An X-ray scatter detection system comprising an X-ray source, a secondary collimator, and a scatter detector, wherein: said X-ray source is configured to emit an X-ray pencil beam (70, 202); said secondary collimator is configured to ensure that a portion of the scattered radiation arriving at said scatter detector has a constant scatter angle with respect to the X-ray pencil beam; and said scatter detector is configured to receive scattered radiation having a scatter angle from the X-ray pencil beam, the scattered radiation comprising a plurality of portions of the scattered radiation, said scatter detector located substantially in a plane, said scatter detector comprising a plurality of detector strips (100, 102, 104, 106, 108), said plurality of detector strips comprising: a first detector strip (104, 212) having a first width equal to and parallel to a linear extent of the X-ray pencil beam where the X-ray pencil beam crosses the plane, said first detector strip is configured to receive a first portion of the plurality of portions of scattered radiation, the first portion originating from a first distance, measured perpendicular to the plane, from the plane; and a second detector strip (100, 102, 106, 108) that is configured to receive a second portion of the plurality of portions of scattered radiation, the second portion originating from a second distance, measured perpendicular to the plane, from the plane, characterised in that said second detector strip comprises a second width defined by: b = b m L 2 L 2 m wherein b is the second width, b m is the first width, L 2m is the first distance, and L 2 is the second distance. said X-ray source is configured to emit an X-ray pencil beam (70, 202); said secondary collimator is configured to ensure that a portion of the scattered radiation arriving at said scatter detector has a constant scatter angle with respect to the X-ray pencil beam; and said scatter detector is configured to receive scattered radiation having a scatter angle from the X-ray pencil beam, the scattered radiation comprising a plurality of portions of the scattered radiation, said scatter detector located substantially in a plane, said scatter detector comprising a plurality of detector strips (100, 102, 104, 106, 108), said plurality of detector strips comprising: a first detector strip (104, 212) having a first width equal to and parallel to a linear extent of the X-ray pencil beam where the X-ray pencil beam crosses the plane, said first detector strip is configured to receive a first portion of the plurality of portions of scattered radiation, the first portion originating from a first distance, measured perpendicular to the plane, from the plane; and a second detector strip (100, 102, 106, 108) that is configured to receive a second portion of the plurality of portions of scattered radiation, the second portion originating from a second distance, measured perpendicular to the plane, from the plane, a first detector strip (104, 212) having a first width equal to and parallel to a linear extent of the X-ray pencil beam where the X-ray pencil beam crosses the plane, said first detector strip is configured to receive a first portion of the plurality of portions of scattered radiation, the first portion originating from a first distance, measured perpendicular to the plane, from the plane; and a second detector strip (100, 102, 106, 108) that is configured to receive a second portion of the plurality of portions of scattered radiation, the second portion originating from a second distance, measured perpendicular to the plane, from the plane, characterised in that said second detector strip comprises a second width defined by: b = b m L 2 L 2 m wherein b is the second width, b m is the first width, L 2m is the first distance, and L 2 is the second distance.