Antoine Rosset

OsiriX: An Open-Source Software for Navigating in Multidimensional DICOM Images

A multidimensional image navigation and display software was designed for display and interpretation of large sets of multidimensional and multimodality images such as combined PET-CT studies. The software is developed in Objective-C on a Macintosh platform under the MacOS X operating system using the GNUstep development environment. It also benefits from the extremely fast and optimized 3D graphic capabilities of the OpenGL graphic standard widely used for computer games optimized for taking advantage of any hardware graphic accelerator boards available. In the design of the software special attention was given to adapt the user interface to the specific and complex tasks of navigating through large sets of image data. An interactive jog-wheel device widely used in the video and movie industry was implemented to allow users to navigate in the different dimensions of an image set much faster than with a traditional mouse or on-screen cursors and sliders. The program can easily be adapted for very specific tasks that require a limited number of functions, by adding and removing tools from the program’s toolbar and avoiding an overwhelming number of unnecessary tools and functions. The processing and image rendering tools of the software are based on the open-source libraries ITK and VTK. This ensures that all new developments in image processing that could emerge from other academic institutions using these libraries can be directly ported to the OsiriX program. OsiriX is provided free of charge under the GNU open-source licensing agreement at http://homepage.mac.com/rossetantoine/osirix.

Self-contained off-line media for exchanging medical images using DICOM-compliant standard

The goal of this project is to develop and implement off-line DICOM-compliant CD ROMs that contain the necessary software tools for displaying the images and related data on any personal computer. We implemented a hybrid recording technique allowing CD-ROMs for Macintosh and Windows platforms to be fully DICOM compliant. A public domain image viewing program (OSIRIS) is recorded on the CD for display and manipulation of sequences of images. The content of the disk is summarized in a standard HTML file that can be displayed on any web-browser. This allows the images to be easily accessible on any desktop computer, while being also readable on high-end commercial DICOM workstations. The HTML index page contains a set of thumbnails and full-size JPEG images that are directly linked to the original high-resolution DICOM images through an activation of the OSIRIS program. Reports and associated text document are also converted to HTML format to be easily displayable directly within the web browser. This portable solution provides a convenient and low cost alternative to hard copy images for exchange and transmission of images to referring physicians and external care providers without the need for any specialized software or hardware.

Color fusion MRI: an effective technique for image visualization in a variety of clinical applications

This paper reports the application of an innovative technique of image fusion of color-coded fluid-sensitive MRI images with high-resolution anatomical images. Image fusion of corresponding slices from two imaging sequences is obtained in real time allowing the user to navigate interactively through large image sets. This technique was applied and evaluated in cases of a variety of musculoskelettal diseases. A color image, overlaying conspicuous findings of fluid-sensitive images, on high resolution spin-echo images, providing accurate anatomical localization were obtained. Compared with traditional side-by-side reviews of these images, this interactive technique it was found to facilitates the correlation of information of different imaging sequences. Furthermore the color images that are generated greatly facilitate the communication of the diagnostic findings to referring physicians.

Navigating the fifth dimension: new concepts in interactive multimodality and multidimensional image navigation

Display and interpretation of multi dimensional data obtained from the combination of 3D data acquired from different modalities (such as PET-CT) require complex software tools allowing the user to navigate and modify the different image parameters. With faster scanners it is now possible to acquire dynamic images of a beating heart or the transit of a contrast agent adding a fifth dimension to the data. We developed a DICOM-compliant software for real time navigation in very large sets of 5 dimensional data based on an intuitive multidimensional jog-wheel widely used by the video-editing industry. The software, provided under open source licensing, allows interactive, single-handed, navigation through 3D images while adjusting blending of image modalities, image contrast and intensity and the rate of cine display of dynamic images. In this study we focused our effort on the user interface and means for interactively navigating in these large data sets while easily and rapidly changing multiple parameters such as image position, contrast, intensity, blending of colors, magnification etc. Conventional mouse-driven user interface requiring the user to manipulate cursors and sliders on the screen are too cumbersome and slow. We evaluated several hardware devices and identified a category of multipurpose jogwheel device that is used in the video-editing industry that is particularly suitable for rapidly navigating in five dimensions while adjusting several display parameters interactively. The application of this tool will be demonstrated in cardiac PET-CT imaging and functional cardiac MRI studies.

OSIRIX: open source multimodality image navigation software

The goal of our project is to develop a completely new software platform that will allow users to efficiently and conveniently navigate through large sets of multidimensional data without the need of high-end expensive hardware or software. We also elected to develop our system on new open source software libraries allowing other institutions and developers to contribute to this project. OsiriX is a free and open-source imaging software designed manipulate and visualize large sets of medical images: http://homepage.mac.com/rossetantoine/osirix/

Peer-to-peer architecture for multi-departmental distributed PACS

We have elected to explore peer-to-peer technology as an alternative to centralized PACS architecture for the increasing requirements for wide access to images inside and outside a radiology department. The goal being to allow users across the enterprise to access any study anytime without the need for prefetching or routing of images from central archive. Images can be accessed between different workstations and local storage nodes. We implemented bonjour a new remote file access technology developed by Apple allowing applications to share data and files remotely with optimized data access and data transfer. Our Open-source image display platform called OsiriX was adapted to allow sharing of local DICOM images through direct access of each local SQL database to be accessible from any other OsiriX workstation over the network. A server version of Osirix Core Data database also allows to access distributed archives servers in the same way. The infrastructure implemented allows fast and efficient access to any image anywhere anytime independently from the actual physical location of the data. It also allows benefiting from the performance of distributed low-cost and high capacity storage servers that can provide efficient caching of PACS data that was found to be 10 to 20 x faster that accessing the same date from the central PACS archive. It is particularly suitable for large hospitals and academic environments where clinical conferences, interdisciplinary discussions and successive sessions of image processing are often part of complex workflow or patient management and decision making.

