Gerald Glombitza

Three-dimensional color Doppler: a clinical study in patients with mitral regurgitation.

OBJECTIVES The purpose of this study was to assess the clinical feasibility of three-dimensional (3D) reconstruction of color Doppler signals in patients with mitral regurgitation. BACKGROUND Two-dimensional (2D) color Doppler has limited value in visualizing and quantifying asymmetric mitral regurgitation. Clinical studies on 3D reconstruction of Doppler signals in original color coding have not yet been performed in patients. We have developed a new procedure for 3D reconstruction of color Doppler. METHODS We studied 58 patients by transesophageal 3D echocardiography. The jet area was assessed by planimetry and the jet volumes by 3D Doppler. The regurgitant fractions, the volumes, and the angiographic degree of mitral regurgitation were assessed in 28 patients with central jets and compared with those of 30 patients with eccentric jets. RESULTS In all patients, jet areas and jet volumes significantly correlated with the angiographic grading (r = 0.73 and r = 0.90), the regurgitant fraction (r = 0.68 and r = 0.80) and the regurgitant volume (r = 0.66 and r = 0.90). In patients with central jets, significant correlations were found between jet area and angiography (r = 0.86), regurgitant fraction (r = 0.64) and regurgitant volume (r = 0.78). No significant correlations were found between jet area and angiography (r = 0.53), regurgitant fraction (r = 0.52) and regurgitant volume (r = 0.53) in the group of patients with eccentric jets. In contrast, jet volumes significantly correlated with angiography (r = 0.90), regurgitant fraction (r = 0.75) and regurgitant volume (r = 0.88) in the group of patients with eccentric jets. CONCLUSIONS Three-dimensional Doppler revealed new images of the complex jet geometry. In addition, jet volumes, assessed by an automated voxel count, independent of manual planimetry or subjective estimation, showed that 3D Doppler is also capable of quantifying asymmetric jets.

Virtual planning of liver resections: image processing, visualization and volumetric evaluation

Operability of a liver tumor depends on its three dimensional relation to the intrahepatic vascular trees as well as the volume ratio of healthy to tumorous tissue. Precise operation planning is complicated by anatomic variability and distortion of the vascular trees by the tumor or preceding liver resections. We have developed a computer based 3D virtual operation planning system which is ready to go in routine use. The main task of a system in this domain is a quantifiable patient selection by exact prediction of post-operative liver function. It provides the means to measure absolute and relative volumes of the organ structures and resected parenchyma. Another important step in the pre-operative phase is to visualize the relation between the tumor, the liver and the vessel trees for each patient. The new 3D operation planning system offers quantifiable liver resection proposals based on individualized liver anatomy. The results are presented as 3D movies or as interactive visualizations as well as in quantitative reports.

THREE-DIMENSIONAL COLOR DOPPLER : A NEW APPROACH FOR QUANTITATIVE ASSESSMENT OF MITRAL REGURGITANT JETS

Color Doppler echocardiography does not provide adequate information about the severity of mitral regurgitation in patients with eccentric mitral regurgitation. We have developed a new procedure for 3-dimensional (3D) color Doppler reconstruction and for segmentation of regurgitant jets. The volume of regurgitant jets was compared with jet area in 63 patients with mitral regurgitation. Mitral regurgitation was assessed by angiography, regurgitant fraction and volume by pulsed Doppler, JA by planimetry, and JV by 3-dimensional Doppler. Twenty-eight patients with central jets were compared with 35 patients with eccentric jets. In the patients with eccentric jets, JV showed significant correlations with regurgitant volume (r = 0.90; P <.01) and regurgitant fraction (r = 0.76; P < .01) and was able to separate groups with different degrees of mitral regurgitation (P <.01). Three-dimensional Doppler revealed origin, direction, and spatial spreading of complex jet geometry. JV, a new parameter of mitral regurgitation, was also capable of quantifying asymmetrical jets.

Virtual surgery in a (tele-)radiology framework

Presents telemedicine as an extension of a teleradiology framework through tools for virtual surgery. To classify the described methods and applications, the research field of virtual reality (VR) is broadly reviewed. Differences with respect to technical equipment, methodological requirements and areas of application are pointed out. VR, desktop VR and augmented reality are differentiated and discussed in some typical contexts of diagnostic support, surgical planning, therapeutic procedures, simulation and training. Visualization techniques are compared as a prerequisite for VR and assigned to distinct levels of immersion. The advantage of a hybrid visualization kernel is emphasized with respect to the desktop VR applications that are subsequently shown. Moreover, software design aspects are considered by outlining functional openness in the architecture of the host system. A teleradiology workstation was extended by dedicated tools for surgical planning through a plug-in mechanism. Examples of recent areas of application are introduced, such as liver tumor resection planning, diagnostic support in heart surgery, and craniofacial surgery planning. In the future, surgical planning systems will become more important. They will benefit from improvements in image acquisition and communication, new image processing approaches and techniques for data presentation. This will facilitate pre-operative planning and intra-operative applications.

Assessment of mitral regurgitant jets by three-dimensional color Doppler

BACKGROUND Color Doppler echocardiography is a standard technique for assessing mitral regurgitation before and after mitral valvuloplasty. Mitral valve prolapse produces complex eccentric jet flows that cannot be visualized and measured by two-dimensional color Doppler echocardiography. The aim of this study was to evaluate the clinical impact of three-dimensional color Doppler echocardiography, a new technique developed at our institution, for assessing mitral regurgitation. METHODS Forty-five patients with mitral regurgitation underwent intraoperative transesophageal echocardiography and three-dimensional Doppler data acquisition. The grade of mitral regurgitation was assessed by angiography. The jet areas were calculated by planimetry from conventional color Doppler; the jet volumes were obtained by three-dimensional Doppler data. RESULTS New patterns of mitral regurgitant flows were recognized according to the origin, direction, and spatial spreading into the left atrium. Conventional jet areas failed to separate the groups of patients with different degrees of regurgitation, whereas the jet volumes were able to divide patients with different regurgitation grades. No significant correlation was found between jet area and angiographic grading (r = 0.63, p = NS). Jet volumes were significantly correlated to angiography (r = 0.89, p < 0.001). CONCLUSIONS Three-dimensional color Doppler echocardiography revealed new patterns of regurgitant flow and allowed a more accurate semiquantitative assessment of complex asymmetrical regurgitant jets.

