Simulation des Blutflusses in der abdominellen Aorta: Die numerische Simulation des Blutflusses in abdominellen Aortenaneurysmen vor und nach Intervention

Zusammenfassung: Das Ziel der numerischen Simulation des Blutflusses in der Aorta ist, die Mechanik der Entstehung von Aortenaneurysmen im Hinblick auf das Rupturrisiko zu untersuchen und die Wirkungen interventioneller Maßnahmen zu beschreiben. Die Grundlage der numerischen Simulation sind virtuelle Modelle von Gefäßen und die physikalischen Eigenschaften der Gefäßbestandteile, des Blutes und der Strömung. Basierend auf diesen Angaben werden mit Hilfe numerischer Methoden die strömungsmechanischen Probleme des Blutflusses näherungsweise gelöst. Die Ergebnisse können dann quantitativ und qualitativ dargestellt werden. Die Ergebnisse der numerischen Flusssimulation zeigen, dass in abdominellen Aortenaneurysmen die Höhe des Wanddrucks, der von entscheidender Bedeutung für das Rupturrisiko ist, von verschiedenen Faktoren, wie z.B. der Lage des Wandthrombus, abhängt. In Modellen mit Stentgrafts wurden mit Hilfe der numerischen Simulation Faktoren, welche die Stentgraftmigration beeinflussen, untersucht. Obwohl die numerische Simulation des Blutflusses noch einige Limitationen aufweist, zeigen aktuelle Studien, dass die Methode das Potenzial hat, um in Zukunft eine dedizierte Beurteilung des Rupturrisikos von Aortenaneurysmen vorzunehme

Kardiale Niedrigdosis-Computertomographie

Cardiac CT has evolved to a robust and accurate imaging modality in the cardiac diagnostic armamentarium. However, technical developments had been accompanied with an overall increase in radiation exposure. In the last years, several technical developments and algorithms aimed at the reduction of radiation exposure in cardiac CT. The most relevant dose reduction strategies will be highlighted in this article including appropriate indications for cardiac CT, different ECG synchronization techniques, reduction of tube voltage, and high-pitch CT studies

Untersuchungstechniken und Stellenwert der CT bei der Diagnostik von Herzklappenerkrankungen

Zusammenfassung: Klinisches/methodisches Problem: Die Herz-CT wird in erster Linie anlässlich einer Koronarabklärung durchgeführt. Sie ist aber auch in der Lage, wichtige Informationen über die Morphologie und teilweise auch Herzklappenfunktion zu liefern. Radiologische Standardverfahren: Die primäre Modalität zur Evaluation der Herzklappen ist die Echokardiographie, gefolgt von der Magnetresonanztomographie. Methodische Innovationen: Durch die kontinuierliche technische Weiterentwicklung der CT-Geräte erfolgte eine markante Verbesserung der räumlichen und zeitlichen Auflösung, welche für die artefaktfreie Darstellung schnell bewegender und kleiner Strukturen, wie etwa der Koronargefäße und Herzklappen, entscheidend sind. Leistungsfähigkeit: Die CT liefert eine ausgezeichnete Bildqualität der Aorten- und Mitralklappe und erlaubt somit eine präzise Beurteilung ihrer Morphologie. Zudem ermöglicht die CT eine gute Beurteilung der Aortenklappenfunktion mit einer Graduierung von Stenose und Insuffizienz. Bewertung: Die CT ist nicht die primäre Modalität zur Beurteilung der Herzklappen. Sie kann aber wichtige Informationen über ihre Morphologie und Funktion liefern. Empfehlung für die Praxis: Sind die Echokardiographie und/oder die Herzmagnetresonanztomographie eingeschränkt beurteilbar, inkonklusiv oder nicht durchführbar, ist die Herz-CT eine gute Alternative zur Bildgebung der Herzklappe

Vascular Abnormalities Detected with Chest CT in COVID-19: Spectrum, Association with Parenchymal Lesions, Cardiac Changes, and Correlation with Clinical Severity (COVID-CAVA Study).

