Publications by authors named "Bernd Hamm"

536 Publications

A reporting and analysis framework for structured evaluation of COVID-19 clinical and imaging data.

NPJ Digit Med 2021 Apr 12;4(1):69. Epub 2021 Apr 12.

Computational Radiology, Dept. of Radiology, German Cancer Research Center (DKFZ), Heidelberg, Germany.

The COVID-19 pandemic has worldwide individual and socioeconomic consequences. Chest computed tomography has been found to support diagnostics and disease monitoring. A standardized approach to generate, collect, analyze, and share clinical and imaging information in the highest quality possible is urgently needed. We developed systematic, computer-assisted and context-guided electronic data capture on the FDA-approved mint Lesion software platform to enable cloud-based data collection and real-time analysis. The acquisition and annotation include radiological findings and radiomics performed directly on primary imaging data together with information from the patient history and clinical data. As proof of concept, anonymized data of 283 patients with either suspected or confirmed SARS-CoV-2 infection from eight European medical centers were aggregated in data analysis dashboards. Aggregated data were compared to key findings of landmark research literature. This concept has been chosen for use in the national COVID-19 response of the radiological departments of all university hospitals in Germany.
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http://dx.doi.org/10.1038/s41746-021-00439-yDOI Listing
April 2021

Dual-energy computed tomography: Tube current settings and detection of uric acid tophi.

Eur J Radiol 2021 Apr 1;139:109692. Epub 2021 Apr 1.

Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Mitte, Humboldt-Universität zu Berlin, Freie Universität Berlin, Charitéplatz 1, 10117, Berlin, Germany.

Purpose: To derive optimal scanning parameters for single-source dual-energy computed tomography (DECT) in the detection of urate by analyzing influence of tube current ratio (TCR) and total radiation exposure in a phantom.

Method: Specimens with different urate concentrations in a realistic porcine bio-phantom were repeatedly imaged with sequential single-source DECT scans at 80 kVp (16.5-220 mA s) and 135 kVp (2.75-19.25 mA s). Detection index (DI - true positive minus false positive urate volume) was calculated for every possible tube current combination. Optimal tube current combinations reaching at least 85 % of the highest measured DI of all combinations without exceeding 150 % of equivalent single-energy radiation dose were identified. TCR, DLP and DI were plotted and compared.

Results: Cubic regression analysis showed a flattening increase in the DI with increasing tube currents. Five out of the 100 tube current combinations analyzed achieved the detection target: the lowest DLP of 53.9 mGy*cm at 19.25/16.5 mAs (135/80 kVp) achieved a DI of 2.07 mL and the highest DI of 2.11 mL at a dose of 65.3 mGy*cm and 8.25/79.75 mAs. The optimal TCR is between two and four, while both, higher and lower ratios decreased DI.

Conclusions: A minimum tube current of the high-energy scans is needed before an acceptable overall sensitivity is achieved and before increases in low-energy exposure result in more urate detection. High TCRs above 10 are not beneficial while the optimal TCR ranges between two and four, indicating that special care has to be taken in designing a suitable DECT protocol.
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http://dx.doi.org/10.1016/j.ejrad.2021.109692DOI Listing
April 2021

Deep learning for detection of radiographic sacroiliitis: achieving expert-level performance.

Arthritis Res Ther 2021 04 8;23(1):106. Epub 2021 Apr 8.

Department of Gastroenterology, Infectious Diseases and Rheumatology, Charité - Universitätsmedizin Berlin, Berlin, Germany.

Background: Radiographs of the sacroiliac joints are commonly used for the diagnosis and classification of axial spondyloarthritis. The aim of this study was to develop and validate an artificial neural network for the detection of definite radiographic sacroiliitis as a manifestation of axial spondyloarthritis (axSpA).

Methods: Conventional radiographs of the sacroiliac joints obtained in two independent studies of patients with axSpA were used. The first cohort comprised 1553 radiographs and was split into training (n = 1324) and validation (n = 229) sets. The second cohort comprised 458 radiographs and was used as an independent test dataset. All radiographs were assessed in a central reading session, and the final decision on the presence or absence of definite radiographic sacroiliitis was used as a reference. The performance of the neural network was evaluated by calculating areas under the receiver operating characteristic curves (AUCs) as well as sensitivity and specificity. Cohen's kappa and the absolute agreement were used to assess the agreement between the neural network and the human readers.

Results: The neural network achieved an excellent performance in the detection of definite radiographic sacroiliitis with an AUC of 0.97 and 0.94 for the validation and test datasets, respectively. Sensitivity and specificity for the cut-off weighting both measurements equally were 88% and 95% for the validation and 92% and 81% for the test set. The Cohen's kappa between the neural network and the reference judgements were 0.79 and 0.72 for the validation and test sets with an absolute agreement of 90% and 88%, respectively.

Conclusion: Deep artificial neural networks enable the accurate detection of definite radiographic sacroiliitis relevant for the diagnosis and classification of axSpA.
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http://dx.doi.org/10.1186/s13075-021-02484-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028815PMC
April 2021

Dual-energy computed tomography of the neck-optimizing tube current settings and radiation dose using a 3D-printed patient phantom.

Quant Imaging Med Surg 2021 Apr;11(4):1144-1155

Department of Radiology, Charité - Universitätsmedizin Berlin, Campus Mitte, Humboldt-Universität zu Berlin, Freie Universität Berlin, Berlin, Germany.

Background: Dual-energy computed tomography (DECT) is increasingly used in studies and clinical practice. However, the best protocol is controversially discussed and whether it exhibits more radiation exposure compared to conventional protocols. Thus, the purpose of the study was to determine optimal tube current settings for DECT in a 3D-printed anthropomorphic phantom of the neck.

Methods: A 3D-printed iodinated ink based phantom of a contrast enhanced CT of the neck was imaged. Six dual-energy multi-detector computed tomography scans were performed with six different tube currents (80 kVp: 30-400 mAs; 135 kVp: 5-160 mAs). 120 virtual blended images (VBIs) and 66 virtual monochromatic images (VMIs) were reconstructed and 12 regions of interest (bilaterally: common carotid arteries, subcutaneous soft tissue, mandibular bone, sternocleidomastoid muscle, submandibular gland, and mid-image: vertebral body of C2 and pharyngeal space) in six consecutive slices resulting in 96 measurements per scan were performed. Hounsfield units and signal- and contrast-to-noise ratio were compared to single-energy computed tomography as standard of reference.

Results: VBIs overestimated the Hounsfield units (P<0.0001). Optimal dual-energy scanning parameters resulted in 120% (100 kVe: 51.2 61.7 and 65.2, for signal and contrast-to-noise ratio, respectively; 120 kVe: 60.8 72.1 128.3) of the radiation exposure with about 80% of the signal/contrast-to-noise ratio of the corresponding single-energy images. However, optimal weighting of tube currents for both voltages depended on the desired reconstruction.

Conclusions: Dual-energy protocols apply an estimated 120% of the single-energy radiation exposure and result in approximately 80% of the image quality. Tube current settings should be adapted to the desired information.
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http://dx.doi.org/10.21037/qims-20-854DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7930688PMC
April 2021

Dynamic Contrast-Enhanced MRI of Prostate Lesions of Simultaneous [Ga]Ga-PSMA-11 PET/MRI: Comparison between Intraprostatic Lesions and Correlation between Perfusion Parameters.

