A realistic spline-based dynamic heart phantom

We develop a realistic computerized heart phantom for use in medical imagin g research. This phantom is a hybrid of; realistic patient-based phantoms a nd flexible geometry-based phantoms. The surfaces of heart structures are d efined using non-uniform rational B-splines (NURBS), as used in 3D computer graphics. The NURBS primitives define continuous surfaces allowing the pha ntom to be defined at any resolution. Also, by fitting NURBS to patient dat a, the phantom is more realistic than those based on solid geometry. An imp ortant innovation is the extension of NURBS to the fourth dimension, time, to model heart motion. Points on the surfaces of heart structures were sele cted from a gated MRI study of a normal patient. Polygon surfaces were fit to the points for each time frame, and smoothed. 3D NURBS surfaces were fit to the smooth polygon surfaces and then a 4D NURBS surface was fit through these surfaces. Each of the principal 4D surfaces (atria, ventricles, inne r and outer walls) contains approximately 200 control points. We conclude t hat 4D NURBS are an efficient and flexible way to describe the heart and ot her anatomical objects for a realistic phantom.