Prenatal growth map of the mouse knee joint by means of deformable registration technique

Abstract

Joint morphogenesis is the process during which distinct and functional joint shapes emerge during pre- and post-natal joint development. In this study, a repeatable semi-automatic protocol capable of providing a 3D realistic developmental map of the prenatal mouse knee joint was designed by combining Optical Projection Tomography imaging (OPT) and a deformable registration algorithm (Sheffield Image Registration toolkit, ShIRT). Eleven left limbs of healthy murine embryos were scanned with OPT (voxel size: 14.63μm) at two different stages of development: Theiler stage (TS) 23 (approximately 14.5 embryonic days) and 24 (approximately 15.5 embryonic days). One TS23 limb was used to evaluate the precision of the displacement predictions for this specific case. The remaining limbs were then used to estimate Developmental Tibia and Femur Maps. Acceptable uncertainties of the displacement predictions computed from repeated images were found for both epiphyses (between 1.3μm and 1.4μm for the proximal tibia and between 0.7μm and 1.0μm for the femur, along all directions). The protocol was found to be reproducible with maximum Modified Housdorff Distance (MHD) differences equal to 1.9 μm and 1.5 μm for the tibial and femoral epiphyses respectively. The effect of the initial shape of the rudiment affected the developmental maps with MHD of 21.7 μm and 21.9 μm for the tibial and femoral epiphyses respectively, which correspond to 1.4 and 1.5 times the voxel size. To conclude, this study proposes a repeatable semi-automatic protocol capable of providing mean 3D realistic developmental map of a developing rudiment allowing researchers to study how growth and adaptation are directed by biological and mechanobiological factors.

Fig 1. Reconstructed epiphyses used for the study and example of rigid registration.

(a) femoral and tibial epiphyses (TS23 and TS24) used for the study; (b) example of rigidly registered femoral (top) and tibial (bottom) epiphyses. The TS23 epiphyses are represented in blue and the TS24 epiphyses in yellow.

Fig 2. Methodological pipeline.

Two OPT images at different developmental stages were acquired and rigidly registered. The new resampled images, together with a B/W image of the latest developmental stage (TS24) were then given as input to ShIRT. The calculated displacement were then filtered thought the Voxel detection toolkit.

Fig 3. Schematic representation for the generation of both tibial and femoral maps.

(a) Schematic representation of the twenty displacement maps (green box) and five displacement maps (blue box) generated by deformable registration for the tibia. The obtained maps were then averaged in order to generate a Developmental Tibia Map (DTM), and a Single Tibia Map (STM); (b) Schematic representation of the fifteen displacement maps (green box) and five displacement maps (blue box) generated by deformable registration for the femur. The obtained maps were then averaged in order to generate a Developmental Femur Map (DFM), and a Single Femur Map (SFM); (c) qualitative comparison between the DTM and the STM showing similar developmental patterns; (d) qualitative comparison between the DFM and the SFM showing similar developmental patterns.

Fig 4. Qualitative comparison between maps.

(a) Qualitative comparison between DTM (red) and STM (blue). (b) Qualitative comparison between DFM (red) and SFM (blue). (c) Qualitative comparison between the DTM (red) and STM (blue) for the two tibial femoral intra-operator tests. (d) Qualitative comparison between the DTM (red) and STM (blue) for the two tibial femoral inter-operator tests. (e) Qualitative comparison between the DFM (red) and SFM (blue) for the two tibial femoral intra-operator tests.