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[IEEE 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - Atlanta, GA (2017.10.21-2017.10.28)] 2017 IEEE Nuclear Science Symposium and Medical Imaging Conference (NSS/MIC) - SIRF: Synergistic Image Reconstruction Framework
摘要： The combination of positron emission tomography (PET) with magnetic resonance (MR) imaging opens the way to more accurate diagnosis and improved patient management. At present, the data acquired by PET and MR scanners are essentially processed separately, and the search for ways to improve accuracy of the tomographic reconstruction via synergy of the two imaging techniques is an active area of research. The aim of the collaborative computational project on PET and MR (CCP-PETMR), supported by the UK engineering and physical sciences research council (EPSRC), is to accelerate research in synergistic PET-MR image reconstruction by providing an open access software platform for efficient implementation and validation of novel reconstruction algorithms. In this paper, we present the first release of the Synergistic Image Reconstruction Framework (SIRF) software suite from the CCP-PETMR. SIRF provides user-friendly Python and MATLAB interfaces to advanced PET and MR reconstruction packages written in C++ (currently this uses STIR, Software for Tomographic Image Reconstruction, for PET and Gadgetron for MR, but SIRF will be able to link to other reconstruction engines in the future as appropriate). The software is capable of reconstructing images from real scanner data. Both of the available integrated clinical PET-MR systems (Siemens and GE) are being targeted, and a suitable data format exchange is being negotiated with the manufacturers.
关键词： Magnetic Resonance Imaging,Research Software Engineering,Scientific Programming,Positron Emission Tomography
更新于2025-09-09 09:28:46
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Controlling the white phosphorescence ZnGa2O4 phosphors by surface defects
摘要： White phosphorescence that lasted ≈ 212 seconds, being the longest phosphorescence time reported so far for any Ga based material, has been observed in undoped ZnGa2O4 (ZGO) phosphors. The samples were synthesized by a simple combustion method by using two different Gallium precursors (Gallium nitrate and Gallium Acetylacetonate). According to the X-ray diffraction analysis, the samples prepared with the two different precursors presented the same single cubic phase. TEM images demonstrated that the ZGO phosphors made with both precursors are formed by nanoparticles with quasi-spherical shape, and they have nanoparticle sizes in the range of 17-43 nm. When excited with UV light (400 nm), these phosphors produced a broad blue-green-yellow luminescence. The blue band was associated to transitions from the Ga-O levels, while that of green-yellow band was attributed to radiative transitions from oxygen vacancies. Particularly, the sample synthesized with Gallium acetylacetone precursor presented the highest phosphorescent emission intensity and had a CIE coordinates of (x= 0.27, y= 0.33), which is close to that for pure white light (x=0.33, y=0.33). Since the ZGO presented a white phosphorescent emission without doping with rare earths, they could be good candidates for lighting or signaling applications.
关键词： White emission,Zinc-gallate,phosphorescence,Oxygen-vacancies,luminescence
更新于2025-09-09 09:28:46
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Integrated Whole Body MR/PET: Where Are We?
摘要： Whole body integrated magnetic resonance imaging (MR)/positron emission tomography (PET) imaging systems have recently become available for clinical use and are currently being used to explore whether the combined anatomic and functional capabilities of MR imaging and the metabolic information of PET provide new insight into disease phenotypes and biology, and provide a better assessment of oncologic diseases at a lower radiation dose than a CT. This review provides an overview of the technical background of combined MR/PET systems, a discussion of the potential advantages and technical challenges of hybrid MR/PET instrumentation, as well as collection of possible solutions. Various early clinical applications of integrated MR/PET are also addressed. Finally, the workflow issues of integrated MR/PET, including maximizing diagnostic information while minimizing acquisition time are discussed.