Cancers (Basel) 2021 Mar 19;13(6). Epub 2021 Mar 19.

Institute of Radiology and Nuclear Medicine, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany.

We aimed to retrospectively compare the perfusion parameters measured from dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) of prostate benign lesions and malignant lesions to determine the relationship between perfusion parameters. DCE-MRI was performed in patients with PCa who underwent simultaneous [Ga]Ga-prostate-specific membrane antigen (PSMA)-11 positron emission tomography (PET)/MRI. Six perfusion parameters (arrival time (AT), time to peak (TTP), wash-in slope (W-in), wash-out slope (W-out), peak enhancement intensity (PEI), and initial area under the 60-s curve (iAUC)), and a semi-quantitative parameter, standardized uptake values maximum (SUVmax) were calculated by placing regions of interest in the largest area of the lesions. The DCE-MRI parameters between prostate benign and malignant lesions were compared. The DCE-MRI parameters in both the benign and malignant lesions subgroup with SUVmax ≤ 3.0 and SUVmax > 3.0 were compared. The correlation of DCE-MRI parameters was investigated. Malignant lesions demonstrated significantly shorter TTP and higher SUVmax than did benign lesions. In the benign and malignant lesions subgroup, perfusion parameters of lesions with SUVmax ≤ 3.0 show no significant difference to those with SUVmax > 3.0. DCE-MRI perfusion parameters show a close correlation with each other. DCE-MRI parameters reflect the perfusion characteristics of intraprostatic lesions with malignant lesions, demonstrating significantly shorter TTP. There is a moderate to strong correlation between DCE-MRI parameters. Semi-quantitative analysis reflects that malignant lesions show a significantly higher SUVmax than benign lesions.
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http://dx.doi.org/10.3390/cancers13061404DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8003484PMC
March 2021

Targeting the Extracellular Matrix in Abdominal Aortic Aneurysms Using Molecular Imaging Insights.

Int J Mol Sci 2021 Mar 7;22(5). Epub 2021 Mar 7.

Charité-Universitaetsmedizin Berlin Corporate Member of Freie Universität Berlin Humboldt-Universitaet zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany.

This review outlines recent preclinical and clinical advances in molecular imaging of abdominal aortic aneurysms (AAA) with a focus on molecular magnetic resonance imaging (MRI) of the extracellular matrix (ECM). In addition, developments in pharmacologic treatment of AAA targeting the ECM will be discussed and results from animal studies will be contrasted with clinical trials. Abdominal aortic aneurysm (AAA) is an often fatal disease without non-invasive pharmacologic treatment options. The ECM, with collagen type I and elastin as major components, is the key structural component of the aortic wall and is recognized as a target tissue for both initiation and the progression of AAA. Molecular imaging allows in vivo measurement and characterization of biological processes at the cellular and molecular level and sets forth to visualize molecular abnormalities at an early stage of disease, facilitating novel diagnostic and therapeutic pathways. By providing surrogate criteria for the in vivo evaluation of the effects of pharmacological therapies, molecular imaging techniques targeting the ECM can facilitate pharmacological drug development. In addition, molecular targets can also be used in theranostic approaches that have the potential for timely diagnosis and concurrent medical therapy. Recent successes in preclinical studies suggest future opportunities for clinical translation. However, further clinical studies are needed to validate the most promising molecular targets for human application.
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http://dx.doi.org/10.3390/ijms22052685DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7962044PMC
March 2021

Hepatic Radiofrequency Ablation: Monitoring of Ablation-Induced Macrophage Recruitment in the Periablational Rim Using SPION-Enhanced Macrophage-Specific Magnetic Resonance Imaging.

Invest Radiol 2021 Mar 19. Epub 2021 Mar 19.

From the Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health Berlin Institute of Health Department of Veterinary Medicine, Institute of Animal Welfare, Animal Behavior and Laboratory Animal Science, Freie Universität Berlin, Berlin, Germany Department of Radiology and Biomedical Imaging, Yale University School of Medicine, New Haven, CT Institute of Inorganic and Analytical Chemistry, Westfälische Wilhelms-Universität Münster, Münster, Germany Department of Radiology, Hadassah Hebrew University Medical Center, Jerusalem, Israel King's College London, School of Biomedical Engineering and Imaging Sciences, United Kingdom, St Thomas' Hospital British Heart Foundation Centre of Research Excellence, King's College London, London, United Kingdom Department of Radiology, TU München, München, Germany.

Objectives: Macrophages accumulating in the periablational rim play a pivotal role in initiating and sustaining the perifocal inflammatory reaction, which has been shown to be at least 1 of the mechanisms responsible for the systemic pro-oncogenic effects of focal hepatic radiofrequency ablation (RFA). Herein, we tested the hypothesis to use superparamagnetic iron oxide nanoparticle (SPION)-enhanced magnetic resonance imaging (MRI) for noninvasive quantification of iron-loaded macrophages in the periablational rim of VX2 tumor-bearing rabbits.

Materials And Methods: Twelve VX2 tumor-bearing rabbits underwent MRI immediately after and up to 3 weeks after focal hepatic RFA. For noninvasive quantification of macrophage accumulation in the periablational rim, animals were scanned before and 24 hours after SPION injection. T2*-weighted images were analyzed and correlated with histopathological and immunohistochemical findings. Furthermore, correlations with quantitative measurements (ICP-MS [inductively coupled plasma-mass spectrometry] and LA-ICP-MS [laser ablation-ICP-MS]) were performed.

Results: SPION-enhanced T2*-weighted MRI scans displayed a progressive increase in the areas of signal intensity (SI) loss within the periablational rim peaking 3 weeks after RFA. Accordingly, quantitative analysis of SI changes demonstrated a significant decline in the relative SI ratio reflecting a growing accumulation of iron-loaded macrophages in the rim. Histological analyses confirmed a progressive accumulation of iron-loaded macrophages in the periablational rim. The ICP-MS and LA-ICP-MS confirmed a progressive increase of iron concentration in the periablational rim.

Conclusions: SPION-enhanced MRI enables noninvasive monitoring and quantification of ablation-induced macrophage recruitment in the periablational rim. Given the close interplay between ablation-induced perifocal inflammation and potential unwanted tumorigenic effects of RFA, SPION-enhanced MRI may serve as a valuable tool to guide and modulate adjuvant therapies after hepatic RFA.
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http://dx.doi.org/10.1097/RLI.0000000000000777DOI Listing
March 2021

Elastin-specific MRI of extracellular matrix-remodelling following hepatic radiofrequency-ablation in a VX2 liver tumor model.

Sci Rep 2021 Mar 25;11(1):6814. Epub 2021 Mar 25.

Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität Zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117, Berlin, Germany.

