A number of schemes employing coded apertures are currently under investigation for in vivo imaging of gamma-emitting tracers. These schemes are based on stationary aperture codes, which depend upon having a cleanly peaked spatial auto-correlation function to facilitate faithful recovery of the source distribution. The image is recovered by performing a spatial integration optically, digitally, or by some other suitable means. This paper describes an alternate method based on time modulated apertures with digital image reconstruction. In contrast to the stationary aperture, the time modulated aperture requires no spatial integration to achieve faithful reproduction of the source distribution. This solves the problem of false structure arising from out-of-focus sources. Good 3-dimensional point response functions free of side lobes have been obtained and it is expected that this approach will yield high quality clinical images.