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Indigo2 IMPACT: Medical Imaging

High Performance for Critical Applications

[Interactive volume rendering and classification on the
desktop] Faster 2D Performance, New 3D Capabilities

Despite the volumetric nature of most medical modalities, the diagnosis and planning tools for radiologists, surgeons, and other medical professionals are traditionally 2D. Creating interactive 3D views, while much more effective for understanding complex anatomical features and their spatial relationships, used to be too costly.

The Indigo2 IMPACT workstation from Silicon Graphics brings interactive 3D imaging to the desktop. For the first time, key features and relationships in a volume of data can be isolated in about the time it takes to input the volume from an archive or scanner. In an era in which cost reductions and quality improvements are expected simultaneously, 3D views bring much-needed productivity gains and better outcomes.

Indigo2 IMPACT meets the complex visualization requirements of the medical community. Providing low cost, compliance with industry standards, and high-performance MIPS CPU technology, Indigo2 IMPACT integrates 2D and 3D interactive imaging and graphics features that deliver unparalleled capabilities for medical imaging applications. Based on the UNIX operating system, Indigo2 IMPACT integrates easily with existing computer environments, including those using standards such as Dicom. Indigo2 IMPACT also supports the industry-standard OpenGL API for widespread, high-performance application support.

Breakthrough Architecture for Medical Workstations

Volume visualization (3D imaging) is rapidly becoming the preferred tool for understanding anatomical features and their interrelationships for volume modalities such as MR and CT. Volume visualization implies the processing of an enormous amount of data, that has, in the past, required a supercomputer. Indigo2 IMPACT is the first workstation to achieve the interactivity and quality needed for clinical use.

Indigo2 IMPACT accelerates voxel and image processing operations in the graphics subsystem. The combination of real-time 2D window leveling, high-performance volume rendering, multiplanar reconstruction (MPR), region-of-interest isolation, and quality interpolation makes it possible to thoroughly explore volume data. For example, a radiologist or surgeon can transfer a volume consisting of 64 512x512 images from a scanner and have a rendered image on screen several seconds after the last image enters the workstation. The volume can then be classified to see the appropriate features. Cut away and rotate the volume to the best view, or cut back and forth through the 3D volume to better view anterior features - all in less than 60 seconds. Even the rendering techniques can be altered to further understand anatomical structure or metabolic functions.

Traditional surface rendering techniques also benefit from Indigo2 IMPACT. With substantially more powerful performance than other desktop graphics workstations, Indigo2 IMPACT can render the most complex surface descriptions at interactive rates.

In applications such as surgical simulation, which require geometric complexity, realism, and high frame rates, the hardware image mapping of Indigo2 IMPACT ensures optimum performance.

OpenGL provides software access to the imaging and graphics features. Among its benefits is the ability to mix geometric and volumetric data in a single visual for new application possibilities.


Image resampling is the limiting factor in the majority of image processing and rendering applications. Indigo2 IMPACT excels at pixel/voxel resampling. For rendering, the primary performance consideration is the number of trilinear interpolations per second (MTRIPS) that must be performed for each rendered voxel. Indigo2 IMPACT can deliver in excess of 80 MTRIPS. This improvement, compared with CPU-based approaches, transforms volume rendering from a tool only for special cases to one that will soon be commonplace.

Interactive 3D Volume Visualization

Volume Rendering

Multiplanar Reformat

Hardware slicing planes let the user sample (trilinearly) the volume and interactively slice through it at an arbitrary orientation. The ability to create a slice across axes ensures that non-orthogonal features can be imaged interactively.

The slicing planes may also be used to isolate a region of interest within the volume (ie. remove those portions of no interest from the field of view).

2D Imaging

Indigo2 IMPACT accelerates commonly used 2D operators such as window level, convolve, flip, rotate, bilinear zoom, and pan. Operators can be linked together to create powerful imaging pipelines appropriate for any application. Indigo2 IMPACT supports 12-bit data paths, removing the necessity for truncating data in many cases and also preserving accuracy, since all intermediate imaging operations are performed on 12-bit data.


More and more, communications are being enhanced with video, particularly in 3D and dynamic studies. The low-cost print-to-video option of Indigo2 IMPACT provides roaming-window or full-screen scan conversion. Frame rate video capture also provided by Indigo2 IMPACT brings the advanced visualization capabilities of Indigo2 IMPACT to modalities such as ultrasound.

The Ideal Medical Workstation

Indigo2 IMPACT does more than advance performance and lower cost. Its breakthrough architecture enables radiologists and surgeons to apply advanced visualization techniques to a broad class of applications for higher productivity and better decision making.

Typed up by Ian Mapleson (mapleson@gamers.org)
Original Document Code: I2-Imp-Medical-IB (10/95)
Last Change: 10/Jun/98

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