Figure 1.

MR phantom estimation. Five objects of different diameter are shown in (a). Purple = 20 cm diameter; green = 6 cm diameter; red = 3 cm diameter; yellow = 1.5 cm diameter, and turquoise = 1 cm diameter. (b) Point counting grids with difference area per point for volume estimation. This is an example for the phantom 1 cm in diameter. (c) As the phantoms are spherical and isotropic, perpendicular test lines were used to estimate surface. Only red lines intersect with the surface. This is an example for a phantom 6 cm in diameter.