Polychromatic Source Research Articles

Effects of Photobiomodulation Application on Glutathione-Related Antioxidant Defense System in Rabbit Eye Tissues.

Photobiomodulation (PBM) has emerged as a potentially effective therapeutic approach to modulate cellular functions. This study aimed to examine the impact of PBM on reactive oxygen species (ROS), lipid peroxidation, and glutathione-related antioxidant defense systems in rabbit eye tissues. A polychromatic light source with an intensity of 2.6 J/cm2/min was used for PBM treatment in New Zealand White rabbits for 12 min. The PBM group (n = 8) received treatments every 2 days for a total of 12 sessions, whereas the control group (n = 8) did not undergo any PBM light exposure during the same period. The application of PBM significantly elevated ROS-mediated glutathione levels, along with increased activities of glutathione peroxidase and reductase, particularly in corneal tissue (p ≤ 0.05). In conclusion, PBM treatment effectively enhances antioxidant defense mechanisms in the eye, particularly in corneal tissue, suggesting its potential as a therapeutic strategy for managing oxidative stress-related ocular conditions.

Exploring single-shot propagation and speckle based phase recovery techniques for object thickness estimation by using a polychromatic X-ray laboratory source.

Propagation and speckle-based techniques allow reconstruction of the phase of an X-ray beam with a simple experimental setup. Furthermore, their implementation is feasible using low-coherence laboratory X-ray sources. We investigate different approaches to include X-ray polychromaticity for sample thickness recovery using such techniques. Single-shot Paganin (PT) and Arhatari (AT) propagation-based and speckle-based (ST) techniques are considered. The radiation beam polychromaticity is addressed using three different averaging approaches. The emission-detection process is considered for modulating the X-ray beam spectrum. Reconstructed thickness of three nylon-6 fibers with diameters in the millimeter-range, placed at various object-detector distances are analyzed. In addition, the thickness of an in-house made breast phantom is recovered by using multi-material Paganin's technique (MPT) and compared with micro-CT data. The best quantitative result is obtained for the PT and ST combined with sample thickness averaging (TA) approach that involves individual thickness recovery for each X-ray spectral component and the smallest considered object-detector distance. The error in the recovered fiber diameters for both techniques is , despite the higher noise level in ST images. All cases provide estimates of fiber diameter ratios with an error of 3% with respect to the nominal diameter ratios. The breast phantom thickness difference between MPT-TA and micro-CT is about 10%. We demonstrate the single-shot PT-TA and ST-TA techniques feasibility for thickness recovery of millimeter-sized samples using polychromatic microfocus X-ray sources. The application of MPT-TA for thicker and multi-material samples is promising.

Chromatic bleaching and fractionation effects on optically stimulated luminescent dosimeter reuse.

Optically stimulated luminescent dosimeters (OSLDs) can be bleached and reused, but questions remain about the effects of repeated bleaching and fractionation schedules on OSLD performance. The aim of this study was to investigate how light sources with different wavelengths and different fractionation schemes affect the performance of reused OSLDs. OSLDs (N=240) were irradiated on a cobalt-60 beam in different step sizes until they reached an accumulated dose of 50Gy. Between irradiations they were bleached using light sources of different wavelengths: the Imaging and Radiation Oncology Core (IROC) bleaching system (our control); monochromatic red, green, yellow, and blue lights; and a polychromatic white light. Sensitivity and linearity-based correction factors were determined as a function of dose step-size. The rate of signal removal from different light sources was characterized by sampling these OSLDs at various time points during their bleaching process. Relative doses were calculated according to the American Association of Physicists in Medicine Task Group-191. Signal repopulation was investigated by irradiating OSLDs (N=300) to various delivered doses of 2, 10, 20, 30, 40, and 50Gy in a single fraction, bleached with one of the colors, and read over time. Fractionation effects were evaluated by irradiating OSLDs up to 30Gy in different size steps. After reading, the OSLDs were bleached following IROC protocol. OSLDs (N=40) received irradiations in 5, 10, 15, 30Gy fractions until they had an accumulated dose of 30Gy; The sensitivity response of these OSLDs was compared with reference OSLDs that had no accumulated dose. Light sources with polychromatic spectrums (IROC and white) bleached OSLDs faster than did sources with monochromatic spectra. Polychromatic light sources (white light and IROC system) provided the greatest dose stability for OSLDs that had larger amounts of accumulated dose. Signal repopulation was related to the choice of bleaching light source, timing of bleaching, and amount of accumulated dose. Changes to relative dosimetry were more pronounced in OSLDs that received larger fractions. At 5-Gy fractions and above, all OSLDs had heightened sensitivity, with OSLDs exposed to 30-Gy fractions being 6.4% more sensitive than reference dosimeters. The choice of bleaching light plays a role in how fast an OSLD is bleached and how much accumulated dose an OSLD can be exposed to while maintaining stable signal sensitivity. We have expanded upon investigations into signal repopulation to show that bleaching light plays a role in the migration of deep traps to dosimetric traps after bleaching. Our research concludes that the bleaching light source and fractionation need to be considered when reusing OSLD.

