Introduction: The measurement of cranial shape

This chapter surveys some approaches to craniometry, each of them designed to represent the surface or internal morphology in 3-D. The reason for using 3-D measurements is to prevent an irreversible loss of data in the first phase of numerical description. Simplifications leading to 2-D data, or other processes to reduce the number of descriptors, can be carried out subsequently. In contrast to the fixed sequence of conventional caliper measurements, such sets of variables can be redefined later (Moyers and Bookstein, 1979). Moreover, new types of variables, for example, spatial measures, might be added. Furthermore, landmarks can be included that are not necessarily defined by conventional anatomical descriptions. An additional advantage with such 3-D measures, besides an increase in efficiency, is that problems of biomechanical function may be correlated with morphology and other biological approaches can be analyzed more adequately (Jacobshagen, 1985).

The range of 3-D measuring techniques includes mechanical contact devices, such as 3-D digitizers (Menk, 1978), and noncontact methods (see Table 10.1). The latter methods utilize visible light, X-rays, electron spin resonance (ESR), nuclear magnetic resonance (NMR), and other techniques. In the morphometry of bony structures, those methods, like ESR and NMR, that are primarily used to measure physiological parameters (soft tissue), have no particular advantages.