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Publication Date: 12/1/2010
Archive >  December 2010 Issue >  Special Features: Test and Measure > 

What Are the Risks Buying Used X-Ray Systems?
Wire test gauges.

Buying a new X-ray system can be an expensive proposition; there are numerous models and an unlimited number of features. One option is to buy a used X-ray system. Used X-ray systems can be a good value for the money spent if you apply some caution.

Buying a used X-ray system with a non-functioning X-ray tube is always a risky purchase; it totally eliminates the ability to evaluate the imaging chain and overall X-ray system properly — operations that must be performed.

If the X-ray system is not producing X-rays there could be a simple problem with a control circuit board, interlock switch, or low voltage power supply. In most cases, however, the X-ray tube or high voltage power supply has failed and will require replacement before the X-ray system can be properly evaluated. This would also be the time to check for arcing in the X-ray tube or high voltage supply. If the X-ray system has a separate high voltage power supply it' not unusual to have arcing in the high voltage power supply cable that connects the X-ray tube to the high voltage supply. Such arcing in the HV power supply well can often be eliminated by cleaning and applying high voltage standoff grease.

Because X-ray tubes operate at very high voltages and have the ability to injure untrained personnel, any service to the X-ray tube and the high voltage power supply should only be performed by a trained X-ray service engineer.

Focal Spots
The heart of the X-ray system is the X-ray tube; the ability of the system to image small defects depends on the X-ray tube focal spot (point source). Focal spots degrade as the X-ray system is used, and after a few years, the focal spot on a closed X-ray tube could be degraded as much as 25 percent depending upon the usage. The focal spot can be measured by using a pinhole camera set up with a piece of X-ray film or by using a high-precision star X-ray test pattern with X-ray film. Checking the focal spot using these methods can provide a good indication of expected X-ray tube performance. Image Intensifiers will degrade with use, and bombarding the image intensifier input window with higher X-ray energies will cause the image intensifier to lose the ability to convert X-rays into a visible image. Image intensifiers produce an image by converting X-rays into visible light; this visible light image is projected onto the image intensifier output window. Image intensifiers operate at around 24,000 volts; an older image intensifier could have problems with the high voltage power supply, and could require that the image intensifier be returned to the manufacturer to be serviced. A properly trained X-ray service engineer will have the ability to check the image intensifier for sharpness and contrast by removing the CCD camera and using a line pair gauge and contrast phantom while observing the output window of the image intensifier with X-rays on. This is a test that only a properly trained X-ray service engineer should perform using specialized X-ray test equipment. Image intensifiers operate at very high voltages and should only be serviced by a trained X-ray service engineer to avoid damaging the image intensifier and to also prevent personal injury.
Line pair gauge.

Older X-ray systems use a CCD camera to capture the image that is projected onto the output window. CCD cameras can lose their ability to capture a sharp, well-defined image over time. Always check to see if a megapixel digital camera is available for the system that you are considering. The major areas of concern when replacing the older CCD technology is that you will need to upgrade the image capture board and possibly the image processing software.

Outdated Hardware
You have checked the image quality and feel the imaging chain is sound but the system seems to have a stage axis that is not working properly. This type of problem could involve major repair issues. Replacing an older outdated motor driver control card could be quite an expensive repair and in some cases might require all of the stage axis motor drivers to be replaced.

X-ray system manufactures often use proprietary X-ray control boards that have elaborate X-ray interlock, X-ray control and stage control schemes. Obtaining replacement control boards can be difficult and expensive if the original manufacturer is no longer in business. In some cases, the X-ray control panel and stage control may need to be rewired to allow for proper operation of the system. This would also be the time to check the X-ray on indicators and door interlocks for proper operation. Non operational door interlocks and X-ray on indicators could point to problems on the X-ray control board and can be a major safety issue.

Does the X-ray system have a complete set of documentation? Items that are needed in case of a computer failure would be the operating system CD and serial number. Other important items would be the install disks for the X-ray control/image processing software. Most of the time, the image processing software will be configured to the existing computer hardware at the time of manufacture. Thus, replacing the hardware after a few years could cause the X-ray control/image processing software to become inoperable. There could be some instances that would require a software dongle to allow the software to operate; losing the dongle would require you to purchase a new copy of the image processing software. If the image processing software/computer is more than five years old you should always look into purchasing a new version of the software/hardware combination to take advantage of new features and insure that your image processing system remains operational over the remaining years of use.
Electronics test gauges.

One of the most overlooked items on the X-ray system is the system monitor; CRT and LCD monitors degrade with use and should be evaluated and replaced. Replacing the existing monitor is a cheap and easy way to improve an older system's performance. Don't forget to optimize the grayscale contrast and brightness settings on your new monitor by using a monitor test program. The auto setup on most monitors will not give the best performance when viewing grayscale X-ray images.

System Modifications
Some companies buy an X-ray system for a specific application and modify the X-ray system to better perform this specific task. Common modifications are additional ports or apertures to accept wiring, hoses and samples. Modifications like these sometimes compromise the shielding and would need to be checked by performing a radiation survey. Simple modifications are easy to repair, larger modifications may require that the X-ray system be recertified to the CFR 21 1020.40 regulations.
X-ray test system, X-SCOPE 1800 has wide inspection area with tilting X-ray tube and detector capability..

One area of concern is if the X-ray tube has been upgraded to a higher kV X-ray tube, most X-ray cabinets are shielded to an acceptable kV level based upon the original OEM specifications. The most common field upgrade is to replace a 90kV tube with a 120 or 130kV X-ray tube and power supply. The major area of concern is the sample viewing window; the glass that is used in X-ray systems has a lead equivalent and is based upon thickness. The glass that is used in a 90kV system will be thinner and have less lead equivalence than the glass that would be used in a 130kV system. The only way to fix this type of issue is to add more glass if the door or window design allows for additional thickness. If the X-ray tube has been upgraded, have a radiation survey performed before you purchase the X-ray system. Installing additional shielding in the field can be difficult, costly and require that the cabinet be recertified to CFR 1020.40.

Shipping The X-Ray System
The most overlooked item when buying a used X-ray system is getting the X-ray system safely into your facility. X-ray systems are heavy due to the lead shielding and mishandling the X-ray system during shipment could cause the lead shielding to fail. X-ray systems should always be transported in an air-ride van to minimize shipping damage. X-ray tubes and image intensifiers are vulnerable to vibration during shipment and could fail very quickly after the setup if not properly isolated from vibration. When shipping an older X-ray system it's a good idea to remove the X-ray tube and image intensifier from the system and package them in the original OEM packaging if available. Calling the X-ray tube and image intensifier vendor to obtain the proper packaging is much cheaper than purchasing replacement components.

Buying a used X-ray system always has risks that could become very expensive; those risks can be minimized by having the X-ray system inspected by a trained X-ray service engineer prior to the purchase.

Contact: Scienscope International, 5751 Schaefer Ave., Chino, CA 91710 800-216-1800 or 909-590-7273 fax: 909-494-5513 E-mail: Web:

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