Calibration of MAJIS (Moons And Jupiter Imaging Spectrometer). III. Spectral calibration.

The Moons And Jupiter Imaging Spectrometer (MAJIS) is the visible and near-infrared imaging spectrometer onboard the European Space Agency (ESA)'s Jupiter Icy Moons Explorer mission. Before its integration into the spacecraft, the instrument undergoes an extensive ground calibration to establish its baseline performances. This process prepares the imaging spectrometer for flight operations by characterizing the behavior of the instrument under various operative conditions and uncovering instrumental distortions that may depend on instrumental commands. Two steps of the on-ground calibration campaigns were held at the instrument level to produce the data. Additional in-flight measurements have recently been obtained after launch during the Near-Earth Commissioning Phase. In this article, we present the analyses of these datasets, focusing on the characterization of the spectral performances. First, we describe and analyze the spectral calibration datasets obtained using both monochromatic sources and polychromatic sources coupled with solid and gas samples. Then, we derive the spectral sampling and the spectral response function over the entire field of view. These spectral characteristics are quantified for various operational parameters of MAJIS, such as temperature and spectral binning. The derived on-ground performances are then compared with in-flight measurements obtained after launch and presented in the framework of the MAJIS performance requirements.

Quantifying salivary iodine biomarker using total reflection X-ray fluorescence (TXRF): A method for assessing and monitoring iodine status simulated by Monte Carlo

Iodine stands as a vital trace element essential crucial for synthesizing thyroid hormones, which are essential for regulating metabolism and tissue growth. The “gold standard” for assessing iodine status in a population quantifies the iodine content in urine samples and is based on Inductively Coupled Plasma - Mass Spectrometry (ICP-MS). Such method, or methods involving the readings of the Sandell-Kolthoff (SK) reaction, require complex sample preparations and the use of several toxic chemical elements. However, recent studies have shown a strong correlation between urinary iodine content (UIC) and iodine present in saliva. Using Monte Carlo simulations, this paper presents a TXRF-based method to quantify salivary iodine biomarker for assessing and monitoring iodine status. In the theoretical analysis, mono and polychromatic (filtered) excitation sources are considered. The detection and quantification limits of iodine, as well as the calibration curves for mass recovery, used the strong I Kα1 and I Kα2 lines. It was found that the optimal X-ray excitation source energy for iodine detection is 50 keV monochromatic X-rays. In contrast, using simulated spectra from a tungsten anode target, the best result was found at 70 kVp (peak voltage), after filtering the white beam with a copper absorber. Detection limits of iodine are 0.121 ng and 2.292 ng, for mono and polychromatic sources, respectively. The theoretical results of this paper show that TXRF could be a fast, simple and accurate alternative to ICP-MS or SK reaction-based methods. Of clinical significance, quantifying salivary iodine using TXRF to assess and monitor iodine status could be particularly helpful to patients undertaking 131I treatment. In addition, it could be used in epidemiological field studies to determine iodine deficiency/excess in children and pregnant women.

Off-Grid Electrogenerated Chemiluminescence with Customized p-i-n Photodiodes.

Electrochemiluminescence (ECL) is the generation of light induced by an electrochemical reaction, driven by electricity. Here, an all-optical ECL (AO-ECL) system is developped, which triggers ECL by the illumination of electrically autonomous "integrated" photoelectrochemical devices immersed in the electrolyte. Because these systems are made using small and cheap devices, they can be easily prepared and readily used by any laboratories. They are based on commercially available p-i-n Si photodiodes (≈1€unit-1), coupled with well-established ECL-active and catalytic materials, directly coated onto the component leads by simple and fast wet processes. Here, a Pt coating (known for its high activity for reduction reactions) and carbon paint (known for its optimal ECL emission properties) are deposited at cathode and anode leads, respectively. In addition to its optimized light absorption properties, using the commercial p-i-n Si photodiode eliminates the need for a complicated manufacturing process. It is shown that the device can emit AO-ECL by illumination with polychromatic (simulated sunlight) or monochromatic (near IR) light sources to produce visible photons (425nm) that can be easily observed by the naked eye or recorded with a smartphone camera. These low-cost off-grid AO-ECL devices open broad opportunities for remote photodetection and portable bioanalytical tools.

