Direct beta autoradiography using microchannel plate (MCP) detectors

We describe a new form of detector for digital autoradiography which combines high sensitivity and good spatial resolution (< 100 mu m). The detector is based on proximity registration of betas by radioisotope-free ''low noise'' microchannel plates (MCPs) developed for photon counting X-ray astronomy. Low dark count rates (<0.1 cm(-2)s(-1)) are combined with the high (> 50%) electron detection efficiency of small pore MCPs for common beta emitting isotopes (H-3, C-14, S-35...). In particular, the MCP detector is highly sensitive to the biologically important but previously difficult to detect low energy (average 6keV, endpoint 18.6keV) beta emission from tritium. We report H-3 sensitivities and linearity derived from images of a H-3 standard, together with images of H-3-Putrescine doped semi-thin-tissue sections of rat lung and isolated single cells from rabbit lung. We compare these results with those of previous attempts to digitally image tritium.