Hepatic radiofrequency ablation (RFA) induces a drastic alteration of the biomechanical environment in the peritumoral liver tissue. The resulting increase in matrix stiffness has been shown to significantly influence carcinogenesis and cancer progression after focal RF ablation. To investigate the potential of an elastin-specific MR agent (ESMA) for the assessment of extracellular matrix (ECM) remodeling in the periablational rim following RFA in a VX2 rabbit liver tumor-model, twelve New-Zealand-White-rabbits were implanted in the left liver lobe with VX2 tumor chunks from donor animals. RFA of tumors was performed using a perfused RF needle-applicator with a mean tip temperature of 70 °C. Animals were randomized into four groups for MR imaging and scanned at four different time points following RFA (week 0 [baseline], week 1, week 2 and week 3 after RFA), followed by sacrifice and histopathological analysis. ESMA-enhanced MR imaging was used to assess ECM remodeling. Gadobutrol was used as a third-space control agent. Molecular MR imaging using an elastin-specific probe demonstrated a progressive increase in contrast-to-noise ratio (CNR) (week 3: ESMA: 28.1 ± 6.0; gadobutrol: 3.5 ± 2.0), enabling non-invasive imaging of the peritumoral zone with high spatial-resolution, and accurate assessment of elastin deposition in the periablational rim. In vivo CNR correlated with ex vivo histomorphometry (ElasticaVanGiesson-stain, y = 1.2x - 1.8, R = 0.89, p < 0.05) and gadolinium concentrations at inductively coupled mass spectroscopy (ICP-MS, y = 0.04x + 1.2, R = 0.95, p < 0.05). Laser-ICP-MS confirmed colocalization of elastin-specific probe with elastic fibers. Following thermal ablation, molecular imaging using an elastin-specific MR probe is feasible and provides a quantifiable biomarker for the assessment of the ablation-induced remodeling of the ECM in the periablational rim.
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http://dx.doi.org/10.1038/s41598-021-86417-6DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7994448PMC
March 2021

DWI of Autoimmune Pancreatitis: Is It an Imaging Biomarker for Disease Activity?

AJR Am J Roentgenol 2021 Mar 24:1-7. Epub 2021 Mar 24.

Department of Gastroenterology, Peking Union Medical College Hospital, Beijing, China.

The purpose of this article was to evaluate the DWI features of autoimmune pancreatitis (AIP) at baseline, under treatment, and at relapse, and to assess the diagnostic accuracy of the ADC for determining disease activity. This retrospective study was approved by the institutional review board. Sixty-two patients with AIP (48 at initial attack and 14 at relapse) underwent MRI with DWI (b = 0 and 800 s/mm) at 3 T before receiving corticosteroid therapy (CST) and during follow-up. Seventeen patients had disease relapse during follow-up, whereas the others remained clinically stable. Forty age- and sex-matched patients without pancreatic disease served as the control group. The ADC value of AIP at baseline was significantly lower than that for a disease-free pancreas (0.99 ± 0.12 vs 1.26 ± 0.10 × 10 mm/s, < .001). Under CST, the ADC value increased gradually at the short-term and long-term follow-up (1.16 ± 0.12 and 1.23 ± 0.12 × 10 mm/s, respectively, both < .001). At relapse, the ADC had a relative decrease (1.11 ± 0.20 × 10 mm/s) but was significantly higher compared with the initial attack ( = .003). The AUC of ADC serum IgG4 level at ROC analysis for baseline versus clinically stable AIP was 0.867 and 0.700, the AUC for clinically active AIP versus clinically stable AIP was 0.762 and 0.686, and the AUC for relapsed AIP versus clinically stable AIP was 0.648 and 0.669. DWI reflected the dynamic change of AIP under CST, and the ADC value for DWI outperformed the serum IgG4 value for determining disease activity. However, relapsed disease showed less diffusion restriction, and the ADC value was less accurate for predicting relapse.
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http://dx.doi.org/10.2214/AJR.20.23368DOI Listing
March 2021

Correction to: Introducing the Node Reporting and Data System 1.0 (Node-RADS): a concept for standardized assessment of lymph nodes in cancer.

Eur Radiol 2021 Mar 19. Epub 2021 Mar 19.

Department of Radiology, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117, Berlin, Germany.

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http://dx.doi.org/10.1007/s00330-021-07795-zDOI Listing
March 2021

Decreased Medical Care During the COVID-19 Pandemic - A Comprehensive Analysis of Radiological Examinations.

Rofo 2021 Mar 18. Epub 2021 Mar 18.

Department of Radiology, Charité-Universitätsmedizin Berlin, Germany.

Objectives:  As a cross-section discipline within the hospital infrastructure, radiological departments might be able to provide important information regarding the impact of the COVID-19 pandemic on healthcare. The goal of this study was to quantify changes in medical care during the first wave of the pandemic using radiological examinations as a comprehensive surrogate marker and to determine potential future workload.

Methods:  A retrospective analysis of all radiological examinations during the first wave of the pandemic was performed. The number of examinations was compared to time-matched control periods. Furthermore, an in-depth analysis of radiological examinations attributed to various medical specialties was conducted and postponed examinations were extrapolated to calculate additional workload in the near future.

Results:  A total of 596,760 examinations were analyzed. Overall case volumes decreased by an average of 41 % during the shutdown compared to the control period. The most affected radiological modalities were sonography (-54 %), X-ray (-47 %) followed by MRI (-42 %). The most affected medical specialty was trauma and orthopedics (-60 % case volume) followed by general surgery (-49 %). Examination numbers increased during the post-shutdown period leading to a predicted additional workload of up to 22 %.

Conclusion:  This study shows a marked decrease in radiological examinations in total and among several core medical specialties, indicating a significant reduction in medical care during the first COVID-19 shutdown.

Key Points: · Number of radiological examinations decreased by 41 % during the first wave of the COVID-19 pandemic.. · Several core medical specialties were heavily affected with a reduction of case volumes up to 60 %.. · When extrapolating postponed examinations to the near future, the overall workload for radiological departments might increase up to 22 %..

Citation Format: · Fleckenstein FN, Maleitzke T, Böning G et al. Decreased Medical Care During the COVID-19 Pandemic - A Comprehensive Analysis of Radiological Examinations. Fortschr Röntgenstr 2021; DOI: 10.1055/a-1368-5047.
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http://dx.doi.org/10.1055/a-1368-5047DOI Listing
March 2021

Impact of age, sex, and joint form on degenerative lesions of the sacroiliac joints on CT in the normal population.

Sci Rep 2021 Mar 15;11(1):5903. Epub 2021 Mar 15.

Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.

Degeneration of the sacroiliac joints (SIJs) is a common finding, while its underlying cause and development remain incompletely understood. The aim of this investigation was to describe the spatial distribution of degenerative SIJ changes across age groups and to investigate for the first time their relationship to anatomical form and sex. For this IRB-approved investigation, demographic data of 818 patients without SIJ disease were retrieved from electronic patient records. High-resolution computed tomography (CT) datasets of all patients were analysed retrospectively for seven predefined age groups (ten-year increments, from < 25 to ≥ 75). A structured scoring system was applied to assess sclerosis, osteophytes, joint space alterations, and anatomical form. Chi-square tests were used to compare frequencies of degenerative lesions, and logistic regression analyses were performed to investigate associations between demographic data, anatomical form, and the presence of structural lesions. Sclerosis and osteophytes were common findings, with an overall prevalence of 45.7% and 46.8%, respectively. Female sex had an odds ratio (OR) of 0.15 (95% CI: 0.08-0.27) for the presence of ventral osteophytes and of 4.42 (95% CI: 2.77-7.04) for dorsal osteophytes. Atypical joint forms were significantly more prevalent in women with 62.1% vs. 14.1% in men (p < 0.001). Accessory joints increased the likelihood of dorsal sclerosis (OR 2.735; 95% CI 1.376-5.436) while a typical joint form decreased its likelihood (OR 0.174; 95% CI 0.104-0.293). Sex and anatomical joint form have a major impact on the development of degenerative lesions of the SIJs and their spatial distribution.
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http://dx.doi.org/10.1038/s41598-021-85303-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7960989PMC
March 2021

Use of TDI during MRI/US fusion-guided biopsy for suspected prostate cancer.

