Tracked medical ultrasound allows for cost-effective and radiation-free imaging of anatomy featuring a very high spatial resolution. To overcome the limitations of the small field-of-view, sonographers can acquire multiple adjacent sweeps and compound them into a single volumetric representation. However, due to the inherent local and non-uniform compression of the underlying anatomy (caused by the ultrasound probe) the adjacent sweeps often exhibit poor alignment and discontinuities. We propose a novel decompression model to compensate for probe pressure related artifacts. It incorporates domain knowledge of the global acquisition pattern for regularization and allows for seamless stitching of multiple overlapping 3D freehand sweeps into one volume. The resulting extended field-of-view visualization provides the clinician with spatial context so that the relationship between individual features are easier to understand. Our experiments show that the resulting extended field-of-view reconstructions have a superior image quality in terms of alignment and continuity of the visible anatomy compared to the original acquisitions. Comparison to ground truth MRI data demonstrates the plausibility of our non-rigid decompression model.

Quantifiable parameters to evaluate the effectiveness of flow diverters (FDs) are desirable. We measured time-density curves (TDCs) and calculated quantifiable parameters in the rabbit elastase-induced aneurysm model after stent (Neuroform [NF]) and FD (Pipeline embolisation device [PED]) treatment.

Ziele: Flow Diverter (FD) und Stents werden zunehmend zur Therapie von Aneurysmen eingesetzt. Eine objektive Messmethode zur Darstellung der hämodynamischen Auswirkungen eines FD oder Stents wäre wünschenswert. Methode: Bei 10 Kaninchen wurden Aneurysmen (Elastase Modell) induziert und mit Flow Divertern (Pipeline n=5) oder einem konventionellen Aneurysma Stent (Neuroform n=3) behandelt. Zwei Tiere dienten als Kontrollen. Vor und nach Implantation wurden Angiographieserien mit einer Bildfrequenz von 30 Bildern/Sekunde angefertigt. Mit einer neuen Software zur Analyse von DSA-Serien (prototypische Weiterentwicklung syngo iFlow, Siemens AG, Healthcare Sector, Forchheim) wurden Zeit-Kontrast Kurven (ZKK) erstellt. Es wurde das Time to Peak (TTP, maximaler Kontrast im Aneurysma), die volle Halbwertsbreite (VHB) sowie die durchschnittliche Steigung der Kurve (KM-Dichteänderung/Zeit) zur Darstellung der Durchschnittliche Ein- und Ausstromrate (ESÄ, ASÄ) ermittelt. Vor, unmittelbar nach Implantation und im Verlauf nach 8 Monaten wurden Kontrollangiographien durchgeführt. Ergebnis: Bei allen Versuchstieren konnten DSA-Serien und ZKK erstellt werden. Die Mittelwerte vor Therapie waren TTP=0,6sec, VHB=0,9sec, ESÄ=216,1 und ASÄ=81,5. Nach FD war das TTP mit 1,4sec und die VHB mit 14,6sec deutlich länger. Die ESÄ war mit 60,7 und die ASÄ mit 6,2 deutlich verzögert. Die Werte nach Stent Therapie (TTP=0,6sec, VHB=0,8sec, ESÄ=198, ASÄ=81,3) unterschieden sich nicht relevant von den Mittelwerten über alle Tiere vor Therapie. Nach 8 Monaten waren alle mit FD versorgten Aneurysmen verschlossen, die der Neuroform- und Kontroll-Gruppe waren weiterhin perfundiert. Schlussfolgerung: Mittels geeigneter Software zur DSA-Analyse können im Tiermodell ZKK erstellt und der hämodynamische Effekt eines Implantates quantitativ beurteilt werden. Der hämodynamische Effekt ist bei einem FD stärker als bei einem konventionellen Stent. Die von uns dargestellten Messwerte könnten als objektive Parameter und als und prädiktive Marker dienen.

BACKGROUND AND PURPOSE: CBV is a key parameter in distinguishing penumbra from ischemic core. The purpose of this study was to compare CBV measurements acquired with standard PCT with ones obtained with C-arm CT in a canine stroke model.MATERIALS AND METHODS: Under an institutionally approved protocol, unilateral MCA strokes were created in 10 canines. Four hours later, DWI was used to confirm the presence of an infarct. CBV maps acquired with PCT were compared with ones acquired by using C-arm CT. Three experienced observers, blinded to the technique used for acquisition, evaluated the CBV maps.RESULTS: An ischemic stroke was achieved in 9 of the 10 animals. Areas of reduced CBV were detected in 70%-75% of the PCT studies and in 83%-87% of the C-arm CT examinations, with false-positives in 1.7% and 3.3%, respectively. False-negatives were found in 25% of the PCT and 12.2% of the C-arm CT studies. In all studies, there was a significant difference between the absolute CBV values in normal and abnormal tissue (P < .005) and no significant difference between PCT and C-arm CT CBV values in either the normal or the abnormal parenchyma (P > .05).CONCLUSIONS: CBV measurements made with C-arm CT compare well with ones made with PCT. While further work is required both to fully validate the technique and to define its ultimate clinical value, it appears that it offers a feasible method for assessing CBV in the angiography suite.