关键词： Positron emission tomography,MR/PET,Magnetic resonance imaging,Hybrid imaging
更新于2025-09-09 09:28:46
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Assessment of 68Ga-PSMA-11 PET positivity predictive factors in prostate cancer
摘要： Purpose: Positron emission tomography (PET) studies with 68Ga-PSMA-11 (68Ga-HBED-CC-PSMA) have earned the attention of researchers, due to overexpression of PSMA in the tumoral tissues of prostate cancer. Our aim was to analyze the potential benefit of this radiotracer in the biochemical relapse of prostate cancer. Material and methods: This retrospective analysis included 53 studies, performed on 50 male prostate cancer patients referred due to biochemical recurrence. In all cases, previous imaging techniques were negative or inconclusive. Results: Of the 53 studies, 36 (68%) were positive. Significant differences were found between the positive and negative PET groups in Gleason’s scale, PSA levels, PSAdt, late acquisition and the administration of androgen deprivation therapy during treatment (p < .05). Regarding PSA levels, 10 (48%) of the 21 patients with PSA < 1 ng/ml, obtained a pathological PET result. When the PSAdt was below six months, 86.7% of the patients obtained an abnormal PET. In the multivariate analysis, only Gleason’s scale was associated independently with an abnormal PET result. Conclusions: 68Ga-PSMA-11 PET shows a high disease detection rate in patients where other techniques showed negative or doubtful images. Almost 50% of patients with prostate cancer biochemical recurrence and low PSA levels (<1 ng/ml) have active disease on 68Ga-PSMA-11 PET, precisely where other radiotracers lack sensitivity.
关键词： Prostate-specific membrane antigen,68Ga-PSMA-11,Prostate cancer,Positron emission tomography
更新于2025-09-09 09:28:46
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Effect of PET-MR Inconsistency in the Kernel Image Reconstruction Method
摘要： Anatomically-driven image reconstruction algorithms have become very popular in positron emission tomography (PET) where they have demonstrated improved image resolution and quantification. This work, consider the effect of spatial inconsistency between MR and PET images in hot and cold regions of the PET image. We investigate these effects on the kernel method from machine learning, in particular, the hybrid kernelized expectation maximization (HKEM). These were applied to Jaszczak phantom and patient data acquired with the Biograph Siemens mMR. The results show that even a small shift can cause a significant change in activity concentration. In general, the PET-MR inconsistencies can induce the partial volume effect, more specifically the 'spill-in' of the affected cold regions and the 'spill-out' from the hot regions. The maximum change was about 100% for the cold region and 10% for the hot lesion using KEM, against the 37% and 8% obtained with HKEM. The findings of this work suggest that including PET information in the kernel enhances the flexibility of the reconstruction in case of spatial inconsistency. Nevertheless, accurate registration and choice of the appropriate MR image for the creation of the kernel is essential to avoid artifacts, blurring, and bias.
关键词： hybrid kernel,image prior,expectation maximization (EM),kernel method,positron emission tomography (PET),iterative reconstruction,anatomically-driven
更新于2025-09-09 09:28:46
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Simulating X-ray emission spectroscopy with algebraic diagrammatic construction schemes for the polarization propagator
摘要： The calculation of X-ray emission spectra has been addressed with the algebraic diagrammatic construct (ADC) scheme, using a core-ionized wave function as the reference state. With this, the valence-to-core transitions are found as the first eigenstates with negative eigenvalues. The performance of the ADC hierarchical methods ADC(2), ADC(2)-x, and ADC(3/2) has been investigated on 17 transition of second-row elements (C, N, O, F, and Ne), and 5 transitions of third-row elements (S and Cl). We report ADC(2) results within 0.28±0.35 eV of experimental values with an appropriate choice of basis set and when accounting for relativistic effects, with a slight tendency towards underestimating emission energies. By comparison, ADC(2)-x yields a similar spread in relative energies, but a consistent overestimation of approximately 1.5 eV. Going to ADC(3/2), we now observe an underestimation of emission energies and a larger error spread. By comparison, calculations of X-ray absorption spectra have been reported to favour the ADC(2)-x method, with ADC(2) showing the largest error when comparing to experimental values. The difference in ADC performance trends between these core spectroscopies are attributed to the different electron rearrangement effects in X-ray absorption and emission processes.
关键词： valence-to-core transitions,core-hole,X-ray emission spectroscopy,polarization propagator,algebraic diagrammatic construction
更新于2025-09-09 09:28:46
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Influence of the Cathode Material Properties in Reducing the Back-Bombardment Effect in Thermionic RF Gun
摘要： The effect of back-bombardment (BB) electrons is considered one of the main obstacles for extensive use of thermionic RF guns (T-RF). The 10 hexaboride materials named (Ca, Sr, Ba, La, Ce, Pr, Nd, Sm, Eu, and Gd) B6 are investigated in this paper to survey the effect of the cathode material on reducing BB electrons and compare them with LaB6 (which is widely used as a thermionic cathode). A numerical model was used to conduct this paper. Besides the numerical calculations, an experiment has been performed to determine the work functions of CeB6 and LaB6. The results from the numerical calculations revealed that (Ba, Ca, and Nd) B6 are less affected by BB electrons: 42%, 50%, and 59%, respectively, compared with LaB6, for low beam current applications. In contrast, for high beam current duties, (Nd, Ce, and Sm) B6 have minimum influence by BB electrons compared with other hexaborides. The study concluded that BB electrons are strongly affected by the properties of the cathode material, especially thermionic emission and material density. Moreover, the study suggests that it is worthwhile to prepare BaB6, CaB6, NdB6, and SmB6 as cathode materials, then to subject them to a real experimental test using T-RF gun to compare their performance and BB effect against LaB6.
