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 3 Group systematic error (M), systematic error (Σ), and random error (σ) for intrafractional error of the prostate with OBI-FM and CBCT-ST for 206 post-treatment datasets

	AP /mm	SI /mm	LR /mm
OBI-FM for 1177 treatment including 971 and 206 treatments
M	0.56	0.22	0.34
Σ	0.68	0.76	0.26
σ	1.66	1.62	0.75
OBI-FM for 206 treatments
M	0.49	0.22	0.24
Σ	0.85	1.00	0.43
σ	1.47	1.66	0.75
CBCT-ST for 206 treatments
M	0.00	−0.04	0.12
Σ	0.68	0.66	0.25
σ	1.08	1.21	0.50

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