Clin Hemorheol Microcirc 2021 Feb 26. Epub 2021 Feb 26.

Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Department of Radiology, Berlin, Germany.

Background: Tissue Doppler imaging (TDI) uses the Doppler principle to quantify the movement of biological tissues.

Objective: To investigate the contribution of TDI parameters derived during magnetic resonance imaging and ultrasound (MRI/US) fusion-guided biopsy for prostate cancer (PCa) discrimination.

Methods: From March 2016 to Dec. 2018, 75 men with suspected PCa prospectively underwent fusion-guided prostate biopsy. TDI overlaid on predefined target lesion were compared to the confirmed contralateral tumor-free area of the prostate gland (using Image J). Diagnostic value of TDI parameters was assessed using histopathology as standard of reference.

Results: Thirty-seven patients were diagnosed with PCa (49.3%), among them 27 with clinically significant PCa (Gleason score >  3 + 3 = 6 (ISUP 1). The LES/REF ratio was lower in confirmed PCa patients compared to patients without PCa (0.42, IQR, 0.22-0.59 vs. 0.52, IQR, 0.40-0.72, p = 0.017). TDI parameters allowed differentiation of low-risk from high-to-intermediate-risk PCa (ISUP 2 versus ISUP 3) based on lower pixel counts within the target ROI (1340, IQR 596-2430 vs. 2687, IQR 2453-3216, p = 0.004), lower pixel percentage (16.4 IQR 11.4-29.5 vs. 27.3, IQR 22.1-39.5; p = 0.005), and lower LES/REF ratios (0.29, IQR 0.19-0.51 vs. 0.52, IQR 0.47-0.74, p = 0.001).

Conclusion: TDI of prostate lesions prelocated by MRI discriminates between cancerous and noncancerous lesions and further seems to enable characterization of PCa aggressiveness. This widely available US technique may improve confidence in target lesion localization for tissue sampling.
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http://dx.doi.org/10.3233/CH-201035DOI Listing
February 2021

HBP-enhancing hepatocellular adenomas and how to discriminate them from FNH in Gd-EOB MRI.

BMC Med Imaging 2021 Feb 15;21(1):28. Epub 2021 Feb 15.

Klinik Für Radiologie, Campus Virchow-Klinikum, Charité - Universitätsmedizin Berlin, Augustenburger Platz 1, 13353, Berlin, Germany.

Background: Recent studies provide evidence that hepatocellular  adenomas  (HCAs) frequently take up gadoxetic acid (Gd-EOB) during the hepatobiliary phase (HBP). The purpose of our study was to investigate how to differentiate between Gd-EOB-enhancing HCAs and focal nodular hyperplasias (FNHs). We therefore retrospectively included 40 HCAs classified as HBP Gd-EOB-enhancing lesions from a sample of 100 histopathologically proven HCAs in 65 patients. These enhancing HCAs were matched retrospectively with 28 FNH lesions (standard of reference: surgical resection). Two readers (experienced abdominal radiologists blinded to clinical data) reviewed the images evaluating morphologic features and subjectively scoring Gd-EOB uptake (25-50%, 50-75% and 75-100%) for each lesion. Quantitative lesion-to-liver enhancement was measured in arterial, portal venous (PV), transitional and HBP. Additionally, multivariate regression analyses were performed.

Results: Subjective scoring of intralesional Gd-EOB uptake showed the highest discriminatory accuracies (AUC: 0.848 (R#1); 0.920 (R#2)-p < 0.001) with significantly higher uptake scores assigned to FNHs (Cut-off: 75%-100%). Typical lobulation and presence of a central scar in FNH achieved an accuracy of 0.750 or higher in at least one reader (lobulation-AUC: 0.809 (R#1); 0.736 (R#2); central scar-AUC: 0.595 (R#1); 0.784 (R#2)). The multivariate regression emphasized the discriminatory power of the Gd-EOB scoring (p = 0.001/OR:22.15 (R#1) and p < 0.001/OR:99.12 (R#2). The lesion-to-liver ratio differed significantly between FNH and HCA in the PV phase and HBP (PV: 132.9 (FNH) and 110.2 (HCA), p = 0.048 and HBP: 110.3 (FNH) and 39.2 (HCA), p < 0.001)), while the difference was not significant in arterial and transitional contrast phases (p > 0.05).

Conclusion: Even in HBP-enhancing HCA, characterization of Gd-EOB uptake was found to provide the strongest discriminatory power in differentiating HCA from FNH. Furthermore, a lobulated appearance and a central scar are more frequently seen in FNH than in HCA.
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http://dx.doi.org/10.1186/s12880-021-00552-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7885421PMC
February 2021

Introducing the Node Reporting and Data System 1.0 (Node-RADS): a concept for standardized assessment of lymph nodes in cancer.

Eur Radiol 2021 Feb 14. Epub 2021 Feb 14.

Department of Radiology, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117, Berlin, Germany.

"Node-RADS" addresses the lack of consensus in the radiologic assessment of lymph node involvement by cancer and meets the increasing demand for structured reporting on the likelihood of disease involvement. Node Reporting and Data System 1.0 (Node-RADS) systematically classifies the degree of suspicion of lymph node involvement based on the synthesis of established imaging findings. Straightforward definitions of imaging findings for two proposed scoring categories "size" and "configuration" are combined into assessment categories between 1 ("very low likelihood") and 5 ("very high likelihood"). This scoring system is suitable for assessing likely involvement of lymph nodes on CT and MRI scans. It can be applied at any anatomical site, and to regional and non-regional lymph nodes in relation to a primary tumor location. Node-RADS will improve communication with referring physicians and promote the consistency of reporting for primary staging and in response assessment settings. KEY POINTS: • Node-RADS standardizes reporting of possible cancer involvement of regional and distant lymph nodes on CT and MRI. • Node-RADS proposes the scoring categories "size" and "configuration" for assigning the 5-point Node-RADS score from 1 ("very low likelihood") to 5 ("very high likelihood"). • Node-RADS aims to increase consensus among radiologists for primary staging and in response assessment settings.
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http://dx.doi.org/10.1007/s00330-020-07572-4DOI Listing
February 2021

Diagnostic performance of dynamic volume perfusion CT for differentiation of head and neck cancer from healthy tissue and post-therapeutic changes.

Clin Hemorheol Microcirc 2021 Jan 30. Epub 2021 Jan 30.

Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Campus Benjamin Franklin, Berlin, Germany.

Background: Post-therapeutic tissue is bradytrophic and thus has low perfusion values in PCT. In contrast, malignant tissue is expected to show higher perfusion values as cancer growth partially depends on angiogenesis.

Objectives: This prospective study investigates perfusion computed tomography (PCT) for the post-therapeutic detection of cancer in the head and neck region.

