Electron-multiplying Charge-coupled Device Camera Research Articles

High-Speed Fluctuation Analysis of Silver-Nanoparticle SERS in Solutions.

We analyzed the fluctuation of surface-enhanced Raman spectra with a temporal resolution of 25 ms using a conventional electron-multiplying charge-coupled device camera experimental setup. The signal-to-noise ratio of the spectra was improved using density-based spatial cluster analysis with noise. Silver nanoparticles (AgNPs) with different sizes were dispersed as surface-enhanced Raman spectroscopy platforms in violet aqueous solutions. The movement of AgNPs and the fluctuation of the spectra were characterized. The fluctuation (signal ON and OFF) was evaluated on the basis of the time intervals between ON and OFF timing. The behavior of each AgNP solution was explained by a two-dimensional random walk model, which means that the phenomenon was mainly governed by the Brownian motion of the AgNPs in the solution. The fluctuation was also compared among three different Raman modes, one of which showed anomalous behavior.

First spectroscopic study of HFRC plasma

An advanced spectral diagnostic system was developed to measure the electron temperature (T e), electron density (N e), and ion temperature (T i) of the Huazhong University of Science and Technology field-reversed configuration plasma. The system consists of an optic fiber spectrometer with a wide spectral band and a 670 mm focal length high throughout Czerny–Turner monochromator equipped with both a 3600 g mm−1 grating and a 2400 g mm−1 grating to measure the line spectrum. Accompanying these components is an electron-multiplying charge-coupled device camera to capture spectral data. The relative intensity of the optical fiber spectrometer was calibrated using a standard luminance source, and the wavelength calibration of the spectrometer was accomplished using a Hg/Ar lamp. This diagnostic setup was configured to measure electron density based on the Stark effect of Hγ (n = 5 → n = 2; 434.04 nm). Doppler broadening of an O III (2s22p(2P0)3p → 2s22p(2P0)3s; 375.988 nm) emission line was measured and analyzed to obtain the ion temperature, and electron temperatures were estimated from the relative strength of Hβ (n = 4 → n = 2; 486.14 nm) (Dβ) and Hγ (Dγ) spectral lines when the electron density was obtained from Stark effect measurements. The initial experimental results indicate that the highest electron temperature of the formation region was approximately 8 eV, the electron density of the colliding-and-merging region was approaching 1020 m−3, and the ion temperature reached about 40 eV.

Photophysical image analysis: Unsupervised probabilistic thresholding for images from electron-multiplying charge-coupled devices.

We introduce the concept photophysical image analysis (PIA) and an associated pipeline for unsupervised probabilistic image thresholding for images recorded by electron-multiplying charge-coupled device (EMCCD) cameras. We base our approach on a closed-form analytic expression for the characteristic function (Fourier-transform of the probability mass function) for the image counts recorded in an EMCCD camera, which takes into account both stochasticity in the arrival of photons at the imaging camera and subsequent noise induced by the detection system of the camera. The only assumption in our method is that the background photon arrival to the imaging system is described by a stationary Poisson process (we make no assumption about the photon statistics for the signal). We estimate the background photon statistics parameter, λbg, from an image which contains both background and signal pixels by use of a novel truncated fit procedure with an automatically determined image count threshold. Prior to this, the camera noise model parameters are estimated using a calibration step. Utilizing the estimates for the camera parameters and λbg, we then introduce a probabilistic thresholding method, where, for the first time, the fraction of misclassified pixels can be determined a priori for a general image in an unsupervised way. We use synthetic images to validate our a priori estimates and to benchmark against the Otsu method, which is a popular unsupervised non-probabilistic image thresholding method (no a priori estimates for the error rates are provided). For completeness, we lastly present a simple heuristic general-purpose segmentation method based on the thresholding results, which we apply to segmentation of synthetic images and experimental images of fluorescent beads and lung cell nuclei. Our publicly available software opens up for fully automated, unsupervised, probabilistic photophysical image analysis.

