7 research outputs found
Multi-photon time-of-flight MLEM application for the positronium imaging in J-PET
We develop a positronium imaging method for the Jagiellonian PET (J-PET)
scanners based on the time-of-flight maximum likelihood expectation
maximisation (TOF MLEM). The system matrix elements are calculated on-the-fly
for the coincidences comprising two annihilation and one de-excitation photons
that originate from the ortho-positronium (o-Ps) decay. Using the Geant4
library, a Monte Carlo simulation was conducted for four cylindrical 22Na
sources of beta plus decay with diverse o-Ps mean lifetimes, placed
symmetrically inside the two JPET prototypes. The estimated time differences
between the annihilation and the positron emission were aggregated into
histograms (one per voxel), updated by the weights of the activities
reconstructed by TOF MLEM. The simulations were restricted to include only the
o-Ps decays into back-to-back photons, allowing a linear fitting model to be
employed for the estimation of the mean lifetime from each histogram built in
the log scale. To suppress the noise, the exclusion of voxels with activity
below 2-10 percent of the peak was studied. The estimated o-Ps mean lifetimes
were consistent with the simulation and distributed quasi-uniformly at high
MLEM iterations. The proposed positronium imaging technique can be further
upgraded to include various correction factors, as well as be modified
according to realistic o-Ps decay models
Studies of discrete symmetries in decays of positronium atoms
A positronium - a bound state of electron and positron - is an eigenstate of parity and charge conjugation operators which decays into photons. It is a unique laboratory to study discrete symmetries whose precision is limited, in principle, by the effects due to the weak interactions expected at the level of 10−14 and photon-photon interactions expected at the level of 10−9.
The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging as well as for physics studies involving detection of electronpositron annihilation into photons. The physics case covers the areas of discrete symmetries studies and genuine multipartite entanglement. The J-PET detector has high angular and time resolution and allows for determination of spin of the positronium and the momenta and polarization vectors of annihilation quanta. In this article, we present the potential of the J-PET system for studies of discrete symmetries in decays of positronium atoms
Positronium imaging with the novel multiphoton PET scanner
In vivo assessment of cancer and precise location of altered tissues at
initial stages of molecular disorders are important diagnostic challenges.
Positronium is copiously formed in the free molecular spaces in the patient's
body during positron emission tomography (PET). The positronium properties vary
according to the size of inter- and intramolecular voids and the concentration
of molecules in them such as, e.g., molecular oxygen, O2; therefore,
positronium imaging may provide information about disease progression during
the initial stages of molecular alterations. Current PET systems do not allow
acquisition of positronium images. This study presents a new method that
enables positronium imaging by simultaneous registration of annihilation
photons and deexcitation photons from pharmaceuticals labeled with
radionuclides. The first positronium imaging of a phantom built from cardiac
myxoma and adipose tissue is demonstrated. It is anticipated that positronium
imaging will substantially enhance the specificity of PET diagnostics.Comment: 10 pages, 5 figure
ProTheRaMon : a GATE simulation framework for proton therapy range monitoring using PET imaging
Objective. This paper reports on the implementation and shows examples of the use of the ProTheRaMon framework for simulating the delivery of proton therapy treatment plans and range monitoring using positron emission tomography (PET). ProTheRaMon offers complete processing of proton therapy treatment plans, patient CT geometries, and intra-treatment PET imaging, taking into account therapy and imaging coordinate systems and activity decay during the PET imaging protocol specific to a given proton therapy facility. We present the ProTheRaMon framework and illustrate its potential use case and data processing steps for a patient treated at the Cyclotron Centre Bronowice (CCB) proton therapy center in Krakow, Poland. Approach. The ProTheRaMon framework is based on GATE Monte Carlo software, the CASToR reconstruction package and in-house developed Python and bash scripts. The framework consists of five separated simulation and data processing steps, that can be further optimized according to the user’s needs and specific settings of a given proton therapy facility and PET scanner design. Main results. ProTheRaMon is presented using example data from a patient treated at CCB and the J-PET scanner to demonstrate the application of the framework for proton therapy range monitoring. The output of each simulation and data processing stage is described and visualized. Significance. We demonstrate that the ProTheRaMon simulation platform is a high-performance tool, capable of running on a computational cluster and suitable for multi-parameter studies, with databases consisting of large number of patients, as well as different PET scanner geometries and settings for range monitoring in a clinical environment. Due to its modular structure, the ProTheRaMon framework can be adjusted for different proton therapy centers and/or different PET detector geometries. It is available to the community via github (Borys et al 2022)
Transformation of PET raw data into images for event classification using convolutional neural networks
In positron emission tomography (PET) studies, convolutional neural networks (CNNs) may be applied directly to the reconstructed distribution of radioactive tracers injected into the patient's body, as a pattern recognition tool. Nonetheless, unprocessed PET coincidence data exist in tabular format. This paper develops the transformation of tabular data into
-dimensional matrices, as a preparation stage for classification based on CNNs. This method explicitly introduces a nonlinear transformation at the feature engineering stage and then uses principal component analysis to create the images. We apply the proposed methodology to the classification of simulated PET coincidence events originating from NEMA IEC and anthropomorphic XCAT phantom. Comparative studies of neural network architectures, including multilayer perceptron and convolutional networks, were conducted. The developed method increased the initial number of features from 6 to 209 and gave the best precision results (79.8) for all tested neural network architectures; it also showed the smallest decrease when changing the test data to another phantom
Studies of discrete symmetries in decays of positronium atoms
A positronium - a bound state of electron and positron - is an eigenstate of parity and charge conjugation operators which decays into photons. It is a unique laboratory to study discrete symmetries whose precision is limited, in principle, by the effects due to the weak interactions expected at the level of 10−14 and photon-photon interactions expected at the level of 10−9.
The Jagiellonian Positron Emission Tomograph (J-PET) is a detector for medical imaging as well as for physics studies involving detection of electronpositron annihilation into photons. The physics case covers the areas of discrete symmetries studies and genuine multipartite entanglement. The J-PET detector has high angular and time resolution and allows for determination of spin of the positronium and the momenta and polarization vectors of annihilation quanta. In this article, we present the potential of the J-PET system for studies of discrete symmetries in decays of positronium atoms