Coincidence Imaging Research Articles

Synchrotron-based double imaging photoelectron/photoion coincidence spectroscopy of radicals produced in a flow tube: OH and OD

We present a microwave discharge flow tube coupled with a double imaging electron/ion coincidence device and vacuum ultraviolet (VUV) synchrotron radiation. The system has been applied to the study of the photoelectron spectroscopy of the well-known radicals OH and OD. The coincidence imaging scheme provides a high selectivity and yields the spectra of the pure radicals, removing the ever-present contributions from excess reactants, background, or secondary products, and therefore obviating the need for a prior knowledge of all possible byproducts. The photoelectron spectra encompassing the X(3)Σ(-) ground state of the OH(+) and OD(+) cations have been extracted and the vibrational constants compared satisfactorily to existing literature values. Future advantages of this approach include measurement of high resolution VUV spectroscopy of radicals, their absolute photoionization cross section, and species/isomer identification in chemical reactions as a function of time.

Shot-by-shot imaging of Hong-Ou-Mandel interference with an intensified sCMOS camera.

We report the first observation of Hong-Ou-Mandel (HOM) interference of highly indistinguishable photon pairs with spatial resolution. Direct imaging of two-photon coalescence with an intensified sCMOS camera system clearly reveals spatially separated photons appearing pairwise within one of the two modes. With the use of the camera system, we quantified the number of pairs and recovered the full HOM dip yielding 96.3% interference visibility, as well as counted the number of coalesced pairs. We retrieved the spatial modes of both interfering photons by performing a proof-of-principle demonstration of a new, low-noise, high-resolution coincidence imaging scheme.

Application of the 18F-FDGSPECT-CT combined with the images of CT in the diagnosis of lung cancer

Objective To investigate the clinical value of the 18F- FDG SPECT- CT combined with the image of CT in the diagnosis of lung cancer. Methods Retrospectively analysis images of 18 F- FDG SPECTCT and CT of 162 patients pulmonary tumor- like lesions from January 2013 to October 2013 were conducted. All the patients have been confirmed by the pathological mechanism or cytologic examination. Each patient has been firstly diagnosed by the 18 F- FDG SPECT- CT along and then combined with the images of CT. The sensitive rate and the accurate rate of two methods were compared byχ2 test. Results There were 40 benign lesions and 114 malignant ones in 162 patients. The sensitive rates of the two methods were 86.0% and 96.5% (χ2= 6.63,P< 0.05). The accurate rates of the two ways were 79% and 96.3%(χ2= 7.76,P< 0.05). The differences were statistically significant. Conclusion 18F-FDG SPECT-CT combined with the images of CT can increase the diagnostic sensitivity and accuracy. It has important clinical value. Key words: Lung cancer; Deoxyglucose; Coincidence imaging; CT

Radar Coincidence Imaging With Random Microwave Source

The radar coincidence imaging (RCI), as a novel radar imaging method, is presented in this letter. Firstly, the relationship between the deployment of general random microwave array source and the resolution of RCI under second-order correlation methods (SOCM) is presented. Then, the super-resolution RCI is obtained assisted by optimization algorithms based on the matrix form of measurement data. Finally, the mirror phenomenon of RCI, which is caused by the spacing of radar elements, is presented. In experiments, we form RCI using uniform 1-D antenna array with random phase and random amplitude modulated excitation signal for each radar element. The proposed analysis is validated through numerical simulations and experiments.

Chiral asymmetry in the multiphoton ionization of methyloxirane using femtosecond electron-ion coincidence imaging.

Multiphoton photoelectron circular dichroism (MP-PECD) has been observed as an asymmetry in the angular distribution of photoelectrons emitted in the ionization of pure enantiomers of the small chiral molecule methyloxirane using a femtosecond laser operated at 420 nm. Energetically, this requires the uptake of four photons. By switching the laser between left- and right-circular polarization, and observing the differences in the full three-dimensional electron momentum distribution recorded in an electron-ion coincidence technique, the chiral (odd) terms in the angular distribution expression can be isolated. Electron events can additionally be filtered by coincident ion mass, providing mass-tagged electron distributions and quantitative measures of the MP-PECD asymmetry that help characterize the different ionization channels. For the production of ground state parent cation, the magnitude of the mean chiral asymmetry is measured to be 4.7%, with a peak magnitude exceeding 10%

800-fs, 330-μJ pulses from a 100-W regenerative Yb:YAG thin-disk amplifier at 300 kHz and THz generation in LiNbO₃.

