Abstract: A structure for detecting radiation, useful in an imaging camera for nuclear medicine, comprising a plurality of tubes, each of said tubes having (1) an electrically conductive wall structure defining a tube internal radius and a proximal and a distal end, (2) a pressure retaining and electrically insulative tube end closure means at each tube end, (3) a coaxial electrically conductive element located between said insulative tube end closure means; said tubes containing xenon at a pressure sufficient to provide for a photoelectron range there within of or less than that distance existing between the proximal and distal ends thereof and a maximum ionization collection distance of or less than the tube internal radius; said tubes positioned in a honeycomb-like array such that each proximal and distal tube end is in a common plane one with another, respectively.