The present application provides techniques and/or systems for inspecting a pipe, or rather measuring one or more characteristics of a pipe, using radiation. A carriage, mounted to the pipe, may provide a mechanism for propelling a radiation source and a detector along the pipe. The detector is configured such that it can receive radiation that has traversed both a wall of the pipe and an obstacle, such as a pipe support. In this way, portions of a pipe that are traditionally difficult to inspect may be inspected easily with minimal human intervention.