Yb:YAG thin-disk lasers offer extraordinary output power, but systems delivering femtosecond pulses at a repetition rate of hundreds of kilohertz are scarce, even though this regime is ideal for ultrafast electron diffraction, coincidence imaging, attosecond science, and terahertz (THz) spectroscopy. Here we describe a regenerative Yb:YAG amplifier based on thin-disk technology, producing 800-fs pulses at a repetition rate adjustable between 50 and 400 kHz. The key design elements are a short regenerative cavity and fast-switching Pockels cell. The average output power is 130 W before the compressor and 100 W after compression, which at 300 kHz corresponds to pulse energies of 430 and 330 μJ, respectively. This is sufficient for a wide range of nonlinear conversions and broadening/compression schemes. As a first application, we use optical rectification in LiNbO₃ to produce 30-nJ single-cycle THz pulses with 6 W pump power. The electric field exceeds 10 kV/cm at a central frequency of 0.3 THz, suitable for driving structural dynamics or controlling electron beams.

Error Analysis of Radar Coincidence Imaging in the Presence of Noise

Error Analysis of Radar Coincidence Imaging in the Presence of Noise

Development of [62Zn/62Cu]-DOTA-rituximab as a possible novel in vivo PET generator for anti-CD20 antigen imaging

Abstract In this study, zinc-62 was prepared at radiopharmaceutical grade (for 62Zn/62Cu generator production) using natCu(p, xn) reaction with the production yield of 5.9 mCi/μAh at 30 MeV proton energy (radiochemical separation yield &gt;95%, radionuclidic purity &gt;99% and radiochemical purity &gt;99%). In the next step, rituximab was successively labeled with [62Zn]-ZnCl2 after conjugation with p-SCN-Bz-DOTA followed by molecular filtration and determination of the average number of DOTA conjugated per mAb (6:1) by spectrophotometric method. Radiochemical purity (&gt;97%, measured by ITLC and HPLC), integrity of protein after radiolabeling (gel electrophoresis) and stability of [62Zn]-DOTA-rituximab (in final formulation, and human serum) were determined 1–8 h as well as biodistribution studies in wild-type rats followed by coincidence imaging for 6 h. However, the accumulation of the radiolabeled antibody was not consistent with the former reported rituximab conjugates. [62Zn]-labeled monoclonal antibodies and fragments can be prepared as potential in vivo PET generators for molecular imaging however, the search for application of stable zinc complexes must be continued.

Radar Coincidence Imaging under Grid Mismatch

Radar coincidence imaging is an instantaneous imaging technique which does not depend on the relative motion between targets and radars. High-resolution, fine-quality images can be obtained using a single pulse either for stationary targets or for complexly maneuvering ones. There are two image-reconstruction algorithms used for radar coincidence imaging, that is, the correlation method and the parameterized method. In comparison with the former, the parameterized method can achieve much higher resolution but is seriously sensitive to grid mismatch. In the presence of grid mismatch, neither of the two algorithms can obtain recognizable high-resolution images. The above problem largely limits the applicability of radar coincidence imaging in actual imaging scenes where grid mismatch generally exists. This paper proposes a joint correlation-parameterization algorithm, which uses the correlation method to estimate the grid-mismatch error and then iteratively modifies the results of the parameterized method. The proposed algorithm can achieve high resolution with fine imagery quality under the grid mismatch. Examples are provided to illustrate the improvement of the proposed method.

