COMPUTATIONAL TOOLS 111
FIGURE 4.5 Visualizations of mutant (left) and normal (right) mice embryos.
CT values are inspected by maximum intensity projection in (a) and with standard isosurface rendering in (b).
Volume rendering (c) using multidimensional opacity functions allows more accurate bone emphasis, depth cue-
ing, and curvature-based transfer functions to enhance bone contours in image space. In this case, Drs. Keller and
Capecchi are investigating the birth defects caused by a mutation in the Pax3 gene, which controls musculoskeletal
development in mammalian embryos. In their model, they have activated a dominantly acting mutant Pax3 gene
and have uncovered two of its effects: (1) abnormal formation of the bones of the thoracolumbar spine and
cartilaginous rib cage and (2) cranioschisis, a more drastic effect in which the dermal and skeletal covering of the
brain is missing. Imaging of mutant and normal mouse embryos was performed at the University of Utah Small
Animal Imaging Facility, producing two 1.2 GB 16-bit volumes of 769 × 689 × 1173 samples, with resolution of 21 ×
21 × 21 microns.
SOURCE: Courtesy of Chris Johnson, University of Utah; see also http://www.sci.utah.edu/stories/2004/
spr_imaging.html.