Philips Healthcare was the first to bring liquid metal bearing CT tube technology to the market 30 years ago.
The innovation resulted in a collective sigh of relief from cardiologists, who often feared the tubes would overheat while a catheter was in their patient’s heart area.
“If they suddenly got an overheat alarm on the tube, they were going to power through and destroy the tube if they had to in order to get through the exam,” said Patrick Fitzgerald, president of Chronos Imaging, a replacement tube provider.
Ninety-nine percent of the energy pushed into CT tubes comes out as heat and not X-rays, according to Jason Launders, director of operations of device evaluation at ECRI.
“It’s a remarkably inefficient way of making X-rays, but it’s what we have,” he said. “You have to get rid of that heat as quickly as you can, and liquid bearing is one of the technologies used to do that.”
Conventional ball bearing tubes have mechanical bearing components that wear over time and can potentially shorten the lifespan of the tube, whereas liquid metal bearing technology provides a lubricant to keep bearing surfaces separated while the scanner is in use.
“At the end of the day, the true advantages are those that help support an improved patient experience,” said Aaron Goryl, general manager of in-house and on-demand service for the U.S. and Canada at GE Healthcare. “Liquid bearing tubes can potentially deliver enhanced clinical and operational capabilities, including faster access to CT scanning, given the tube rotor is routinely spinning, and lower audible noise.”
An increasing amount of new CT scanners are using liquid metal bearing tubes. Some OEMs have incorporated it into their entire platform and others are using it exclusively on their high-end systems.
“Of the major companies, there are very few who aren’t using liquid metal bearing tubes to some degree,” according to Fitzgerald.
Dunlee (owned by Philips) and Varex Imaging Corporation, a leading independent tube manufacturer, have both succeeded in deploying their own liquid metal bearing CT tube technology.
Dunlee’s CT4000, CT6000 and CT8000 tubes feature its CoolGlide liquid metal bearing technology, which continuously circulates fluid transferring heat away from the anode. The CT4000 tube was designed for mid-range CT scanners, the CT6000 for mid-range to high-end scanners and the CT8000 solely for high-end scanners.
At the 2019 Radiological Society of North America (RSNA) annual meeting, Varex introduced liquid metal bearing technology to its X-ray tube portfolio including its FP-1596-LMB tube for cardiovascular applications and its G-507X-LMB for CT applications. For the first time, Varex offers a lease option on these new tubes.
Also at the 2019 RSNA meeting, Dunlee announced plans to launch a liquid metal bearing tube in the replacement space.
“Currently, all dealers and customers have no choice but to buy from the OEM, because today there are no alternatives for liquid bearing technology in the market,” said Alexander Eitel, head of marketing and business development at Dunlee. “By bringing the product to the market, we are giving them a choice to manage their cost and it means they don’t have to be as dependent on the OEM.”
The case for conventional tubes
Despite its revolutionary cooling benefits, liquid metal bearing technology does come with a few drawbacks — cost being the main one.
Replacing one of these tubes can cost between a third or half of the cost of the original CT scanner, according to Jerald Olsen, vice president of sales and business development at Richardson Healthcare. Because of that, a service contract with the OEM is needed to mitigate that risk.
In addition, liquid metal bearing technology may limit the gantry rotation speed. As gantry speed is increased, it requires a more precise liquid metal bearing to handle the increased G loads, according to Olsen.
“A liquid metal bearing requires a special drive motor for the anode and these need to be incorporated into the design of the CT scanner,” he added. The torque required to start the bearing in rotation is high, and up-to-speed time is not as fast as a conventional ball bearing.”
These tubes tend to last longer than conventional ball bearing tubes, but in general, CT tube life varies greatly. A tube in similar scanners can last anywhere from two months to two years, according to Launders.
“One of the issues I see is that the manufacturers own the data on the longevity of the tubes,” he said. “Unless you have your own biomeds that service your CT scanners and you’re a large hospital, you probably have very little idea of the longevity of the CT tube because you won’t have enough CT scanners at the same site to track that data.”
