Simultaneous Images Research Articles

Attitude Estimation for Space Targets by Exploiting the Quadratic Phase Coefficients of Inverse Synthetic Aperture Radar Imagery

This paper proposes a novel approach to interpreting the satellite attitude based on inverse synthetic aperture radar (ISAR) images. In the conventional viewpoint, quadratic and higher order phase terms of ISAR imagery are regarded as negative factors causing the defocusing phenomenon. In this paper, we introduce how to apply quadratic phase coefficients to estimate target attitude from the ISAR imagery. A geometric projection model of ISAR imaging is built according to radar line of sight, and an explicit expression is also derived to connect target attitude parameters and the image defocusing property. With the accommodation of Broyden–Fletcher–Goldfarb–Shanno algorithm, spatial-variant quadratic phase coefficients together with attitude parameters are determined by an image contrast maximization. We also extend the proposed algorithm to multistatic ISAR applications, where the quadratic phase information lying in simultaneous multistatic ISAR images can be mined to enhance the performance of target attitude estimation. Experimental results illustrate the feasibility of the proposed algorithm.

Determining switching threshold for NIR-SWIR combined atmospheric correction algorithm of ocean color remote sensing

Accurate atmospheric correction is decisive for ocean color remote sensing applications. Near infrared (NIR)-based algorithm performs well for clear waters; while shortwave infrared (SWIR)-based algorithm can obtain good results for turbid waters, however, it tends to produce noisy patterns for clear waters. A practical strategy is to apply NIR- and SWIR-based algorithm for clear and turbid waters, respectively, which is called NIR-SWIR combined atmospheric correction algorithm. However, the currently applied switching scheme for the NIR-SWIR algorithm undermines the atmospheric correction performance. This study aimed to find an applicable switching scheme for NIR-SWIR algorithm. Four MODIS land bands were used to switch the NIR- and SWIR-based algorithms. A simulated dataset was used to evaluate atmospheric performance of NIR- and SWIR-based algorithm. The switching threshold for each MODIS land band was determined as an Rrs value at which SWIR-based algorithm performed better than NIR-based algorithm. The switching scheme was evaluated using matchups of simultaneous MODIS Aqua images and AERONET-OC data, and then tested with a MODIS Aqua image over the western Pacific Ocean. Results showed that the switching threshold for Rrs(469), Rrs(555), Rrs(645) and Rrs(859) were 0.009, 0.016, 0.009 and 0.0006 sr−1, respectively; Rrs(645) with a threshold of 0.009 sr−1 and Rrs(555) with a threshold of 0.016 sr−1 worked well for NIR-SWIR algorithm, while Rrs(469) and Rrs(859) produced worse performance. Therefore, Rrs(555) > 0.016 sr−1 or Rrs(645) > 0.009 sr−1 was recommended as the switching scheme for NIR-SWIR algorithm. Considering contrasted estuarine, coastal and some inland waters, combining NIR- and SWIR-based atmospheric correction algorithm with the proposed switching scheme should be useful for remote sensing monitoring over these waters.

Diagnostic tools for female urethral diverticulum: Current perspectives

Although once considered quite a rare condition in the past, female urethral diverticulum (UD) would now appear to have a higher frequency, perhaps due to greater attention from physicians. To date, there is no agreement on which is the best method for diagnosis of female UD. Traditionally, the approach was based on quite invasive techniques, such as voiding cystourethrography, and double-balloon urethrography, with satisfactory results but relevant limitations. More recent high-resolution imaging techniques, such as 2D-3D ultrasonography (US) and magnetic resonance imaging (MRI) have also been applied in the study of the abnormalities of the female urethra. US had the advantage of the outpatient setting, non-invasiveness and absence of contrast medium use; MRI, is characterized by high sensitivity thanks to multiplanar capability, with an optimal characterization of periurethral diseases or its abnormalities, and lack of ionizing radiation. A real innovation is represented by computer tomography-voiding cystourethrography, a rapid technique that allows for high quality simultaneous 2D and 3D images of the urethra, well correlated to MRI and consequently with surgical results. Here, we report and comment the available tools in the diagnosis of female UD, focusing particularly on pros and contra of different methods.

Tear-film dynamics by combining double-pass images, pupil retro-illumination, and contrast sensitivity.

