I add here part of those AlignRT/Laser FB n0 setup results: Systematic, random, margin (cm). AP=vertical, SI=longitudinal, LAT=Lateral (in this order). L=Laser setup, A=AlignRT setup. Daily IGRT=D, no IGRT = N#. Residual errors=R, errors from structure to structure=S. 1) Isocenter (N, R): L 0.09,0.17,0.17, 0.22,0.39,0.34, 0.39,0.70,0.67; A 0.09,0.15,0.13, 0.18,0.22,0.21, 0.35,0.52,0.48. 2) TH1 (N, R): L 0.12,0.26,0.21, 0.25,0.42,0.39, 0.48,0.95,0.8; A 0.16,0.21,0.21,0.18,0.25,0.27,0.53,0.71,0.71. (D, R): L 0.16,0.14,0.08,0.19,0.22,0.17, 0.54, 0.51, 0.32; A 0.13,0.07,0.10,0.15,0.13,0.15,0.43,0.28,0.34. 3) Shoulder joint SI, LAT (N, R): L 0.35,0.20,0.36,0.36,1.13,0.75; A 0.31,0.24,0.33,0.27,1.00,0.79. (D, R): L 0.28,0.16,0.31,0.19,0.92,0.53 ; A 0.25,0.23,0.28,0.21,0.82,0.72. 4) Tangential image MID_PTV ribs VRT/LAT, SI (D pre orthogonal kV/kV!, R): L 0.06,0.08,0.05,0.08,0.18,0.25; A 0.06,0.08,0.08,0.12,0.22,0.29. 5) th1-th10 (S): L 0.17,0.06,0.13,0.15,0.11,0.21; A 0.09,0.04,0.12,0.15,0.08,0.17. 6) th6-sternum (S): L 0.22,0.26,0.21,0.27; A 0.15,0.26,0.16,0.18. 7) th1-shoulder joint (S): L 0.40,0.16,0.36,0.23; A 0.28,0.28,0.29,0.21.
#Isocenter error is corrected in both groups during the first three fractions and the data is collected beginning from the fourth fraction.
As seen, in laser group with the daily AP+LAT IGRT residual margins are adequate and near daily SGRT+IGRT margins. Main conclusion is that with AlignRT isocenter and patient posture variation is small enough in n0 group in most cases to go on with the tangential images only, which is not possible in laser group mostly due to larger isocenter variation.