Registration points for 3-D visualization of normal growth are found in the cranial base of the New Zealand white rabbit

The objective of this study was to determine the most invariant landmarks in the cranial base of the New Zealand White rabbit to be used for registration of a growth sequence. Visualization of the growth process require a minimum of four landmarks to determine the unique transformation necessary to register the cranium in 3-D space. Nine New Zealand White rabbits (Qryctolagus cuniculus) were obtained at six weeks of age, and high resolution CT scans of the skull base of each individual were taken at 7, 9, 11, 13, and 15 weeks of age. Transaxial images were obtained using a GE 9800 scanner, collected on 9 inch magnetic tape, and loaded onto the ISG Camra S200 system. Euclidean Distance Matrix Analysis (EDMA) was used to calculate all possible linear distances between landmarks for each individual at each age. A Form Difference Matrix (FDM) of ratios of like linear distances between ages, was determined using EDMA. The FDM was calculated between each age and between the youngest and oldest ages. A ratio of 1.00 indicates that the distance between landmarks was invariant with growih. The most invariant landmarks for all rabbits had a FDM ratio of 1.00 ±13% between each age and between the youngest and oldest ages. Our findings suggest thai the best possible landmarks to use for registration of the cranial base in the New Zealand White rabbit are opisthion, right foramen lacerum, left foramen lacerum, left posterior maxilla, and left posterior paraflocculus. The same landmarks may not be invariant during growth in the human craniofacial complex, but our methods for determining the optimal landmarks for registration of a growth sequence are applicable to humans. This work is supported in part by NIDR grant I P50 DEI 1131-01.