The health care landscape is always shifting, but some things have remained fairly constant, including the high cost of X-ray tubes.

It’s no secret that these powerful, vacuum sealed, and fragile tubes are one of the most important components of a CT scanner or X-ray system. And while most imaging professionals know how they work, the process of how these tubes are created is not common knowledge.

For its annual industry sector report, DOTmed Healthcare Business News decided to demystify the X-ray tube manufacturing process a bit, speaking with two of the major players — Varian Medical Systems, which builds tubes and private labels equipment for OEMs, and Dunlee, a division of Philips Healthcare which, in addition to supplying its parent company, also makes private label tubes for other manufacturers and CT tubes for the mulit-vendor marketplace.

The hope is that when it again comes time to replace the tubes, you’ll have a clearer picture of where your money is going.
 


Materials
Before things even get going in the factory, it all starts with the materials, which are the most expensive part of the manufacturing process. The refractory metals — oxygen free high thermal conductivity copper, high grades of nickel, tungsten, silver, rhenium, and Kovar — are costly and the prices often fluctuate. The metals are mined and sourced from several different countries including China, Russia, Australia, Peru, and Canada.
 


Parts are also sourced from a few suppliers. For example, targets, big metal pieces made out of refractory metals, generally tungsten, that produce X-rays when struck by electrons, are only made by a few big companies, such as GE Healthcare and Plansee. Both Dunlee and Varian purchase targets from these outside companies, because the level of investment it would take to produce them would be high, according to Mark Jonaitis, general manager of X-ray tube products at Varian.
 


1. Parts preparation
Preparing the expensive materials also requires a major capital investment. Inside large furnaces that cost a few million dollars and range in size from 10 square feet to 50 square feet, all gases and other materials are removed from the metal components to ensure there’s a solid vacuum environment — kind of like water being wrung out from a sponge. Varian uses a variety of furnaces manufactured by Thermal Technology, Vacuum Industries, and Astro, to name a few. Dunlee also uses furnaces manufactured by Thermal Technology along with a variety of others including T-M Vacuum Products.

Depending on the type of part being outgassed and/or brazed, temperatures can range from 475 to 1,800 degrees Celsius. This outgassing and brazing, or high-temperature soldering, which on average takes about six hours, creates a complete and airtight envelope for X-rays to be produced.

Next comes the plasma coating to create surfaces that either absorb or reflect the incredible amount of heat that builds up in the tubes — a target can get as hot as a 2,700 degrees centigrade. The tube produces 99 percent heat and 1 percent X-rays, Jonaitis says. Much of the technology and design of the tubes is for heat management. Cleaning, while it sounds simple, is an important step, and requires an investment in ultrasonic waterand solvent-based cleaning systems, which can be as tall as 15 feet.

Cleaning helps to prevent arcing, which occurs when there is a short circuit within the tube, usually caused by residual gas or an improper electrical path, and stops the X-ray output — not something you want to happen mid-scan. Warming up your tube before use can also prevent arcing.
 


After degassing and cleaning, the parts, which can absorb gases from the atmosphere, must be stored in cabinets filled with nitrogen which boils away from liquid air at a lower temperature than oxygen, to prevent reabsorption. Varian partnered with their supplier to build a 100-foot by 100-foot on-site nitrogen plant, Dunlee buys large quantities of liquid nitrogen, and then lets it evaporate and collects the gas, creating ultra-pure nitrogen used during many of the operation steps.
 


2. Assembly
The two major parts of the X-ray tube — the negatively charged cathode, which contains the filament wire, usually made of tungsten, that generates the electrons used to produce X-rays, and the positively charged anode, which contains the target that the electrons collide into — are assembled in a clean, HEPA-filtered space similar to a sterile operating room, where workers don gowns, gloves, and headcovers. There must be a strong connection between the target and its stem, otherwise the anode assembly can become unbalanced and the tube will not function correctly.
 


3. Final seal
This is the most visual part of the process, and for anyone who has toured an X-ray tube factory, it can be as interesting as a visit to the Simon Pearce glassblowing facility in Vermont (though without the gourmet food). The assembled cathodes and anodes are placed depending on the product, into metal or glass inserts (also called envelopes).

“Forming the glass envelope is fascinating and requires a high level of glass technology as some glass doesn’t seal to the metal parts and requires ‘transition’ glass to be used,” says Tom Spees, director of sales, North America for Dunlee, the GTC division of Philips Healthcare. “The welding of the tube parts into the metal frame construction of high-end CT tubes is equally as fascinating, although perhaps not as visually stimulating, as watching the glass blowing,” he says.
 


4. Pump
At this stage, the anode and cathode are heated and cooled repeatedly to remove unwanted gasses. The length of the pumping process varies by the size of the tube and the application, and can range from eight hours to three days, using equipment that’s about the size of a large closet. Because tubes are run actively and produce X-rays during the process, the equipment housing the tubes during the process is lead lined for the safety of the operators. The vacuum is very strong to create a stable high voltage environment. According to Dunlee, the vacuum levels achieved in their processing is better than those which surround the International Space Station. At this point, it is sealed off from the atmosphere.
 


