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The medical imaging field relies increasingly on imaging and graphics techniques in diverse applications with needs similar to
(or more stringent than) those of the military, industrial and scientific communities. However, most image processing and
graphics systems available for use in medical imaging today are either expensive, specialized, or in most cases both. High
performance imaging and graphics workstations which can provide real-time results for a number of applications, while
maintaining affordability and flexibility, can facilitate the application of digital image computing techniques in many different
areas.
This paper describes the hardware and software architecture of a medium-cost floating-point image processing and display
subsystem for the NeXT computer, and its applications as a medical imaging workstation. Medical imaging applications of
the workstation include use in a Picture Archiving and Communications System (PACS), in multimodal image processing
and 3-D graphics workstation for a broad range of imaging modalities, and as an electronic alternator utilizing its multiple
monitor display capability and large and fast frame buffer.
The subsystem provides a 2048 x 2048 x 32-bit frame buffer (16 Mbytes of image storage) and supports both 8-bit gray scale
and 32-bit true color images. When used to display 8-bit gray scale images, up to four different 256-color palettes may be
used for each of four 2K x 2K x 8-bit image frames. Three of these image frames can be used simultaneously to provide pixel
selectable region of interest display. A 1280 x 1024 pixel screen with 1: 1 aspect ratio can be windowed into the frame buffer
for display of any portion of the processed image or images. In addition, the system provides hardware support for integer
zoom and an 82-color cursor. This subsystem is implemented on an add-in board occupying a single slot in the NeXT
computer. Up to three boards may be added to the NeXT for multiple display capability (e.g., three 1280 x 1024 monitors,
each with a 16-Mbyte frame buffer).
Each add-in board provides an expansion connector to which an optional image computing coprocessor board may be added.
Each coprocessor board supports up to four processors for a peak performance of 160 MFLOPS. The coprocessors can
execute programs from external high-speed microcode memory as well as built-in internal microcode routines. The internal
microcode routines provide support for 2-D and 3-D graphics operations, matrix and vector arithmetic, and image processing
in integer, IEEE single-precision floating point, or IEEE double-precision floating point.
In addition to providing a library of C functions which links the NeXT computer to the add-in board and supports its various
operational modes, algorithms and medical imaging application programs are being developed and implemented for image
display and enhancement. As an extension to the built-in algorithms of the coprocessors, 2-D Fast Fourier Transform (FF1),
2-D Inverse FFF, convolution, warping and other algorithms (e.g., Discrete Cosine Transform) which exploit the parallel
architecture of the coprocessor board are being implemented.
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