Modeling respiratory mechanics in the MCAT and spline-based MCAT phantoms

Respiratory motion can cause artifacts in myocardial SPECT. The authors incorporate respiratory mechanics into the current 4D MCAT and into the next generation spline-based MCAT phantoms. In order to simulate respiratory motion in the current MCAT phantom, the geometric solids for the diaphragm, heart, ribs, and lungs were altered through manipulation of parameters defining them. Affine transformations were applied to the control points defining the same respiratory structures in the spline-based MCAT phantom to simulate respiratory motion. The NURBS surfaces for the lungs and body outline were constructed in such a way as to be linked to the surrounding ribs. Expansion and contraction of the thoracic cage then coincided with expansion and contraction of the lungs and body. The changes both phantoms underwent were splined over time to create time continuous 4D respiratory models. It is concluded that both respiratory models are effective tools for researching effects of respiratory motion