BACKGROUND AND PURPOSE: Color has been shown to facilitate both visual search and recognition tasks. It was our purpose to examine the impact of a color-coding algorithm on the interpretation of 2D-DSA acquisitions by experienced and inexperienced observers. MATERIALS AND METHODS: Twenty-six 2D-DSA acquisitions obtained as part of routine clinical care from subjects with a variety of cerebrovascular disease processes were selected from an internal data base so as to include a variety of disease states (aneurysms, AVMs, fistulas, stenosis, occlusions, dissections, and tumors). Three experienced and 3 less experienced observers were each shown the acquisitions on a prerelease version of a commercially available double-monitor workstation (XWP, Siemens Healthcare). Acquisitions were presented first as a subtracted image series and then as a single composite color-coded image of the entire acquisition. Observers were then asked a series of questions designed to assess the value of the color-coded images for the following purposes: 1) to enhance their ability to make a diagnosis, 2) to have confidence in their diagnosis, 3) to plan a treatment, and 4) to judge the effect of a treatment. The results were analyzed by using 1-sample Wilcoxon tests. RESULTS: Color-coded images enhanced the ease of evaluating treatment success in >40% of cases (P < .0001). They also had a statistically significant impact on treatment planning, making planning easier in >20% of the cases (P = .0069). In >20% of the examples, color-coding made diagnosis and treatment planning easier for all readers (P < .0001). Color-coding also increased the confidence of diagnosis compared with the use of DSA alone (P = .056). The impact of this was greater for the naïve readers than for the expert readers. CONCLUSIONS: At no additional cost in x-ray dose or contrast medium, color-coding of DSA enhanced the conspicuity of findings on DSA images. It was particularly useful in situations in which there was a complex flow pattern and in evaluation of pre- and posttreatment acquisitions. Its full potential remains to be defined.

Nowadays, abdominal catheterizations are mainly guided by 2D fluoroscopic imaging from one view, which complicates this task due to missing depth information, vessel invisibility, and patient motion. We propose a new technique for 3D navigation of guide wires based on single-plane 2D fluoroscopic views and a previously extracted 3D model of the vasculature. In order to relate the guide wire, which is only visible in the fluoroscopic view, to the 3D vasculature, we comprise methods for 2D–3D registration, apparent breathing motion compensation, guide wire detection, and robust backprojection. With this 2D-to-3D transfer, the navigation can be performed from arbitrary viewing angles, disconnected from the static perspective view of the fluoroscopic sequence.

Despite rapid advances in interventional imaging, the navigation of a guide wire through abdominal vasculature remains, not only for novice radiologists, a difficult task. Since this navigation is mostly based on 2D fluoroscopic image sequences from one view, the process is slowed down significantly due to missing depth information and patient motion. We propose a novel approach for 3D dynamic roadmapping in deformable regions by predicting the location of the guide wire tip in a 3D vessel model from the tip’s 2D location, respiratory motion analysis, and view geometry. In a first step, the method compensates for the apparent respiratory motion in 2D space before backprojecting the 2D guide wire tip into three dimensional space, using a given projection matrix. To countervail the error connected to the projection parameters and the motion compensation, as well as the ambiguity caused by vessel deformation, we establish a statistical framework, which computes a reliable estimate of the guide wire tip location within the 3D vessel model. With this 2D-to-3D transfer, the navigation can be performed from arbitrary viewing angles, disconnected from the static perspective view of the fluoroscopic sequence. Tests on a realistic breathing phantom and on synthetic data with a known ground truth clearly reveal the superiority of our approach compared to naïve methods for 3D roadmapping. The concepts and information presented in this paper are based on research and are not commercially available.

2D-3D registration of abdominal angiographic data is a difficult problem due to hard time constraints during the intervention, different vessel contrast in volume and image, and motion blur caused by breathing. We propose a novel method for aligning 2D Digitally Subtracted Angiograms (DSA) to Computed Tomography Angiography (CTA) volumes, which requires no user interaction intrainterventionally. In an iterative process, we link 2D segmentation and 2D-3D registration using a probability map, which creates a common feature space where outliers in 2D and 3D are discarded consequently. Unlike other approaches, we keep user interaction low while high capture range and robustness against vessel variability and deformation are maintained. Tests on five patient data sets and a comparison to two recently proposed methods show the good performance of our method.

Minimal invasive catheter-guided interventions play an important role in most hospitals all over the world. During the treatment physicians have to rely on 2D information that is acquired through a fluoroscopic imaging device. In those fluoroscopic images, catheter, bone structures, and (if contrast agent added) blood vessels are visualized in real-time. Those low resolution images can be enhanced by high resolution DSAs where only vessel structures are visible. In difficult interventions these 2D views might not be adequate and it is challenging to navigate the catheter to a region of interest. In this thesis we present a method that allows the physician to use information from a pre-operatively taken 3D CTA scan during the intervention. In the first part we introduce an innovative approach for 2D/3D registration which forms the basis for the second part of the thesis, the development of an estimation procedure to resolve the 3D location of the catheter tip in real-time. This transfers the navigation process to the three-dimensional space and leads to a faster and smoother workflow.