<title>Self-gridding and signal formation in the kinestatic charge detector for digital mammography</title>

Abstract

Various designs of the kinestatic charge detector (KCD) have used a Frisch Grid--a planar, meshed electrode sandwiched between the detector's anode and cathode. The grid shields the cathode from effects of drifting ions until they reach the region between the cathode and the grid. Including the grid, however, has made detector design difficult because of electric field non-uniformities and microphonics. Recent studies have shown that the KCD may not need a grid. `Self-gridding,' an effect which produces the same results, occurs when the ratio of cathode's collector width to the drift gap is sufficiently small. The greater this ratio, the more self-gridding takes place. The process of signal formation has been analyzed for the self- gridding geometry using ExcelTM (Microsoft Corporation, Redmond, WA). Detector response to microcalcifications has been simulated by small, drifting volumes with a steep dip in ion count; low-contrast lesions by larger volumes with a shallow dip in ion count. Both of these typical breast lesions can be detected with self-gridding geometry. This geometry will soon be tested in an experiment for validity as a detector design.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.