Schenectady, NY--Pull 6.5 g while sustaining high temperatures. Sounds like the requirements for a spacecraft component--but they're not. These are the conditions General Electric's new Performix 630 x-ray tube for computed tomography (CT) must withstand. During a CT scan, the tube whips around the patient several times within the scanner to create x-ray "slices" of the internal anatomy of interest--producing the high g loads along with heat from the x-ray generation.
Key to such performance is the tube's metal-ceramic frame, or housing, that gives it greater strength and mechanical stability compared to previous tubes made of glass. Heat dissipation is also improved. Thus, inside the new tube, the largest rotating anode available, according to the company, can operate at higher powers than before.
The anode is bombarded by electrons to generate the x-rays. Heat resistance is so great that there is no need to cool the tube between scans, resulting in more patients examined in a given time. The fast travel (one rotation in as little as 0.8 sec) permits the scanning of large volumes--such as the chest, abdomen, or pelvis--within a single breathhold.
Mary Olson, physican at Loyola University Medical Center (Chicago), adds such speed is "particularly advantageous for several groups, including children who may be sedated or uncooperative, or trauma patients having multiple body parts evaluated. This results in faster diagnosis."
The Performix 630 is produced at GE Medical Systems (Milwaukee, WI) and is in clinical trials at more than 100 hospitals. It is the first product designed under GE's Six Sigma quality program. The analytical tools and techniques in the program allow "designing products that meet or exceed customer specifications and can be produced with near perfect quality," according to Lonnie Edelheit, corporate R&D senior vice president. The effort, coupled with advanced computer modeling and extensive testing, allows each tube to be used for upwards of 400,000 rotations. "It is exceeding customer expectations in both clinical performance and reliability," notes Michael Idelchik, manger of global x-ray tube engineering at GE Medical Systems.