In this work, a Monte Carlo software package, PET-EGS, designed to simulate realistic PET clinical studies, was used to assess three different approaches to scatter correction in 3D PET: analytical (gaussian fitting technique), experimental (dual energy window technique) and probabilistic (Monte Carlo technique).Phantom'and clinical studies were carried out by 3D PET and simulated by PET-EGS. A clinical study (I8F-FDG brain study) was simulated assuming PET emission/transmission multiple-volume images as a voxelised source object describing the distribution of both the radioactivity and attenuation coefficients and accounting for out-of-field activity and media.The accuracy of PET-EGS in modelling the physical response of a 3D PET scanner was assessed by statistical comparison between measured and total (scatter + unscatter) simulated distributions (probability for the two distributions to be the same distribution: p > 0.95). The accuracy of the scatter models, for each scatter correction technique, was evaluated on sinograms by statistical comparison between the estimated and the simulated scatter distributions (agreement < 1 a). The accuracy of scatter correction was evaluated on sinograms by comparison between scatter corrected and simulated unscatter distributions, proving a comparable accuracy of all the considered scatter correction techniques for brainlike distributed sources.
The physical performances of two current state-of-the-art scanners dedicated to functional imaging of the brain, one a single-photon emission tomography (SPET) scanner and the other a positron emission tomography (PET) scanner, have been compared under identical conditions. The aim of the study was to compare the capabilities of the devices under conditions resembling the routine clinical environment, as well as to consider other issues such as radiation burden for some common investigations. Both systems have slightly less than 11-cm axial fields of view. The PET system can be operated in a septa-less (3D) mode as well as conventionally with septa (2D). The spatial resolution of both devices was less than 8 mm in all dimensions in scattering media. On average, the PET scanner's resolution was approximately 10%-15% better than the SPET system. Energy resolution on the SPET system was superior due the scintillator used [NaI(Tl)]. Sensitivity in air with a line source on the PET system was found to be approximately 150 times greater in 3D and approximately 25 times greater in 2D than with the SPET system. A normal subject was studied on each system in an attempt to obtain the highest quality data possible for a subjective comparison. It is clear that, while PET retains the advantages of more desirable radiopharmaceuticals and higher sensitivity, the quality obtainable from SPET devices has improved markedly. SPET may prove as useful for many clinical investigations.
Physical parameters and performance of a new brain-dedicated tomograph (CERASPECT) were measured and compared to those of a state-of-the-art single-headed rectangular rotating gamma camera Spatial resolution, sensitivity, scatter fraction, contmt, uniformity and image quality of the two systems were evaluated using the same radioactive source geometry. The CERASPECT's spatial resolution was 23% higher and its sensitivity was three times greater than those of the gamma camera. The contrast measured with a 15 mm cold lesion was 60% for the CERASPECT and 45% for the gamma camera Tomographic nonuniformities were measured as the percentage integral and differential uniformiq of a cylindrical uniform phantom At low-statistics comls per slice the integral uniformity was comparable and at high-statistics counts per slice it was equal to 11% and 20% for CERASPECT and the gamma camera, respectively. Image quality is generally superior with the dedicated brain system. The use of new devices with improved physical performance allows more accurate quantitative SECT functional brain studies
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