Methods: 85 patients underwent PCT for 1) initial work-up of head and neck cancer (HNC; n=22) or 2) for follow-up (n=63). Regions of interest (ROIs) were placed in confirmed tumour, a corresponding location of benign tissue, and reference tissue. Perfusion was calculated using a single input maximum slope algorithm. Statistical analysis was performed with the Mann-Whitney U-test.

Results: PCT allowed significant differentiation of malignant tissue from post-therapeutic tissue after treatment for HNC (p=0.018). Significance was even greater after normalization of perfusion values (p=0.007). PCT allowed highly significant differentiation of HNC from reference tissue (p<0.001).

Conclusions: PCT provides significantly distinct perfusion values for malignant and benign as well as post-therapeutically altered tissue in the head and neck area, thus allowing differentiation of cancer from healthy tissue. Our results show that PCT in conjunction with a standard algorithm is a potentially powerful HNC diagnostic tool.
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http://dx.doi.org/10.3233/CH-200919DOI Listing
January 2021

Iron(III)-tCDTA derivatives as MRI contrast agents: Increased T relaxivities at higher magnetic field strength and pH sensing.

Magn Reson Med 2021 Jun 4;85(6):3370-3382. Epub 2021 Feb 4.

Department of Radiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.

Purpose: Low molecular weight iron(III) complex-based contrast agents (IBCA) including iron(III) trans-cyclohexane diamine tetraacetic acid [Fe(tCDTA)] could serve as alternatives to gadolinium-based contrast agents in MRI. In search for IBCA with enhanced properties, we synthesized derivatives of [Fe(tCDTA)] and compared their contrast effects.

Methods: Trans-cyclohexane diamine tetraacetic acid (tCDTA) was chemically modified in 2 steps: first the monoanhydride of Trans-cyclohexane diamine tetraacetic acid was generated, and then it was coupled to amines in the second step. After purification, the chelators were analyzed by high-performance liquid chromatography, mass spectrometry, and NMR spectrometry. The chelators were complexed with iron(III), and the relaxivities of the complexes were measured at 0.94, 1.5, 3, and 7 Tesla. Kinetic stabilities of the complexes were analyzed spectrophotometrically and the redox properties by cyclic voltammetry.

Results: Using ethylenediamine (en) and trans-1,4-diaminocyclohexane, we generated monomers and dimers of tCDTA: en-tCDTA, en-tCDTA-dimer, trans-1,4-diaminocyclohexane-tCDTA, and trans-1,4-diaminocyclohexane-tCDTA-dimer. The iron(III) complexes of these derivatives had similarly high stabilities as [Fe(tCDTA)] . The iron(III) complexes of the trans-1,4-diaminocyclohexane derivatives had higher T relaxivities than [Fe(tCDTA)] that increased with increasing magnetic field strengths and were highest at 6.8 L·mmol ·s per molecule for the dimer. Remarkably, the relaxivity of [Fe(en-tCDTA)] had a threefold increase from neutral pH toward pH6.

Conclusion: Four iron(III) complexes with similar stability in comparison to [Fe(tCDTA)] were synthesized. The relaxivities of trans-1,4-diaminocyclohexane-tCDTA and trans-1,4-diaminocyclohexane-tCDTA-dimer complexes were in the same range as gadolinium-based contrast agents at 3 Tesla. The [Fe(en-tCDTA)] complex is a pH sensor at weakly acidic pH levels, which are typical for various cancer types.
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http://dx.doi.org/10.1002/mrm.28664DOI Listing
June 2021

Tomoelastography for Longitudinal Monitoring of Viscoelasticity Changes in the Liver and in Renal Allografts after Direct-Acting Antiviral Treatment in 15 Kidney Transplant Recipients with Chronic HCV Infection.

J Clin Med 2021 Feb 1;10(3). Epub 2021 Feb 1.

Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany.

Besides the liver, hepatitis C virus (HCV) infection also affects kidney allografts. The aim of this study was to longitudinally evaluate viscoelasticity changes in the liver and in kidney allografts in kidney transplant recipients (KTRs) with HCV infection after treatment with direct-acting antiviral agents (DAAs). Fifteen KTRs with HCV infection were treated with DAAs (daclatasvir and sofosbuvir) for 3 months and monitored at baseline, end of treatment (EOT), and 3 (FU1) and 12 (FU2) months after EOT. Shear-wave speed (SWS) and loss angle of the complex shear modulus (φ), reflecting stiffness and fluidity, respectively, were reconstructed from multifrequency magnetic resonance elastography data with tomoelastography post-processing. After virus elimination by DAAs, hepatic stiffness and fluidity decreased, while kidney allograft stiffness and fluidity increased compared with baseline (hepatic stiffness change at FU1: -0.14 m/s, < 0.01, and at FU2: -0.11 m/s, < 0.05; fluidity at FU1: -0.05 rad, = 0.04 and unchanged at FU2: = 0.20; kidney allograft stiffness change at FU1: +0.27 m/s, = 0.01, and at FU2: +0.30 m/s, < 0.01; fluidity at FU1 and FU2: +0.06 rad, = 0.02). These results suggest the restoration of mechanically sensitive structures and functions in both organs. Tomoelastography can be used to monitor the therapeutic results of HCV treatment non-invasively on the basis of hepatic and renal viscoelastic parameters.
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http://dx.doi.org/10.3390/jcm10030510DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7867050PMC
February 2021

Reliability of NI-RADS criteria in the interpretation of contrast-enhanced magnetic resonance imaging considering the potential role of diffusion-weighted imaging.

Eur Radiol 2021 Feb 3. Epub 2021 Feb 3.

Department of Radiology, Campus Benjamin Franklin, Charité- Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Hindenburgdamm 30, 12203, Berlin, Germany.

Objectives: To assess inter- and intrareader agreement of the Neck Imaging Reporting and Data System (NI-RADS) used in contrast-enhanced magnetic resonance imaging (MRI) including analysis of diffusion-weighted imaging (DWI), which is currently not part of the NI-RADS criteria.

Methods: This retrospective study included anonymized surveillance contrast-enhanced MRI datasets of 104 patients treated for different head and neck cancers. Three radiologists experienced in head and neck imaging reported findings for the primary site and the neck using NI-RADS criteria in a first step and evaluated DWI sequences for the primary site in a second step. Thirty randomly selected imaging datasets were again presented to the readers. Kappa statistics and observed agreement (A) were calculated.

Results: Interreader agreement across all MRI datasets was moderate (κ = 0.53) for NI-RADS categories assigned to the primary site, substantial for NI-RADS categories of the neck (κ = 0.67), and almost perfect for DWI of the primary site (κ = 0.83). Interreader agreement for the primary site was particularly low in cases of cancer recurrence (κ = 0.35) and when categories 2a, 2b, and 3 were combined (κ = 0.30). Intrareader agreement was considerably lower for NI-RADS categories of the primary site (range A = 53.3-70.0%) than for NI-RADS categories of the neck (range A = 83.3-90.0%) and DWI of the primary site (range A = 93.3-100.0%).

Conclusion: Interreader agreement of NI-RADS for reporting contrast-enhanced MRI findings is acceptable for the neck but limited for the primary site. Here, DWI has the potential to serve as a reliable additional criterion.

