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 μm). 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−2s−1) are combined with the high (>50%) electron detection efficiency of small pore MCPs for common beta emitting isotopes (3H, 14C, 35S…). In particular, the MCP detector is highly sensitive to the biologically important but previously difficult to detect low energy (average 6 keV, endpoint 18.6 keV) beta emission from tritium. We report 3H sensitivities and linearity derived from images of a 3H standard, together with images of 3H-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.