Page 112 - Organ motion in children for high-precision radiotherapy - Sophie Huijskens

Appendix 6
Supplementary Figure 6.1 | Schematic overview of diaphragm motion tracking and respiratory-induced diaphragm motion characteristics and analysis, acquired from [16].
a) A region of interest (ROI) was selected including the top of the right diaphragm (blue box).
b) The derivative of the grey values along the cranial-caudal (CC) direction (indicated by v) of the ROI was taken and the pixel values along each line (perpendicular to the CC direction, indicated by u) were summed, creating a one-
dimensional image. This was repeated for all projection images.
c) Accumulating all one-dimensional images created a two-dimensional Amsterdam Shroud image. Subsequently,
the pixel coordinates corresponding to the position of the diaphragm top were translated to millimeters relative to the patients’ planned isocenter and were also corrected for the geometry of the CBCT scanner, resulting in a respiratory signal as shown in d).
d) The amplitude was defined as the difference between the diaphragm position in the end-inhale and end-exhale phase. The cycle time equals inspiratory time plus expiratory time. Results were analysed per fraction,
e) per patient (over multiple fractions) and over the whole study population.
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