Computational Fluid Dynamics: Hemodynamic Changes in Abdominal Aortic Aneurysm After Stent-Graft Implantation

The aim of this study was to demonstrate quantitatively and qualitatively the hemodynamic changes in abdominal aortic aneurysms (AAA) after stent-graft placement based on multidetector CT angiography (MDCT-A) datasets using the possibilities of computational fluid dynamics (CFD). Eleven patients with AAA and one patient with left-side common iliac aneurysm undergoing MDCT-A before and after stent-graft implantation were included. Based on the CT datasets, three-dimensional grid-based models of AAA were built. The minimal size of tetrahedrons was determined for grid-independence simulation. The CFD program was validated by comparing the calculated flow with an experimentally generated flow in an identical, anatomically correct silicon model of an AAA. Based on the results, pulsatile flow was simulated. A laminar, incompressible flow-based inlet condition, zero traction-force outlet boundary, and a no-slip wall boundary condition was applied. The measured flow volume and visualized flow pattern, wall pressure, and wall shear stress before and after stent-graft implantation were compared. The experimentally and numerically generated streamlines are highly congruent. After stenting, the simulation shows a reduction of wall pressure and wall shear stress and a more equal flow through both external iliac arteries after stenting. The postimplantation flow pattern is characterized by a reduction of turbulences. New areas of high pressure and shear stress appear at the stent bifurcation and docking area. CFD is a versatile and noninvasive tool to demonstrate changes of flow rate and flow pattern caused by stent-graft implantation. The desired effect and possible complications of a stent-graft implantation can be visualized. CFD is a highly promising technique and improves our understanding of the local structural and fluid dynamic conditions for abdominal aortic stent placemen

Diagnostic accuracy and added value of dual-energy subtraction radiography compared to standard conventional radiography using computed tomography as standard of reference

PURPOSE: To retrospectively evaluate diagnostic performance of dual-energy subtraction radiography (DESR) for interpretation of chest radiographs compared to conventional radiography (CR) using computed tomography (CT) as standard of reference. MATERIAL AND METHODS: A total of 199 patients (75 female, median age 67) were included in this institutional review board (IRB)-approved clinical trial. All patients were scanned in posteroanterior and lateral direction with dual-shot DE-technique. Chest CT was performed within ±72 hours. The system provides three types of images: bone weighted-image, soft tissue weighted-image, herein termed as DESR-images, and a standard image, termed CR-image (marked as CR-image). Images were evaluated by two radiologists for presence of inserted life support lines, pneumothorax, pleural effusion, infectious consolidation, interstitial lung changes, tumor, skeletal alterations, soft tissue alterations, aortic or tracheal calcification and pleural thickening. Inter-observer agreement between readers and diagnostic performance were calculated. McNemar's test was used to test for significant differences. RESULTS: Mean inter-observer agreement throughout the investigated parameters was higher in DESR images compared to CR-images (kDESR = 0.935 vs. kCR = 0.858). DESR images provided significantly increased sensitivity compared to CR-images for the detection of infectious consolidations (42% vs. 62%), tumor (46% vs. 57%), interstitial lung changes (69% vs. 87%) and aortic or tracheal calcification (25 vs. 73%) (p<0.05). There were no significant differences in sensitivity for the detection of inserted life support lines, pneumothorax, pleural effusion, skeletal alterations, soft tissue alterations or pleural thickening (p>0.05). CONCLUSION: DESR increases significantly the sensibility without affecting the specificity evaluating chest radiographs, with emphasis on the detection of interstitial lung diseases

Dedicated Spiral Breast Computed Tomography With a Single Photon-Counting Detector: Initial Results of the First 300 Women

OBJECTIVES The aim of this study was to describe our initial clinical experiences using a dedicated spiral breast computed tomography (B-CT) with a single photon-counting detector. MATERIALS AND METHODS This retrospective study was approved by the institutional review board. Examinations of 300 consecutive women undergoing B-CT were evaluated on reason of assignment for B-CT instead of mammography, detection rate of breast cancer, and quality criteria of data acquisition. Further evaluated performance indicators were the number of additional ultrasounds examinations due to unclear findings or dense breast tissue and reliability of the technical data acquisition. RESULTS Five hundred ninety-one B-CT acquisitions in 300 women were performed. The main reason for preference of B-CT over mammography was the lack of breast compression (254 of 300, 84.7%), which was desired due to personal reasons or mastodynia, whereas 10 patients (0.3%) had implants hampering mammography. One hundred two possible lesions were detected in B-CT including 4 cases of breast cancer (1.3% of all patients). Additional ultrasound was performed in 226 patients (102 due to detected lesions and 124 due to dense breast tissue). Three malignant lesions were only detected in an additional ultrasound (1% of all patients). As a quality criterion, the pectoralis muscle was included in 341 of 591 examinations, but complete assessment of breast tissue was only possible in 149, respectively 140 examinations. No movement artifacts were noted. In 99% of all women, the examination could be realized. CONCLUSIONS The dedicated B-CT provides high-quality images. It can be used as alternative particularly in those patients not otherwise willing to perform mammography because of the breast compression

