Performance analysis of an improved 3-D PET Monte Carlo simulation and scatter correction

Abstract

We are developing an accelerated Monte Carlo simulation of positron emission tomography (PET) that can be used for scatter correction of three-dimensional (3-D) PET data. Our Monte Carlo technique accurately accounts for single, multiple, and dual Compton scatter events, attenuation through the patient bed, and activity from outside the field of view. We have incorporated innovative sampling techniques that are compatible with our simulation approach, increasing computational efficiency by a factor of seven while improving accuracy through more sophisticated stratification and by incorporating the true energy response of the scanner. The required execution time to acquire 10 million scatter coincidence events for a 3-D thorax PET scan is only 4 min on a 300-MHz Sun dual-processor workstation. We demonstrate that for a low-noise thorax phantom study, image data corrected using the Monte Carlo 3-D PET scatter correction demonstrate no statistically significant deviation from the true activity concentration provided corresponding input data are accurate. The speed and accuracy of our simulation makes it an efficient research tool for studying scatter effects in PET and a practical scatter correction for 3-D PET clinical imaging.

Positron Emission Tomography: Current Challenges and Opportunities for Technological Advances in Clinical and Preclinical Imaging Systems

“…Because photons can undergo multiple scatters prior to detection, scatter is most accurately estimated using Monte Carlo photon-tracking simulations (62). However, these simulations are still computationally intractable (63). The distribution of scattered photons can be estimated much more quickly by using single-scatter approximation (SSA), which can be analytically calculated using the Klein–Nishina equation, as first proposed by Barney et al (64).…”

An outlook on future design of hybrid PET/MRI systems

“…[135][136][137][138] Although computationally intensive, more refined algorithms that use a patient-specific attenuation map, an estimate of the emission image and Monte Carlo-based radiation transport calculations to estimate the magnitude and spatial distribution of Compton scattered events that would be detected were also considered. [139][140][141] The major difficulty facing MRI-guided attenuation correction lies in the fact that the MR signal or tissue intensity level is not directly related to electron density, which renders conversion of MR images to attenuation maps less obvious compared to CT. The basic problem of attenuation map determination from MRI is to locate and map the major attenuating structures in the body.…”

Free Software for PET Imaging

“…Additionally, one may have some statistical models Interestingly, system modeling plays a very important role in ET for optimizing detector design, configuration and materials (see Levin & Zaidi (2007) and Stickel & Cherry (2005)) 2 and for assesing acquisition and processing protocols, for example to study differences in image quality when using radionuclides with various positron ranges (Bai et al (2005)) or properties that are not possible to measure directly like the behavior of scattered photons (Dewaraja et al (2000)). Likewise, it is also a valuable tool in the design and assessment of correction and reconstruction methods (Zaidi & Koral (2004), Holdsworth et al (2002)) and in the study of an imaging system response (Alessio et al (2006)). System modeling, may also be used in the generation of the system matrix either by means of analytical calculations (see previous section) or by Monte Carlo computations (Rafecas, Mosler, Dietz, Pogl, Stamatakis, McElroy & Ziegler (2004), Alessio et al (2006), Vandenberghe et al (2006), Rahmim et al (2008)).…”