The potential failure risk of the cone-beam computed tomography-based planning target volume margin definition for prostate image-guided radiotherapy based on a prospective single-institutional hybrid analysis

Table 2 Group systematic error (M), systematic error (Σ), and random error (σ) when comparing prostate deviations between kV OBI-FM and CBCT-ST for 971 pre-treatment and 206 post-treatment datasets

OBI-FM vs CBCT-ST	AP /mm	SI /mm	LR /mm
971 pre-treatments (CBCT dependent on kV OBI)
M	−0.10	−0.06	−0.16
Σ	0.35	0.33	0.22
σ	0.85	0.80	0.44
206 post-treatments (CBCT independent on kV OBI)
M	−0.49	− 0.26	− 0.12
Σ	0.69	0.85	0.39
σ	1.23	1.41	0.76

kV kilo voltage, OBI on-board imaging; CBCT cone-beam computed tomography, FM fiducial marker matching, ST soft tissue matching, AP anterior to posterior, SI superior to inferior, LR left to right

ISSN: 1748-717X