Non-invasive Assessment of in Vivo Auricular Cartilage by Ultra-short Echo Time (UTE) T2* Mapping

In this paper, Ultra-short Echo Time (UTE) T-2* mapping is proposed to non-invasively evaluate auricular cartilages from volunteers and donated bodies. The mono- and bi-exponential models were used for mono- and bi-component analysis (short component T-2* and long component T-2*) respectively. The external ears were manually segmented from images and then reconstructed into 3D T-2* mappings. In the monocomponent analysis, the mean T-2* value for 3 volunteers was 34.987 +/- 2.266 ms. As for results from the bi-component analysis, the mean values for 3 volunteers were 8.992 +/- 0.466 ms and 53.648 +/- 1.961 ms for short component T-2* and long component T-2* respectively, with the ratio of bound water to free water of 0.464 +/- 0.020. The bi-exponential fitting model performed better than the mono-exponential fitting model on the curve fitting in volunteers, with R-2[bi] = 0.999 +/- 0.131 vs. R-2 [mono] = 0.972 +/- 0.144. According to the bi-component analysis from donated specimens of auricular cartilage, the ratio of bound water to free water was 0.023 +/- 0.018, which was significantly different from that of volunteers (p < 0.01), but the fitting curves of specimens showed similar findings with volunteers, with R-2 [bi] = 0.999 +/- 0.001 vs. R-2 [mono] = 0.903 +/- 0.005. Our preliminary results demonstrated that the proposed UTE T-2* apping is a feasible non-invasive means for evaluating the development of auricular cartilage scaffold with bio-inks in reconstructive surgery using 3D bioprinting technique.