Characterisation and Optimisation of Respiratory Gating Applied to a Siemens Biograph
We aim to characterise the respiratory gating features of the Siemens Biograph. In clinical practice, a strain gauge is used to analyse the breathing cycle of a patient and insert a gating signal into the list mode stream. The study is rebinned into time slots and reconstructed using FORE and OSEM.
We use a simplified approach to investigate the gating system. A moving rod source is used to simulate oscillating movement in the superior-inferior direction. The motor driving the rod source applies a proportional force on the strain gauge and the respiratory gating signal is recorded. We examine the resolution and contrast variation between individual time bins of the gated scan.
We show that there is an inverse relationship between contrast and resolution when gating a single source.
We demonstrate loss in resolution when respiratory movement is irregular and show how amplitude gating can be implemented to avoid this.
We propose a method for re-ordering list mode events to ensure the same contrast and resolution for all time bins.
We investigate loss in resolution as a function on the number of bins. We find that irregular respiratory movement has a larger effect as the number of bins increase.