1. A computer-implemented method of compressing data in a materials-detection system, the method comprising: generating a first multi-dimensional digital image of a scan region, the scan region being included in a materials-detection system and being configured to receive a container, wherein the first multi-dimensional digital image comprises at least one voxel that represents a space that is at least partially inside of the container; accessing a pre-defined background range of values, the background range of values representing a range of values associated with non-target materials and the background range of values being distinct from values associated with target materials; comparing a value of the at least one voxel that represents a space that is at least partially inside the container to the background range of values to determine whether the value of the at least one voxel is within the background range of values; if the value of the at least one voxel is within the background range of values, identifying the at least one voxel as an identified voxel that represents a non-target material; and generating a second multi-dimensional digital image that disregards the identified voxel to compress the first multi-dimensional digital image.