Although vascular abnormalities are thought to affect coronavirus disease 2019 (COVID-19) patients' outcomes, they have not been thoroughly characterized in large series of unselected patients. The Swiss national registry coronavirus-associated vascular abnormalities (CAVA) is a multicentric cohort of patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection who underwent a clinically indicated chest computed tomography (CT) aiming to assess the prevalence, severity, distribution, and prognostic value of vascular and non-vascular-related CT findings. Clinical outcomes, stratified as outpatient treatment, inpatient without mechanical ventilation, inpatient with mechanical ventilation, or death, will be correlated with CT and biological markers. The main objective is to assess the prevalence of cardiovascular abnormalities-including pulmonary embolism (PE), cardiac morphology, and vascular congestion. Secondary objectives include the predictive value of cardiovascular abnormalities in terms of disease severity and fatal outcome and the association of lung inflammation with vascular abnormalities at the segmental level. New quantitative approaches derived from CT imaging are developed and evaluated in this study. Patients with and without vascular abnormalities will be compared, which is supposed to provide insights into the prognostic role and potential impact of such signs on treatment strategy. Results are expected to enable the development of an integrative score combining both clinical data and imaging findings to predict outcomes

Computed tomography for planning and postoperative imaging of transvenous mitral annuloplasty: first experience in an animal model

To investigate the use of computed tomography (CT) to measure the mitral valve annulus size before implantation of a percutaneous mitral valve annuloplasty device in an animal trial. Seven domestic pigs underwent CT before and after implantation of a Cardioband™ (a percutaneously implantable mitral valve annuloplasty device) with a second-generation 128-section dual-source CT machine. Implantation of the Cardioband™ was performed in a standard fashion according to a protocol. Animals were sacrificed afterwards and the hearts explanted. The Cardioband™ was found to be adequately implanted in all animals, with no anchor dehiscence and no damage of the circumflex artery (CX) or the coronary sinus (CS). The correct length of the band as chosen according to the length of the posterior mitral annulus measured in CT before implantation was confirmed in gross examination in all animals. The device did not result in a metal artifact-related degradation of image quality. The closest distance from the closest anchor to the CX was 2.1 ± 0.7 mm in diastole and 1.6 ± 0.5 mm systole. Mitral annulus distance to the CS was 6.4 ± 1.3 mm in diastole and 7.7 ± 1.1 mm in systole. CT visualization and measurement of the mitral valve annulus dimensions is feasible and can become the imaging method of choice for procedure planning of Cardioband™ implantations or other transcatheter mitral annuloplasty devices

Metallic artefact reduction with monoenergetic dual-energy CT: systematic ex vivo evaluation of posterior spinal fusion implants from various vendors and different spine levels

Objectives: To evaluate optimal monoenergetic dual-energy computed tomography (DECT) settings for artefact reduction of posterior spinal fusion implants of various vendors and spine levels. Methods: Posterior spinal fusion implants of five vendors for cervical, thoracic and lumbar spine were examined ex vivo with single-energy (SE) CT (120 kVp) and DECT (140/100 kVp). Extrapolated monoenergetic DECT images at 64, 69, 88, 105keV and individually adjusted monoenergy for optimised image quality (OPTkeV) were generated. Two independent radiologists assessed quantitative and qualitative image parameters for each device and spine level. Results: Inter-reader agreements of quantitative and qualitative parameters were high (ICC = 0.81-1.00, κ = 0.54-0.77). HU values of spinal fusion implants were significantly different among vendors (P < 0.001), spine levels (P < 0.01) and among SECT, monoenergetic DECT of 64, 69, 88, 105keV and OPTkeV (P < 0.01). Image quality was significantly (P < 0.001) different between datasets and improved with higher monoenergies of DECT compared with SECT (V = 0.58, P < 0.001). Artefacts decreased significantly (V = 0.51, P < 0.001) at higher monoenergies. OPTkeV values ranged from 123-141keV. OPTkeV according to vendor and spine level are presented herein. Conclusions: Monoenergetic DECT provides significantly better image quality and less metallic artefacts from implants than SECT. Use of individual keV values for vendor and spine level is recommended. Key Points: • Artefacts pose problems for CT following posterior spinal fusion implants. • CT images are interpreted better with monoenergetic extrapolation using dual-energy (DE) CT. • DECT extrapolation improves image quality and reduces metallic artefacts over SECT. • There were considerable differences in monoenergy values among vendors and spine levels. • Use of individualised monoenergy values is indicated for different metallic hardware device