Key Points: • NI-RADS was originally designed for contrast-enhanced computed tomography with or without positron emission tomography but can also be used for contrast-enhanced magnetic resonance imaging alone. • Overall interreader agreement was acceptable for NI-RADS categories assigned to the neck but should be improved for the primary site, where it was inferior to DWI; similar tendencies were found for intrareader agreement. • DWI is currently no criterion of NI-RADS, but has shown potential to improve its reliability, especially for categories 2a, 2b, and 3 of the primary site.
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http://dx.doi.org/10.1007/s00330-021-07693-4DOI Listing
February 2021

Cost-effectiveness analysis of multiple imaging modalities in diagnosis and follow-up of intermediate complex cystic renal lesions.

BJU Int 2021 Feb 2. Epub 2021 Feb 2.

Department of Radiology.

Objectives: To compare health-economic aspects of multiple imaging modalities used to monitor renal cysts, the present study evaluates costs and outcomes of patients with Bosniak IIF and III renal cysts detected and followed-up by either contrast-enhanced computed tomography (ceCT), contrast-enhanced magnetic resonance imaging (ceMRI), or contrast-enhanced ultrasonography (CEUS).

Patients And Methods: A simulation using Markov models was implemented and performed with 10 cycles of 1 year each. Proportionate cohorts were allocated to Markov models by a decision tree processing specific incidences of malignancy and levels of diagnostic performance. Costs of imaging and surgical treatment were investigated using internal data of a European university hospital. Multivariate probabilistic sensitivity analysis was performed to confirm results considering input value uncertainties. Patient outcomes were measured in quality-adjusted life years (QALY), and costs as averages per patient including costs of imaging and surgical treatment.

Results: Compared to the 'gold standard' of ceCT, ceMRI was more effective but also more expensive, with a resulting incremental cost-effectiveness ratio (ICER) >€70 000 (Euro) per QALY gained. CEUS was dominant compared to ceCT in both Bosniak IIF and III renal cysts in terms of QALYs and costs. Probabilistic sensitivity analysis confirmed these results in the majority of iterations.

Conclusion: Both ceMRI and CEUS can be used as alternatives to ceCT in the diagnosis and follow-up of intermediately complex cystic renal lesions without compromising effectiveness, while CEUS is clearly cost-effective. The economic results apply to a large university hospital and must be adapted for smaller hospitals.
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http://dx.doi.org/10.1111/bju.15353DOI Listing
February 2021

Multiparametric ultrasound findings in acute kidney failure due to rare renal cortical necrosis.

Sci Rep 2021 Jan 21;11(1):2060. Epub 2021 Jan 21.

Department of Radiology, Charité - Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität Zu Berlin, Campus Charité Mitte, Charitéplatz 1, 10117, Berlin, Germany.

Renal cortical necrosis (RCN) is a rare cause of acute kidney failure and is usually diagnosed on the basis of characteristic enhancement patterns on cross-sectional imaging. Contrast-enhanced ultrasound (CEUS) offers benefits in patients with kidney failure in the clinical setting including the use of a nonnephrotoxic intravascular contrast agent and the fact that it can be performed at the bedside in critical cases. Therefore, the aim of this study is to investigate whether CEUS can reliably identify typical imaging features of RCN. We retrospectively analyzed 12 patients with RCN examined in our department and confirmation of the diagnosis by either histopathology, other contrast-enhanced cross-sectional imaging tests, and/or CEUS follow-up. Assessed parameters in conventional US were reduced echogenicity, loss of corticomedullary differentiation, length and width of kidney, hypoechoic rim, resistance index and in CEUS delayed wash-in of contrast agent (> 20 s), reverse rim sign, maximum nonenhancing rim and additional renal infarction. Furthermore, imaging features in RCN were compared with the findings in renal vein thrombosis (RVT), among them echogenicity, corticomedullar differentiation, hypoechoic rim, RI value, delayed cortical enhancement, total loss of cortical perfusion and enhancement of renal medulla. All 12 patients showed the reverse rim sign, while a hypoechogenic subcapsular rim was only visible in four patients on B-mode ultrasound. A resistance index (RI) was available in 10 cases and was always less than 1. RI was a strong differentiator in separating RVT from RCN (RI > 1 or not measurable due to hypoperfusion as differentiator, p = 0.001). CEUS showed total loss of medullary enhancement in all cases of RVT. With its higher temporal resolution, CEUS allows dynamic assessment of renal macro- and microcirculation and identification of the typical imaging findings of RCN with use of a nonnephrotoxic contrast agent.
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http://dx.doi.org/10.1038/s41598-021-81690-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7820240PMC
January 2021

Imaging coronary plaques using 3D motion-compensated [F]NaF PET/MR.

Eur J Nucl Med Mol Imaging 2021 Jan 21. Epub 2021 Jan 21.

Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Berlin, Germany.

Background: Cardiac PET has recently found novel applications in coronary atherosclerosis imaging using [F]NaF as a radiotracer, highlighting vulnerable plaques. However, the resulting uptakes are relatively small, and cardiac motion and respiration-induced movement of the heart can impair the reconstructed images due to motion blurring and attenuation correction mismatches. This study aimed to apply an MR-based motion compensation framework to [F]NaF data yielding high-resolution motion-compensated PET and MR images.

Methods: Free-breathing 3-dimensional Dixon MR data were acquired, retrospectively binned into multiple respiratory and cardiac motion states, and split into fat and water fraction using a model-based reconstruction framework. From the dynamic MR reconstructions, both a non-rigid cardiorespiratory motion model and a motion-resolved attenuation map were generated and applied to the PET data to improve image quality. The approach was tested in 10 patients and focal tracer hotspots were evaluated concerning their target-to-background ratio, contrast-to-background ratio, and their diameter.

Results: MR-based motion models were successfully applied to compensate for physiological motion in both PET and MR. Target-to-background ratios of identified plaques improved by 7 ± 7%, contrast-to-background ratios by 26 ± 38%, and the plaque diameter decreased by -22 ± 18%. MR-based dynamic attenuation correction strongly reduced attenuation correction artefacts and was not affected by stent-related signal voids in the underlying MR reconstructions.

Conclusions: The MR-based motion correction framework presented here can improve the target-to-background, contrast-to-background, and width of focal tracer hotspots in the coronary system. The dynamic attenuation correction could effectively mitigate the risk of attenuation correction artefacts in the coronaries at the lung-soft tissue boundary. In combination, this could enable a more reproducible and reliable plaque localisation.
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http://dx.doi.org/10.1007/s00259-020-05180-4DOI Listing
January 2021

Does Hepatic Steatosis Influence the Detection Rate of Metastases in the Hepatobiliary Phase of Gadoxetic Acid-Enhanced MRI?

J Clin Med 2020 Dec 30;10(1). Epub 2020 Dec 30.

Klinik und Poliklinik für Diagnostische und Interventionelle Radiologie, Universitätsklinikum Leipzig, 04103 Leipzig, Germany.