Pixel-wise beam-hardening correction for dark-field signal in X-ray dual-phase grating interferometry.

The dark-field signal provided by X-ray grating interferometry is an invaluable tool for providing structural information beyond the direct spatial resolution and their variations on a macroscopic scale. However, when using a polychromatic source, the beam-hardening effect in the dark-field signal makes the quantitative sub-resolution structural information inaccessible. Especially, the beam-hardening effect in dual-phase grating interferometry varies with spatial location, inter-grating distance, and diffraction order. In this work, we propose a beam-hardening correction algorithm, taking into account all these factors. The accuracy and robustness of the algorithm are then validated by experimental results. This work contributes a necessary step toward accessing small-angle scattering structural information in dual-phase grating interferometry.

High filler content acrylonitrile‐butadiene‐styrene composites containing tungsten and bismuth oxides for effective lead‐free x‐ray radiation shielding

AbstractAcrylonitrile‐butadiene‐styrene (ABS) based composites with a high content of tungsten and bismuth oxide were developed using an innovative process to obtain lead‐free x‐ray shielding materials. ABS was chosen for its good mechanical properties and its widespread availability as a recycled material. The composites underwent flexural tests, Shore D hardness tests, thermogravimetric and morphological analysis, and their x‐ray attenuation properties were determined through numerical simulations and experimental measurements. Despite their high filler content (up to 75 wt%), the composites showed good filler dispersion within the polymeric matrix and maintained their mechanical properties. Across the investigated energy range (50–150 kV), the lead equivalence for x‐ray shielding was achieved with composite plates containing 75 wt% of tungsten and bismuth oxide, at thickness values corresponding to a weight increase of only 29% and 36%, respectively, in comparison to lead. These findings pave the way for a new generation of lead‐free x‐ray shielding materials. Moreover, their mechanical properties, including flexibility for potential application in wearable personal protective equipment, can be tailored by adjusting the filler content.Highlights High filler content lead‐free ABS composites with WO3 and Bi2O3 were developed. They show good polymer/filler interfacial adhesion and flexural properties. Numerical simulations of their x‐ray shielding properties were performed. Experimental tests with polychromatic sources confirmed good x‐ray attenuation. Results pave the way for the development of new lead‐free x‐ray shielding systems.

Flexible fiber optoelectrodes integrating Perovskite-Nafion-ITO layers for efficient photoelectrocatalytic water purification

Photoelectrocatalytic processes (PECs) combine photocatalysis and electrochemical principles to enhance charge carrier generation and stability within nanomaterials (NMs). Nano-enabled PECs can be used for water purification or hydrogen production. While most PEC studies focus on nanomaterial discovery to improve charge carriers generation and separation, PEC reactor design is important to maximize energy efficiency of light delivery to activate photocatalysts. Current designs face challenges due to low energy efficiencies because most reactor designs orientate light sources perpendicular to flat photocatalyst-coated electrode surfaces, and light must pass through glass materials plus water. We developed a low-cost, physically flexible catalytic polymeric optical fiber (POF) architecture, called optoelectrode fibers, embedded with electrically-conductive indium tin oxide (ITO) nanomaterials (NMs) plus TAB3Bi2Br7I2 perovskite (ABI) visible-photocatalysts in Nafion-PVDF polymers surface layer. The PEC-POF architecture achieves > 6000% larger surface area than flat glass electrodes, > 90% organic pollutant removal in water, and > 300% better incident photon-to-current than the same ABI-NM deposited on a conventional ITO-coated flat glass-plate under low energy irradiation. POFs are useful because are agonistic to the type of NM, facilitating deposition of NMs tunable to specific wavelengths using LED or polychromatic light sources. Bundling large numbers of POF optoelectrodes together achieves reactors with orders of magnitude higher packing geometries (m2 of catalyst surface per m3 of reactor volume) than flat-electrode PEC reactors, enabling the optoelectrode fiber to address environmental problems.