5. Tank testing/housing load
Once the final seal is in place, all of the gas has been removed and the insets are placed in their lead housings, which have small windows that allow X-rays to exit, Dielectric oil, nonconductive oil that acts as a cooling agent, is added, and the oil is specially processed so X-rays don’t break it down. The fully assembled tubes are then put into test tanks and are exposed to the type of voltage they will run on, on a gantry system similar to one used in the field, preparing the tube for its role in a medical application. Varian always exposes the tubes to 50 percent more voltage, so if the tube will run on 140 kV then it’s exposed to 210 kV. Dunlee also exceeds the high voltage rating.
 


6. Housing test
This part of the process gets to the heart of what a tube manufacturer’s customers care about — the focal spot of the radiation source that they’re buying. This process, which is where the rubber meets the road for X-ray tubes, quantifies levels of output.

The focal spot sizes are measured to make certain they are within the industry tolerances and the final assembly is checked for any stray radiation leakage to assure X-ray output is only from the desired window.

“We test our products on actual customer generators and scanners to ensure optimal performance in the field,” says Laura Hafner, senior director of global sales and marketing for Dunlee.

7. Finish-off
This part may seem to be only cosmetic, and on some level it is. Tubes are painted to match the shade of the OEM machines. But tubes also have to be labeled as part of regulatory compliance, with different countries having different requirements.

For Dunlee, the entire process, from degassing and cleaning to being able to ship, generally takes four to five days to many weeks, depending on the tube type.

Jonaitis, of Varian, notes that part preparation can take one month, while the rest of the process takes about two weeks.

For both companies, materials and parts make up the majority of the cost of the tube, followed by overhead and then labor, even though at Dunlee, 90 percent of the manufacturing is done by hand, while the remaining 10 percent is robotic, with robots mainly used during the Housing Test step.

For Varian, probably 70 percent of the original labor content has been replaced by automation. Jonaitis says this keeps the company competitive on cost and allows them to “tune a process to an optimum point and reproduce that point consistently.”

Fast facts:
Varian
Varian first started building X-ray tubes in 1970, but the plant has been there since the 1940s, producing vacuum tubes under a different company name (EIMAC).

Headcount: 959
Number of tubes manufactured per year: 22,000 to 25,000
How many different models of tubes are manufactured: 400+
Square footage of the Salt Lake City plant: 340,000 square feet
Location of manufacturing facilities: Salt Lake City, Charleston, South Carolina; Las Vegas, Nevada, Syracuse, New York; Dusseldorf, Germany; Beijing

Dunlee
Dunlee was founded in 1946 by two former GE tube engineers and began building X-ray tubes in Chicago. Following a move to Bellwood, a Chicago suburb, the company built a new factory in Aurora, Illinois and moved into its present 140,000-square-foot facility in 1994.
Headcount: 600+
Number of tubes manufactured per year: More than 10,000
How many different models of tubes are manufactured: 100+
Combined square footage of the plants: More than 350,000 square feet
Location of manufacturing facilities: Aurora, Illinois and Hamburg, Germany

Click here to check out the DOTmed Virtual Trade Show for X-ray tubes.



DOTmed Registered HCBN September 2014 - X Ray Tube Companies
Names in boldface are Premium Listings.
Domestic
Sean Wang, Advanced Imaging Services, Inc., CA
Robert Costa, Oxford Instruments Service, LLC, CA
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Elie Semaan, Rayon-x Engineering, LLC, CA
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Melissa Garske, R-Tron Medical, Inc., CA
David Denholtz, Integrity Medical Systems, Inc., FL
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Larry Sprague, Imaging Resources, GA
Michael Dingel, Turn-Key Medical, ID
James Blandi, LFC Capital, IL
Chad Seelye, Block Imaging Parts & Service, Inc., MI
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Ric Arcadi, Sunset Medical Equipment and Finance, LLC, OH
David Hurlock, Varian Medical Systems, SC
Rick Stockton, Atlas Medical Technologies, CA
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Pete Cawley, Kimtron, Inc., CT
Ed Ruth, Managed Medical Imaging, LLC, FL
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Rodrigo Henao, Medilab Global Corp., FL
Robert Serros, Amber Diagnostics, FL
Ronen Bechor, ElsMed Ltd. & Relaxation, Inc., FL
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Stephanie Moretti, Dunlee Division, Philips Healthcare, IL
Mike Ghazal, Zetta Mdical Technologies, IL
Charles Gauthier, Imaging Services, IL
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Michael McKinney, Imaging Affiliates, Inc., NC
Jeremy Probst, Technical Prospects, WI
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DOTmed 100
Norine Carlson-Weber, Alpha Source, WI
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Amy Belcher, First Call Parts, VA
DOTmed 100
Trey McIntyre, International Medical Equipment and Service, Inc., SC
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Tim Davis, Stat Medical X-Ray Tubes, SC
Josh Glas, ADAM Imaging Parts, NY
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DOTmed 100
Tim Wright, Virtual Medical Sales, Inc., NY
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Ryan Gilday, Clinical Imaging Systems, NJ
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Larry Cornell, Meridian DR, OH
Melany Eckstein, Classic Diagnostic Imaging, LLC, OH
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International
Florian Dickopp, Medicopex GmbH, Germany
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Jose Morillo, J Morillo Sistemas Biomedicos, Venezuela
Mads Vittrup, AGITO Medical, Denmark
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