RTNCAT (Real Time NCAT): Implementing Real Time physiological movement of voxellized phantoms in GATE

GATE figures among existing MC simulation codes for emission tomography applications. Although it allows working with voxellized activity distributions it does not enable the incorporation of physiological motion in a real time sense for such distributions. This restriction causes substantial drawbacks where dynamic phenomena such as respiratory or radiotracer motion are of interest. A new C++ class, named "GateRTPhantom" has been introduced in GATE to enable simulation of physiological motion in real time within voxellized phantoms. These objects are managed by a class named "GateRTPhantomMgr". The new approach has been assessed using the 4D NCAT phantom. The real time implementation approach (RTNCAT: Real Time NCAT) was compared with the classic implementation of dynamic processes through the individual simulation of a number of static frames. A total of 20 frames throughout a respiratory cycle were produced (0.250 ms each). The accuracy of the RTNCAT module was validated through a qualitative and quantitative comparison of 3D images containing the emission locations of single photons in the phantom. Parameters such as the total number, the mean value and the standard deviation of the number of emitted photons per voxel were evaluated. In all of these parameters a high level of agreement was observed supporting the developed approach for the real time modelling of physiological motion. In addition, practically identical times of execution were seen for the two approaches.