Radar Coincidence Imaging: an Instantaneous Imaging Technique With Stochastic Signals

Motivated by classical coincidence imaging which has been realized in optical systems, an instantaneous microwave-radar imaging technique is proposed to obtain focused high-resolution images of targets without motion limitation. Such a radar coincidence imaging method resolves target scatterers based on measuring the independent waveforms of their echoes, which is quite different from conventional radar imaging techniques where target images are derived depending on time-delay and Doppler analysis. Due to the peculiar features of coincidence imaging, there are two potential advantages of the proposed imaging method over the conventional ones: 1) shortening the imaging time to even a pulse width without resolution deterioration so as to improve the performance of processing noncooperative targets and 2) simplifying the receiver complexity, resulting in a lower cost and platform flexibility in application. The basic principle of radar coincidence imaging is to employ the time-space independent detecting signals, which are produced by a multitransmitter configuration, to make scatterers located at different positions reflect independent waveforms from each other, and then to derive the target image based on the prior knowledge of this detecting signal spatial distribution. By constructing the mathematic model, the necessary conditions of the transmitting waveforms are analyzed for achieving radar coincidence imaging. A parameterized image-reconstruction algorithm is introduced to obtain high resolution for microwave radar systems. The effectiveness of this proposed imaging method is demonstrated via a set of simulations. Furthermore, the impacts of modeling error, noise, and waveform independence on the imaging performance are discussed in the experiments.

Radar coincidence imaging in the presence of target-motion-induced error

Radar coincidence imaging (RCI) is a new instantaneous imaging technique that does not depend on Doppler frequency for resolution. Such an imaging method does not require target relative motion and has an imaging interval that is even shorter than a pulse width. The potential advantages in processing both the relatively stationary and maneuvering targets make RCI provide a supplementary imaging approach for the conventional range Doppler imaging methods. The simulation experiments have preliminarily demonstrated the feasibility of the RCI technique. However, further investigations show that the imaging error arises for mov- ing targets, and moreover, it is particularly related to target scattering maps. The paper analyzes the target- motion-induced error and points out that three factors are involved: target velocity, target scattering map, and the time-space independence of detecting signals. The current image-reconstruction algorithms of RCI, which are based on the least-square (LS) principle, are found to be seriously sensitive to the motion-induced errors and will be limited in practical imaging scenarios. Accordingly, the compressive sensing (CS) recovery algo- rithm is employed, which can utilize sparsity restriction to diminish the effect of the motion-induced error on image reconstruction. Simulations are designed to illustrate the three factors of the target-motion-induced error. The imaging performance of the LS and the CS methods in RCI image recovery are compared as well. ©T he Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI. (DOI: 10.1117/1.JEI.23.2.023014)

E16. Breast cancer: recent advances in PET imaging

The assessment and management of breast disease involves an integrated multidisciplinary approach, with the imaging component often being multifaceted and incorporating multiple modalities. Conventional mammography and ultrasound have major roles in both diagnostic evaluation and image-guided sampling/intervention in primary breast disease. Conventional computed tomography (CT) and magnetic resonance imaging (MRI) rely on anatomical changes for diagnosis, staging, and followup of cancer. There are evolving applications for functional imaging investigations, including positron emission tomography/computed tomography (PET/CT) [1−3]. The advent of combined PET/CT over a decade ago enabled more precise localisation of isotope activity to anatomical sites, resulting in increased sensitivity and specificity when compared with stand-alone PET imaging; diagnostic accuracy was increased [1]. PET is based on the detection of photons released when radionuclides emit positrons (positively charged electrons). A positron undergoes annihilation with an electron within milliseconds of emission, releasing two photons moving in opposite directions; these are detected by coincidence imaging as they strike scintillation crystals. Spatial resolution is inherently limited by the mean positron range, with the annihilation reaction occurring up to 5 mm from the event. Respiratory movement results in limitation in resolution within lung parenchyma, with nodules 10 mm in size regarded as often below the resolution of PET. Developments in respiratory gating during acquisition − 4D scanning with ‘bin allocation’ of data − increases the sensitivity of assessing lung lesions [4]. Detector technology is evolving with the development of digital detectors. In most centres the CT component of an integrated PET/CT study is currently low-dose and of relatively low resolution, enabling anatomical placement of lesions but not evaluation of inherent tissue characteristics or very clear discrimination between adjacent structures. Newer PET/CT systems incorporate multi-slice (up to 128) CT, enabling very high resolution, multiplanar and volume rendered images; in some institutions there is a gradual shift towards undertaking ‘diagnostic’ intravenous contrast-enhanced CT as part of the PET/CT study. This enables higher resolution and delineation of structures, with increased conspicuity and identification of lesions, particularly in organs such as the liver where uptake of tracer maybe heterogeneous. The utilisation of contrastenhanced ‘diagnostic’ CT as part of PET/CT may simplify the patient pathway with a single investigation being undertaken rather than a number of potential alternative studies. The true potential benefit of this approach may be established if robust cost/benefit analysis studies are undertaken. The main isotope utilised in current clinical oncological practice is 2-deoxy-2-( 18 F)fluoro-D-glucose (FDG), a glucose analogue, with the positron-emitting radioactive isotope fluorine-18 substituted for the normal hydroxyl group at the 2 � position in the glucose molecule [1].

