Apparatus and method for scanning a structure
An apparatus and method for scanning a structure for detecting variations in density of a structure, the apparatus ( 10 ) includes: a source of radiation ( 20 ); a plurality of detectors ( 30 ), arranged for receiving radiation emitted by the source along a plurality of respective paths ( 26 ); the apparatus configured such that, a structure ( 100 ) to be scanned is positionable between the detectors and the source; collimation elements ( 40 ) including a plurality of collimator channels ( 42 ), each located between a respective detector and the source; and collimation adjustment element ( 60 ). The apparatus, in a first configuration, provides a first resolution (r 1 ) in an axial direction substantially orthogonal to a plane including the source and plurality of paths; and, in a second configuration, the collimation adjustment element is positioned between the collimation elements and the source such that the apparatus provides a second resolution (r 2 ) in the axial direction; wherein r 2 <r 1.
1. An apparatus for scanning a subsea pipeline for detecting variations in density of the subsea pipeline, the apparatus comprising:
a source of gamma radiation;
a plurality of detectors, arranged for receiving gamma radiation emitted by said source along a plurality of respective paths;
wherein said apparatus is configured such that, in use, a structure to be scanned is positionable between said detectors and said source;
collimation means comprising a plurality of collimator channels, each located between a respective detector and said source; and
collimation adjustment means wherein said collimation adjustment means comprises at least one pair of plates or blocks, arranged to define a slit between their edges and extending across more than one said collimator channel;
wherein, at least one said plate or block is moveable between a first position corresponding to a first configuration of said apparatus, in which said apparatus provides a first resolution in an axial direction substantially orthogonal to a plane passing through said source and said plurality of paths, and a second position corresponding to a second configuration of said apparatus, in which said collimation adjustment means is positioned between said collimation means and said subsea pipeline to be scanned such that said apparatus provides a second resolution in said axial direction;
wherein said second resolution is smaller than said first resolution.
2. The apparatus according to claim 1 , wherein said first resolution is determined by said detectors and/or said collimation means.
3. The apparatus according to claim 1 , wherein, in said first configuration, said first resolution is determined, at least in part, by said collimation adjustment means.
4. The apparatus according to claim 1 , further comprising at least one actuator for moving said plate or block between said first and second positions.
5. The apparatus according to claim 1 , wherein at least one said pair of plates or blocks comprises a plate or block which is fixed relative to said collimation means.
6. The apparatus according to claim 1 , wherein at least one said plate or block is curved.
7. The apparatus according to claim 1 , wherein at least one said plate or block is coupled to said collimation means.
8. The apparatus according to claim 1 , further comprising processing means for processing signals to detect artefacts in said structure, and actuation means for moving said collimation adjustment means between a first position and a second position in response to detecting an artefact in said structure.
9. The apparatus according to claim 1 , wherein said collimator channels are substantially aligned with respective radii of a circle centred on said source.
10. The apparatus according to claim 1 , wherein, in use, said detectors and said source are rotatable in a fixed relationship with respect to each other about said structure.
11. A method for scanning a subsea pipeline for detecting variations in density of the subsea pipeline, the method comprising:
providing a source of gamma radiation;
providing a plurality of detectors, arranged for receiving gamma radiation emitted by said source along a plurality of respective paths;
arranging the apparatus such that a structure to be scanned is positioned between said detectors and said source;
providing collimation means comprising a plurality of collimator channels, each located between a respective detector and said source; and
providing collimation adjustment means wherein said collimation adjustment means comprises at least one pair of plates or blocks, arranged to define a slit between their edges and extending across more than one said collimator channel;
wherein, in at least one said plate or block is moveable between a first position corresponding to a first configuration of said apparatus, in which said apparatus provides a first resolution in an axial direction substantially orthogonal to a plane passing through said source and said plurality of paths, and a second position corresponding to a second configuration of said apparatus, in which said collimation adjustment means is positioned between said collimation means and said subsea pipeline such that said apparatus provides a second resolution in said axial direction,
wherein said second resolution is smaller than said first resolution;
said method further comprising:
scanning a part of said subsea pipeline with said apparatus in said first configuration;
moving said at least one plate or block between said first position and said second position; and
scanning a part of said subsea pipeline with said apparatus in said second configuration.