Biomedical Engineering Reference
In-Depth Information
Table 2.1 Mean magnitude with standard deviations (SD) of translational and rotational head
motion for the three motion scenarios restrain, rest and freely at six different time points
5 min
10 min
15 min
20 min
25 min
30 min
Translational (mm)
Restrain
7 : 7 3 : 1 : 2 5 : 6 : 4 7 : 8 : 7 8 : 6 : 0 8 : 2 : 5 8 : 7
Rest
5 : 7 5 : 5 : 4 8 : 5 : 8 10 : 215 : 3 12 : 116 : 3 15 : 016 : 4 15 : 1
Freely
29 : 5 28 : 050 : 5 39 : 656 : 1 50 : 162 : 0 48 : 752 : 6 20 : 062 : 7 22 : 2
Rotational ( )
Restrain
2 : 8 1 : 9 : 9 1 : 8 : 1 2 : 7 : 5 2 : 8 : 8 3 : 2 : 3 3 : 4
Rest
2 : 2 1 : 4 : 0 2 : 2 : 6 2 : 2 : 8 2 : 6 : 3 3 : 5 : 4 3 : 7
Freely
7 : 7 5 : 6 : 9 7 : 9 : 9 11 : 615 : 2 10 : 113 : 7 5 : 8 : 8 5 : 9
After 30 min, the mean translational head motion is 18.5, 16.4 and 62.7 mm
with a mean rotational motion of 5.3 , 5.4 and 15.8 for scenarios (a), (b) and (c),
respectively. However, the maximal head motion after 30 min is quite large with a
translation of 31.3, 45.9 and 102.2 mm, respectively, and a rotation of 10.1 , 11.6
and 23.9 , respectively. For an overview, the mean values and SDs at six different
time points are summarized in Table 2.1 for changes in position and orientation.
Furthermore, we calculate the velocities for the different scenarios. On average,
the translational velocity is 1.18, 1.16 and 1.71 mm/s for restrain, rest and freely,
respectively, with a SD of 1.19, 1.20 and 2.25 mm/s, respectively. However, the
maximum translation velocity is 32.32, 86.17 and 77.86 mm/s, respectively. The
rotational velocity is on average 3.21, 1.9 and 3.28 /s, respectively. Interestingly,
the maximum rotational velocity is 34.56 /s for restrain, 28.28 /s for rest and
2.3.2 End-to-End Accuracy
On average, the induced electric field in the sensor has had a electric field strength
of 77.5 V/m with a SD of 4.0 V/m at starting time of the measurements. Taking
the stimulation intensity of 50 % of MSO into account, the measured electric field
strength is in the expected range and therefore suggests that the measurements
have been performed correctly.
Figure 2.8 a illustrates the average decrease in the magnitude of the induced
electric fields. After 30 min the mean induced electric field is 32 : 0 % lower than
the initial value for hold-and-restrain and 19 : 7 % lower for hold-and-rest.In
contrast, the field is 4.9, 1.3 and 1 : 9 % lower than the initial value for setups using
the robotized TMS system: robot-freely, robot-and-restrain and robot-and-rest,
respectively. The decrease for all measurement setups is summarized in Table 2.2
for six different time points. Additionally, the mean values and the Standard
Deviation (SD) are given in the table. The accuracy of robotized TMS (robot-
freely) compared to the two standard setups (hold-and-restrain and hold-and-rest)
is significantly improved (p\0 : 05). In the worst case, the induced electric field

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