Non-invasive diffused reflected/transmitted signature accompanied with hyperspectral imaging for breast cancer early diagnosis

IntroductionBreast cancer (BC) is a prevalent form of cancer worldwide and a leading cause of cancer-related deaths. There is an urgent need for the development of new methods to detect, diagnose, and monitor BC at an early stage. Light propagation and interaction with molecular species, could be utilized for diagnostic purposes. Incident light reflection and transmission are influenced by the changes of cell structure and dielectric properties. Any variations in these components could impact the reflected and transmitted signals, offering potential diagnostic applications. MethodsIn this study, non-invasive, polychromatic light source over the visible range (400–900 nm) was employed to illuminate controlled normal and BC tissue samples. The resulted diffused reflected and transmitted spectra were captured and analyzed using hyperspectral (HS) camera and designed cross-correlation algorithm. ResultsDiffused reflected signature demonstrated significant difference between normal and BC tissues over the band 500–700 nm. At 600 nm, normal tissue demonstrated diffused reflection intensity of 2304 relative to 764 for malignant tissues. Transmitted signature exhibited good discrimination capabilities over the band 600–900 nm. At 750 nm, normal tissue demonstrated transmission signal intensity of 34 relative to 21 for malignant tissues.Results were validated via generated HS 2D images, for diffused reflected and transmitted signals. Noise reduction, using moving average filter (K = 10), was adopted to enhance HS images. Contrast was improved through de-convolution with reference. Magnitude was calculated using fast Fourier transform for the concated diffused reflected and transmitted HS images. Additionally, phase shift analysis was performed to assess the differences in arrival time. ConclusionThe optimal wavelength to distinguish between normal and malignant breast tissues was 600 nm for the diffused reflected HS images; Furthermore, the transmitted HS images at 750 nm demonstrated high contrast and specificity. The developed HS imaging technique secured high levels of accuracy, specificity, and sensitivity for diffused reflected and transmitted images at 600 nm and 750 nm, respectively; K-means clustering algorithm offered precise outline and delineation of malignant areas at these wavelengths.

Development of a custom optical imaging system for non-invasive monitoring and delineation of lower limb varicose veins using hyperspectral imaging and quantitative phase analysis

BackgroundVaricose veins (VV) are a prevalent chronic venous disorder, particularly affecting women of childbearing age. This condition is associated with significant complications, including pain, discomfort, leg cramps, ulceration, reduced quality of life, absenteeism, and even mortality. This study aims to develop a custom non-invasive, non-contact optical imaging system combined with magnitude and phase image calculation to monitor and visualize varicose veins and their tributaries using hyperspectral imaging and quantitative phase analysis with a k-means clustering algorithm. ResultsTen volunteers participated in the optical imaging system study. They were exposed to a polychromatic light source spanning the wavelength range of 400 nm–950 nm. The diffuse reflection spectra for varicose veins exhibited a peak at 530 nm, while leg veins showed a peak at 780 nm. Hyperspectral images obtained at these specific wavelengths were normalized in order to homogenize the spectral signatures of each pixel (converting the hyperspectral image to 8 bit RGB image) and filtered using a moving average filter. Subsequently, the varicose veins and leg veins were delineated and detected using quantitative phase analysis and a k-means clustering algorithm. ConclusionIn conclusion, the custom optical imaging system, utilizing hyperspectral imaging and the associated clustering algorithm, provides detailed information regarding the spatial distribution of varicose veins. This information can assist vascular physicians in facilitating easier diagnosis and treatment planning.

IN-LINE METHOD OF X-RAY PHASE-CONTRAST MICRO-CT USING A WIDE-FOCUS LABORATORY SOURCE

An experimental implementation of the “in-line” method of X-ray phase contrast using a standard wide-focus X-ray tube as a polychromatic source is described. Using the proposed experimental scheme, in vitro tomographic measurements of a sample of human brain pineal gland are carried out, and the morphological structure of the soft tissues of this organ is visualized based on the results obtained. The advantage of phase-contrast tomography in comparison with traditional absorption tomography for studying the structural features of soft tissues is experimentally demonstrated. The “in-line” phase-contrast scheme, implemented on a laboratory setup, allows tomographic study of samples with linear dimensions of several millimeters and a resolution of ∼20 μm.

