Dynamic Elasticity Sonogram of Plantar Heel Pad
Date Issued
2005
Date
2005
Author(s)
Hsu, Chin-Yuan
DOI
zh-TW
Abstract
A loading-unloading apparatus that combined clinical ultrasound and load cell was built to investigate the mechanical properties of the plantar heel pad tissues in living activities. A 5-10 MHz 26mm compact linear array transducer was used to record the continuous B-mode images of the deformation of the plantar heel pad, and then derive their mechanical properties. Elastography of the plantar heel pad were constructed to investigate the biomechanics during normal walking condition. The boundaries of each layer of the soft tissue were estimated by tracking either by the maximum gradient of gray scale or by the k-value of correlative deformation.
Axial strain, lateral strain, elastic modulus, and the ratio of axial strain to lateral strain were computed in various layers of tissues. Compressive index, stiffness, loading and unloading strain rate were taken into account for the quantification of mechanical properties of soft tissues. The elastic modulus of heel pad, at eight different depths calculated, were 124.8 (19.7) kPa, 119.6 (13.7) kPa, 92.6 (32.1) kPa, 73.0 (30.6) kPa, 62.5 (15.4) kPa, 62.2 (14.7) kPa, 55.0 (14.1) kPa and 58.4 (10.2) kPa respectively, which resulted in an equivalent elastic modulus of 39.5 (7.401) kPa. Moreover, the overall stiffness, compressive index, loading and unloading strain rate measured were about 247.5 (58.7) kPa, 0.593 (0.008), 0.315 (0.0387) s-1 and -0.292 (0.0524) s-1 respectively.
The macro-chamber near the calcaneus has a lower stiffness than the micro-chamber next to the plantar skin. Under the action of larger strain rate, the macro-chamber reduces shock from ground effectively. Because of hysteresis, the larger loading strain rate, results a steeper slope in stress-strain curve. There is a large lateral deformation in the transverse scanning plane of the calcaneus, and the amount of lateral distortion is affected by boundary condition and the collagen fibrous spacing.
Subjects
足跟墊
彈性影像
超音波影像
機械特性
heel pad
elastography
sonogram
mechanical property
Type
thesis
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