Hierarchical storage of large volume of multidector CT data using distributed servers

Multidector scanners and hybrid multimodality scanners have the ability to generate large number of high-resolution images resulting in very large data sets. In most cases, these datasets are generated for the sole purpose of generating secondary processed images and 3D rendered images as well as oblique and curved multiplanar reformatted images. It is therefore not essential to archive the original images after they have been processed. We have developed an architecture of distributed archive servers for temporary storage of large image datasets for 3D rendering and image processing without the need for long term storage in PACS archive. With the relatively low cost of storage devices it is possible to configure these servers to hold several months or even years of data, long enough for allowing subsequent re-processing if required by specific clinical situations. We tested the latest generation of RAID servers provided by Apple computers with a capacity of 5 TBytes. We implemented a peer-to-peer data access software based on our Open-Source image management software called OsiriX, allowing remote workstations to directly access DICOM image files located on the server through a new technology called bonjour. This architecture offers a seamless integration of multiple servers and workstations without the need for central database or complex workflow management tools. It allows efficient access to image data from multiple workstation for image analysis and visualization without the need for image data transfer. It provides a convenient alternative to centralized PACS architecture while avoiding complex and time-consuming data transfer and storage.

New GRID-computing platforms for high performance multi-dimensional and multimodality image rendering

With the increasing number of imaging modalities generating very large image datasets such as multidetector CT scanners, ultrafast scanners and more recently multimodality scanners such as PET-CT, there is an increasing need for high performance image manipulation and rendering of these data. Three-dimensional and volume rendering as well as interactive multiplanar navigation across these large data sets usually require high performance workstations equipped with multiprocessors, high memory capacity and dedicated hardware accelerators. An emerging alternative to a single high performance workstation is the ability to share processing power among multiple computers using grid architectures. Such architecture provides the ability to perform parallel tasks assigned to each computer separately by a single software application.

General consumer communication tools for improved image management and communication in medicine

We elected to explore emerging consumer technologies that can be adopted to improve and facilitate image and data communication in medical and clinical environment. The wide adoption of new communication paradigm such as instant messaging, chatting and direct emailing can be integrated in specific applications. The increasing capacity of portable and hand held devices such as iPod music players offer an attractive alternative for data storage that exceeds the capabilities of traditional offline storage media such as CD or even DVD. We adapted medical image display and manipulation software called OSIRIX to integrate different innovative technologies facilitating the communication and data transfer between remote users. We integrated email and instant messaging features to the program allowing users to instantaneously email an image or a set of images that are displayed on the screen. Using iChat instant messaging application from Apple a user can share the content of his screen with a remote correspondent and communicate in real time using voice and video. To provide convenient mechanism for exchange of large data sets the program can store the data in DICOM format on CD or DVD, but was also extended to use the large storage capacity of iPod hard disks as well as Apple’s online storage service dot Mac that users can subscribe to benefit from scalable secure storage that accessible from anywhere on the internet. The adoption of these innovative technologies is likely to change the architecture of traditional picture archiving and communication systems and provide more flexible and efficient means of communication.

Temporal analysis of regional wall motion from cine cardiac MRI

The purpose of this work is to develop and to evaluate an automatic analysis technique for quantitative assessment of cardiac function from cine MRI and to identify regional alterations in synchronicity based on Fourier analysis of ventricular wall motion (WM). A temporal analysis technique of left ventricular wall displacement was developed for quantitative analysis of temporal delays in wall motion and applied to gated cine dark blood cardiac MRI. This imaging technique allows the user to saturate the blood both above and below the imaging slice simultaneously by using a specially designed rf presaturation pulse. The acquisition parameters are: TR equals 25 - 60 msec, TE equals 5 - 7 msec, 0 equals 25 degrees, slice thickness equals 10 mm, 16 to 32 frames/cycle. Automatic edge detection was used to outline the ventricular cavities on all frames of a cardiac cycle. Two different segmentation techniques were applied to all studies and lead to similar results. Further improvement in edge detection accuracy was achieved by temporal interpolation of individual contours on each image of the cardiac cycle. Radial analysis of the ventricular wall motion was then performed along 64 radii drawn from the center of the ventricular cavity. The first harmonic of the Fourier transform of each radial motion curve is calculated. The phase of the fundamental Fourier component is used as an index of synchrony (delay) of regional wall motion. Results are displayed in color-coded maps of regional alterations in the amplitude and synchrony of wall motion. The temporal delays measured from individual segments are evaluated through a histogram of phase distribution, where the width of the main peak is used as an index of overall synchrony of wall motion. The variability of this technique was validated in 10 normal volunteers and was used to identify regions with asynchronous WM in 15 patients with documented CAD. The standard deviation (SD) of phase distribution measured in short axis views was calculated and used to identify regions with asynchronous wall motion in patients with coronary artery disease. Results suggest that this technique is more sensitive than global functional parameters such as ejection fraction for the detection of ventricular dysfunction. Color coded parametric display offers a more convenient way for the identification and localization of regional wall motion asynchrony. Data obtained from endocardial wall motion analysis were not significantly different from wall thickening measurements. The innovative approach of evaluating the temporal behavior of regional wall motion anomalies is expected to provide clinically relevant data about subtle alteration that cannot be detected through simple analysis of the extent (amplitude) of wall motion or myocardial thickening. Temporal analysis of regional WM abnormality from cine MRI offers an innovative and promising means for objective quantitative evaluation of subtle regional abnormalities. Color coded parametric maps allowed a better identification and localization of regional WM asynchrony.