A method for estimating the incident directions of alpha particles in 2-dimensional trajectory images in a GAGG plate

An imaging technique utilizing a scintillator plate in conjunction with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera shows promise for capturing high-resolution trajectory images. Nevertheless, in the 2-dimensional trajectory images, the incident directions of the alpha particles entering the scintillator plate remained unknown due to the line-shaped trajectories. To elucidate the incident directions in our trajectory images, we conducted experiments capturing trajectory images of alpha particles under off-focus conditions. To capture off-focus images of alpha particles, we systematically varied the distance between the GAGG plate and the lens during imaging using an americium-241 (Am-241) source. Through images obtained at different distances between the GAGG plate and the lens, we successfully acquired trajectory images with varying degrees of off-focus, revealing that trajectory images focused on the upper surface of the GAGG plate exhibited blurred and wider trajectories in the deeper regions, making the incident directions of the alpha particles evident. We conclude that the proposed off-focus method for trajectory imaging of alpha particles holds promise for estimating the incident directions in the trajectory images.

A comparative study of EM-CCD and CMOS cameras for particle ion trajectory imaging

High-resolution and real-time imaging of particle ion trajectories is essential in nuclear medicine and nuclear engineering. One potential method to achieve high-resolution real-time trajectory imaging of particle ions involves utilizing an imaging system that integrates a scintillator plate with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera. However, acquiring an EM-CCD camera might prove challenging due to the discontinuation of CCD sensor manufacturing by vendors. As an alternative imaging approach, a low-noise, high-sensitivity camera utilizing a cooled complementary metal-oxide-semiconductor (CMOS) sensor offers a promising solution for imaging particle ion trajectories. Yet, it remains uncertain whether CMOS-based cameras can perform as effectively as CCD-based cameras in capturing particle ion trajectories. To address these concerns, we conducted a comparative analysis of the imaging performance between a CMOS-based system and an EM-CCD-based system for capturing alpha particle trajectories. The results revealed that both systems could image the trajectories of alpha particle, but the spatial resolution with the CMOS-based camera exceeded that of the EM-CCD-based camera, primarily due to the smaller pixel size of the sensor. While the signal-to-noise ratio (SNR) of the trajectory image from the CMOS-based camera initially lagged behind that from the EM-CCD-based camera, this disparity was mitigated by implementing binning techniques on the CMOS-based camera images. In conclusion, our findings suggest that a cooled CMOS camera could serve as a viable alternative for imaging particle ion trajectories.

A preliminary study of multispectral Cherenkov imaging and a Fricke-xylenol orange gel film (MCIFF) for online, absolute dose measurement.

Cherenkov luminescence imaging has shown potential for relative dose distribution and field verification in radiation therapy. However, to date, limited research utilizing Cherenkov luminescence for absolute dose calibration has been conducted owing to uncertainties arising from camera positioning and tissue surface optical properties. This paper introduces a novel approach to multispectral Cherenkov luminescence imaging combined with Fricke-xylenol orange gel (FXG) film, termed MCIFF, which can enable online full-field absolute dose measurement. By integrating these two approaches, MCIFF allows for calibration of the ratio between two spectral intensities with absorbed dose, thereby enabling absolute dose measurement. All experiments are conducted on a Varian Clinac 23EX, utilizing an electron multiplying charge-coupled device (EMCCD) camera and a two-way image splitter for simultaneous capture of two-spectral Cherenkov imaging. In the first part of this study, the absorbance curves of the prepared FXG film, which receives different doses, are measured using a fluorescence spectrophotometer to verify the correlation between absorbance and dose. In the second part, the FXG film is positioned directly under the radiation beam to corroborate the dose measurement capacity of MCIFF across various beams. In the third part, the feasibility of MCIFF is tested in actual radiotherapy settings via a humanoid model, demonstrating its versatility with various radiotherapy materials. The results of this study indicate that the logarithmic ratios of spectral intensities at wavelengths of 550±50 and 700±100nm accurately reflect variations in radiation dose (R2>0.96) across different radiation beams, particle energies, and dose rates. The slopes of the fitting lines remain consistent under varying beam conditions, with discrepancies of less than 8%. The optical profiles obtained using the MCIFF exhibit a satisfactory level of agreement with the measured results derived from the treatment planning system (TPS) and EBT3 films. Specifically, for photon beams, the lateral distances between the 80% and 20% isodose lines, referred to as the penumbra (P80-20) values, obtained through TPS, EBT3 films, and MCIFF, are determined as 0.537, 0.664, and 0.848cm, respectively. Similarly, for electron beams, the P80-20 values obtained through TPS, EBT3 films, and MCIFF are found to be 0.432, 0.561, and 0.634cm, respectively. Furthermore, imaging of the anthropomorphic phantom demonstrates the practical application of MCIFF in real radiotherapy environments. By combining an FXG film with Cherenkov luminescence imaging, MCIFF can calibrate Cherenkov luminescence to absorbed dose, filling the gap in online 2D absolute dose measurement methods in clinical practice, and providing a new direction for the clinical application of optical imaging to radiation therapy.

