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Purpose Artificial intelligence in computer vision has been increasingly adapted in clinical application since the implementation of neural networks, potentially providing incremental information beyond the mere detection of pathology. As its algorithmic approach propagates input variation, neural networks could be used to identify and evaluate relevant image features. In this study, we introduce a basic dataset structure and demonstrate a pertaining use case. Methods A multidimensional classification of ankle x-rays (n = 1493) rating a variety of features including fracture certainty was used to confirm its usability for separating input variations. We trained a customized neural network on the task of fracture detection using a state-of-the-art preprocessing and training protocol. By grouping the radiographs into subsets according to their image features, the influence of selected features on model performance was evaluated via selective training. Results The models trained on our dataset outperformed most comparable models of current literature with an ROC AUC of 0.943. Excluding ankle x-rays with signs of surgery improved fracture classification performance (AUC 0.955), while limiting the training set to only healthy ankles with and without fracture had no consistent effect. Conclusion Using multiclass datasets and comparing model performance, we were able to demonstrate signs of surgery as a confounding factor, which, following elimination, improved our model. Also eliminating pathologies other than fracture in contrast had no effect on model performance, suggesting a beneficial influence of feature variability for robust model training. Thus, multiclass datasets allow for evaluation of distinct image features, deepening our understanding of pathology imaging.

Background Intraoperative incorporation of radiopaque fiducial markers at the tumor resection surface can provide useful assistance in identifying the tumor bed in postoperative imaging for RT planning and radiological follow-up. Besides titanium clips, iodine containing injectable liquid fiducial markers represent an option that has emerged more recently for this purpose. In this study, marking oral soft tissue resection surfaces, applying low dose injections of a novel Conformité Européenne (CE)-marked liquid fiducial marker based on sucrose acetoisobutyrate (SAIB) and iodinated SAIB (x-SAIB) was investigated. Methods Visibility and discriminability of low dose injections of SAIB/x-SAIB (10 µl, 20 µl, 30 µl) were systematically studied at different kV settings used in clinical routine in an ex-vivo porcine mandible model. Transferability of the preclinical results into the clinical setting and applicability of DE-CT were investigated in initial patients. Results Markers created by injection volumes as low as 10 µl were visible in CT imaging at all kV settings applied in clinical routine (70–120 kV). An injection volume of 30 µl allowed differentiation from an injection volume of 10 µl. In a total of 118 injections performed in two head and neck cancer patients, markers were clearly visible in 83% and 86% of injections. DE-CT allowed for differentiation between SAIB/x-SAIB markers and other hyperdense structures. Conclusions Injection of low doses of SAIB/x-SAIB was found to be a feasible approach to mark oral soft tissue resection surfaces, with injection volumes as low as 10 µl found to be visible at all kV settings applied in clinical routine. With the application of SAIB/x-SAIB reported for tumors of different organs already, mostly applying relatively large volumes for IGRT, this study adds information on the applicability of low dose injections to facilitate identification of the tumor bed in postoperative CT and on performance of the marker at different kV settings used in clinical routine.

BACKGROUND AND AIMS Chronic kidney disease (CKD) affects around 10% of adults worldwide and an estimated 13–17% in Germany1. Imaging is a novel, promising approach to identify additional markers of kidney function and CKD2. Within a large, population-based cohort study, the German National Cohort study (NAKO/GNC), 30 000 participants underwent a whole-body MRI protocol3. The goal of our project was to develop an automated kidney segmentation workflow and to examine distributions of the segmented kidneys and kidney sub-compartments. METHOD Data from the first 11 207 participants were used to develop a robust image processing pipeline for kidney segmentation and apply it to participants’ abdominal MRI images. After importing 3D gradient echo and 2D haste images into the imaging platform NORA (www.nora-imaging.org), an in-house ‘patchwork’-framework (https://bitbucket.org/reisert/patchwork) based on deep-learning convolutional neural networks was trained on data from 300 persons to automatically segment different kidney compartments (cortex, hilus, medulla and cysts). After an initial training round, the model was improved over four iterations by a loop of prediction, manual correction and retraining. The final model was then applied to the full dataset of 11 207 abdominal MR images, followed by manual quality control prior to statistical analysis. Volumetric parameters for total kidney volume [TKV, defined as cortex + medulla] and compartments were calculated from the segmentations. Values were calculated in absolute units of mL and normalized to body-surface-area (BSA) defined as sqrt(weight in kg*height in cm)/3600. RESULTS TKV and the kidney compartments cortex, medulla and hilus could be segmented robustly with the trained network (Fig. 1A). After exclusion of approximately 10% of images because of insufficient segmentation quality due to initial imaging artifacts or poor image quality, the mean (SD) TKV was 364 (±60) mL for men and 290 (±51) mL for women. This difference was markedly attenuated after normalisation to BSA (Fig. 1B). The right kidney was systematically smaller than the left kidney by approximately 5% (Fig. 1C). There was a strong association between participants’ BSA with TKV (Fig. 1D). The normalized kidney sub-compartment volumes showed different patterns across age, with medullary volume decreasing and hilus increasing (Fig. 2). CONCLUSION The developed framework enables robust segmentation of kidneys in abdominal MRI data from a nonspecific clinical routine protocol of a large cohort study. Basic parameters such as TKV and sub-compartment volumes of the kidney show correlations with participants’ height, weight, sex and age that are consistent with prior knowledge and may enable an estimation of ‘kidney age’. This is an optimal starting point to identify more advanced imaging biomarkers of kidney function and CKD.