Tear-film dynamics were analyzed by a synchronizing recording of double-pass (DP) and pupil retro-illumination (RI) images with contrast sensitivity (CS) measurements. Simultaneous DP and RI images were acquired in three subjects wearing contact lenses while keeping the eye open. Changes in contrast sensitivity for an 18 c/deg green grating were also estimated. From the DP retinal images, the effect of the tear film is described through the objective scattering index (OSI). This presented a negative correlation with the increase in CS during tear-film deterioration (as observed by RI imaging). These results show a relationship between visual outcome degradation due to tear-film breakup and the increase in intraocular scattering. This work shows a combined methodology for the evaluation of tear-film dynamics.

Haptic interface using tendon electrical stimulation with consideration of multimodal presentation

Background Our previous studies have shown that electrical stimulation from the skin surface to the tendon region (Tendon Electrical Stimulation: TES) can elicit a force sensation, and adjusting the current parameters can control the amount of the sensation. TES is thought to present a proprioceptive force sensation by stimulating receptors or sensory nerves responsible for recognizing the magnitude of the muscle contraction existing inside the tendon, so it can be a proprioceptive module of a small-size, low-cost force feedback device. But there is also suspect that TES presents only strong, noisy skin sensation. From previous study, it was found that TES has some limitation on varying sensations. Methods In this study, in addition to characterizing the proprioceptive sensation induced by TES, we constructed a multimodal presentation system reproducing a situation in which force is applied to the hand was offered, so as to investigate whether TES contributed to the reproduction of haptics cooperating with other modalities, rather than disturbing them. Specifically, we used vibration to present a cutaneous sensation and a visual head mounted display (HMD) system to present simultaneous images. Using this system, we also evaluated the efficacy of TES itself and that of the multimodal system involving TES. Results We found that TES, along with visual and vibration stimulation, contributed to the perception of a certain force. Conclusions Thus, TES appears to be an effective component of multimodal force sense presentation systems.

Three-dimensional reconstruction of CME-driven shock–streamer interaction from radio and EUV observations: a different take on the diagnostics of coronal magnetic fields

On 2014 October 30, a band-splitted type II radio burst associated with a coronal mass ejection (CME) observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamic Observatory (SDO) occurred over the southeast limb of the Sun. The fast expansion in all directions of the plasma front acted as a piston and drove a spherical fast shock ahead of it, whose outward progression was traced by simultaneous images obtained with the Nançay Radioheliograph (NRH). The geometry of the CME/shock event was recovered through 3D modeling, given the absence of concomitant stereoscopic observations, and assuming that the band-splitted type II burst was emitted at the intersection of the shock surface with two adjacent low-Alfvén speed coronal streamers. From the derived spatiotemporal evolution of the standoff distance between shock and CME leading edge, we were finally able to infer the magnetic field strength B in the inner corona. A simple radial profile of the form B(r) = (12.6 ± 2.5)r−4 nicely fits our results, together with previous estimates, in the range r = 1.1−2.0 R⊙.

Feasibility of multiple-view myocardial perfusion MRI using radial simultaneous multi-slice acquisitions.

PurposeDynamic contrast enhanced MRI of the heart typically acquires 2–4 short-axis (SA) slices to detect and characterize coronary artery disease. This acquisition scheme is limited by incomplete coverage of the left ventricle. We studied the feasibility of using radial simultaneous multi-slice (SMS) technique to achieve SA, 2-chamber and/or 4-chamber long-axis (2CH LA and/or 4CH LA) coverage with and without electrocardiography (ECG) gating using a motion-robust reconstruction framework.Methods12 subjects were scanned at rest and/or stress, free breathing, with or without ECG gating. Multiple sets of radial SMS k-space were acquired within each cardiac cycle, and each SMS set sampled 3 parallel slices that were either SA, 2CH LA, or 4CH LA slices. The radial data was interpolated onto Cartesian space using an SMS GRAPPA operator gridding method. Self-gating and respiratory states binning of the data were done. The binning information as well as a pixel tracking spatiotemporal constrained reconstruction method were applied to obtain motion-robust image reconstructions. Reconstructions with and without the pixel tracking method were compared for signal-to-noise ratio and contrast-to-noise ratio.ResultsFull coverage of the heart (at least 3 SA and 3 LA slices) during the first pass of contrast at every heartbeat was achieved by using the radial SMS acquisition. The proposed pixel tracking reconstruction improves the average SNR and CNR by 21% and 30% respectively, and reduces temporal blurring for both gated and ungated acquisitions.ConclusionAcquiring simultaneous multi-slice SA, 2CH LA and/or 4CH LA myocardial perfusion images in every heartbeat is feasible in both gated and ungated acquisitions. This can add confidence when detecting and characterizing coronary artery disease by revealing ischemia in different views, and by providing apical coverage that is improved relative to SA slices alone. The proposed pixel tracking framework improves the reconstruction while adding little computational cost.