Analysis of 18F-FDG maximum standardized uptake value in gastric cancer with coincidence imaging

Objective To investigate the value of 18F-FDG SUVmax in gastric cancer diagnosis with coincidence imaging.Methods The coincidence imaging was performed in 92 patients with gastric diseases (60 males,32 females,age 65 (32-85) years; 78 malignant cases,14 benign cases).The malignant cases included 3 remnant gastric cancers and 75 primary gastric cancers (staging: 4 of Tis,13 of T1,9 of T2,33 of T3,11 of T4 and 5 without surgery).The well-,moderately-and poorly-differentiated adenocarcinomas were 22,15 and 28,respectively.Images were analyzed retrospectively with visual method and 18F-FDG SUVmax,and the diagnostic results were compared with the histopathological findings.The ROC curve was used to analyze the SUVmax.The Pearson's correlation analysis was performed to evaluate the relationship between SUVmax and tumor size.The Wilcoxon rank sum test was applied to determine the difference of SUVmax between early and advanced gastric cancers.The Kruskal-Wallis test was used to analyze the difference of SUVmax in various types of differentiated adenocarcinoma.Results No matter visual method or SUVmax was used,the sensitivity,specificity and accuracy of coincidence imaging in diagnosis of gastric cancer were 64.1％(50/78),64.3％(9/14) and 64.1％(59/92),respectively.The AUC of SUVmax was 0.695 and the cut-off value was 0.700.SUVmax Was positively correlated with tumor size significantly(r=0.489,P＜0.001).There was statistically significant difference between SUVmax of Tis-1 and that of T2-4(0.676± 1.288 vs 3.851 ±3.764;Z=-3.754,P＜0.001).However,there was no statistically significant difference among SUVmax of various grades of differentiated adenocarcinoma(2.805±4.008,3.447±2.365,3.413± 3.737 ; x2 =2.459,P＞ 0.05).Conclusions SUVmax provides more information than visual method in assessing gastric cancer with 18F-FDG coincidence imaging.Appropriate cut-off value of SUV is necessary for improvement of the diagnostic efficiency.Relationships between SUV and pathological T stage,histopathological types and differentiation degree need further investigation. Key words: Stomach neoplasms; Tomography, emission-computed, single-photon; Deoxyglucose

Clinical Value of Dual-phase18F-FDG SPECT with Serum Procalcitonin for Identification of Etiology in Tumor Patients with Fever of Unknown Origin

The purpose of the study was to evaluate clinical value of dual-phase 18F-FDG SPECT with serum procalcitonin (PCT) in identifying cancers in patients with fever of unknown origin (FUO). PCT test and dual-phase 18F-FDG SPECT were sequentially performed on 50 consecutive patients with FUO. Two radiologists evaluated all 18F-FDG SPECT data independently. A consensus was reached if any difference of opinions existed. Final diagnosis was based on a comprehensive analysis of results for the PCT test, dual- phase 18F-FDG SPECT and bacterial cultivation, regarded as a gold standard. Among 50 patients, 34 demonstrated PCT ≥ 0.5 μg/L. Coincidence imaging showed in 37 patients with inflammatory lesions, and 13 with malignancy. Finally, 36 bacterial, 1 fungal and 1 viral infections, as well as 12 cancerous fevers were confirmed by dual-phase 18F-FDG SPECT with PCT, combined with bacterial cultivation and clinical follow-up. Our study demonstrated that dual-phase 18F-FDG SPECT in association with PCT could be a valuable tool for diagnosis in tumor patients with FUO.

