Biomedical Engineering Reference
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Fig. 5.16 a-f: transversal MR-images of the buttock region showing tissue deformation from
a 0.0 mm to f 44 mm indenter displacement with tablets incorporated into the indenter head at
position [1] and pelvic bone [2]
displacement assured intense ascent of the indentation force, to capture a wide
range of gluteal tissue behaviour.
Figure 5.15 c illustrates, in addition to force-time data (red), the corresponding
oxygen saturation and blood flow of the tissue under loading and unloading. This
was accomplished employing a microperfusion sensor, integrated into the indenter
head. Oxygen saturation and blood flow decreased while increasing the tissue load,
at unloading, the process was reversed. Similar to polymer foam materials
( Sect. 4.2.1.2 ) , a relaxation tissue behaviour can be observed with exponentially
increasing and decreasing forces in the force-time diagram. In addition, higher
oxygen saturation and blood flow values were observed at 2 mm tissue depth,
compared to a depth of 8 mm.
5.2.2.2 MRI Scan Data
Transversal MR-images of the unloaded and stepwise loaded tissue in the gluteal
region were performed as depicted in Fig. 5.16 , initially in the undeformed
configuration progressing to the last deformation state at (here) Du = 44 mm. The
tablets incorporated into the indenter head are displayed by light spots [1] in the
lower left corner of Fig. 5.16 a. With the aid of the pelvic bone (indicated position
[2]), defined muscle tissue displacement and bearing of the indentation forces was
achieved.
The data was acquired using a 1.5 T M AGNETOM S ONATA (S IEMENS , Erlangen/
Germany) scanner. The slice thickness was set to 2 mm without a slice gap using a
matrix size of 512 9 512. To initially detect the desired indenter position, a turbo
spin echo sequence with transversal orientation and a repetition time (TR) of
3,000 ms and an echo time (TE) of 93 ms was applied. For the actual scan of the
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