It was possible to observe the median nerve displacement in axial and longitudinal acquisitions using ROI Tracking,
Point-wise Tracking and Contour Tracking methods.
Displacement values,
structure dimensions and histogram representative of the frequency and direction of movement in each direction were achieved.
The histogram descriptors enable compact assessment of principal motion properties.
Longitudinal acquisition during wrist extension
According to the ROI Tracking method the median nerve travelled space was 3,1mm on the distal direction.
It was noticeable that there was no significant movement on the other directions as it can be seen in Figure 3.
For the Point-wise Tracking,
results were similar,
ranging from 3,2mm for Point 0 and 3,4mm for Point 1,
which can be seen in Figure 4.
Displacement values ranged from 2,2mm to 2,4mm for Point 0 and Point 1 respectively.
Contour Tracking showed 4,0mm of travelled space and 2,7mm of displacement on the same direction.
All methods were able to show the movement of the median nerve towards the distal direction.
Similar results were obtained in the work of Echigo [6],
where an average displacement of 3,0mm was obtained (Table 1).
Longitudinal acquisition during wrist flexion
ROI Tracking’s travelled space value of 2,0mm is slightly smaller than the remaining results since it’s a partial result obtained from the histogram.
The small movement on the distal direction recorded at the end of the movement influenced the travelled space for the Point 0 and Point 1 in the Point-wise Tracking,
creating a larger value compared to their displacement values (2,9mm and 1,3mm,
respectively).
Contour Tracking showed 4,3mm of travelled space and 3,3mm of displacement.
This exact movement was not referenced in the literature,
although Echigo [6] suggested there was a different amount of movement depending on the type of movement (extension or flexion) for the fingers.
Which means,
it is expected to have different results for both extension and flexion (Table 2).
Axial acquisition during wrist extension
All methods showed that the nerve had small displacement and travelled space values in the axial compared to the longitudinal acquisitions.
ROI Tracking had a 0,5mm of travelled space on the preferential direction.
For Point-wise Tracking,
displacement values of 0,6mm and 0,7mm and travelled space of 2,3mm and 2,1 for both Point 0 and Point 1,
respectively.
Contour Tracking also showed a travelled space value similar to Point-wise Tracking of 2,0mm and a displacement of 0,5mm.
Values of height and width of the nerve were measured and slight variations were observed for both of them.
From 2,8mm to 3,0mm for height and 4,4mm to 4,1mm for width (Table 3).
Axial acquisition during wrist flexion
ROI Tracking results showed a 0,8mm travelled space value on the anatomical left direction leaning towards the centre of the forearm.
Point-wise Tracking showed travelled space values of 3,4mm and 3,0mm and displacement values of 1,6mm and 1,3mm for Point 0 and Point 1,
respectively.
Contour Tracking showed a travelled space value of 3,1mm and a displacement of 1,3mm.
Values of height range from 2,7mm to 2,8mm and width from 3,1mm to 3,0mm.
Similar results of movement quantification were achieved in the work of Wang [7],
where an average displacement value of 2,7mm was obtained.
Differences in results might be due to the small sample size,
since these values can be different depending on the individual (Table 4).