LMB CT Tube Technology



Dunlee’s CoolGlide™ Liquid Metal Bearings are designed and manufactured in Hamburg, Germany, based on knowledge gained from over 30 years of LMB technology development and over 100,000 LMB units sold worldwide.
The invention of Liquid Metal Bearing Technology by the Hamburg R&D team in 1989 had an enormous impact on performance and ease-of-use, becoming the gold standard for CT and Image Guided Therapy systems.

Continued refinements led to the introduction of CoolGlide™, the LMB technology now employed in Dunlee tubes. In comparison to traditional ball bearing tubes, CoolGlide™ LMB tubes are designed for higher throughput, faster workflow, lower noise, higher reliability and lower total cost. Let's compare:



CoolGlide™ LMB – High Troughput

CoolGlide™ LMB – High Throughput / Excellent cooling capacity


A cooling channel within the bearing shaft* directs cooling fluid to the anode. This design provides much higher heat conduction and cooling capacity than traditional ball bearing tubes.


* Related to the Coolglide LMB design used in Dunlee‘s Xpert bundles. Dunlee  offers different LMB designs, all designs provide high throughput / excellent cooling capacity.

CoolGlide™ LMB – High Troughput

Traditional Ball Bearing – Lower cooling capacity


Lower heat conduction from the anode through the bearing as there is no direct cooling through the shaft. In contrast to CoolGlide™ LMB the ball bearing is an insulating barrier against heat conduction. This can result in overheating which requires pauses to wait for the tube to cool between studies, slowing down throughput.


CoolGlide™ LMB – High Troughput

CoolGlide™ LMB – Faster Workflow / Continuous Anode Rotation


The anode rotates continuously and provides constant high speed through the entire working day without stopping, speeding up workflow and facilitating productivity. There is no preparation time necessary between every scan, as there is for ball bearing tubes.

CoolGlide™ LMB – High Troughput

Traditional Ball Bearing – Anode rotation stopped after every scan


Anode rotation for ball bearing tubes is started prior to a scan and stopped when the scan is finished. This approach requires preparation time for the tube for every scan.


CoolGlide™ LMB – High Troughput

CoolGlide™ LMB – High Reliability / virtually no wear


The bearing shaft and sleeve glide on a liquid film. The liquid is pumped  to the interior of the bearing by spiral grooves. As there is no direct contact during operation, there‘s virtually no wear.

CoolGlide™ LMB – High Troughput

Traditional Ball Bearing – Wear off, risk of binding and jamming


With operation, the lubricant (which is usually silver or lead metal) wears off of the ball and race surfaces, resulting in steel-to-steel contact that leads to binding or jamming. High temperature and high speed will reduce bearing life the most.


CoolGlide™ LMB – High Troughput

CoolGlide™ LMB – Low Noise / No contact of bearing and shaft


As there is no direct contact , there is no audible bearing noise during operation.

CoolGlide™ LMB – High Troughput

Traditional Ball Bearing – Noise and Vibration


The movement of the ball bearings result in noise and vibrations whenever the CT scanner is used.


LMB Lifetime

The average lifetime of CoolGlide™ LMB tubes exceeds traditional ball bearing tubes.

The blue bar on the left shows an example of a Dunlee Xceed X-Ray bundle including CoolGlide™ LMB.


Scan Seconds is a measure of the duration of the tube exposures:  how much time has the tube been used for.


Total CT Tube consumption over lifetime

CT utilization: 150.000 scan seconds p.a.

Example of typical lifetimes of Ball Bearing tubes³ and CoolGlide™ LMB tubes²

LMB Costs

Due to frequent replacement, ball bearing tubes can create  not only higher tube material costs, but also


  • higher service costs related to the tube replacement like
     - costs for field service personel
     - inventory, freight and handling costs
  • and higher system downtime.

Sources & Remarks

  1. Lifetime of X-ray tubes is  dependent on usage and application, lifetime indicated here is an average value and may differ significantly for individual usage and application patterns.
  2. Based on Dunlee internal reliability records. Xceed is a product bundle including X-ray tube and generator and high voltage cables.
  3. “CT X-ray tube lifetime Analysis: A Multiyear study”, by Yusuf Emre Erdi published in “RADIOLOGIC TECHNOLOGY, July/August 2013, Volume 84, Number 6”.
  4. Varex Imaging Corporation Fiscal Year 2020 Annual Report on Form 10-K; Page 4 ; “(….) CT X-ray tubes generally need to be replaced every 2 to 4 years. In China, the replacement cycle for CT X-ray tubes can be as every 6 to 12 months due to high utilization of imaging equipment.”

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About Dunlee

Dunlee is a brand of the Philips Company Group and distributes all products, solutions and services for the third-party imaging business. The product portfolio includes CT, MR and X-ray solutions for OEMs and 3D printed tungsten products.

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