A Framework for Measuring the Time-Varying Shape and Full-Field Deformation of Residual Limbs Using 3-D Digital Image Correlation.

This study proposes a novel framework for the measurement and analysis of residual limb shape and deformation, using a high-resolution and low-cost system. A multi-camera system was designed to capture sets of simultaneous images of the entire residuum surface. The images were analyzed using a specially developed open-source three-dimensional digital image correlation (3D-DIC) toolbox, to obtain the accurate time-varying shapes as well as the full-field deformation and strain maps on the residuum skin surface. Measurements on a transtibial amputee residuum were obtained during knee flexions, muscle contractions, and swelling upon socket removal. It was demonstrated that 3D-DIC can be employed to quantify with high resolution time-varying residuum shapes, deformations, and strains. Additionally, the enclosed volumes and cross-sectional areas were computed and analyzed. This novel low-cost framework provides a promising solution for the in vivo evaluation of residuum shapes and strains, as well as has the potential for characterizing the mechanical properties of the underlying soft tissues. These data may be used to inform data-driven computational algorithms for the design of prosthetic sockets, as well as of other wearable technologies mechanically interfacing with the skin.

Tensorized Principal Component Alignment: A Unified Framework for Multimodal High-Resolution Images Classification

High-resolution (HR) remote sensing (RS) imaging opens the door to very accurate geometrical analysis for objects. However, it is difficult to simultaneous use massive HR RS images in practical applications, because these HR images are often collected in different multimodal conditions (multisource, multiarea, multitemporal, multiresolution, and multiangular) and learning method trained for one situation is difficult to use for others. The key problem is how to simultaneously tackle three main problems: spectral drift, spatial deformation, and band inconsistency. To deal with these problems, we propose an unsupervised tensorized principal component alignment framework in this paper. In this framework, local spatial–spectral patch data are used as basic units in order to achieve simultaneously multidimensional alignment. This framework seeks a domain-invariant tensor feature space by learning multilinear mapping functions which align the source tensor subspace with the target tensor subspace on different dimensions. In addition, an approach based on the Mahalanobis distance for dimensionality estimation of tensor subspace is proposed to determine best sizes of the aligned tensor subspace for reducing computational complexity. HR images from GF-1, GF-2, DEIMOS-2, WorldView-2, and WorldView-3 satellites are used to evaluate the performance. The experimental results show the following two points: first, the proposed alignment framework for multimodal HR images not only can align the different multimodal data more accurately than existing state-of-the-art domain adaptation methods, but also has a fast and simple procedure for large-scale data situation which is caused by HR imaging. Second, the proposed tensor dimensionality estimation method is an efficient technology for seeking the intrinsic dimensions of high-order data.

Evolution of Asymmetrically Displaced Footpoints During Substorms

AbstractIt is well established that a transverse (y) component in the interplanetary magnetic field (IMF) induces a By component in the closed magnetosphere through asymmetric loading and/or redistribution of magnetic flux. Simultaneous images of the aurora in the two hemispheres have revealed that conjugate auroral features are displaced longitudinally during such conditions. Although the direction and magnitude of this displacement show correlations with IMF clock angle and dipole tilt, single events show large temporal and spatial variability of this displacement. For instance, we know little about how the displacement changes during a substorm. A previous case study demonstrated that displaced auroral forms, associated with the prevailing IMF orientation, returned to a more symmetric configuration during the expansion phase of two substorms. Using the far ultraviolet cameras on board the Imager for Magnetopause‐to‐Aurora Global Exploration and Polar satellites, we have identified multiple events where conjugate auroral images are available during periods with substorm activity and IMF By≠0. We identify conjugate auroral features and investigate how the asymmetry evolves during the expansion phase. We find that the system returns to a more symmetric state in the events with a clear increase in the nightside reconnection rate and that the displacement remains unchanged in the events with little or no net closure of open magnetic flux. The return to a more symmetric state can therefore be interpreted as the result of increased reconnection rate in the magnetotail during the expansion phase, which reduces the asymmetric lobe pressure.

