Original Date: 04/26/1999
Revision Date: 01/18/2007
Best Practice : Computed Tomography Imaging
In 1988, Marshall Space Flight Center (MSFC) purchased a state-of-the-art Computed Tomography (CT) scanner. Over the years, this device increasingly began to fail, averaging a 50% downtime by 1996. Since replacement parts became difficult to locate, engineers resorted to troubleshooting and replacing individual components on the memory boards. In addition, the customized computer operating system made the scanner difficult to master, the storage media (reel-to-reel) was bulky to maintain, and a replacement would cost several million dollars. A cost-effective alternative for MSFC was to upgrade its own system.
A CT scanner is used to produce an internal structural image by taking sequential, repetitive x-ray images along the length of an object. Each image represents an individual layer of the total picture. By combining these layers, a 3-D image of an object is produced. MSFC’s primary use for its scanner is to analyze composite solid rocket nozzles. By using a 3-D image, engineers can easily view the internal structure of a rocket nozzle and identify potential anomalies, such as cracks or voids. MSFC’s scanner is similar to those used in the medical industry for creating 3-D images of the human body, but operates at higher energy levels (420 keV tube with a 2-MeV linear accelerator) to image through much denser material.
MSFC modernized its CT scanner system by using commercial-off-the-shelf (COTS) imaging software and computer resources (e.g., dual processor motherboards, memory chips, video controllers). In addition, the Center also upgraded the operating system to UNIX; added special features such as a re-writeable CD-ROM drive and a backup tape drive; automated the diminish and measure capabilities for analyzing suspected anomalies; and set up a Tagged Image File Format for transporting images which are external to the system. The project took seven months and was completed in September 1997. The availability of the new system is currently at 95%.
The CT scanner was upgraded at a fraction of its replacement cost, approximately $225,000, which resulted in considerable cost savings for MSFC. Within the last 20 months, the system produced 8,500 images primarily for the Fastrac program. Prior to renovations, this scanner had produced only 13,300 images over a nine-year period. Future plans include upgrading the system to achieve higher resolution and constructing a smaller CT scanner from existing components.
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