Single Shot X-ray Speckle Tracking Phase Contrast Imaging with a Low Brilliance Lab Source

In this paper, we present a single-shot X-ray speckle tracking (XST) phase-contrast imaging (PCI) method for a non-coherent polychromatic laboratory source. XST typically requires a coherent X-ray source, such as a synchrotron, to produce speckle. For a laboratory source without sufficient coherence, the absorption pattern of a random mask, such as sandpaper, have been proposed. However, to track the very small phase shifts in the absorption speckle below the size of the pixels of a standard flat panel detector in the range of 100μm, hundreds of detector images are taken, each moved by a linear stage by a fraction of a pixel to determine the phase shift. As a result, both acquisition time and radiation dose are high. Moreover, precise linear stages are required for sub-pixel movement of the random mask during acquisition of the projection images. In contrast, in this paper we propose a neural network called PCINet to acquire the differential phase image with only one reference image without the sample and one sample image. The proposed system does not require precise linear stages because only a single acquisition is needed. Due to the incoherent source, an absorption-based pseudo-speckle is generated as a reference image. In order to increase the contrast of the pseudo-speckle, a novel, cheap and easy to manufacture tungsten random spatial distrubution of particles is proposed as an alternative to sandpaper. A method for generating realistic training data for the neural network using real X-ray images in a laboratory setup was developed. The training data of the neural network was generated as close as possible to the real data by constructing the input image pairs pixel by pixel from multiple real X-ray images of the pseudo-speckle. The experimental resukts show that it is possible to obtain the differential phase image with only one reference image and one sample image with superimposed absorption speckles in the case of an incoherent laboratory setup.

Trifocal Intraocular Lens Selection: Predicting Visual Function From Optical Quality Measurements.

To apply in vitro quality metrics to assess and compare three trifocal intraocular lenses (IOLs). The optical performance of the AT LISA tri 839MP (Carl Zeiss Meditec AG), AcrySof IQ PanOptix (Alcon Laboratories, Inc), and TECNIS Synergy (Johnson & Johnson Vision) was compared. The modulation transfer function (MTF) metrics were obtained using an optical bench set-up. A polychromatic light source and a model cornea inducing chromatic and spherical aberrations were used to mimic in vivo characteristics. The area under the MTF was calculated at each defocus position, which served as a parameter in a nonlinear formula applied to predict postoperative visual acuity (VA). All of the studied IOLs had a predicted VA of 0.2 logMAR or better throughout the range of 0.00 to -3.00 diopters (D). Simulated VA differences between the IOLs were negligible (< 0.01 logMAR) at the far point. Although the three models were comparable at -1.00 D, at -2.00 D the AT LISA tri 839MP's VA was 0.06 and 0.08 logMAR worse than with the TECNIS Synergy and AcrySof IQ PanOptix, respectively. At near focus, the AcrySof IQ PanOptix's estimated VA was 0.06 logMAR (40 cm); for the AT LISA tri 839MP and TECNIS Synergy, it was 0.06 and 0.03 logMAR, respectively, at 36 cm. Although simulated distance VA was comparable between the studied models, differences can be found in the intermediate focus' position and quality and the expected reading distance. Therefore, simulations of defocus curves from optical quality metrics provide insight into IOL characteristics and highlight differences between the IOLs, which may guide the selection of a trifocal lens based on patients' needs. [J Refract Surg. 2023;39(2):111-118.].

Laboratory demonstration of the birefrigent point-diffraction interferometer wavefront sensor

The direct imaging of extrasolar planets requires extreme adaptive optics (ExAO) in the near-infrared wavelengths. The ExAO needs a high-efficient wavefront sensor (WFS) to measure the phase aberration accurately with a small number of photons. In addition, the WFS in the ExAO is required to run at high sampling rates of 1 − 7 kHz. To meet these requirements, we developed the birefringent point-diffraction interferometer (b-PDI) presented in our earlier paper. We tested the b-PDI in the laboratory with a polychromatic light source with wavelengths of 800 ± 100 nm. The b-PDI showed a relatively high efficiency, comparable to that of a fixed pyramid WFS. The b-PDI has a low calculation cost and a small readout region, which are suitable for high-speed sampling at 6.5 kHz.

