Optical projection tomography
Optical projection tomography is a form of tomography involving optical microscopy. The OPT technique is sometimes referred to as optical computed tomography (optical-CT) and optical emission computed tomography (optical-ECT) in the literature, to address the fact that the technique bears similarity to X-ray computed tomography (CT) and single-photon emission computed tomography (SPECT).
Source: Wikipedia — Optical projection tomography (CC BY-SA 4.0)