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

347.70
/s for freely.

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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