Range and light output measurements of trajectory images in a GAGG plate with different alpha particle energies

An imaging method that utilizes a scintillator plate combined with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera shows promise for obtaining high-resolution trajectory images. However, it is not yet clear whether the ranges of the trajectory images change with the energy of the alpha particles. Additionally, it remains unclear whether the intensity of the trajectory images is affected by the energy of the alpha particles. To address these questions in our trajectory imaging research, we conducted experiments to capture trajectory images of alpha particles with varying energy levels. To generate alpha particles with different energies, we modulated the energy using an americium-241 (Am-241) source covered with varying numbers of Mylar films. With this alpha source and imaging system, we successfully captured trajectory images with different alpha particle energies and were able to assess the ranges and intensities of these trajectories at various energy levels. The estimated ranges from the measured images with different alpha particle energies closely matched the results obtained through simulations. However, it's worth noting that the light output, as evaluated for the measured trajectory images, was slightly lower than the simulated results at lower energy levels probably due to the non-proportionality of the GAGG plate with respect to alpha particle energies.

Design of a Scanning Module in a Confocal Microscopic Imaging System for Live-Cell Imaging

This study proposes a Nipkow-based pinhole disk laser scanning confocal microscopic imaging system for ordinary optical microscopy, fluorescence microscopy, and confocal microscopy imaging of biological samples in order to realize the dynamic experimental monitoring of space-based life science experiments and the fine observation of biological samples. Confocal microscopic imaging is mainly completed by a scanning module that is composed of a spinning disk and other components. The parameters of the spinning disk directly determine the quality of the image. During the design process, the resolution and signal-to-noise ratios caused by different pinhole diameters in the spinning disk are the main considerations. Changes and image blurring caused by crosstalk due to the pinhole arrangement and different pinhole spacings are addressed. The high photon efficiency of the new EMCCD (electron-multiplying charge-coupled device) and CMOS (complementary metal-oxide-semiconductor) camera reduces the exposure time as much as possible, reduces damage to living cells, and achieves high-speed confocal imaging. It is shown in a confocal imaging experiment with a variable magnification of 1–40× that the imaging resolution of the system can reach a maximum of 2592 × 1944, the spatial resolution can reach 1 μm, and the highest sampling frequency is 10 fps, thus meeting the design requirements for high-speed live-cell imaging.

Ultrahigh resolution real-time trajectory imaging of neutron induced particles in a scintillator from lithium-6 plate

It is known that a lithium-6 (6Li) absorbs a neutron and is divided into a triton and an alpha particle. However, the trajectories of the produced tritons have not yet been imaged in real time and high resolution. We developed an ultrahigh-resolution imaging system that can clearly observe the trajectories of neutron induced particles in real time. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera combined with a 6Li plate and a Ce-doped Gd3Al2Ga3O12(GAGG) scintillator plate. Neutrons from a californium-252 (252Cf) source were irradiated to the 6Li plate, which produced tritons and alpha particles. The produced tritons or alpha particles entered the GAGG plate and produced scintillation light along the trajectories. The scintillation trajectories were magnified by the unit, light intensified, and imaged by the EM-CCD camera. Using our system, we could measure the elongated trajectory images of the particles in real time. Most of these trajectories had Bragg peak like shapes in the images. The average range was 15 μm and the width was 4.6 μm FWHM. From the ranges we estimated, we found that these trajectories could be attributed to the induced tritons. Consequently, the developed real time imaging system is promising for research on the ultrahigh resolution imaging of neutron produced particles.