Impact of Photon Counting Detector CT Derived Virtual Monoenergetic Images on the Diagnosis of Pulmonary Embolism

Purpose: To assess the impact of virtual-monoenergetic-image (VMI) energies on the diagnosis of pulmonary embolism (PE) in photon-counting-detector computed-tomography (PCD-CT). Methods: Eighty patients (median age 60.4 years) with suspected PE were retrospectively included. Scans were performed on PCD-CT in the multi-energy mode at 120 kV. VMIs from 40-70 keV in 10 keV intervals were reconstructed. CT-attenuation was measured in the pulmonary trunk and the main branches of the pulmonary artery. Signal-to-noise (SNR) ratio was calculated. Two radiologists evaluated subjective-image-quality (noise, vessel-attenuation and sharpness; five-point-Likert-scale, non-diagnostic-excellent), the presence of hardening artefacts and presence/visibility of PE. Results: Signal was highest at the lowest evaluated VMI (40 keV; 1053.50 HU); image noise was lowest at the highest VMI (70 keV; 15.60 HU). Highest SNR was achieved at the lowest VMI (p &lt; 0.05). Inter-reader-agreement for subjective analysis was fair to excellent (k = 0.373-1.000; p &lt; 0.001). Scores for vessel-attenuation and sharpness were highest at 40 keV (both:5, range 4/3-5; k = 1.000); scores for image-noise were highest at 70 keV (4, range 3-5). The highest number of hardening artifacts were reported at 40 keV (n = 22; 28%). PE-visualization was rated best at 50 keV (4.7; range 4-5) and decreased with increasing VMI-energy (r = -0.558; p &lt; 0.001). Conclusions: While SNR was best at 40 keV, subjective PE visibility was rated highest at 50 keV, potentially owing to the lower image noise and hardening artefacts

Structure of retracted tendons after staged repair following continuous traction

Purpose: The effect of staged repair involving continuous re-lengthening of the retracted musculotendinous unit after rotator cuff tear is not known. We quantified changes in chronically retracted tendons undergoing no repair or a staged repair involving an initial re-lengthening of the musculotendinous unit by traction in a sheep model of massive rotator cuff tear. Materials and methods: Infraspinatus tendons of 12 sheep were released and allowed to retract for 4months. Repair was performed after the retracted musculotendinous unit had been progressively returned to its original length through continuous traction in 8 sheep (group I). In the other 4 sheep (group II) traction was not successful and the tendons remained retracted. Tendon structure was assessed macroscopically, by MRI, histology, and TEM. Results: Normalized to their contralateral controls, at sacrifice, tendon thickness was unchanged in group I (116%, n.s) and increased in group II (129%, P<0.05), however with substantial shortening. Increased collagen fiber crimping and disorganization was found in group II, whereas in group I the differences from normal tendon were less pronounced. Conclusion: Retracted musculotendinous units have deteriorated tendons, characterized by increased collagen fiber crimp, and ultrastructural collagen fibril atrophy and disorganization. Continuous traction may arrest and partially restore degenerative changes in retracted tendon. The findings of this study might contribute to new approaches for the treatment of chronic "irreparable” rotator cuff tear

Moderne Bildgebung des Lungenhilus : Anatomie, Pathologien, Pitfalls

BACKGROUND Modern medical imaging is a key component of efficient in- and out-patient precision medicine. Conventional radiography and computer tomography scans (CT) are among the most frequent radiologic exams. Medical imaging plays a key role in target-oriented medicine. OBJECTIVES The purpose of this article is to review the anatomy of the hilum of the lung and its most frequent associated pathologies since it is an important gateway of elementary structures of the thorax. Important signs and patterns for image interpretation in different modalities are also reviewed. RESULTS Thorough knowledge of anatomy, signs, and patterns of pathologies especially in conventional radiography and pitfalls of the more sensitive cross-sectional imaging is essential to support target-oriented patient care. CONCLUSION Conventional radiography is affordable and readily available. It is very suitable for pathology screening, i.e., at the hilum of the lung. Cross-sectional imaging specifies diagnostics due to superior anatomic discrimination

