Injection of hydrogel spacer increased maximal intrafractional prostate motion in anterior and superior directions during volumetric modulated arc therapy-stereotactic body radiation therapy for prostate cancer

Table 2 Mean of the intrafractional displacements per patient

Direction	Non-spacer group	Spacer group	P value^a
	N = 30	N = 8
	mm, Mean ± SE	mm, Mean ± SE
Maximum intrafractional displacements
Superior	0.47 ± 0.07	0.97 ± 0.24	0.014^†
Inferior	1.07 ± 0.11	1.03 ± 0.25	0.88
Left	0.74 ± 0.08	0.87 ± 0.27	0.55
Right	0.67 ± 0.08	0.92 ± 0.21	0.17
Anterior	0.45 ± 0.06	1.16 ± 0.35	0.0023^†
Posterior	1.57 ± 0.17	1.37 ± 0.22	0.56
Vector length	2.24 ± 0.19	2.89 ± 0.62	0.19
Mean intrafracitonal displacements^b
Superior-inferior	− 0.34 ± 0.06	− 0.12 ± 0.19	0.16
Left–right	0.02 ± 0.04	0.04 ± 0.25	0.93
Anterior–posterior	− 0.55 ± 0.09	− 0.21 ± 0.27	0.13
Vector length	1.05 ± 0.10	1.56 ± 0.43	0.10
95th percentile intrafractional displacements
Superior	0.27 ± 0.05	0.74 ± 0.19	0.0029^†
Inferior	0.87 ± 0.09	0.83 ± 0.25	0.87
Left	0.51 ± 0.07	0.61 ± 0.24	0.60
Right	0.41 ± 0.06	0.64 ± 0.18	0.17
Anterior	0.23 ± 0.04	0.85 ± 0.31	0.0020^†
Posterior	1.31 ± 0.16	1.05 ± 0.14	0.42
Vector length	1.89 ± 0.18	2.51 ± 0.55	0.19

ISSN: 1748-717X