Jaebin Choi, Adriaan J. Taal, William L. Meng, Eric H. Pollmann, John W. Stanton,  Changhyuk Lee, Sajjad Moazeni, Laurent C. Moreaux, Michael L. Roukes, and Kenneth L. Shepard, “Fully Integrated Time-Gated 3D Fluorescence Imager for Deep Neural Imaging,”   IEEE Transactions on Biomedical Circuits and Systems 14, no. 4, pages 636-645 (2020).

This paper reports an implantable 3D imager for time-gated fluorescence imaging in the deep brain. Fluorescence excitation is provided by dual ns-pulsed blue micro-light-emitting diodes (μLED), and fluorescence emission is collected by an 8-by64 single-photon avalanche diode (SPAD) array, together packaged to a width of 420 μm to allow deep insertion through a cannula. Each SPAD is masked by a repeating pattern of Talbot gratings that give each pixel a different angular sensitivity, allowing three-dimensional image reconstruction to a resolution of ~20 μm. The integrated imager is able to monitor fluorescent targets across a field of view of 1000 μm by 600 μm by 500 μm at arbitrary tissue depths.