GEMini detector system

GEMini™ is an X-ray detector optimized for Electronic Portal Imaging Device (EPID) in radiation therapy. A strong trend has recently developed for using EPID for online verification of the actually delivered dose distribution (Portal Dosimetry), an application for which none of the standard EPID detectors were designed nor optimized. The GEMini detector has been developed from the beginning to comply with these new requirements.

Since EPID alone is used for all dosimetry measurements, no phantoms or other dosimetry equipment need to be placed on the couch or the patient. Plan verification can be done either before the patient arrives (pre-treatment) or online (during treatment). The delivered dose can be compared against the original treatment plan, and any deviations can be presented by an external software system.

The unique design of the GEMini detector makes it highly radiation-resistant while at the same time providing optimal dosimetry performance. The detector will mechanically fit in select LINAC models from major vendors, ensuring a smooth installation.

The original technology is licensed from CERN in Geneva, Switzerland, and has been further developed by C-RAD through a number of its own patents.

In 2014 C-RAD intensified its cooperation with CERN on physics simulations and production technology. This resulted in a detector system with significantly improved image quality as well as robustness.

C-RAD started performance tests to verify the detector against existing standards as well as competitive products. While GEMini is still under development, C-RAD has also started commercialization of the new detector system. In the first phase we are addressing the detector to dedicated clinical sites. Commercial activities with larger customers have been initiated.

The C-RAD GEMini ED, tailored for both Imaging and Portal Dosimetry applications, gives you:

  • Long expected lifetime
  • Real-time imaging with no ghosting artifacts
  • Linear response also during high dose rate treatments

Selected specifications


  • Active Area: 40 cm x 40 cm *Gas Electron Multiplier, licensed from CERN

Electron Collection and Readout

  • 2D Image Matrix: 886 x 886, 450 μm pixel pitch
  • Max. Bad Pixels: < 1 %
  • Charge Integration: 16 x 128 channels ASIC with selectable gain
  • ADC: 16 x 16 bit A/D at 6 MSPS
  • Min. Integration Time: 25 ms

Image Export

Images can be delivered as raw data, offset corrected and flat field/ gain calibrated. The calibration data, the offset data and the bad pixel map can be exported. System commands and image data are transferred using a Gigabit Ethernet interface. Other interfaces are optionally available.

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