Selling, inspecting, buying, servicing – there are a number of reasons to access usage information for a CT scanner’s X-ray tube. Coincidentally, there are also a number of ways to measure tube usage that, taken together, can create an approximation of how much and how hard a tube has been used. We’ll discuss three usage metrics you’re likely to run across and exactly what they mean for the X-ray tube in question.
Total Patient Exams
Total patient exams is the sum of individual cases conducted with a particular tube. Patient exam count is useful as a ballpark metric of tube usage. Unfortunately, its reliability as a definitive indicator of tube usage is limited. These limitations stem from the fact that not all types of CT studies are conducted at the same power level or for the same duration of time.
When checking total patient count, an additional factor to consider is the specialty of the facility using it. What kind of studies are they doing most often? Think of the difference between flooring the accelerator in your car to win a drag race and giving your grandma a ride to church on Sunday morning – both may rack up only a few miles on your odometer, but one creates much more wear and tear on your engine than the other. In CT scanners, a trauma facility, for example, will use their X-ray tube much harder than a facility that performs primarily sinus studies.
mAs (milliampere seconds)
An X-ray tube’s mAs count represents the total number of seconds that power has been applied to the tube, whether it was scanning a patient, testing, or performing quality assurance calibrations.
The real usefulness of the mAs count is to determine the average mA a site has been running their tube at. To do this, divide the total mAs reading by the number of scan seconds. Speaking of which…
This metric tells how many seconds the tube was both powered and scanning a patient. Once again, in this case, the metric will not tell you exactly how much power was applied during all of those seconds, so noting the specialty of the facility will be helpful in determining a typical current level across the life of the tube.
Ultimately, it is best to have as many of these numbers as possible. Together, they form a composite of what usage a tube has undergone. This, combined with an understanding of which techniques were most frequently performed on the system, will help you form reasonable expectations of the remaining lifespan on a given X-ray tube.
Ride It Out
If your cost of ownership and your revenue stream are both low, you may consider riding out your current CR until it “dies of natural causes.” At low patient volumes, a seven percent reduction in revenue may not justify the cost of upgrading. Additionally, DR panel prices have fallen over the last few years and riding out your CR may result in slightly lower DR prices when you are eventually ready to upgrade.
Jordan Batterbee is the Content Manager for Block Imaging International, refurbished medical imaging equipment, parts and service company.