Cannulas with multi-staged side holes are the method of choice for femoral cannulation in extracorporeal therapies today. A variety of differently designed products is available on the market. While the preferred tool for the performance assessment of such cannulas are pressure-flow curves, little is known about the flow and velocity distribution. Within this work flow and velocity patterns of a femoral venous cannula with multi-staged side holes were investigated. A mock circulation loop for cannula performance evaluation was built and reproduced using a computer-aided design system. With computational fluid dynamics, volume flows and fluid velocities were determined quantitatively and visually with hole-based precision. In order to ensure the correctness of the flow simulation, the results were subsequently validated by determining the same parameters with four-dimensional flow-sensitive magnetic resonance imaging. Measurement data and numerical solution differed 7% on average throughout the data set for the examined parameters. The highest inflow and velocity were detected at the most proximal holes, where half of the total volume flow enters the cannula. At every hole stage a Y-shaped inflow profile was detected, forming a centered stream in the middle of the cannula. Simultaneously, flow separation creates zones with significant lower flow velocities. Numerical simulation, validated with four-dimensional flow-sensitive magnetic resonance imaging, is a valuable tool to examine flow and velocity distributions of femoral venous cannulas with hole-based accuracy. Flow and velocity distribution in such cannulas are not ideal. Based on this work future cannulas can be effectively optimized.

Objective To evaluate a novel liquid fiducial marker for intraoperative marking of the tumour resection surface in oral cancer patients to facilitate precise postoperative delineation of the interface between the tumour resection border and reconstructed tissue for intensity-modulated radiation therapy. Methods A total of 200 markers were created by injecting the volumes of 10 µl, 20 µl, 30 µl, 40 µl and 50 µl of a liquid marker composed of sucrose acetoisobutyrate (SAIB) and iodinated sucrose acetoisobutyrate (x-SAIB) into the soft tissue of porcine mandible segments. Visibility of the resulting markers was quantified by threshold-based segmentation of the marker volume in CT- and CBCT imaging and by a comparison of signal intensities in MRI. Results Even the lowest volume of SAIB-/x-SAIB investigated (10 µl) resulted in a higher visibility (CTSoft tissue: 88.18 ± 13.23 µl; CTBone: 49.55 ± 7.62 µl; CBCT: 54.65 ± 12.58 µl) than observed with the incorporation of titanium ligature clips (CTSoft tissue: 50.15 ± 7.50 mm3; CTBone: 23.90 ± 3.39 mm3; CBCT: 33.80 ± 9.20 mm3). Markers created by the injection of 10 µl and 20 µl could reliably be delineated from markers created by the injection of higher volumes. Conclusion SAIB/x-SAIB, which has recently become available as a Conformité Européenne (CE)-marked fiducial marker, provides an option for fast and reliable production of markers with excellent visibility in imaging modalities used in oral cancer radiation therapy (RT) planning routine.