Pulmonale Rundherde und Pneumonie : Ein diagnostischer Leitfaden

Hintergrund Das konventionelle Röntgenbild zählt zu den am häufigsten durchgeführten radiologischen Untersuchungen. Seine Interpretation gehört zu den Grundkenntnissen jedes Radiologen. Fragestellung Ziel dieses Artikels ist es, häufige Zeichen und Muster der Pneumonie sowie Merkmale von Pseudoläsionen im konventionellen Röntgenbild zu erkennen und einen diagnostischen Leitfaden für junge Radiologen zu schaffen. Methoden Analyse aktueller Studien und Daten sowie eine Übersicht der häufigsten Zeichen und Muster im konventionellen Röntgenbild. Ergebnisse Die Kenntnis über häufige Zeichen und Muster im Röntgenbild bietet eine Hilfestellung in der Diagnostik und kann hinweisend für die Ursache einer Infektion sein. Häufig sind diese Zeichen jedoch unspezifisch und sollten daher immer in klinische Korrelation gesetzt werden. In der Detektion und Beurteilung von pulmonalen Rundherden gewinnt die Computertomographie (CT) durch ihre deutlich höhere Sensitivität in der Primärdiagnostik immer mehr an Bedeutung. Schlussfolgerung Das konventionelle Röntgenbild bildet weiterhin eine führende Rolle in der Primärdiagnostik; der Radiologe sollte jedoch die Limitationen des konventionellen Bildes kennen. = Background: Chest X‑ray is one of the most frequent examinations in radiology and its interpretation is considered part of the basic knowledge of every radiologist. Objectives: The purpose of this article is to recognize common signs and patterns of pneumonias and pseudonodules in chest X‑rays and to provide a diagnostic guideline for young radiologists. Materials and methods: Recent studies and data are analyzed and an overview of the most common signs and patterns in chest X‑ray is provided. Results: Knowledge about common signs and patterns in chest X‑ray is helpful in the diagnosis of pneumonias and can be indicative for the cause of an infection. However, those signs are often unspecific and should, therefore, be set in clinical content. Computed tomography is becoming increasingly important in the primary diagnosis of pulmonary lesions because of its much higher sensitivity. Conclusion: Chest X‑ray is still the first-line modality in the diagnosis of pneumonia and pulmonary nodules; however, radiologists should be aware of its limitations. Keywords: Computed tomography; Infections; Lung; Thoracic radiography; Thorax

Efficiency evaluation of leaded glasses and visors for eye lens dose reduction during fluoroscopy guided interventional procedures

PURPOSE Fluoroscopy guided interventional procedures guarantee high benefits for patients, but are associated with high levels of radiation exposure for the medical staff. Their increasing use and complexity results in even higher radiation exposures, with a risk to exceed the annual dose limit of 20 mSv for the eye lens. The aim of the study was to evaluate the potential dose reduction of eye lens exposure for lead glasses and for two types of visors (half and full), used by physicians performing interventional procedures. METHODS Eye lens dose measurements were carried out on an anthropomorphic phantom simulating a physician performing a fluoroscopy guided interventional procedure. Dose reduction factors were calculated using high sensitivity thermoluminescent dosimeters. Moreover, a spatial dose distribution was generated for the two visors. RESULTS The dose reduction coefficient was found to be 1.6 for the glasses, 1.2 for the half visor and 4.5 for the full visor. CONCLUSIONS Optimal radiation protection requires a combination of different radiation protection equipment. Full visors that cover all the face of the operator are recommended, as they absorb scattered radiation reaching the eyes from all directions. Full visors should be prioritized over radiation protection glasses for cases where other protective equipment such as ceiling shielding cannot be used

Hybrid-repair of thoraco-abdominal or juxtarenal aortic aneurysm: what the radiologist should know

Purpose: Endovascular aneurysm repair of the infrarenal or thoracic aorta has been shown to be a less invasive alternative to open surgery. A combined aneurysm of the thoracic and abdominal aorta is complex and challenging; the involvement of renal and/or visceral branches requires new treatment methods. Methods: A hybrid approach is currently an accepted alternative to conventional surgery. Renal and/or visceral revascularisation enables subsequent stent-graft placement into the visceral portion of the aorta. Results: Knowledge of the surgical procedure and a precise assessment of the vascular morphology are crucial for pre-procedural planning and for detection of post-procedural complications. Multi-detector computed tomography angiography (MDCTA) combined with two- and three-dimensional (2D and 3D) rendering is useful for pre-interventional planning and for the detection of post-procedural complications. Three-dimensional rendering allows proper anatomical analyses, influencing interventional strategies and resulting in a better outcome. Conclusions: With the knowledge of procedure-specific MDCTA findings in various vascular conditions, the radiologist and surgeon are able to perform an efficient pre-interventional planning and follow-up examination. Based on our experience with this novel technique of combined open and endovascular aortic aneurysm treatment, this pictorial review illustrates procedure-specific imaging findings, including common and rare complications, with respect to 2D and 3D post-processing technique