Sub-micrometer real-time imaging of trajectory of alpha particles using GAGG plate and CMOS camera

High-resolution and real-time imaging of the trajectories of alpha particles is desired in nuclear medicine and nuclear engineering. Although an imaging method using a scintillator plate combined with a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera is a possible method of obtaining high-resolution trajectory images, the spatial resolution of the system is limited to ∼2 μm. To overcome the spatial resolution limitations of this method on trajectory imaging, we used a cooled complementally metal oxide (CMOS) camera in which the sensor had a much larger number of pixels, which were also smaller. Using the CMOS camera based imaging system, we could measure the trajectories of alpha particles in real time with the spatial resolution of 0.34 μm FWHM. With smoothing of the images to reduce image noise, spatial resolution was still kept to less than 0.75 μm. We conclude that this CMOS camera-based alpha-particle trajectory-imaging system is promising for alpha-particle or other particles imaging where ultrahigh spatial resolution is required.

A high-resolution real-time imaging system for observing the trajectories of neutron induced particles in a scintillator

High-resolution imaging of neutron induced particles is required in such methods as neutron radiography. However, the scintillation spots in a neutron-sensitive scintillator have not yet been imaged nor measured for size. We developed a high-resolution, real-time neutron induced particle imaging system for observing these particles' trajectories in a scintillator. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera combined with a lithium-containing silver-doped zinc sulfide (Li-ZnS(Ag)) scintillator plate. Neutrons from a californium-252 (252Cf) source were irradiated to the Li-ZnS(Ag) scintillator and imaged with the system. Using our system, we measured the scintillation spots of the neutron induced particles having different shapes in real time. In some of these measured scintillation spots, those with elliptical shapes were observed due to the trajectories of the particles in the scintillator. The spatial resolution calculated from the widths of the scintillation spots was ∼56 μm. Consequently, the developed imaging system is promising for research on neutron imaging that requires high spatial resolution.

Bichromatic UV detection system for atomically-resolved imaging of ions.

We present a compact bichromatic imaging system, located outside of the vacuum chamber of a trapped ion apparatus that collects the fluorescence of 230.6 and 369.5nm photons simultaneously on a shared electron-multiplying charge-coupled device (EMCCD) camera. The system contains two lens doublets, consisting of a sphere and an asphere. They provide a numerical aperture of 0.45 and 0.40 at 230.6 and 369.5nm, respectively, and enable spatially resolved state detection with a large field of view of 300 μm for long 115In+/172Yb+ Coulomb crystals. Instead of diffraction-limited imaging for one wavelength, the focus in this system is on simultaneous single-ion resolved imaging of both species over a large field, with special attention to the deep UV wavelength (230.6nm) and the low scattering rate of In+ ions. The introduced concept is applicable to other dual-species applications.

Development of an ultrahigh resolution real time alpha particle imaging system for observing the trajectories of alpha particles in a scintillator

High-resolution imaging of alpha particles is required in the detection of alpha radionuclides in cells or small organs for the development of radio-compounds for targeted alpha-particle therapy or other purposes. We developed an ultrahigh resolution, real time alpha-particle imaging system for observing the trajectories of alpha particles in a scintillator. The developed system is based on a magnifying unit and a cooled electron multiplying charge-coupled device (EM-CCD) camera, combined with a 100-µm-thick Ce-doped Gd3Al2Ga3O12 (GAGG) scintillator plate. Alpha particles from an Am-241 source were irradiated to the GAGG scintillator and imaged with the system. Using our system, we measured the trajectories of the alpha particles having different shapes in real time. In some of these measured trajectories, the line shapes of the alpha particles that flew in the GAGG scintillator were clearly observed. The lateral profiles of the alpha-particle trajectories were imaged with widths of ~ 2 µm. We conclude that the developed imaging system is promising for research on targeted alpha-particle therapy or other alpha particle detections that require high spatial resolution.

Evaluation of a therapeutic carbon beam using a G2000 glass scintillator

A G2000 glass scintillator (G2000-SC) was used to determine the carbon profile and range of a 290-MeV/n carbon beam used in heavy-ion therapy because it was sensitive enough to detect single-ion hits at hundreds of mega electron Volts. An electron-multiplying charge-coupled device camera was used to detect the ion luminescence generated during the irradiation of G2000-SC with the beam. The resulting image showed that the position of the Bragg peak can be determined. The beam passes through the 112-mm-thick water phantom and stops 5.73 ± 0.03 mm from the incident side to the G2000-SC. Additionally, the location of the Bragg peak was simulated when irradiating G2000-SC with the beam using the Monte Carlo code particle and heavy ion transport system (PHITS). Simulation results show that the incident beam stops at 5.60 mm after entering G2000-SC. The beam stop location obtained from images and the PHITS code is defined at 80% distal fall-off from the Bragg peak position. Consequently, G2000-SC provided effective profile measurements of therapeutic carbon beams.