A 58-year-old man with progressive dyspnea and recurrent extensive left-sided pleural effusion underwent pulmonary ventilation/perfusion SPECT/CT, which showed a pronounced mismatched perfusion deficit of the entire, normally ventilated left lung. As unilateral perfusion deficits of an entire lobe are generally not due to pulmonary embolism, further CT angiography and cardiac MRI were conducted. These examinations revealed high-grade left pulmonary vein stenosis (PVS) caused by pulmonary vein isolation performed for atrial fibrillation 3 and 4 years earlier. Thus, in addition to, for example, neoplastic processes or pulmonary congenital vascular abnormalities, PVS must be considered as a differential diagnosis and possible pitfall in ventilation/perfusion SPECT/CT in dyspneic patients with prior pulmonary vein isolation.

The development and successful implementation of cutting-edge imaging technologies to visualise cardiac anatomy and function is a key component of effective diagnostic efforts in cardiology. Here, we describe a number of recent exciting advances in the field of cardiology spanning from macro- to micro- to nano-scales of observation, including magnetic resonance imaging, computed tomography, optical mapping, photoacoustic imaging, and electron tomography. The methodologies discussed are currently making the transition from scientific research to routine clinical use, albeit at different paces. We discuss the most likely trajectory of this transition into clinical research and standard diagnostics, and highlight the key challenges and opportunities associated with each of the methodologies.

The impact of specific blood flow patterns within ascending aortic and/or aortic root aneurysms on aortic morphology is unknown. We investigated the interrelation of ascending aortic flow compression/peripheralization and aneurysm morphology with respect to sinotubuar junction (STJ) definition.Thirty-one patients (aortic root/ascending aortic aneurysm45 mm) underwent flow-sensitive 4D magnetic resonance thoracic aortic flow measurement at 3 Tesla (Siemens, Germany) at two different institutions (Freiburg, Germany, and San Francisco, CA, USA). Time-resolved image data post-processing and visualization of mid-systolic, mid-ascending aortic flow were performed using local vector fields. The Flow Compression Index (FCI) was calculated individually as a fraction of the area of high-velocity mid-systolic flow over the complete cross-sectional ascending aortic area. According to aortic aneurysm morphology, patients were grouped as (i) small root, eccentric ascending aortic aneurysm (STJ definition) and (ii) enlarged aortic root, non-eccentric ascending aortic aneurysm with diffuse root and tubular enlargement.The mean FCI over all patients was 0.47 ± 0.5 (0.37-0.99). High levels of flow compression/peripheralization (FCI0.6) were linked to eccentric aneurysm morphology (Group A, n = 11), while low levels or absence of aortic flow compression/peripheralization (FCI0.8) occurred more often in Group B (n = 20). The FCI was 0.48 ± 0.05 in Group A and 0.78 ± 0.14 in Group B (P0.001). Distribution of bicuspid aortic valve (P = 0.6) and type of valve dysfunction (P = 0.22 for aortic stenosis) was not found to be different between groups.Irrespective of aortic valve morphology and function, ascending aortic blood flow patterns are linked to distinct patterns of ascending aortic aneurysm morphology. Implementation of quantitative local blood flow analyses might help to improve aneurysm risk stratification in the future.

Purpose Cardiovascular diseases remain the number one death cause worldwide. Preclinical 4D flow phase contrast magnetic resonance imaging can provide substantial insights in the analysis of aortic pathophysiologies in various animal models. These insights may allow a better understanding of pathophysiologies, therapy monitoring, and can possibly be translated to humans. This study provides a framework to acquire the velocity field within the aortic arch. It analyses important flow values at different locations within the aortic arch. Imaging parameters with high temporal and spatial resolution are provided, that still allow combining this time-consuming method with other necessary imaging-protocols. Methods A new setup was established where a prospectively gated 4D phase contrast sequence is combined with a highly sensitive cryogenic coil on a preclinical magnetic resonance scanner. The sequence was redesigned to maintain a close to steady state condition of the longitudinal magnetization and hence to overcome steady state artifacts. Imaging parameters were optimized to provide high spatial and temporal resolution. Pathline visualizations were generated from the acquired velocity data in order to display complex flow patterns. Results Our setup allows data acquisition with at least two times the rate than that of previous publications based on Cartesian encoding, at an improved image quality. The "steady state" sequence reduces observed artifacts and provides uniform image intensity over the heart cycle. This made possible quantification of blood speed and wall shear stress (WSS) within the aorta and its branches. The highest velocities were observed in the ascending aorta with 137.5 ± 8 cm/s. Peak velocity values in the Brachiocephalic trunk were 57 ± 12 cm/s. Quantification showed that the peak flow occurs around 20 ms post R-wave in the ascending aorta. The highest mean axial wall shear stress was observed in the analysis plane between the left common carotid artery (LCCA) and the left subclavian artery. A stable image quality allows visualizing complex flow patterns by means of streamlines and for the first time, to the best of our knowledge, pathline visualizations from 4D flow MRI in mice. Conclusion The described setup allows analyzing pathophysiologies in mouse models of cardiovascular diseases in the aorta and its branches with better image quality and higher spatial and temporal resolution than previous Cartesian publications. Pathlines provide an advanced analysis of complex flow patterns in the murine aorta. An imaging protocol is provided that offers the possibility to acquire the aortic arch at sufficiently high resolution in less than one hour. This allows the combination of the flow assessment with other multifunctional imaging protocols.

