Apparatus and systems may operate to enable positron emission imaging with a unitary chamber body having an open end that defines a hollow interior portion shaped to completely contain a flexible sleeve that is used to cover a core sample when the sleeve is seated within the hollow interior portion. An end cap may be formed to engage the open end of the chamber body, which is configured to attenuate gamma rays approximately eight times less than stainless steel, while supporting a pressure differential of at least 3 MPa between the chamber inlet and the outlet when fluid carrying a radioactive tag to generate the gamma rays flows through the hollow interior portion and the core sample via the inlet and the outlet. Additional apparatus, systems, and methods are disclosed.