Precise measurement of spatial gas concentrations in an uncontrolled outdoor environment is needed for environmental studies. In this effort, a multispectral imaging system has been developed incorporating quantum cascade laser (QCL) modules with an iterative computed tomography algorithm to sense a transmission spectrum response for each voxel. With spatially distributed spectral data, researchers will be able to identify gas composition and concentration distributions over a region of interest. The QCL system uses multiple modules covering wavelength ranges from 3.77μm to 12.5μm to detect both carbon dioxide (4.2μm) and methane (7.5μm) greenhouse gasses. Simulation and lab studies have been performed for a system using a circular arrangement of mirrors to transmit and reproject the QCL beam around the detector circle. The QCL transmission system has been tested in both controlled indoor environments and uncontrolled outdoor environments to quantify sensitivity.