The anatomy of the aorta changes in the course of life. Up to the age of 15, its diameter and length increase relatively swiftly. It continues to grow in adulthood: the diameter of the ascending aorta is 20 to 30% greater in 70-year-olds than in 20-year-olds (1). Rapid growth of the aorta—usually segmental—causes an aneurysm. Three quarters of all aneurysms occur in the abdominal aorta. The annual incidence of abdominal aortic aneurysm (diameter >3.0 cm) is 40 in every 100 000 population. Six times more men than women are affected (2– 4). Intervention is required (aneurysmal diameter >5.0 cm) in 10% of patients with a diagnosed abdominal aortic aneurysm (3). In up to 55% of these persons the aneurysm is not amenable to insertion of a conventional tube graft or Y-graft (5). The annual incidence of thoracic aneurysm is 10–15 per 100 000 (6, 7). Men are 1.8 times more frequently affected than women. No population studies of the incidence of thoracic abdominal aneurysm have been published. The pathological aorta can be treated surgically or via the endovascular route. One crucial advantage of the endovascular approach is the minimally invasive access with relatively low strain on the cardiovascular system and thus lower perioperative mortality. In a total of 22 830 patients, mortality was 1.2% for endovascular treatment and 4.8% for open surgery (8, 9). Not every affected aorta is amenable to insertion of a thoracic tube stent graft or infrarenal Y-stent graft. In patients with a juxtarenal or thoracoabdominal aneurysm there is no proximal or distal zone for anchorage (landing zone) and therefore conventional tube and Y-grafts cannot be safely attached. These patients therefore often undergo open surgery. Relatively young and otherwise healthy patients recover comparatively quickly from an open thoracic, thoracoabdominal, or abdominal intervention. However, patients with vascular disease are usually of advanced age and not uncommonly have numerous comorbidities. One of the endovascular treatment options in such cases is the chimney technique. Chimney grafts are placed in the visceral vessels so that their aortic segments lie parallel to the aortic stent graft. However, use of this technique is limited by the elevated risk of leakage between the chimney graft, the aortic stent graft, and the aorta (10, 11). The very first implantation of a stent graft into the thoracic aorta was performed by Volodos in 1987 (12). The first such interventions in Germany—in centers including Freiburg (13)—were carried out in 1995. There have been rapid developments in stent grafts, pre- and intraoperative diagnostic procedures, endovascular instrumentation, catheter techniques, and many other relevant areas. Preoperative diagnostic, high-resolution computed tomography, three-dimensional (3-D) reconstruction of the aorta, preoperative simulation of the intraoperative angiographic visualization, the possibility of treatment in hybrid operating suites, and printing of 3-D models all help in planning the intervention and now form part of standard management. Hydrophilic coating and reduced diameter of the insertion port permit access via distinctly sclerosed vessels. The first fenestrated endovascular aneurysm repair (fEVAR) was carried out by Park in 1996 (14). Fenestrated (Figures 1a ​,, ​,2)2) and branched stent grafts (bEVAR) (Figure 1b) were developed for treatment of patients with juxtarenal, perirenal, or thoracoabdominal aneurysms. Now, with the sole exceptions of the aortic root and the proximal ascending aorta, all segments of the aorta are amenable to endovascular treatment with standard stent grafts. Figure 1 Stent grafts Figure 2 Treatment of a juxtarenal abdominal aortic aneurysm with a fenestrated stent graft