31 research outputs found
GATE simulation study of yhe 24-module J-PET scanner : data analysis and image reconstruction
The Jagiellonian Positron Emission Tomograph (J-PET) is a novel PET device that, in contrast to commercial PET scanners, is based on plastic scintillator strips. Modular J-PET is the latest prototype that consists of 24 modules arranged in a cylinder. In this study, 6 point-like sources defined in the NEMA spatial resolution standard were simulated twice with total activities of 60 kBq and 60 MBq, respectively. Results of simulations were processed with the GOJA software and reconstructed with the QETIR package
Walk-through flat panel total-body PET: a patient-centered design for high throughput imaging at lower cost using DOI-capable high-resolution monolithic detectors.
PURPOSE
Long axial field-of-view (LAFOV) systems have a much higher sensitivity than standard axial field-of-view (SAFOV) PET systems for imaging the torso or full body, which allows faster and/or lower dose imaging. Despite its very high sensitivity, current total-body PET (TB-PET) throughput is limited by patient handling (positioning on the bed) and often a shortage of available personnel. This factor, combined with high system costs, makes it hard to justify the implementation of these systems for many academic and nearly all routine nuclear medicine departments. We, therefore, propose a novel, cost-effective, dual flat panel TB-PET system for patients in upright standing positions to avoid the time-consuming positioning on a PET-CT table; the walk-through (WT) TB-PET. We describe a patient-centered, flat panel PET design that offers very efficient patient throughput and uses monolithic detectors (with BGO or LYSO) with depth-of-interaction (DOI) capabilities and high intrinsic spatial resolution. We compare system sensitivity, component costs, and patient throughput of the proposed WT-TB-PET to a SAFOV (= 26 cm) and a LAFOV (= 106 cm) LSO PET systems.
METHODS
Patient width, height (= top head to start of thighs) and depth (= distance from the bed to front of patient) were derived from 40 randomly selected PET-CT scans to define the design dimensions of the WT-TB-PET. We compare this new PET system to the commercially available Siemens Biograph Vision 600 (SAFOV) and Siemens Quadra (LAFOV) PET-CT in terms of component costs, system sensitivity, and patient throughput. System cost comparison was based on estimating the cost of the two main components in the PET system (Silicon Photomultipliers (SiPMs) and scintillators). Sensitivity values were determined using Gate Monte Carlo simulations. Patient throughput times (including CT and scout scan, patient positioning on bed and transfer) were recorded for 1 day on a Siemens Vision 600 PET. These timing values were then used to estimate the expected patient throughput (assuming an equal patient radiotracer injected activity to patients and considering differences in system sensitivity and time-of-flight information) for WT-TB-PET, SAFOV and LAFOV PET.
RESULTS
The WT-TB-PET is composed of two flat panels; each is 70 cm wide and 106 cm high, with a 50-cm gap between both panels. These design dimensions were justified by the patient sizes measured from the 40 random PET-CT scans. Each panel consists of 14 × 20 monolithic BGO detector blocks that are 50 × 50 × 16 mm in size and are coupled to a readout with 6 × 6 mm SiPMs arrays. For the WT-TB-PET, the detector surface is reduced by a factor of 1.9 and the scintillator volume by a factor of 2.2 compared to LAFOV PET systems, while demonstrating comparable sensitivity and much better uniform spatial resolution (< 2 mm in all directions over the FOV). The estimated component cost for the WT-TB-PET is 3.3 × lower than that of a 106 cm LAFOV system and only 20% higher than the PET component costs of a SAFOV. The estimated maximum number of patients scanned on a standard 8-h working day increases from 28 (for SAFOV) to 53-60 (for LAFOV in limited/full acceptance) to 87 (for the WT-TB-PET). By scanning faster (more patients), the amount of ordered activity per patient can be reduced drastically: the WT-TB-PET requires 66% less ordered activity per patient than a SAFOV.
CONCLUSIONS
We propose a monolithic BGO or LYSO-based WT-TB-PET system with DOI measurements that departs from the classical patient positioning on a table and allows patients to stand upright between two flat panels. The WT-TB-PET system provides a solution to achieve a much lower cost TB-PET approaching the cost of a SAFOV system. High patient throughput is increased by fast patient positioning between two vertical flat panel detectors of high sensitivity. High spatial resolution (< 2 mm) uniform over the FOV is obtained by using DOI-capable monolithic scintillators
Optimisation of the event-based TOF filtered back-projection for online imaging in total-body J-PET
We perform a parametric study of the newly developed time-of-flight (TOF)
image reconstruction algorithm, proposed for the real-time imaging in
total-body Jagiellonian PET (J-PET) scanners. The asymmetric 3D filtering
kernel is applied at each most likely position of electron-positron
annihilation, estimated from the emissions of back-to-back -photons.