Self-powered photodetector based on direct vapour transfer (DVT) method grown tin selenide (SnSe) crystals

The 2D-TMDC (transition metal dichalcogenides) formed thin films have attracted more attention due to their tuneable optoelectronic properties that improved the application of the photo-sensing device. SnSe single crystals were grown in the current work utilising the direct vapour transfer (DVT) technique. The elemental proportion and 2D surface structural analysis of grown crystal SnSe are carried out using Energy-dispersive X-ray analysis (EDAX) and Scanning electron microscopy (SEM). The orthorhombic crystal system of grown SnSe confirmed by high resolution transmission electron microscopy (HRTEM), and Powder X-ray diffractometer (XRD), the regular spot patter of HRTEM and Sharp pick in XRD graph indicated that the SnSe are highly crystalline in nature. The X-ray photoelectron spectroscopy (XPS) is carried out for confirming the binding states and chemical composition of grown SnSe single crystal. The A1g, β3g and A2g vibration mode of SnSe single crystal confirmed using Raman Spectroscopy. In the application part, SnSe exhibits high photodetection capability under the monochromatic and polychromatic light sources at self-bias mode (photoresponsivity of 71.20 µA/W and photo-detectivity of 3.45 × 108 Jones). The optoelectronic characteristics of SnSe devices including dependent photo-responses have also been carried out. Additionally, the important factors affecting photodetection characteristics are assessed, including photocurrent (Iph), sensitivity (S), photoresponsivity (R), Specific detectivity (D*), rise time, and decay time.

Study of Einstein Equivalence Principle with Sagnac Effect in Lorentz and Galilean Frame

Sagnac effect has been studied in terms of Gyroscopic system in both Lorentz frame as well as flat Einstein frame. The Einstein equivalence principle has been used to determine the phase shift due to pseudo force in the transformation from rotating earth frame to stationary frame. A polychromatic broadband source has been considered for the discussion. The Langevin-Landau-Lifschitz metric has been used during the incorporation of General theory of relativity. The square type sagnac interferometer has been used in theory establishment.

Reference-free X-ray fluorescence analysis using well-known polychromatic synchrotron radiation

A reliable and reference-free X-ray fluorescence (XRF) analysis can be achieved by using accurate knowledge of the spectral distribution of the polychromatic excitation source.

Dispersion correction in the advanced volume holographic filter.

Thick volume Bragg gratings (VBG) have been used for wavefront selectivity in various applications such as data storage, endoscopy, or astronomic observation. However, a single thick grating is also selective in wavelength, severely limiting the spectral throughput of the system. Recently, our group introduced a two element Advanced Volume Holographic Filter (AVHF) where the first, dispersive Bragg grating is coupled to a thick VBG such that it dramatically improves the spectral bandwidth, and ultimately enhances the signal to noise ratio of polychromatic sources. Still, the two grating AVHF configuration introduced wavelength dispersion which prevents usage of the filter in imaging systems. Here, we present a solution to this problem by introducing a third diffraction grating that compensates for the dispersion of the two initial gratings. Using both simulation and experimental implementation of a visible-based, broadband AVHF system, the spectral dispersion was improved by a factor of up to 41 × compared to our previous system, re-collimating the output filtered beam. This new AVHF system can be utilized in imaging applications with noisy environments requiring filtration of a polychromatic source.

Imaging of polychromatic sources through Compton spectral reconstruction

Objective. Study the performance of a spectral reconstruction method for Compton imaging of polychromatic sources and compare it to standard Compton reconstruction based on the selection of photopeak events. Approach. The proposed spectral and the standard photopeak reconstruction methods are used to reconstruct images from simulated sources emitting simultaneously photons of 140, 245, 364 and 511 keV. Data are simulated with perfect and realistic energy resolutions and including Doppler broadening. We compare photopeak and spectral reconstructed images both qualitatively and quantitatively by means of activity recovery coefficient and spatial resolution. Main results. The presented method allows improving the images of polychromatic sources with respect to standard reconstruction methods. The main reasons for this improvement are the increase of available statistics and the reduction of contamination from higher initial photon energies. The reconstructed images present lower noise, higher activity recovery coefficient and better spatial resolution. The improvements become more sensible as the energy resolution of the detectors decreases. Significance. Compton cameras have been studied for their capability of imaging polychromatic sources, thus allowing simultaneous imaging of multiple radiotracers. In such scenarios, Compton images are conventionally reconstructed for each emission energy independently, selecting only those measured events depositing a total energy within a fixed window around the known emission lines. We propose to employ a spectral image reconstruction method for polychromatic sources, which allows increasing the available statistics by using the information from events with partial energy deposition. The detector energy resolution influences the energy window used to select photopeak events and therefore the level of contamination by higher energies. The spectral method is expected to have a more important impact as the detector resolution worsens. In this paper we focus on energy ranges from nuclear medical imaging and we consider realistic energy resolutions.