Remote monitoring during the pandemic
Since it’s challenging to determine when a CT tube is at the end of its life, OEM remote monitoring technology has historically helped facilities avoid unplanned downtime. However, the current global COVID-19 pandemic is highlighting the importance of this technology in an entirely different way.
“Remote monitoring is playing a significant role to which COVID-19 has only strengthened the need and importance of this type of capability and solution,” said GE’s Goryl. “Remote fix and monitoring technologies are being implemented to assist in reducing direct human contact within patient and clinical environments in an effort to help minimize potential exposure to COVID-19 for the patients, clinical staff and service personnel.”
With resources like OnWatch and Tube Watch, GE has expanded its remote tube maintenance capabilities by providing direct healthcare technology management (HTM) support through its service management system.
OnWatch is fully automated and continuously monitors critical subsystem elements within the CT scanner to detect any deviations from normal performance. If there is an issue, a GE engineer can remotely diagnose it and may be able to fix it remotely as well. Tube Watch leverages artificial intelligence, machine learning and software analytics to monitor and analyze tube health.
“We have just been taught a lesson, over the past [few] months with COVID-19, where a lot of support shifted from an onsite visit to remote monitoring support,” said Dunlee’s Eitel. “I think our industry has been slow in catching up to this trend [of digitization] and I think it’s a very important thing to do.”
Dunlee is also helping during the pandemic in other ways. Since CT scanners can detect the opacities in the lungs that are indicative of COVID-19, there is an increasing demand for tubes. Therefore, the company has escalated the production of its CT4000, CT6000 and CT8000 liquid metal bearing tubes.
Busy imaging departments don’t have the time to wait for the tubes to cool down between CT exams, Eitel explained. By increasing production, Dunlee is ensuring that CT system manufacturers that use their tubes can supply hospitals with CT scanners that can tolerate high patient volumes.
Varex, which is based in Salt Lake City, Utah, is also seeing a spike in global orders due to the pandemic. The company’s global manufacturing facilities currently remain open and in operation, including its facility in Wuxi, China, which resumed normal operations in early March.
Big picture challenges for tube service
The question still remains: under normal conditions, is remote monitoring technology necessary? It’s something not everyone seems to agree on.
Chronos’ Fitzgerald, who held positions at Richardson Healthcare, Dunlee, TREX Medical Corporation, Continental X-ray and Eureka X-ray Tube Corporation, doesn’t think the technology is worth the price tag.
“I know some OEMs are doing this and I’m sure their solutions work well, but for me, I would have to think twice before I used a solution like that if I had to pay a lot for it,” he explained. “Tubes are so much more reliable now than they used to be, and can last years.”
Many OEMs offer remote monitoring services as an option when purchasing service contracts. Yet there are large hospital groups out there that refuse to have anything to do with it and will take the risk themselves, said Launders.
“Remote monitoring is essentially insurance, and if you are big enough then you can self-insure and save money that way,” he added.
Richardson’s Olsen acknowledges the benefits of remote monitoring, but also points to the challenges that in-house hospital teams may face when they want to do things themselves. He said sometimes OEMs don’t give control to individual hospitals because they want to maintain the software control.
“In some cases, remote diagnosis is not widely available to anyone but the OEM,” he added. “It’s not that the hospital wouldn’t like it — it’s that they either didn’t pay for it or it isn’t available to someone outside the OEM.”
Remote monitoring also comes with a learning curve. If a hospital has one CT scanner, that makes it difficult to learn; but if they have 20 scanners, then they start to learn the different characteristics of the scanners and tubes and how they typically fail, said Olsen.
In order to install a replacement tube, the in-house biomed needs to be trained on that specific CT platform. The OEMs can lock out those service features until the biomeds have gone through the proper training, said Launders.
If a hospital doesn’t have a service contract with the manufacturer, they may also face issues when trying to get a replacement tube. It doesn’t make sense to have an inventory, because the tubes can cost up to $200,000 and they will deteriorate over time while in storage.
“If you don’t have a service contract with a manufacturer, they will probably put you low in the list because they are going to look after their own customers first,” said Launders. “The manufacturers hold most of the cards when it comes to tubes.”