text: Use of a diagnostic positron emission tomography-computed tomography system for planning radiotherapy positioning: distortion of the tabletop.
  The aim of this study was to evaluate distortion of the tabletop in a diagnostic positron emission tomography-computed tomography (PET-CT) system to determine its suitability for planning radiotherapy positioning. Distortion of the tabletop was compared among PET-CT, lineac CT, and CT simulator systems. A phantom or angiography catheter was fixed to the tabletop and imaged after iron plate weight loading. The acquired images were analyzed using radiotherapy planning software. Distortion of the tabletop was measured based on the displayed coordinates. Sinking represented the greatest distortion of the tabletop in all systems. Using the same baseline, the maximum sinking were -0.4, -0.2, and +0.4 cm, respectively. The distortion of the tabletop in the PET-CT system was more similar to that in the lineac CT than in the CT simulator system. Distortion of the tabletop in a diagnostic PET-CT system may be within the acceptable range to allow its use for planning radiotherapy positioning.