3D Body Surface Measurement and Display in Radiotherapy Part I: Technology of Structured Light Surface Sensing

Research into high performance surface measurement using continuously structured light projection and Fourier transform profilometry is described. It is shown that the capture of single-colour interferometer fringes, modulated by the surface variations of either test ‘phantoms’ or human volunteers can yield body surface height maps in the high radiation environment of the radiotherapy clinic. The 3D surfaces are reconstructed from the spatial phase encoded by the fringe modulation, which is visible in a single video frame. The display of the live fringe pattern is shown to provide a potentially intuitive way of assessing patient setup stability. The ‘draping’ of body surface features or the fringe pattern itself adds to the user friendly nature of the approach. The necessity for full-field and partial-field of view operation is considered for the highly varied topology of breast cancer patients who constitute one of the largest groups receiving radiotherapy. Finally, the cutting edge development of multi-colour fringe projection is described as a way of avoiding gaps in surface displays due to shadowing, and for the construction and quantitative display of wrap-round body features.