Equipment accuracy and calibration are fairly common questions and occasionally concerns, particularly when someone doesn’t necessarily believe or want to believe their results are what they are whether a baseline or comparative analysis. Nonetheless, questions regarding accuracy, calibration, if it’s calibrated or how it’s calibrated are great and I’m happy to address these and shed a little more light on the topic.
At this time, we use the GE Healthcare Lunar unit in both our mobile and storefront operations. All of our machines use the current and latest version (v17) of the GE enCore software, and both have advanced body composition modules including the CoreScan, Visceral Fat quantification module. They also have nice, pricey full-service maintenance contracts.
When it comes to the calibration of one of our DEXA scanners, the fact of the matter is, they are really, truly only calibrated on particular occasions when it’s only necessary. This is because they don’t require or need regular, true calibration, which is referred to as a ‘primary cal.’ A primary calibration is performed when a new unit is installed, a unit is de-installed and re-installed, or if particular mechanical components of a scanning system need to be replaced such as a Tube Head, High Voltage Power Supply, CSBC Board, Detector, or Detector Board and maybe a couple of others.
In short, the scanner is always calibrated and can’t go out of calibration. Instead, parts or mechanical elements may fail, which would need to be replaced and if it was one of the aforementioned parts, it may require a new primary calibration. If and when a mechanical component does fail, it renders the machine useless; we are unable to complete a body scan for whole-body composition or any other DEXA test and therefore, there’s very, very little if not any possible way your results would be negatively affected by a calibration issue. Every mechanical failure or issue we have experienced has been a direct result of usage. Like anything, when you use a piece of equipment regularly, things can eventually wear out or break and require replacement.
However, every day, before being able to complete total body composition scans the scan system has to pass a 7-minute self test for several things such as mechanical issues with limit switches, etc. (these things are very, very, very sensitive, if anything is even slightly off, it will fail and we can’t scan), database validations, ramping and peaking x-ray, etc. If a self-test fails even one of the 20-30 quality assurance points we are unable to perform assessments until the issue has been professionally resolved by a GE field engineer.
The other fact of the matter is, if something is off we will receive errors messages in the form of a software notification, which in most cases prevents us from completing a scan. Most mechanical failures are minor and range from Transverse Errors where a belt or transverse motor has failed, a timeout issue where a cable has failed or broken due to repetitious motions, or where there’s an x-ray ramp failure or power source issue among a few other commons types.
The DEXA scan system design is actually pretty simple. There are not a ton of moving parts but the ones that do exist must work in perfect synchronization, otherwise, we get pinged with an error and we’re done until it can be remediated. In these cases, we have to occasionally force our customers to bear the ever frustrating burden of a last-minute, forced event and/or appointment cancellation. Those scenarios can be a huge stressor for anyone involved. When the occasion calls for it, our protocol is to phone in GE technical support in order to get them on-site within their 72-hour obligation; they generally get to us sooner.
At the end of the day, your results are what they are but you can rest assured that our systems are always on otherwise they’re literally off. DEXA scans for body composition quantification are not only very accurate, they are extremely precise. They will precisely measure any body in any physiological state that we place on the scan bed. Sure, physiological changes can impact your results but that doesn’t make the machine itself innaccurate. It’s important to keep variables, such as hydration, as consistent as possible between assessments. We take quality seriously and we’re here to help you. If you’ve been the victim of a ‘forced cancellation’ or ever become one, we apologize but please know we’re committed to getting you taken care of.