PURPOSE: To analyze three-dimensional setup uncertainties for multiple regions of interest (ROIs) in head-and-neck region. METHODS AND MATERIALS: In-room computed tomography (CT) scans were acquired using a CT-on-rails system for 14 patients. Three separate bony ROIs were defined: C2 and C6 vertebral bodies and the palatine process of the maxilla. Translational shifts of 3 ROIs were calculated relative to the marked isocenter on the immobilization mask. RESULTS: The shifts for all 3 ROIs were highly correlated. However, noticeable differences on the order of 2-6 mm existed between any 2 ROIs, indicating the flexibility and/or rotational effect in the head-and-neck region. The palatine process of the maxilla had the smallest right-left shifts because of the tight lateral fit in the face mask, but the largest superior-inferior movement because of in-plane rotation and variations in jaw positions. The neck region (C6) had the largest right-left shifts. The positioning mouthpiece was found effective in reducing variations in the superior-inferior direction. There was no statistically significant improvement for using the S-board (8 out of 14 patients) vs. the short face mask. CONCLUSIONS: We found variability in setup corrections for different regions of head-and-neck anatomy. These relative positional variations should be considered when making setup corrections or designing treatment margins.
PURPOSE: To analyze three-dimensional setup uncertainties for multiple regions of interest (ROIs) in head-and-neck region. METHODS AND MATERIALS: In-room computed tomography (CT) scans were acquired using a CT-on-rails system for 14 patients. Three separate bony ROIs were defined: C2 and C6 vertebral bodies and the palatine process of the maxilla. Translational shifts of 3 ROIs were calculated relative to the marked isocenter on the immobilization mask. RESULTS: The shifts for all 3 ROIs were highly correlated. However, noticeable differences on the order of 2-6 mm existed between any 2 ROIs, indicating the flexibility and/or rotational effect in the head-and-neck region. The palatine process of the maxilla had the smallest right-left shifts because of the tight lateral fit in the face mask, but the largest superior-inferior movement because of in-plane rotation and variations in jaw positions. The neck region (C6) had the largest right-left shifts. The positioning mouthpiece was found effective in reducing variations in the superior-inferior direction. There was no statistically significant improvement for using the S-board (8 out of 14 patients) vs. the short face mask. CONCLUSIONS: We found variability in setup corrections for different regions of head-and-neck anatomy. These relative positional variations should be considered when making setup corrections or designing treatment margins.
Authors: Hyejoo Kang; Dale M Lovelock; Ellen D Yorke; Sergey Kriminski; Nancy Lee; Howard I Amols Journal: J Appl Clin Med Phys Date: 2010-10-27 Impact factor: 2.102
Authors: Christina Leitzen; Timo Wilhelm-Buchstab; Thomas Müdder; Martina Heimann; David Koch; Christopher Schmeel; Birgit Simon; Sabina Stumpf; Susanne Vornholt; Stephan Garbe; Fred Röhner; Felix Schoroth; Hans Heinz Schild; Heinrich Schüller Journal: Strahlenther Onkol Date: 2018-01-25 Impact factor: 3.621