Detecting chirality in molecules by imaging photoelectron circular dichroism

In this Perspective we discuss photoelectron circular dichroism (PECD), a relatively novel technique that can detect chiral molecules with high sensitivity. PECD has an enantiomeric sensitivity of typically 1-10%, which is two to three orders of magnitude larger than that of the widely employed technique of circular dichroism (CD). In PECD a chiral molecule is photoionized with circular polarized light, and the photoelectron angular scattering distribution is detected using particle imaging techniques. We present the general physical principles of photoelectron circular dichroism and we address both single- and multiphoton excitation. PECD has been measured with synchrotron radiation in single-photon ionization as well as, very recently, with femtosecond laser radiation in multiphoton ionization. We discuss the experimental implementation of PECD, focusing on velocity map coincidence imaging where the momentum distribution of both the electron and the coincident ion is measured. The coincident detection of the mass and momentum of the ion adds very powerful mass-correlated information to the PECD measurement of the chiral molecule. We illustrate the capabilities and the potential of PECD with various experimental examples and introduce computational methods that are able to model quantitatively experimental PECD results. We conclude with an outlook on novel developments and (analytical) implementations of PECD that may further broaden the application of PECD for the sensitive detection of chirality in molecules.

A photoionization investigation of small, homochiral clusters of glycidol using circularly polarized radiation and velocity map electron–ion coincidence imaging

A detailed study of the valence photoionization of small homochiral glycidol (C3O2H6) clusters is carried out with the help of circularly-polarized VUV synchrotron radiation by recording photoionization-based spectroscopic data detected by velocity map electron imaging with coincidence ion selection. We show that information on the stability of cationic as well as neutral chiral clusters can be obtained with enhanced sensitivity by examining the chiral fingerprint encapsulated in Photoelectron Circular Dichroism (PECD) spectra. In particular, by varying the clustering conditions we demonstrate that the PECD signal effectively carries the signature of the neutral precursor species, prior to any fragmentation of the ion, as may be inferred from the below-threshold monomer measurements (including ion imaging). Here the monomer's direct ionization channel is closed and the monomer ion hence must result exclusively as a fragment from dissociative ionization of the dimer (or higher) clusters. At higher photon energies, the mass-selection on the electron spectroscopy data, achieved through filtering the electron images in coincidence with selected ion masses, evidently succeeds in providing a degree of size-selection on the neutral clusters being ionized with, in particular, a clear differentiation of monomer and dimer PECD, showing the strong sensitivity of this chiroptical effect to the non-local long-range molecular potential.

Comparative study of semi-quantitative value based on different reference point in diagnosis of pulmonary lesions with 18F-FDG coincidence imaging

Objective To explore the optimal semi-quantitative uptake ratio for differentiation between benign and malignant lung lesions with 18F-FDG coincidence imaging.Methods One hundred and thirty-seven patients (89 males,48 females,age range:33-78 years) with lung diseases underwent 18 FFDG coincidence imaging.The maximum radioactivity counts of the lung lesions (T),normal chest wall soft tissues (NT1) and the contralateral lung tissue (NT2) were measured.The ratios of R1 (T/NT1) and R2(T/NT2) were calculated.The optimal threshold values of R1(cutoff)and R2(cutoff) were identified by ROC curve analysis.Using the optimal threshold,the sensitivity,specificity and accuracy were calculated.Results The optimal threshold values R1(cutoff)and R2(cutoff) were identified as 3.58 and 4.40.The sensitivity,specificity and accuracy were 90.0％(90/100),89.2％(33/37),89.8％(123/137) according to R1(cutoff) and 90.0％ (90/100),78.4％(29/37),86.9％(119/137) according to R2(cutoff) Conclusion Based on which the chest wall soft tissue is taken as a reference point,the optimal threshold value of T/NT1 is 3.58 in differentiation between benign and malignant lung lesions with 18F-FDG coincidence imaging. Key words: Lung neoplasms ; Coincidence ; Tomography, emission-computed, single-photon ; Tomography, X-ray computed; Deoxyglucose

