2 ± 2.5 cm. Spatial accuracy was 3.1 ± 2.1 mm. Non-completed procedures were due to patient movement and reference fixation problems. Radiation doses (dosis-length-product) were significantly lower (p = 0.012) for EMT-based interventions (732 ± 481 mGy x cm) in comparison to the control group of standard CT-guided interventions (1343 ± 1054 mGy x cm). Electromagnetic navigation can accurately guide percutaneous interventions in a variety of indications. Accuracy and time usage permit the routine use of the utilized system. Lower radiation exposure for EMT-based punctures provides a relevant potential for dose saving.

Purpose: To quantitatively analyze differences in mechanical properties, needle design including signs of wear, subjective handling and specimen quality of bone biopsy needles., Materials and Methods: In this study 19 different bone biopsy systems (total 38; 2 /type) were examined. With each biopsy needle five consecutive samples were obtained from vertebral bodies of swine. During puncture a force-torques sensor measured the mechanical properties and subjective handling was assessed. Before and after each biopsy the needles were investigated using a profile projector and signs of wear were recorded. Afterwards, a pathologist semi-quantitatively examined the specimen regarding sample quality. The overall evaluation considered mechanical properties, needle wear, subjective handling and sample quality. Differences were assessed for statistical significance using ANOVA and t-test., Results: Needle diameter (p = 0.003) as well as needle design (p = 0.008) affect the mechanical properties significantly. Franseen design is significantly superior to other needle designs. Besides, length reduction recorded by the profile projector, as a quality criterion showed notable distinctions in between the needle designs., Conclusion: Bone biopsy needles vary significantly in performance. Needle design has an important influence on mechanical properties, handling and specimen quality. Detailed knowledge of those parameters would improve selecting the appropriate bone biopsy needle., (© Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: To evaluate accuracy and procedure times of electromagnetic tracking (EMT) in a robotic arm mounted flat panel setting using phantom and animal cadaveric models., Methods and Materials: A robotic arm mounted flat panel (RMFP) was used in combination with EMT to perform anthropomorphic phantom (n = 90) and ex vivo pig based punctures (n = 120) of lumbar facet joints (FJ, n = 120) and intervertebral discs (IVD, n = 90). Procedure accuracies and times were assessed and evaluated., Results: FJ punctures were carried out with a spatial accuracy of 0.8 ± 0.9 mm (phantom) and 0.6 ± 0.8 mm (ex vivo) respectively. While IVD punctures showed puncture deviations of 0.6 ± 1.2 mm (phantom) and 0.5 ± 0.6 mm (ex vivo), direct and angulated phantom based punctures had accuracies of 0.8 ± 0.9 mm and 1.0 ± 1.3 mm. Planning took longer for ex vivo IVD punctures compared to phantom model interventions (39.3 ± 17.3 s vs. 20.8 ± 5.0 s, p = 0.001) and for angulated vs. direct phantom FJ punctures (19.7 ± 5.1 s vs. 28.6 ± 7.8 s, p < 0.001). Puncture times were longer for ex vivo procedures when compared to phantom model procedures in both FJ (37.9 ± 9.0 s vs. 23.6 ± 7.2 s, p = 0.001) and IVD punctures (43.9 ± 16.1 s vs. 31.1 ± 6.4 s, p = 0.026)., Conclusion: The combination of RMFP with EMT provides an accurate method of navigation for spinal interventions such as facet joint punctures and intervertebral disc punctures.

Purpose: To test the feasibility of carbon dioxide (CO(2))-enhanced computed tomography (CT)-guided placement of infrarenal abdominal aortic stent-grafts in an animal model., Methods: Appearance of a stent-graft mounted on its deployment system and the feasibility of CT fluoroscopy-guided placement were analyzed in an in vitro setting. Five domestic pigs weighing 70 to 80 kg underwent CO(2)-enhanced 64-slice CT arteriography (CTA). After surgical exposure of the right iliac artery, an 18-mm stent-graft was advanced into the abdominal aorta. Infrarenal position of the graft was monitored using CT fluoroscopy with CO(2) administered intermittently in a flow-regulated manner using a computer-controlled injection system. After the final position of the stent-graft was determined, the graft was deployed under CT fluoroscopy guidance. Graft position was confirmed by contrast enhanced 64-slice CTA and conventional catheter angiography. To quantitatively assess the position of the stent-graft, the distance between the proximal stent struts and the radiopaque marker was determined using an electronic caliper., Results: CT-guided placement of infrarenal aortic stent-grafts was feasible in all animals without complications. CO(2)-enhanced CTA allowed for the identification of the renal arteries in all animals. CT fluoroscopy permitted the continuous online monitoring of stent deployment. In all animals, the grafts were placed without impairment of renal artery flow or stent-graft dislocation. The mean distance between the stent-graft and origin of the more caudal renal artery was 0.9+/-0.3 mm., Conclusion: CO(2)-enhanced CT fluoroscopy permits the precise placement of infrarenal aortic stent-grafts in an animal model.

