HIGH-PRESSURE MULTIWIRE PROPORTIONAL AND GAS MICROSTRIP CHAMBERS FOR MEDICAL RADIOLOGY

Application of MultiWire Proportional Chambers (MWPC) and MicroStrip G as Chambers (MSGC) in medical radiography is discussed. These detector s are capable of detecting X-rays in counting mode with high efficienc y, thus giving essential dose reduction compared to film/screen techni ques. This was demonstrated on several Digital Radiographic Devices (D RD) with one-dimensional MWPC and scanning in the orthogonal direction . Effective pixel sizes of 1 mm and 0.5 mm for different devices with highly parallel readout systems has been achieved. The counting rate c apability of DRDs is similar to 500 kHz/pixel, which is enough to get high statistics of X-rays with a short exposure. Dose saving factors f rom 1 to 2 orders of magnitude for several common examinations were de monstrated. Further development of this approach can be made with MSGC which reproduce operation of MWPC in a much smaller scale. First test s of prototype chambers with 200 mu m pitch of strips at high pressure have shown the possibility to reach a gain of similar to 10(4) in a 6 bar Xe mixture. A proper choice of substrate material permits one to avoid charging problems at high fluxes. These features allow, one to b uild a counting device with 0.2 mm pixels for the detection of X-rays of 20-60 keV.