关键词： Back bombardment (BB),radio frequency (RF) guns,electron acceleration,hexaborides,work function,thermionic emission
更新于2025-09-09 09:28:46
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Extracting the turbulent flow-field from beam emission spectroscopy images using velocimetry
摘要： The 2D turbulent E × B flow-field is inferred from density fluctuation images obtained with the beam emission spectroscopy diagnostic on DIII-D using the orthogonal dynamic programming velocimetry algorithm. A synthetic turbulence model is used to test the algorithm and optimize it for measuring zonal flows. Zonal flow measurements are found to require a signal-to-noise ratio above ～10 and a zonal flow wavelength longer than ～2 cm. Comparison between the velocimetry-estimated flow-field and the E × B flow-field using a nonlinear gyrokinetic GENE simulation finds that the flow-fields have identical spatial structure and differ only by the mean turbulence phase velocity, which is spatially uniform in this flux tube simulation.
关键词： beam emission spectroscopy,turbulent flow-field,zonal flows,velocimetry,GENE simulation
更新于2025-09-09 09:28:46
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Regioisomeric synthesis of chlorin-e6 dimethyl esters and their optical properties
摘要： Chlorin-e6 dimethyl esters possessing a single carboxy group at the 13-, 151-, or 172-position were prepared by chemically modifying chlorophyll-a. These three synthetic regioisomers were fully characterized by their mass, NMR, and visible absorption spectra. Their molecular structures were unambiguously identified by the specific 1H–13C correlation at the 13-, 15-, and/or 17-substituents in their respective HMBC spectra. Methyl esterification of 13/151-COOH and hydrolysis of 13/151-COOMe affected small shifts of the Qy absorption and fluorescence emission maxima in a diluted CH2Cl2 solution, while no substitution effect of 172-COOH/Me was observed.
关键词： fluorescence emission,ester protection,Qy absorption,retro-Dieckmann condensation,chlorophyll-a derivative
更新于2025-09-09 09:28:46
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The attenuated spline reconstruction technique for single photon emission computed tomography
摘要： We present the attenuated spline reconstruction technique (aSRT) which provides an innovative algorithm for single photon emission computed tomography (SPECT) image reconstruction. aSRT is based on an analytic formula of the inverse attenuated Radon transform. It involves the computation of the Hilbert transforms of the linear attenuation function and of two sinusoidal functions of the so-called attenuated sinogram. These computations are achieved by employing the attenuation information provided by computed tomography (CT) scans and by utilizing custom-made cubic spline interpolation. The purpose of this work is: (i) to present the mathematics of aSRT, (ii) to reconstruct simulated and real SPECT/CT data using aSRT and (iii) to evaluate aSRT by comparing it to filtered backprojection (FBP) and to ordered subsets expectation minimization (OSEM) reconstruction algorithms. Simulation studies were performed by using an image quality phantom and an appropriate attenuation map. Reconstructed images were generated for 45, 90 and 180 views over 360 degrees with 20 realizations and involved Poisson noise of three different levels (NL), namely 100% (NL1), 50% (NL2) and 10% (NL3) of the total counts, respectively. Moreover, real attenuated SPECT sinograms were reconstructed from a real study of a Jaszczak phantom, as well as from a real clinical myocardial SPECT/CT study. Comparisons between aSRT, FBP and OSEM reconstructions were performed using contrast, bias and image roughness. The results suggest that aSRT can efficiently produce accurate attenuation-corrected reconstructions for simulated and real phantoms, as well as for clinical data. In particular, in the case of the clinical myocardial study, aSRT produced reconstructions with higher cold contrast than both FBP and OSEM. aSRT, by incorporating the attenuation correction within itself, may provide an improved alternative to FBP. This is particularly promising for ‘cold’ regions as those occurring in myocardial ischaemia.
关键词： analytic image reconstruction,single photon emission computed tomography (SPECT),attenuated Radon transform
更新于2025-09-09 09:28:46