摘要:
A representative positron emission tomography (PET) calibration system includes a PET scanner having a ring detector, a phantom that is placed at approximately the center of the ring detector, and a time alignment calibration manager that is coupled to the PET scanner. The time alignment calibration manager detects coincidence events from the phantom, calculates position of time of flight events from the ring detector based on the detected coincidence events, and calculates time offsets for the ring detector using a mean value calculation based on the calculated position of the time of flight events.
摘要:
A representative positron emission tomography (PET) calibration system includes a PET scanner having a ring detector, a phantom that is placed at approximately the center of the ring detector, and a time alignment calibration manager that is coupled to the PET scanner. The time alignment calibration manager detects coincidence events from the phantom, calculates position of time of flight events from the ring detector based on the detected coincidence events, and calculates time offsets for the ring detector using a mean value calculation based on the calculated position of the time of flight events.
摘要:
Normalization coefficients in are computed for positron emission tomography (PET) continuous bed motion acquisition (CBM). The normalization coefficients for the lines-of-response in CBM account for the change in decay of the injected isotope over time and/or changes in velocity of the bed motion.
摘要:
Normalization coefficients in are computed for positron emission tomography (PET) continuous bed motion acquisition (CBM). The normalization coefficients for the lines-of-response in CBM account for the change in decay of the injected isotope over time and/or changes in velocity of the bed motion.
摘要:
Point spread function (PSF) radial filtering in a line of response space. Modeling a radial component, R, of a point spread filter as a function of at least a radial projection index ρ, a radial image space coordinate r, and an azimuth θ. The index ρ is characterized by an asymmetrical Gaussian distribution having where σleft(r) and σright(r) derived from point source measurements, and an adjustment σJ(r, θ) estimated from point source sinogram by Josephs' projector.
摘要:
Methods, and systems therefrom, for generating images from time of flight (TOF) data associated with a scan of at least one object using a positron emission tomography system are provided. The method includes providing initial values for an activity image to yield a current activity image. The method also includes estimating initial values for an attenuation map (μ-map) image based on the TOF data to yield a current μ-map image. The method further includes repeating, until at least one termination condition is met, the steps of updating the current activity image based on at least the current μ-map and a first update algorithm and updating the current μ-map image based on at least on the updated activity image and a second update algorithm. The method also includes outputting an image of the at least one object based on the current μ-map and the current activity image.
摘要:
Methods, and systems therefrom, for generating images from time of flight (TOF) data associated with a scan of at least one object using a positron emission tomography system are provided. The method includes providing initial values for an activity image to yield a current activity image. The method also includes estimating initial values for an attenuation map (μ-map) image based on the TOF data to yield a current μ-map image. The method further includes repeating, until at least one termination condition is met, the steps of updating the current activity image based on at least the current μ-map and a first update algorithm and updating the current μ-map image based on at least on the updated activity image and a second update algorithm. The method also includes outputting an image of the at least one object based on the current μ-map and the current activity image.
摘要:
Point spread function (PSF) radial filtering in a line of response space. Modeling a radial component, R, of a point spread filter as a function of at least a radial projection index ρ, a radial image space coordinate r, and an azimuth θ. The index ρ is characterized by an asymmetrical Gaussian distribution having where σleft(r) and σright(r) derived from point source measurements, and an adjustment σJ(r, θ) estimated from point source sinogram by Josephs' projector.
摘要:
The use of the ordinary Poisson iterative reconstruction algorithm in PET requires the estimation of expected random coincidences. In a clinical environment, random coincidences are often acquired with a delayed coincidence technique, and expected randoms are estimated through variance reduction (VR) of measured delayed coincidences. In this paper we present iterative VR algorithms for random compressed sonograms, when previously known methods are not applicable. Iterative methods have the advantage of easy adaptation to any acquisition geometry and of allowing the estimation of singles rates at the crystal level when the number of crystals is relatively small. Two types of sonogram compression are considered: axial (span) rebinning and transaxial mashing. A monotonic sequential coordinate descent algorithm, which optimizes the Least Squares objective function, is investigated. A simultaneous update algorithm, which possesses the advantage of easy parallelization, is also derived for both cases of the Least Squares and Poisson Likelihood objective function.
摘要:
The DCC (Data Consistency Condition) algorithm is used in combination with MLAA (Maximum Likelihood reconstruction of Attenuation and Activity) to generate extended attenuation correction maps for nuclear medicine imaging studies. MLAA and DCC are complementary algorithms that can be used to determine the accuracy of the mu-map based on PET data. MLAA helps to estimate the mu-values based on the biodistribution of the tracer while DCC checks if the consistency conditions are met for a given mu-map. These methods are combined to get a better estimation of the mu-values. In gated MR/PET cardiac studies, the PET data is framed into multiple gates and a series of MR based mu-maps corresponding to each gate is generated. The PET data from all gates is combined. Once the extended mu-map is generated the central region is replaced with the MR based mu-map corresponding to that particular gate. On the other hand, in dynamic PET studies the uptake in the patient's arms reaches a steady state only after the tracer distributes throughout the body. Hence, for dynamic scans, the projection data of all frames is summed and used to generate the MLAA based extended mu-map for all frames.