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Technical note: Sinogram merging to compensate for truncation of projection data in tomotherapy imaging
Author(s) -
Hooper H. R.,
Fallone B. G.
Publication year - 2002
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.1514579
Subject(s) - tomotherapy , multileaf collimator , collimator , projection (relational algebra) , computer science , iterative reconstruction , medical imaging , computer vision , optics , offset (computer science) , collimated light , image guided radiation therapy , physics , artificial intelligence , beam (structure) , nuclear medicine , linear particle accelerator , radiation therapy , algorithm , radiology , medicine , laser , programming language
An advantage of helical tomotherapy radiation therapy systems is that on‐line megavoltage computed tomography (CT) images can be reconstructed to verify patient positioning. One limitation of such systems is that the field‐of‐view (FOV) of the photon fan‐beam is limited by the aperture size of the binary multileaf collimator (MLC) used to modulate treatment beams. For patients larger than the FOV the acquired sinograms will be truncated causing artifacts in the resultant megavoltage CT images. Computer simulations are used to demonstrate that such artifacts can be eliminated or at least reduced by merging appropriately acquired truncated fan‐beam sinograms to form a nontruncated parallel‐beam sinogram. The necessary fan‐beam sinograms are acquired with the patient translated to different offset locations within the gantry. The parallel‐beam sinogram is then used to reconstruct the final CT image. The increase in patient dose due to the acquisition of more than one fan‐beam sinogram can be reduced by using properly designed binary MLC fields to block redundant projection rays.