The aim of this exploratory study was to evaluate the influence of hepatic steatosis on the detection rate of metastases in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). A total of 50 patients who underwent gadoxetic acid-enhanced MRI (unenhanced T1w in- and opposed-phase, T2w fat sat, unenhanced 3D-T1w fat sat and 3-phase dynamic contrast-enhanced (uDP), 3D-T1w fat sat hepatobiliary phase (HP)) were retrospectively included. Two blinded observers (O1/O2) independently assessed the images to determine the detection rate in uDP and HP. The hepatic signal fat fraction (HSFF) was determined as the relative signal intensity reduction in liver parenchyma from in- to opposed-phase images. A total of 451 liver metastases were detected (O1/O2, = 447/411). O1/O2 detected 10.9%/9.3% of lesions exclusively in uDP and 20.2%/15.5% exclusively in HP. Lesions detected exclusively in uDP were significantly associated with a larger HSFF (area under curve (AUC) of receiver operating characteristic (ROC) analysis, 0.93; < 0.001; cutoff, 41.5%). The exclusively HP-positive lesions were significantly associated with a smaller diameter (ROC-AUC, 0.82; < 0.001; cutoff, 5 mm) and a smaller HSFF (ROC-AUC, 0.61; < 0.001; cutoff, 13.3%). Gadoxetic acid imaging has the advantage of detecting small occult metastatic liver lesions in the HP. However, using non-optimized standard fat-saturated 3D-T1w protocols, severe steatosis (HSFF > 30%) is a potential pitfall for the detection of metastases in HP.
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http://dx.doi.org/10.3390/jcm10010098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7796028PMC
December 2020

Molecular MR Imaging of Prostate Cancer.

Biomedicines 2020 Dec 22;9(1). Epub 2020 Dec 22.

Department of Radiology, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany.

This review summarizes recent developments regarding molecular imaging markers for magnetic resonance imaging (MRI) of prostate cancer (PCa). Currently, the clinical standard includes MR imaging using unspecific gadolinium-based contrast agents. Specific molecular probes for the diagnosis of PCa could improve the molecular characterization of the tumor in a non-invasive examination. Furthermore, molecular probes could enable targeted therapies to suppress tumor growth or reduce the tumor size.
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http://dx.doi.org/10.3390/biomedicines9010001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7822017PMC
December 2020

Quality Assessment of CEUS in Individuals with Small Renal Masses-Which Individual Factors Are Associated with High Image Quality?

J Clin Med 2020 Dec 17;9(12). Epub 2020 Dec 17.

Department of Radiology, Charité-Universitätsmedizin Berlin, 10117 Berlin, Germany.

Obesity and bowel gas are known to impair image quality in abdominal ultrasound (US). The present study aims at identifying individual factors in B-mode US that influence contrast-enhanced US (CEUS) image quality to optimize further imaging workup of incidentally detected focal renal masses. We retrospectively analyzed renal CEUS of focal renal masses ≤ 4 cm performed at our center in 143 patients between 2016 and 2020. Patient and lesion characteristics were tested for their influence on focal and overall image quality assessed by two experienced radiologists using Likert scales. Effects of significant variables were quantified by receiver operating characteristics (ROC) curve analysis with area under the curve (AUC), and combined effects were assessed by binary logistic regression. Shrunken kidney, kidney depth, lesion depth, lesion size, and exophytic lesion growth were found to influence focal renal lesion image quality, and all factors except lesion size also influenced overall image quality. Combination of all parameters except kidney depth best predicted good CEUS image quality showing an AUC of 0.91 ( < 0.001, 95%-CI 0.863-0.958). The B-mode US parameters investigated can identify patients expected to have good CEUS image quality and thus help select the most suitable contrast-enhanced imaging strategy for workup of renal lesions.
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http://dx.doi.org/10.3390/jcm9124081DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7767001PMC
December 2020

Temperatures in Pigs During 3 T MRI Temperatures, Heart Rates, and Breathing Rates of Pigs During RF Power Deposition in a 3 T (128 MHz) Body Coil.

Bioelectromagnetics 2021 Jan 20;42(1):37-50. Epub 2020 Dec 20.

Institute for Medical Statistics, Programming and Data Science, University Clinic Jena, Jena, Germany.

Exposure to radiofrequency (RF) power deposition during magnetic resonance imaging (MRI) induces elevated body-tissue temperatures and may cause changes in heart and breathing rates, disturbing thermoregulation. Eleven temperature sensors were placed in muscle tissue and one sensor in the rectum (measured in 10 cm depth) of 20 free-breathing anesthetized pigs to verify temperature curves during RF exposure. Tissue temperatures and heart and breathing rates were measured before, during, and after RF exposure. Pigs were placed into a 60-cm diameter whole-body resonator of a 3 T MRI system. Nineteen anesthetized pigs were divided into four RF exposure groups: sham (0 W/kg), low-exposure (2.7 W/kg, mean exposure time 56 min), moderate-exposure (4.8 W/kg, mean exposure time 31 min), and high-exposure (4.4 W/kg, mean exposure time 61 min). One pig was exposed to a whole-body specific absorption rate (wbSAR) of 11.4 W/kg (extreme-exposure). Hotspot temperatures, measured by sensor 2, increased by mean 5.0 ± 0.9°C, min 3.9; max 6.3 (low), 7.0 ± 2.3°C, min 4.6; max 9.9 (moderate), and 9.2 ± 4.4°C, min 6.1, max 17.9 (high) compared with 0.3 ± 0.3°C in the sham-exposure group (min 0.1, max 0.6). Four time-temperature curves were identified: sinusoidal, parabolic, plateau, and linear. These curve shapes did not correlate with RF intensity, rectal temperature, breathing rate, or heart rate. In all pigs, rectal temperatures increased (2.1 ± 0.9°C) during and even after RF exposure, while hotspot temperatures decreased after exposure. When rectal temperature increased by 1°C, hotspot temperature increased up to 42.8°C within 37 min (low-exposure) or up to 43.8°C within 24 min (high-exposure). Global wbSAR did not correlate with maximum hotspot. Bioelectromagnetics. 2021;42:37-50. © 2020 The Authors. Bioelectromagnetics published by Wiley Periodicals LLC on behalf of Bioelectromagnetics Society.
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http://dx.doi.org/10.1002/bem.22311DOI Listing
January 2021

Lesion-to-background ratio threshold value of SUVmax of simultaneous [Ga]Ga-PSMA-11 PET/MRI imaging in patients with prostate cancer.

Insights Imaging 2020 Dec 17;11(1):137. Epub 2020 Dec 17.

Institute of Radiology and Nuclear Medicine, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117, Berlin, Germany.

Purpose: This study aimed to calculate an applicable relative ratio threshold value instead of the absolute threshold value for simultaneous Ga prostate-specific membrane antigen/positron emission tomography ([Ga]Ga-PSMA-11 PET) in patients with prostate cancer (PCa).

Materials And Methods: Our study evaluated thirty-two patients and 170 focal prostate lesions. Lesions are classified into groups according to Prostate Imaging Reporting and Data System (PI-RADS). Standardized uptake values maximum (SUVmax), corresponding lesion-to-background ratios (LBRs) of SUVmax, and LBR distributions of each group were measured based on regions of interest (ROI). We examined LBR with receiver operating characteristic analysis to determine threshold values for differentiation between multiparametric magnetic resonance imaging (mpMRI)-positive and mpMRI-negative lesions.

Results: We analyzed a total of 170 focal prostate lesions. Lesions number of PI-RADS 2 to 5 was 70, 16, 46, and 38. LBR of SUVmax of each PI-RADS scores was 1.5 (0.9, 2.4), 2.5 (1.6, 3.4), 3.7 (2.6, 4.8), and 6.7 (3.5, 12.7). Based on an optimal threshold ratio of 2.5 to be exceeded, lesions could be classified into MRI-positive lesion on [Ga]Ga-PSMA PET with a sensitivity of 85.2%, a specificity of 72.0%, with the corresponding area under the receiver operating characteristic curve (AUC) of 0.83, p < 0.001. This value matches the imaging findings better.

