Enhanced 4D heart model based on high resolution dual source gated cardiac CT images

We have developed a new 4D heart model for use in the 4D NCAT phantom that, through modification of parameters that define it, is capable of modeling a wide variety of beating heart motions, normal and abnormal. High-resolution gated cardiac CT data of a healthy subject obtained from a dual source MSCT scanner was used to define the more detailed anatomy of the model. The study consisted of 100 gated time frames over a complete cardiac cycle. For each time frame, 3D NURBS and subdivision surfaces were created to model the four cardiac chambers as well as the coronary vessels, papillary muscles, valves, and other small details of the heart. The motion vector field of the chamber surfaces between adjacent gated time frames was set up by combining information from the CT data as well as the gated tagged MRI data upon which the original 4D NCAT heart model was based. The cardiac twisting motion of the heart cannot be ascertained from CT imaging data; therefore, the twisting motion in the original heart model was scaled to fit the new heart segmented from the CT data. Once the twisting motion was established, the radial and longitudinal contractions could be obtained by noting the epi- and endocardial borders in the gated MSCT images. The motion of the vessels and other cardiac structures was determined by tracking landmark points located on or within them for each subsequent time frame. Time curves were defined for the control points defining each surface creating a time changing 3D surface or 4D model for each heart structure. The resulting heart model was parameterized (including variables to alter the volume change and time duration of different portions of the cardiac cycle as well as the global and regional motion) so as to simulate normal and abnormal variations in the cardiac motion. The model will provide a useful simulation tool for evaluating and improving existing and emerging high resolution 4D imaging techniques used in the diagnosis of cardiac disease.