Development of a digital phantom for evaluation of fundamental performance on SPECT

We have developed digital phantoms to be used for a basic education on an image quality and a quantification of SPECT data. Differing from the digital phantoms developed by Castiglioni and et al, several SPECT projection data sets were generated by Monte Carlo simulations (EGS4 code) with different acquisition parameters. A physical, brain and cardiac phantoms were generated. An external shape of the physical phantom is a 200 mm diameter and 200 mm long cylinder. Three objects, each of which consists of 4 mm, 10 mm, 20 mm, 40 mm and 60 mm diameter rods (each rod is 30 mm long) , are set in. Shapes of the brain phantom were created using a MRI data set. Shapes of the cardiac phantom were created using a CT image set. Tc-99m was used for the simulations. The Monte Carlo simulations were performed, taking account of Compton scattering, photoelectric effect and degradation of a spatial resolution due to collimator aperture. SPECT acquisition parameters were collimator type, pixel length, acquired photon count, projection number and radius of detector rotation. Ideal SPECT projection data and transaxial image were generated as reference (standard) data. Several attenuation maps with different attenuation coefficients can be used for an evaluation of an attenuation correction. The triple energy window setting was used for an evaluation of a scatter correction such as the TEW method. Overall, primary and scattered photons were saved in different files. By using the proposed phantoms, spatial resolution, contrast, signal to noise ratio and quantification with SPECT data acquisition and processing parameters were evaluated. The phantoms are considered to be useful for understanding the fundamental performance on SPECT.