Almost Not There

T20 is a solid state detector dedicated for measurements on Rad/Fluoro systems when it is crucial that the detector itself does not have any effect on the system output or disturbs the X-ray beam. It complements to the R100B or Piranha Dose Probe (PDP), and together they can handle all applications related to installation, service, acceptance testing and QA/QC. In fact, the T20 is a miniaturized version of the R100B/PDP. The name T20 stands for Translucent Detector with a detector area of 20 square millimeter.

The Invisibility

How can a solid state detector with a dense material in it be invisible to the X-ray system? Although the detector part itself is impenetrable, it has been made very small and hence it is possible to avoid detection of the X-ray system. The detector is separated from the cable attachment by a carbon fiber rod. The rod’s extension is sufficiently long for measurements on a digital detector/image intensifier as large as 45 cm x 45 cm.
To stabilize the positioning and ensuring that the detector surface lies flat against the incident beam, small “wings” of carbon fiber have been added to the small detector. Measurements performed on a GE-OEC Fluorostar shows that the T20 does not affect the automatic exposure control at all.

T20 in the beam. The generator setting is still 74 kV and 2.64 mA. Hence the T20 does not affect the output at all.

A Unique Invention

T20 is developed mainly for measurements of the patient entrance dose (skin dose) and maximum dose rate in the radiographic and fluoroscopic field. Previously, if it was not possible to lock or switch off the automatic exposure function of the X-ray system, our R100B/PDP was the only option. However, even if the R100B/PDP is small, it is not small enough in all situations. It still has to be placed outside the active area to avoid affecting the feedback of the system. T20 can be placed anywhere in the X-ray field.

Specifications

T20 can connect to either Barracuda or Piranha (two different models) and has a built-in correction filter which allows the detector to self-compensate for different beam energies. Therefore it has a flat energy response in the radiographic range with no need for correction factors. It fulfills the IEC directive for dose detectors regarding energy independency, measuring range and angular dependency for RQR50–150 kV.