Three‐Dimensional Color Doppler Flow Reconstruction and Its Clinical Applications

The visualization and quantification of intracardiac blood flow have always been a challenging task for the cardiologist. The advent of color Doppler flow imaging substantially enhanced the clinical diagnosis of heart valve disease. Three‐dimensional (3‐D) color Doppler, a new diagnostic procedure, refines the diagnostic value of color Doppler by providing unique spatial and temporal information about the actual extension, direction, origin, and size of intracardiac flows. Here, we describe the procedure for 3‐D color Doppler reconstruction of intracardiac blood flow velocities and reveal the varied findings in different heart pathologies that cause blood flow disturbances. An automated procedure for the segmentation of turbulent and laminar flows, which allows for the measurement of mitral regurgitant jet volumes, is one of the first 3‐D quantitative approaches to the clinical assessment of mitral valve regurgitation. The major technical advances of this procedure include the direct use of digital color Doppler velocity data and an automatic voxel count of the turbulent jet flows. Three‐dimensional color Doppler not only can disclose the spatial complex geometry of intracardiac blood flow disturbances but also can quantitatively assess the severity of mitral valve regurgitation.

Technical aspects of virtual liver resection planning.

Operability of a liver tumor is depending on its three dimensional relation to the intrahepatic vascular trees which define autonomously functioning liver (sub-)segments. Precise operation planning is complicated by anatomic variability, distortion of the vascular trees by the tumor or preceding liver resections. Because of the missing possibility to track the deformation of the liver during the operation an integration of the resection planning system into an intra-operative navigation system is not feasible. So the main task of an operation planning system in this domain is a quantifiable patient selection by exact prediction of post-operative liver function and a quantifiable resection proposal. The system quantifies the organ structures and resection volumes by means of absolute and relative values. It defines resection planes depending on security margins and the vascular trees and presents the data in visualized form as a 3D movie. The new 3D operation planning system offers quantifiable liver resection proposals based on individualized liver anatomy. The results are visualized in digital movies as well as in quantitative reports.

5D interactive real time Doppler ultrasound visualization of the heart

Heart valve insufficiencies can optimally be assessed using transesophageal, triggered, three-dimensional ultrasound imaging. The dynamic ultrasound data contain morphological as well as functional components which are recorded and displayed simultaneously. It allows the visualization of intracardiac motion which is an important parameter to detect abnormal flow caused by defect valves. A realtime reconstruction is desired to get a spatial impression on the one hand and to interactively clip parts of the volume on the other hand. OpenGL Volumizer is used for visualization. Scalability of the visualization was tested with respect to different workstations and graphics resources using a Multipipe Utility library (MPU). The combination of both APIs enables a visualization of volumetric and functional data with frame rates up to 10 frames per second. By using the proposed method, it is possible to visualize the jet in the original color-coding which is employed during a conventional two- dimensional examination for displaying the velocity values. A good scalability from low cost up to high end graphic workstations is given by the use of the MPU. The quality of the resulting 3D images allows exact differentiation of heart valve insufficiencies to support the diagnostic procedure.

Navigation in der Leberchirurgie

Vorgestellt werden die klinischen und technischen Anforderungen fur ein computergestutztes Navigationssystem in der Leberchirurgie. Diese wurden an mehreren chirurgischen Zentren erhoben. Offene und laparoskopische Operationstechniken stellen jeweils spezifische Anforderungen an ein solches System. Zur notwendigen EchtzeitBildakquisition kommen intraoperativer Ultraschall (IOUS) und offene Magnetresonanztomographie (OMRT) in Frage. Die Eignung von optischen und magnetischen Trackingsystemen zur Positionsbestimmung und von medizinischen Schneidegeraten zur Anbindung an ein Navigationssystem werden diskutiert. Die Ergebnisse der Anforderungsanalyse zeigen, dass ein Navigationssystem fur die Leberchirurgie medizinisch sinnvoll ist und die Genauigkeit der technischen Realisierung untersucht werden muss.

Interactive realtime doppler-uitrasound visualization of the heart

Heart valve insufficiencies can optimally be assessed using transesophageal, triggered, three-dimensional ultrasound imaging. The dynamic ultrasound data contain morphological as well as functional components which are recorded and displayed simultaneously. It allows the visualization of intracardiac motion which is an important parameter to detect abnormal flow caused by defect valves. A realtime reconstruction is desired to get a spatial impression on the one hand and to interactively clip parts of the volume on the other hand. Therefore, we use the OpenGL Volumizer API. Scalability of the visualization was tested with respect to different workstations and graphics resources using a Multipipe Utility library. The combination of both APIs enables a visualization of volumetric and functional data with frame rates up to 10 frames per second. By using the proposed method, it is possible to visualize the jet in the original color-coding which is employed during a conventional two-dimensional examination for displaying the velocity values. The morphological and the functional data are handled as two independent data channels. A good scalability from low cost up to high end graphic workstations is given by the use of the MPU. The quality of the resulting 3D images allows exact differentiation of heart valve insufficiencies to support the diagnostic procedure.