Table 1.

Change in the head position of ten volunteers during the mask‐locking process using the open‐face mask and AlignRT motion monitoring. Three trials for each subject were performed. The first mask locking almost always caused greater head motion than the second and third trials. On average, a second trial in setup could reduce mask‐locking‐induced head shifts by 1 mm and 1°

Volunteer		Translation (mm)				Rotation (°)
Subject	Trial 1	Trial 2	Trial 3	Mean	Trial 1	Trial 2	Trial 3	Mean
1	0.1	0.3	0.9	0.4	1.9	1.9	1.5	1.8
2	4.5	1.8	2.2	2.8	4.0	1.9	1.8	2.6
3	3.5	2.9	3.0	3.2	1.6	0.8	0.8	1.0
4	3.0	2.0	1.2	2.1	2.5	1.3	2.6	2.1
5	2.6	0.5	0.5	1.2	3.0	1.4	2.0	2.1
6	2.2	0.5	1.0	1.2	2.1	0.8	1.4	1.4
7	4.3	3.1	2.6	3.3	1.3	1.4	1.2	1.3
8	1.4	1.2	0.3	1.0	1.0	1.3	0.8	1.0
9	9.9	4.6	4.3	6.3	4.2	1.8	2.1	2.7
10	2.2	1.9	1.4	1.9	3.1	1.0	1.2	1.8
Average	3.4	1.9	1.8	2.3	2.5	1.4	1.5	1.8
St dev	2.7	1.4	1.3	1.7	1.1	0.4	0.6	0.6