Conclusion: The ratio threshold value of SUVmax, LBR, has improved clinical and research applicability compared with the absolute value of SUVmax. A higher threshold value than the background's uptake can dovetail the imaging findings on MRI better. It reduces the bias from using absolute background uptake value as the threshold value.
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http://dx.doi.org/10.1186/s13244-020-00926-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7745090PMC
December 2020

Value of susceptibility-weighted imaging for the assessment of angle measurements reflecting hip morphology.

Sci Rep 2020 12 1;10(1):20899. Epub 2020 Dec 1.

Department of Radiology, Technical University of Munich, Ismaninger Str. 22, 81675, Munich, Germany.

Radiographs are the clinical first line imaging modality for evaluating hip morphology and pathology. MRI offers additional information and is the method of choice to evaluate soft tissue, bone marrow and preradiographic signs of osteoarthritis. Radiographs are used to measure the most morphometric parameters. The aim of this study was to compare susceptibility weighted MRI (SWMR) with radiographs to evaluate hip morphology. 40 Patients were examined with standard MR-sequences, coronal SWMR and radiographs in anteroposterior pelvic view. Coronal maximum intensity projection (MIP) images of both hips were automatically reconstructed on SWMR and T1weighted images. Sharp´s angle, Tönnis angle, lateral center-edge angle of Wiberg and caput-collum-diaphyseal angle were measured on coronal SWMR MIP-images, T1weighted MIP-images and radiographs. Measurements were compared by linear regression analysis and Bland-Altmann Plots, using radiographs as reference standard. Additionally, a ratio between the signal intensity of muscles and bone on SWMR and T1weighted MIP-images was calculated and compared between these two sequences. SWMR enables the reliable assessment of Sharp´s angle (SWMR: R = 0.80; T1weighted: R = 0.37), Tönnis angle (SWMR: R = 0.86; T1weighted: not measurable), lateral center-edge angle of Wiberg (SWMR: R = 0.88; T1weighted: R = 0.40) and caput-collum-diaphyseal angle (SWMR: R = 0.38; T1weighted: R = 0.18) compared to radiographs with a higher accuracy than conventional MR imaging. The ratio between the intensity of muscles and bone was significant higher on SWMR (2.00 and 2.02) than on T1weighted MIP-images (1.6 and 1.42; p < 0.001).
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http://dx.doi.org/10.1038/s41598-020-77671-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7708417PMC
December 2020

Correlation between Intraprostatic PSMA Uptake and MRI PI-RADS of [Ga]Ga-PSMA-11 PET/MRI in Patients with Prostate Cancer: Comparison of PI-RADS Version 2.0 and PI-RADS Version 2.1.

Cancers (Basel) 2020 Nov 26;12(12). Epub 2020 Nov 26.

Institute of Radiology and Nuclear Medicine, Charité-Universitätsmedizin Berlin, Corporate Member of Freie Universität Berlin, Humboldt-Universität zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117 Berlin, Germany.

Purpose: We aimed to evaluate the correlation between PSMA uptake and magnetic resonance imaging (MRI) PI-RADS of simultaneous [Ga]Ga-PSMA-11 PET/MRI regarding PI-RADS version 2.0 and 2.1 respectively and compared the difference between these two versions.

Materials And Methods: We retrospectively analyzed a total of forty-six patients with biopsy-proven prostate cancer who underwent simultaneous [Ga]Ga-PSMA-11 PET/MRI. We classified the lesions regarding PI-RADS version 2.0 and 2.1, peripheral zone (PZ), and transitional zone (TZ), respectively. Based on regions of interest (ROI), standardized uptake values maximum (SUVmax), and corresponding lesion-to-background ratios (LBR) of SUVmax of each category, PI-RADS score 1 to 5, were measured. A comparison between PI-RADS version 2.0 and PI-RADS version 2.1 was performed.

Results: A total of 215 focal prostate lesions were analyzed, including two subgroups, 125 TZ and 90 PZ. Data are reported as median and interquartile range (IQR). Regarding PI-RADS version 2.1, TZ SUVmax of each category were 1.5 (0.5, 1.9), 1.9 (0.8, 2.3), 3.3 (2.1, 4.6), 4.2 (3.1, 5.7), 7.3 (5.2, 9.7). PZ SUVmax of each category were 1.0 (0.8, 1.6), 2.5 (1.5, 3.2), 3.3 (1.9, 4.5), 4.3 (3.0, 5.4), 7.4 (5.0, 9.3). Regarding the inter-reader agreement of the overall PI-RADS assessment category, the kappa value was 0.723 for version 2.0 and 0.853 for version 2.1.

Conclusion: Revisions of PI-RADS version 2.1 results in variations in lesions classification. Lesions with the PI-RADS category of 3, 4, and 5 present relatively higher intraprostatic PSMA uptake, while lesions with the PI-RADS category of 1 and 2 present relatively lower and similar uptake. Version 2.1 has higher inter-reader reproducibility than version 2.0.
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http://dx.doi.org/10.3390/cancers12123523DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7759872PMC
November 2020

Assessment of the hepatic tumor extracellular matrix using elastin-specific molecular magnetic resonance imaging in an experimental rabbit cancer model.

Sci Rep 2020 11 27;10(1):20785. Epub 2020 Nov 27.

Department of Radiology, Charité - Universitätsmedizin Berlin, corporate member of Freie Universität Berlin, Humboldt-Universität Zu Berlin, and Berlin Institute of Health, Charitéplatz 1, 10117, Berlin, Germany.

To investigate the imaging performance of an elastin-specific molecular magnetic resonance imaging (MRI) probe with respect to the extracellular matrix (ECM) in an experimental hepatic cancer model. Twelve rabbits with hepatic VX2 tumors were examined using 3 T MRI 14, 21, and 28 days after tumor implantation for two subsequent days (gadobutrol, day 1; elastin-specific probe, day 2). The relative enhancement (RE) of segmented tumor regions (central and margin) and the peritumoral matrix was calculated using pre-contrast and delayed-phase T1w sequences. MRI measurements were correlated to histopathology and element-specific and spatially resolved mass spectrometry (MS). Mixed-model analysis was performed to assess the performance of the elastin-specific probe. In comparison to gadobutrol, the elastin probe showed significantly stronger RE, which was pronounced in the tumor margin (day 14-28: P ≤ 0.007). In addition, the elastin probe was superior in discriminating between tumor regions (χ(4) = 65.87; P < 0.001). MRI-based measurements of the elastin probe significantly correlated with the ex vivo elastinstain (R = .84; P <0 .001) and absolute gadolinium concentrations (ICP-MS: R = .73, P <0 .01). LA-ICP-MS imaging confirmed the colocalization of the elastin-specific probe with elastic fibers. Elastin-specific molecular MRI is superior to non-specific gadolinium-based contrast agents in imaging the ECM of hepatic tumors and the peritumoral tissue.
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http://dx.doi.org/10.1038/s41598-020-77624-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7695832PMC
November 2020