Usage of two types of high-pressure xenon chambers for medical radiography

Two types of one-dimensional X-ray detectors for scanning radiography are presented. One of them is a fast Multi Wire Proportional Chamber (MWPC) operating in direct photon-counting mode. The MWPC parameters: efficiency – 30%, width of channel – 0.6 mm, total number of channels – 640, maximum counting rate per chamber – 3×10 8 counts/s. Patient irradiation effective dose from lung radiography is 7μSv. Since 1997, the radiographic device based on MWPC went into mass production and 60 devices were in operation in Russian hospitals to the end of 1999. However, progress in design of the low noise electronics allowed to use the Multistrip Ionisation Chamber (MIC) instead of MWPC. The MIC parameters: efficiency close to 80%, width of channel – 0.4 mm, total number of channels – 1024. Application of MIC has some advantages over MWPC. MIC has higher counting rate, higher spatial resolution, low sensitivity to gas impurity and lower cost. The electronics noise is equivalent to signal from 4 photons.