Purpose: To investigate the potential of multi-slice computed tomography (MSCT) as a tool for non-invasive temperature measurement., Materials and Methods: Samples of water, 0.9% saline, sunflower oil and dilutions of (1:32, 1:64, 1:128) contrast agent (Iopromid 370, BayerSchering Pharma, Berlin) were heated in a plexiglass phantom. In a first set-up, samples of 0.9% saline solution were scanned at defined temperatures (25 degrees -75 degrees C; 5 degrees C intervals) using a clinical CT scanner. Scan parameters (tube current-time product, tube voltage, collimation, slice thickness) were systematically varied. In a second set-up samples of the different fluids (water, sunflower oil, contrast agent dilutions) were scanned using the following scan protocol: 250 mAs, 140 kV, 1.2 mm collimation, 9.6 mm slice thickness. CT numbers were measured in reconstructed axial images at the different temperatures. A regression analysis was performed to investigate the relationship between temperature and CT number., Results: Standard deviation of measured CT numbers decreased with increasing tube current-time product, increasing tube voltage, thicker collimation and higher slice thickness. Regression analysis showed an inverse relationship between temperature and CT number for all fluids with regression coefficients of -0.471 (0.9% saline), 0.447 (water), -0.679 (sunflower oil), -0.420 (contrast agent 1:32), -0.414 (contrast agent 1:64) and -0.441 (contrast agent 1:128), respectively., Conclusion: Multi-slice computed tomography can depict thermal density expansion of different fluids. Based on these results the implementation of a temperature discrimination of several degrees C at a high spatial resolution is achievable.

Purpose: Osteoid osteoma is a benign primary bone tumor that typically occurs in children and young adults. Besides local pain, which is often worse at night, prompt relief due to medication with acetylsalicylic acid (ASS) is characteristic for this bone lesion. Because long-term medication with ASS does not represent an alternative treatment strategy due to its potentially severe side effects, different minimally invasive image-guided techniques for the therapy of osteoid osteoma have been developed. In this context radiofrequency (RF) ablation in particular has become part of the clinical routine. The technique and results of image-guided RF ablation are compared to alternative treatment strategies., Materials and Methods: Using this technique, an often needle-shaped RF applicator is percutaneously placed into the tumor under image guidance. Then a high-frequency alternating current is applied by the tip of the applicator which leads to ionic motion within the tissue resulting in local heat development and thus in thermal destruction of the surrounding tissue including the tumor., Results: The published primary and secondary success rates of this technique are 87 and 83 %, respectively. Surgical resection and open curettage show comparable success rates but are associated with higher complication rates. In addition image-guided RF ablation of osteoid osteomas is associated with low costs., Conclusion: In conclusion image-guided RF ablation can be considered the gold standard for the treatment of osteoid osteoma.

An electromagnetic-based tracking and navigation system was evaluated for interventional radiology. The electromagnetic tracking system (CAPPA IRAD EMT, CASinnovations, Erlangen, Germany) was used for real-time monitoring of punctures of the lumbar facet joints and intervertebral disks in a spine phantom, three pig cadavers and three anaesthesized pigs. Therefore, pre-interventional computed tomography (CT) datasets were transferred to the navigation system and puncture trajectories were planned. A coaxial needle was advanced along the trajectories while the position of the needle tip was monitored in real time. After puncture tracts were marked with pieces of wire another CT examination was performed and distances between wires and anatomical targets were measured. Performing punctures of the facet joints mean needle positioning errors were 0.4 +/- 0.8 mm in the spine phantom, 2.8 +/- 2.1 mm ex vivo and 3.0 +/- 2.0 mm in vivo with mean length of the puncture tract of 54.0 +/- 10.4 mm (phantom), 51.6 +/- 12.6 mm (ex vivo) and 50.9 +/- 17.6 mm (in vivo). At first attempt, intervertebral discs were successfully punctured in 15/15 in the phantom study, in 12/15 in the ex-vivo study and 14/15 in the in-vivo study, respectively. Immobilization of the patient and optimal positioning of the field generator are essential to achieve a high accuracy of needle placement in a clinical CT setting.