VIDEO: Cold-cathode X-ray systems may disrupt the medical imaging market

Bhvita Jani, research manager at Signify Research, explains advances in cold-cathode X-ray tube technology, and how this might represent a major shift in radiology imaging systems if the technology can be perfected. 

Cold-cathode X-ray vendor Micro-X signed a deal with large X-ray tube manufacturer Varex to make its cold-cathode tubes. 

"We expect that with such a partnership and the large international sales channel network that Varex has, cold-cathode technology and adoption can be spearheaded by this agreement with Varex," Jani explained. 

Micro-X is already selling a mobile digital radiography (DR) unit. The vendor is also working on an extremely light-weight head and compact cold-cathode computed tomography (CT) scanner. 

The second vendor to gain U.S. Food and Drug Administration (FDA) clearance for a cold-cathode system is the Israel-based vendor Nanox. It gained approval in March 2021 for its single-source Nanox.ARC digital X-ray system. It currently has a multi-source, cone-beam CT X-ray system pending FDA review. 

Nanox proposes a different business model from most vendors, where it wants to concentrate efforts on developing markets and offer the scanners on a fee-per-scan model, rather than clinics and hospitals buying the machines. 

Carestream was the first vendor to commercialize a carbon nano-tube X-ray system in the U.S. in 2018. The system uses cold-cathode technology developed by Micro-X. The Carestream DRX-Revolution Nano mobile DR system significantly reduces size and weight when compared to existing mobile digital X-ray systems. The elimination of heat, cooling components and reduced materials used to construct the system has enabled it to be much more affordable. The system only weighs 220 pounds, as opposed to 1,000-1,500 pounds of most conventional mobile DR systems. 

The Micro-X Rover system displayed at Radiological Society of North America (RSNA) 2022 is essentially the same system as the Carestream Nano. It uses a very light-weight carbon fiber skin and a lightweight support structure for the tube arm.

"One of the advantages of these systems is that they become more lightweight and it allows these systems to be used in more sophisticated ways. And we are seeing how imaging is not just in hospitals and it is moving into outpatient and other non-traditional settings," Jani said. She explained a smaller, lighter weight and less expensive cold-cathode system would be ideal for outpatient settings.

What is Cold-cathode X-ray technology?

For more than 100 years, X-ray tube technology has relied on conventional hot-cathode tubes to produce X-rays. This involves shooting a beam of electrons at a metal anode, usually tungsten, which releases a large amount of heat energy, but also a small portion of X-rays. But since most of the energy released is heat, it gets so hot that a motor is attached to the anode to spin it to prevent the metal disk from melting. An oil bath usually surrounds the X-ray tube to help absorb this heat. The heat becomes a bigger problem in X-ray systems that require live stream viewing, like angiography imaging systems in cath labs and fluoroscopy units, or in the case of CT scanners that create hundreds of images in seconds. 

The need for structures and cooling systems to take away the heat from the tubes and surrounding system components is one of the reasons why these systems are so heavy and often require involvement with engineers or architects to pipe in water supplies, bring in HVAC ventilation and to look at ceiling or floor loads before a new room is built out. 

Even mobile DR X-ray systems have a lot of extra cost built into them because they require extra structural steel to support the heavy tube arm and in addition to motorized systems to be able to move them around easily. The cost for X-ray systems could be greatly reduced and the systems made much lighter and easier to use if reliable cold-cathode technologies can be used. 

Cold-cathode tubes use either microscopic Spindt cone structures or carbon nanotubes. These do not generate large amounts of heat and use less energy and can result in a major reduction in weight.

While both technologies work, the issues with these cold-cathode tubes that have prevented wide adoption has been short tube life that would require much more frequent tube replacements. Electrical discharges can damage the microscopic structures of Spindt cones, and carbon nanotubes also can quickly wear out. However, Nanox and Micro-X both say they have solved this durability issue in their systems.

Watch a related interview with Jani in the VIDEO: Trends in X-ray systems.