Imaging photoelectron circular dichroism of chiral molecules by femtosecond multiphoton coincidence detection

Here, we provide a detailed account of novel experiments employing electron-ion coincidence imaging to discriminate chiral molecules. The full three-dimensional angular scattering distribution of electrons is measured after photoexcitation with either left or right circular polarized light. The experiment is performed using a simplified photoelectron-photoion coincidence imaging setup employing only a single particle imaging detector. Results are reported applying this technique to enantiomers of the chiral molecule camphor after three-photon ionization by circularly polarized femtosecond laser pulses at 400 nm and 380 nm. The electron-ion coincidence imaging provides the photoelectron spectrum of mass-selected ions that are observed in the time-of-flight mass spectra. The coincident photoelectron spectra of the parent camphor ion and the various fragment ions are the same, so it can be concluded that fragmentation of camphor happens after ionization. We discuss the forward-backward asymmetry in the photoelectron angular distribution which is expressed in Legendre polynomials with moments up to order six. Furthermore, we present a method, similar to one-photon electron circular dichroism, to quantify the strength of the chiral electron asymmetry in a single parameter. The circular dichroism in the photoelectron angular distribution of camphor is measured to be 8% at 400 nm. The electron circular dichroism using femtosecond multiphoton excitation is of opposite sign and about 60% larger than the electron dichroism observed before in near-threshold one-photon ionization with synchrotron excitation. We interpret our multiphoton ionization as being resonant at the two-photon level with the 3s and 3p Rydberg states of camphor. Theoretical calculations are presented that model the photoelectron angular distribution from a prealigned camphor molecule using density functional theory and continuum multiple scattering X alpha photoelectron scattering calculations. Qualitative agreement is observed between the experimental results and the theoretical calculations of the Legendre moments representing the angular distribution for the two enantiomers. The electron-ion coincidence technique using multiphoton ionization opens new directions in table-top analytical mass-spectrometric applications of mixtures of chiral molecules.

Ion–ion coincidence imaging of dissociative ionization dynamics of formic acid in intense laser fields

We have studied the dissociative ionization dynamics of formic acid molecules with intense femtosecond laser pulses centered at 800nm, employing the ion–ion coincidence imaging technique. Fragmentation reactions originating from both singly and doubly charged parent formic acid ions are observed. In this paper the kinetic energy distributions of several different ionic fragments will be presented. A clear difference in the kinetic energy distributions is observed between ionic fragments originating from the dissociation of the singly charged parent ion and those from the Coulomb explosion of the doubly charged parent ion. Channels exhibiting the emission of neutral hydrogen and channels exhibiting intra molecular hydrogen migration will also be discussed. We present a combined theoretical and experimental study to get to an understanding of the hydrogen migration mechanism at the molecular level.

Radiosynthesis and biodistribution studies of [62Zn/62Cu]–plerixafor complex as a novel in vivo PET generator for chemokine receptor imaging

In order to develop a possible C-X-C chemokine receptor type 4 (CXCR4) imaging agent for oncological scintigraphy, [62Zn]labeled 1,1′-[1,4-phenylenebis(methylene)]bis-1,4,8,11-tetraazacyclotetradecane ([62Zn]-AMD3100) was prepared using in-house made [62Zn]ZnCl2 and AMD-3100 for 1 h at 50 °C (radiochemical purity: >97 % ITLC, >96 % HPLC, specific activity: 20–22 GBq/mmol) in acetate buffer. The complex showed highly hydrophilic properties (log P = −1.114). Stability of the complex was checked in presence of human serum (37 °C) and in final formulation for 1 day. The biodistribution of the labeled compound in vital organs of wild-type Sprague–Dawdley rats were determined and compared with that of free Zn2+ cation up to 6 h. Co-incidence imaging of the complex was consistent with the distribution data up to 3 h. The complex can be a possible in vivo generator compound for PET imaging in CXCR4 positive tumors.