Iterative Reconstructions in Reduced-Dose CT: Which Type Ensures Diagnostic Image Quality in Young Oncology Patients?

To compare adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) algorithms for reduced-dose computed tomography (CT). Forty-four young oncology patients (mean age 30 ± 9 years) were included. After routine thoraco-abdominal CT (dose 100%, average CTDI javax.xml.bind.JAXBElement@e7f585f 9.1 ± 2.4 mGy, range 4.4-16.9 mGy), follow-up CT was acquired at 50% (average CTDI javax.xml.bind.JAXBElement@2e35610f 4.5 ± 1.2 mGy, range 2.2-8.4 mGy) in 29 patients additionally at 20% dose (average CTDI javax.xml.bind.JAXBElement@37ad3473 1.9 ± 0.5 mGy, range 0.9-3.4 mGy). Each reduced-dose CT was reconstructed using both ASIR and MBIR. Four radiologists (two juniors and two seniors) blinded to dose and technique read each set of CT images regarding objective and subjective image qualities (high- or low-contrast structures), subjective noise or pixilated appearance, diagnostic confidence, and lesion detection. At all dose levels, objective image noise was significantly lower with MBIR than with ASIR (P &lt; 0.001). The subjective image quality for low-contrast structures was significantly higher with MBIR than with ASIR (P &lt; 0.001). Reduced-dose abdominal CT images of patients with higher body mass index (BMI) were read with significantly higher diagnostic confidence than images of slimmer patients (P &lt; 0.001) and had higher subjective image quality, regardless of technique. Although MBIR images appeared significantly more pixilated than ASIR images, they were read with higher diagnostic confidence, especially by juniors (P &lt; 0.001). Reduced-dose CT during the follow-up of young oncology patients should be reconstructed with MBIR to ensure diagnostic quality. Elevated body mass index does not hamper the quality of reduced-dose CT

Computed tomography for evaluation of abdominal wall hernias-what is the value of the Valsalva maneuver?

PURPOSE To investigate the differences in the visibility and size of abdominal wall hernias in computed tomography (CT) with and without Valsalva maneuver. METHODS This single-center retrospective study included consecutive patients who underwent abdominal CTs with Valsalva maneuver between January 2018 and January 2022. Inclusion criteria was availability of an additional non-Valsalva CT within 6 months. A combined reference standard including clinical and surgical findings was used. Two independent, blinded radiologists measured the hernia sac size and rated hernia visibility on CTs with and without Valsalva. Differences were tested with a Wilcoxon signed rank test and McNemar's test. RESULTS The final population included 95 patients (16 women; mean age 46 ± 11.6 years) with 205 hernias. Median hernia sac size on Valsalva CT was 31 mm compared with 24 mm on non-Valsalva CT (p < 0.001). In 73 and 82% of cases, the hernias were better visible on CT with Valsalva as compared to that without. 14 and 17% of hernias were only visible on the Valsalva CT. Hernia visibility on non-Valsalva CT varied according to subtype, with only 0 and 3% of umbilical hernias not being visible compared with 43% of femoral hernias. CONCLUSIONS Abdominal wall hernias are larger and better visible on Valsalva CT compared with non-Valsalva CT in a significant proportion of patients and some hernias are only visible on the Valsalva CT. Therefore, this method should be preferred for the evaluation of abdominal wall hernias