Spatially resolved measurement of the distribution of solid and liquid Si nanoparticles in plasma synthesis through line-of-sight extinction spectroscopy.

In many high-temperature gas-phase nanoparticle synthesis processes, freshly nucleated particles are liquid and solidify during growth and cooling. This study presents an approach to determine the location of the liquid-to-solid phase transition and the volume fraction and number density of particles of both phases within a gas phase reactor. Spectrally-resolved line-of-sight attenuation (LOSA) measurements are applied to a silicon nanoparticle aerosol generated from monosilane in a microwave plasma reactor. A phantom-based analysis using particle number density, particle size, and temperature distribution from direct numerical simulation (DNS) of the reacting flow indicates that the contributions from the two particle phases can be decoupled under practical conditions, even with noisy data. The approach was applied to analyze spatially and spectrally resolved LOSA measurements from the hot gas flow downstream of the plasma zone where both solid and liquid silicon particles coexist. Extinction spectra were recorded along a line perpendicular to the flow direction by a spectrometer with an electron-multiplying charge-coupled device (EMCCD) camera, and two-dimensional projections were deconvolved to obtain radial extinction coefficient distributions of solid and liquid particles across the cross-section of the flow. Particle number densities of both particle phases were retrieved simultaneously based on the size-dependent extinction cross-sections of the nanoparticles. The particle-size distribution was determined via thermophoretic sampling at the same location with subsequent transmission electron microscopy (TEM) analysis. The particle temperature distribution was determined from the particle's thermal radiation based on line-of-sight emission (LOSE) measurements. The approach for phase-selective data analysis can be transferred to other materials aerosol systems as long as significant differences exist in extinction spectra for the related different particle classes.

Enhanced Cherenkov imaging for real-time beam visualization by applying a novel carbon quantum dot sheeting in radiotherapy.

Cherenkov imaging can be used to visualize the placement of the beam directly on the patient's surface tissue and evaluate the accuracy of treatment planning. However, Cherenkov emission intensity is lower than ambient light. At present, time gating is the only way to realize Cherenkov imaging with ambient light. This study proposes preparing a novel carbon quantum dot (cQD) sheeting to adjust the wavelength of Cherenkov emission to obtain the optimal wavelength meeting the sensitive detection region of the camera, meanwhile the total optical signal is also increased. By combining a specific filter, this approach might help in using lower-cost camera systems without intensifier-coupled to accomplish in vivo monitoring of the surface beam profile on patients with ambient light. The cQD sheetings were prepared by spin coating and UV curing with different concentrations. All experiments were performed on the Varian VitalBeam system and optical emission was captured using an electron multiplying charge-coupled device (EMCCD) camera. To quantify the optical characteristics and certify the improvement of light intensity as well as signal-to-noise ratio (SNR) of cQD sheeting, the first part of the study was carried out on solid water with 6 and 10 MV photon beams. The second part was carried out on an anthropomorphic phantom to explore the applicability of sheeting when using different radiotherapy materials and the imaging effect of sheeting with the impact of ambient light sources. Additionally, thanks to the narrow emission spectrum of the cQD, a band-pass filter was tested to reduce the effect from environmental lights. The experimental results show that the optical intensity collected with sheeting has an excellent linear relationship (R2 >0.99) with the dose for 6 and 10 MV photons. The full-width half maximum (FWHM) in x and y axis matched with the measured EBT film image, with accuracy in the range of ±1.2and ±2.7mmstandard deviation, respectively. CQD sheeting can significantly improve the light intensity and SNR of optical images. Using 0.1mg/ml sheeting as an example, the signal intensity is increased by 209%, and the SNR is increased by 147.71% at 6 MV photons. The imaging on the anthropomorphic phantom verified that cQD sheeting could be applied to different radiotherapy materials. The average optical intensity increased by about 69.25%, 63.72%, and 61.78%, respectively, after adding cQD sheeting to bolus, mask sample and the combination of bolus and mask. Corresponding SNR is improved by about 62.78%, 56.77%, and 68.80%, respectively. Through the sheeting, optical images with SNR>5 can be obtained in the presence of ambient light and it can be improved through combining with a band-pass filter. When red ambient lights are on, the SNR is increased by about 98.85% after adding a specific filter. Through a combination of cQD sheeting and corresponding filter, light intensity and SNR of optical images can be increased significantly, and it shed new light on the promotion of the clinical application of optical imaging to visualize the beam in radiotherapy.

