We measure transmitted signals with time, aperture, and angle gating for comparison in micro-sphere suspension, chicken breast and chicken liver tissues. We find that in each sample, the small aperture-gated (angle-gated) signals for imaging are essentially different from those of early time gating. Meanwhile, the signals obtained from aperture and angle gating come from quite different parts of the transmitted photons. For biological tissues of different structures, different gating methods may lead to different levels of imaging quality. Also, the results indicate the generally different scattering characteristics of biological tissues from that of a particle-based phantom. The scattering nature in the biological tissues may imply that random continuum scattering needs to be considered in biological imaging. Between chicken breast and liver tissues, the time-gated data show that the later has stronger scattering and absorption.