The optimisation of its parameters is studied using Monte Carlo simulations of
a 1-mm spherical source, NEMA IEC and XCAT phantoms inside the ideal J-PET
scanner. The combination of high-pass filters which included the TOF filtered
back-projection (FBP), resulted in spatial resolution, 1.5 higher in
the axial direction than for the conventional 3D FBP. For realistic -minute
scans of NEMA IEC and XCAT, which require a trade-off between the noise and
spatial resolution, the need for Gaussian TOF kernel components, coupled with
median post-filtering, is demonstrated. The best sets of 3D filter parameters
were obtained by the Nelder-Mead minimisation of the mean squared error between
the resulting and reference images. The approach allows training the
reconstruction algorithm for custom scans, using the IEC phantom, when the
temporal resolution is below 50 ps. The image quality parameters, estimated for
the best outcomes, were systematically better than for the non-TOF FBP
Simulating NEMA characteristics of the modular total-body J-PET scanner -- an economic total-body PET from plastic scintillators
The purpose of the presented research is estimation of the performance
characteristics of the economic Total-Body Jagiellonian-PET system (TB-J-PET)
constructed from plastic scintillators. The characteristics are estimated
according to the NEMA NU-2-2018 standards utilizing the GATE package. The
simulated detector consists of 24 modules, each built out of 32 plastic
scintillator strips (each with cross section of 6 mm times 30 mm and length of
140 cm or 200 cm) arranged in two layers in regular 24-sided polygon
circumscribing a circle with the diameter of 78.6 cm. For the TB-J-PET with an
axial field-of-view (AFOV) of 200 cm, a spatial resolutions of 3.7 mm
(transversal) and 4.9 mm (axial) are achieved. The NECR peak of 630 kcps is
expected at 30 kBq/cc activity concentration and the sensitivity at the center
amounts to 38 cps/kBq. The SF is estimated to 36.2 %. The values of SF and
spatial resolution are comparable to those obtained for the state-of-the-art
clinical PET scanners and the first total-body tomographs: uExplorer and
PennPET. With respect to the standard PET systems with AFOV in the range from
16 cm to 26 cm, the TB-J-PET is characterized by an increase in NECR
approximately by factor of 4 and by the increase of the whole-body sensitivity
by factor of 12.6 to 38. The TOF resolution for the TB-J-PET is expected to be
at the level of CRT=240 ps (FWHM). For the TB-J-PET with an axial field-of-view
(AFOV) of 140 cm, an image quality of the reconstructed images of a NEMA IEC
phantom was presented with a contrast recovery coefficient (CRC) and a
background variability parameters. The increase of the whole-body sensitivity
and NECR estimated for the TB-J-PET with respect to current commercial PET
systems makes the TB-J-PET a promising cost-effective solution for the broad
clinical applications of total-body PET scanners.Comment: 31 pages, 11 figures, 6 tables, submitted to Physics in Medicine and
Biology 202
Realistic Total-Body J-PET Geometry Optimization -- Monte Carlo Study
Total-Body PET is one of the most promising medical diagnostics modalities.
The high sensitivity provided by Total-Body technology can be advantageous for
novel tomography methods like positronium imaging. Several efforts are ongoing
to lower the price of the TB-PET systems. Among the alternatives, the
Jagiellonian PET (J-PET) technology, based on plastic scintillator strips,
offers a low-cost alternative. The work aimed to compare five Total-Body J-PET
geometries as a possible next generation J-PET scanner design. We present
comparative studies of performance characteristics of the cost-effective
Total-Body PET scanners using J-PET technology. We investigated in silico five
Total-Body scanner geometries. Monte Carlo simulations of the XCAT phantom, the
2-meter sensitivity line source and positronium sensitivity phantoms were
performed. We compared the sensitivity profiles for 2-gamma and 3-gamma
tomography, relative cost of the setups and performed quantitative analysis of
the reconstructed images. The analysis of the reconstructed XCAT images reveals
the superiority of the seven-ring scanners over the three-ring setups. However,
the three-ring scanners would be approximately 2-3 times cheaper. The peak
sensitivity values for two-gamma vary from 20 to 34 cps/kBq. The sensitivity
curves for the positronium tomography have a similar shape to the two-gamma
sensitivity profiles. The peak values are lower compared to the two-gamma
cases, from about 20-28 times, with a maximum of 1.66 cps/kBq. The results show
the feasibility of multi-organ imaging of all the systems to be considered for
the next generation of TB J-PET designs. The relative cost for all the scanners
is about 10-4 times lower compared to the cost of the uExplorer. These
properties coupled together with J-PET cost-effectiveness, make the J-PET
technology an attractive solution for broad application in clinics
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
Testing CPT symmetry in ortho-positronium decays with positronium annihilation tomography
Charged lepton system symmetry under combined charge, parity, and time-reversal transformation (CPT) remains scarcely tested. Despite stringent quantum-electrodynamic limits, discrepancies in predictions for the electron–positron bound state (positronium atom) motivate further investigation, including fundamental symmetry tests. While CPT noninvariance effects could be manifested in non-vanishing angular correlations between final-state photons and spin of annihilating positronium, measurements were previously limited by knowledge of the latter. Here, we demonstrate tomographic reconstruction techniques applied to three-photon annihilations of ortho-positronium atoms to estimate their spin polarisation without magnetic field or polarised positronium source. We use a plastic-scintillator-based positron-emission-tomography scanner to record ortho-positronium (o-Ps) annihilations with single-event estimation of o-Ps spin and determine the complete spectrum of an angular correlation operator sensitive to CPT-violating effects. We find no violation at the precision level of 10−4, with an over threefold improvement on the previous measurement
From tests of discrete symmetries to medical imaging with J-PET detector
We present results on CPT symmetry tests in decays of positronium performed with the precision at the level of 10, and positronium images determined with the prototype of the J-PET tomograph. The first full-scale prototype apparatus consists of 192 plastic scintillator strips readout from both ends with vacuum tube photomultipliers. Signals produced by photomultipliers are probed in the amplitude domain and are digitized by FPGA-based readout boards in triggerless mode. In this contribution we report on the first two- and three-photon positronium images and tests of CPT symmetry in positronium decays
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)