Microscope alignment using real-time Imaging FCS

Modern electron-multiplying charge-coupled device (EMCCD) and scientific complementary metal-oxide semiconductor (sCMOS) cameras read out fluorescence data with single-molecule sensitivity at thousands of frames per second. Exploiting these capabilities in full requires data evaluation in real time. The direct camera-read-out tool presented here allows access to the data while the camera is recording. This provides simplified and accurate alignment procedures for total internal reflection fluorescence microscopy (TIRFM) and single-plane illumination microscopy (SPIM), and simplifies and accelerates fluorescence experiments. The tool handles a range of widely used EMCCD and sCMOS cameras and uses imaging fluorescence correlation spectroscopy for its evaluation. It is easily extendable to other camera models and other techniques and is a base for automated TIRFM and SPIM data acquisition.

Development of two-dimensional qualitative visualization method for isoflavones secreted from soybean roots using sheets with immobilized bovine serum albumin

A visualization method for the qualitative evaluation of soybean isoflavones secreted from soybean roots by transferring them onto a sheet with immobilized bovine serum albumin (BSA) was developed. BSA was chemically bonded onto a glass microfiber filter. The fluorescence quenching resulting from the interaction of BSA with soybean isoflavones such as daidzein and daidzin was utilized. Fluorescence images before and after soybean roots were placed in contact with the sheets with immobilized BSA were taken with an electron-multiplying charge-coupled device camera. The fluorescence quenching in the images was visualized and analyzed. Soybean isoflavones were extracted from the sheets for quantitative analysis, and the correlation coefficient between the quenched fluorescence intensity per sheet and the total amount of soybean isoflavones was 0.78 (p < 0.01), indicating a high correlation. The quenched fluorescence intensity was lower in pumpkin roots, which do not secrete soybean isoflavone. It was found from analyzed images that soybean isoflavone is secreted in larger amounts from the basal region of the taproot and the tips of the lateral roots of soybean.

Observational equipment for asteroseismology at the Observatorio Astronómico Nacional San Pedro Mártir: white dwarfs

Here, we describe an implementation of an electron-multiplying charge-coupled device camera to search for seismological activity in white dwarfs (WD). The equipment was installed on the 2.12-m telescope at the Observatorio Astronómico Nacional San Pedro Mártir, Baja California, México. We have determined the proper operational regime to keep a very low noise while maintaining a high gain. We have also developed software for the instrument control system and data processing. Finally, we report the first results on the seismological activity of WD, obtained using photometry with one-second exposure. The results were compared to the known variables LAMOST J004628.31 + 343319.90 and GD 66. The WD 2255-001 showed very weak periodic activity with a dominant frequency of 67 mHz.

Plutonium dioxide particle imaging using a high-resolution alpha imager for radiation protection

The internal exposure of workers who inhale plutonium dioxide particles in nuclear facilities is a crucial matter for human protection from radiation. To determine the activity median aerodynamic diameter values at the working sites of nuclear facilities in real time, we developed a high-resolution alpha imager using a ZnS(Ag) scintillator sheet, an optical microscope, and an electron-multiplying charge-coupled device camera. Then, we designed and applied a setup to measure a plutonium dioxide particle and identify the locations of the individual alpha particles in real time. Employing a Gaussian fitting, we evaluated the average spatial resolution of the multiple alpha particles was evaluated to be 16.2 ± 2.2 μmFWHM with a zoom range of 5 ×. Also, the spatial resolution for the plutonium dioxide particle was 302.7 ± 4.6 µmFWHM due to the distance between the plutonium dioxide particle and the ZnS(Ag) scintillator. The influence of beta particles was negligible, and alpha particles were discernible in the alpha–beta particle contamination. The equivalent volume diameter of the plutonium dioxide particle was calculated from the measured count rate. These results indicate that the developed alpha imager is effective in the plutonium dioxide particle measurements at the working sites of nuclear facilities for internal exposure dose evaluation.