Varex Z Platform – More than just IGZO

Friday, November 22, 2019


Tuomas Holma

Product Manager, X-ray Detectors

Market Status – Flat Panels in Dynamic Imaging

Flat Panel Detector is the de facto standard solution for dynamic X-ray imaging (dynamic imaging refers here to fluoroscopy and Cone Beam Computed Tomography). In the interventional X-ray imaging market, the vast majority of systems use Amorphous Silicon (a-Si) detectors, with the exception of a small number of high-end systems that have adopted either CMOS (complementary metal–oxide–semiconductor,) or a-Si-CMOS hybrid detectors1 3. Although IHS Markit reports that 74% of worldwide Mobile C-arm shipments and 50% of system revenue are still generated from Image Intensifier based systems6, a clear majority of systems from the biggest OEMs have either an Amorphous Silicon or a CMOS detector2.

Some research papers have been published in the past 2 years to compare the performance of a-Si and CMOS detectors in fluoroscopy and CBCT. Measurements of image noise, spatial resolution, Detective Quantum Efficiency (DQE), and Noise Equivalent Dose (NED) indicate improved low-dose performance for a CMOS-based system, particularly at lower doses and higher spatial frequencies8. Although CMOS detectors benefit performance with respect to high-frequency tasks, these studies did not demonstrate a strong advantage with respect to low-contrast soft-tissue visualization7. Therefore, to truly leverage the benefits of CMOS technology, a smaller pixel size CMOS detector should be used for imaging tasks such as neurovascular imaging, whereas a larger a-Si pixel is sufficient for an imaging task related to cardiac imaging5. In matched resolution CBCT, a-Si and CMOS detectors showed roughly equivalent performance7.

Varex Z Platform – Designed for Fluoroscopy and CBCT

Indium Gallium Zinc Oxide (IGZO) based thin-film transistors (TFTs) were developed in the display industry 15 years ago. As IGZO-TFTs have 20-50 times the electron mobility of a-Si, the TFTs can be miniaturized dramatically, such that IGZO-TFT displays excel in resolution, power saving, and touch capabilities4. Varex Imaging is one of the first flat panel manufacturers to bring IGZO-TFT technology into the detector market. In flat panels, IGZO-TFTs can be used to reduce image noise, increase sensitivity and to improve resolution. Our target, however, is to bring the performance of IGZO-TFT based detectors as close to CMOS as possible. We are therefore launching a new series of detectors under the umbrella of Varex Z Platform. With this new platform, we are introducing brighter scintillators, new readout electronics, and faster interfaces along with the IGZO-TFTs. The purpose of brighter scintillators is to further improve the signal-to-noise ratio, while a new generation of electronics enables on-board image processing and higher frame rates.

Varex has chosen NBASE-T and CoaXPress as interface options for the Z Platform. NBASE-T refers to a series of standards enabling data transfer at up to 10 Gbit/s over a twisted pair ethernet cable for distances up to 100 metres. CoaXPress uses 75-ohm coaxial cables and supports bit rates up to 12.5 Gbit/s for distances up to 30 metres. NBASE-T and CoaXPress enable exceptional frame rates for the Z Platform panels, which can have up to 9 million pixels.

Flat Panel Market Outlook

As the largest global, independent manufacturer of Flat Panel Detectors, Varex Imaging continues to supply a comprehensive range of technologies to its customers. Amorphous Silicon remains a robust platform with excellent performance and competitive costs and is a good option for Image Intensifier replacement in Mobile C-arms, for example. CMOS technology offers high resolution, fast frame rates, and low dose performance, but with a significant cost premium. Test results of the new Varex Z Platform are very promising. Initial tests show significant improvement in performance at low-dose but also in the ability to maintain good DQE at higher spatial frequencies. We believe that Varex Z Platform will offer performance approaching CMOS, but having a better cost reduction runway into the future.  

Varex Imaging plans to release a series of Z Platform products in the next two years for Mobile C-arm, Cardiovascular, and Dental CBCT applications. At RSNA 2019 (December 1-5), Varex will showcase the 31 x 31 cm, 100 µm pixel size, 3131Z detector as first example of the new platform. Come and talk to us in Chicago about your application. We would be happy to get your view on how this new exciting technology can ultimately benefit the healthcare professionals and the patients.

3131Z IGZO flat panel

Varex 3131Z


  1. Comparison Chart of Angiography Systems. Imaging Technology News, Last Updated 6th September 2019.
  2. Comparison Chart of Mobile C-arms. Imaging Technology News, Last Updated 21st August 2019.
  3. Comparison Chart of Vascular Imaging Systems. Imaging Technology News, Last Updated 28th February 2019.
  4. IGZO. A breakthrough in display technology. Sharp Electronics Corporation.
  5. D. Job, A. Ganguly, D. Vernekohl, R. Weisfield, E. Muñoz, J. Zhang, C. Tognina, and R. Colbeth, "Comparison of CMOS and amorphous silicon detectors: determining the correct selection criteria, to optimize system performance for typical imaging tasks", Proc. SPIE 10948, Medical Imaging 2019: Physics of Medical Imaging, 109480F (3 April 2019);
  6. Mobile C-arm & Mini C-arm X-ray Equipment Report – 2019. IHS Markit, 5th April 2019.
  7. N. M. Sheth, M. W. Jacobson, W. Zbijewski, G. Kleinszig, S. Vogt, S. Soellradl, J. Bialkowski, W. S. Anderson, C. R. Weiss, G. M. Osgood, and J. H. Siewerdsen, "Imaging performance of CMOS and a-Si:H flat-panel detectors for C-arm fluoroscopy and cone-beam CT", Proc. SPIE 10573, Medical Imaging 2018: Physics of Medical Imaging, 105730M (9 March 2018);
  8. N. M. Sheth, W. Zbijewski, M.W. Jacobson, G. Abiola, G. Kleinszig, S. Vogt, S. Soellradl, J. Bialkowski, W. S. Anderson, C. R. Weiss, G. M. Osgood, and J. H. Siewerdsen, “Mobile C‐Arm with a CMOS detector: Technical assessment of fluoroscopy and Cone‐Beam CT imaging performance”. Med. Phys., 45: 5420-5436. doi:10.1002/mp.13244