Region adaptive PET gating using internal motion estimation

The purpose of this study was to assess the optimal gates number of each region using estimated internal motion. Internal motion has been demonstrated in lung and liver region of small animal by coated molecular sieve. We coated molecular sieve with Pluronic F-127 hydrogel for keeping the activity in the body. All PET studies were performed with a dedicated small animal PET scanner. Respiratory gating was operated the external trigger device synchronized with the list mode acquisition. The trigger signals were simultaneously reflected motion of heart and breathing. The list mode data were converted to sinogram gated 2~16 bin. In PET image analysis for determining optimal gate number, count and SNR were measured from ROI in the target region. Horizontal and vertical FWHM were measured from line profile in each images. The motion compensation PET image for optimal gate number was confirmed by internal motion. The measured value of lung region showed high count (8.67), high SNR (3.25), and high FWHM (1.83) in 8 bin. In liver region, high count (2.09), high SNR (3.99), and high FWHM (2.23) were revealed in 9 bin. The artificial tumor evaluation study using molecular sieve is a method to assess accurately internal organ motion in the rodent. The gate number for motion correction should be set differently in accordance with the organ because motion level varies as each organ. The estimated internal motion will be a useful method for motion compensation modeling.