WFIRST Exoplanet Mass-measurement Method Finds a Planetary Mass of 39 ± 8 M⊕ for OGLE-2012-BLG-0950Lb

Abstract We present the analysis of the simultaneous high-resolution images from the Hubble Space Telescope and Keck adaptive optics system of the planetary event OGLE-2012-BLG-0950 that determine that the system consists of a 0.58 ± 0.04 host star orbited by a 39 ± 8 planet at a projected separation of 2.54 ± 0.23 au. The planetary system is located at a distance of 2.19 ± 0.23 kpc from Earth. This is the second microlens planet beyond the snow line with a mass measured to be in the mass range 20–80 . The runaway gas accretion process of the core accretion model predicts fewer planets in this mass range. This is because giant planets are thought to be growing rapidly at these masses, and they rarely complete growth at this mass. So this result suggests that the core accretion theory may need revision. This analysis also demonstrates the techniques that will be used to measure the masses of planets and their host stars by the WFIRST exoplanet microlensing survey: one-dimensional microlensing parallax combined with the separation and brightness measurement of the unresolved source and host stars to yield multiple redundant constraints on the masses and distance of the planetary system.

SPHERE/ZIMPOL high resolution polarimetric imager

Context. The SPHERE “planet finder” is an extreme adaptive optics (AO) instrument for high resolution and high contrast observations at the Very Large Telescope (VLT). We describe the Zurich Imaging Polarimeter (ZIMPOL), the visual focal plane subsystem of SPHERE, which pushes the limits of current AO systems to shorter wavelengths, higher spatial resolution, and much improved polarimetric performance. Aims. We present a detailed characterization of SPHERE/ZIMPOL which should be useful for an optimal planning of observations and for improving the data reduction and calibration. We aim to provide new benchmarks for the performance of high contrast instruments, in particular for polarimetric differential imaging. Methods. We have analyzed SPHERE/ZIMPOL point spread functions (PSFs) and measure the normalized peak surface brightness, the encircled energy, and the full width half maximum (FWHM) for different wavelengths, atmospheric conditions, star brightness, and instrument modes. Coronagraphic images are described and the peak flux attenuation and the off-axis flux transmission are determined. Simultaneous images of the coronagraphic focal plane and the pupil plane are analyzed and the suppression of the diffraction rings by the pupil stop is investigated. We compared the performance at small separation for different coronagraphs with tests for the binary α Hyi with a separation of 92 mas and a contrast of Δm ≈ 6m. For the polarimetric mode we made the instrument calibrations using zero polarization and high polarization standard stars and here we give a recipe for the absolute calibration of polarimetric data. The data show small (< 1 mas) but disturbing differential polarimetric beam shifts, which can be explained as Goos-Hähnchen shifts from the inclined mirrors, and we discuss how to correct this effect. The polarimetric sensitivity is investigated with non-coronagraphic and deep, coronagraphic observations of the dust scattering around the symbiotic Mira variable R Aqr. Results. SPHERE/ZIMPOL reaches routinely an angular resolution (FWHM) of 22−28 mas, and a normalized peak surface brightness of SB0 − mstar ≈ −6.5m arcsec−2 for the V-, R- and I-band. The AO performance is worse for mediocre ≳1.0″ seeing conditions, faint stars mR ≳ 9m, or in the presence of the “low wind” effect (telescope seeing). The coronagraphs are effective in attenuating the PSF peak by factors of > 100, and the suppression of the diffracted light improves the contrast performance by a factor of approximately two in the separation range 0.06″−0.20″. The polarimetric sensitivity is Δp < 0.01% and the polarization zero point can be calibrated to better than Δp ≈ 0.1%. The contrast limits for differential polarimetric imaging for the 400 s I-band data of R Aqr at a separation of ρ = 0.86″ are for the surface brightness contrast SBpol( ρ)−mstar ≈ 8m arcsec−2 and for the point source contrast mpol( ρ)−mstar ≈ 15m and much lower limits are achievable with deeper observations. Conclusions. SPHERE/ZIMPOL achieves imaging performances in the visual range with unprecedented characteristics, in particular very high spatial resolution and very high polarimetric contrast. This instrument opens up many new research opportunities for the detailed investigation of circumstellar dust, in scattered and therefore polarized light, for the investigation of faint companions, and for the mapping of circumstellar Hα emission.

A stellar occultation by Vanth, a satellite of (90482) Orcus

A stellar occultation by the large trans-Neptunian object (90482) Orcus was predicted to occur on 2017 March 07. Observations were made at five sites in North and South America: the 0.6-m Astronomical Telescope of the University of Stuttgart (ATUS) at Sierra Remote Observatories, California; Las Cumbres Observatory's 1-m telescope at McDonald Observatory, Fort Davis, Texas (ELP); NASA's 3-m InfraRed Telescope Facility (IRTF) on Mauna Kea, Hawai'i; the 0.6-m Southeastern Association for Research in Astronomy (SARA-CT) telescope at Cerro Tololo, Chile; and the 4.1-m Southern Astrophysical Research (SOAR) telescope on Cerro Pachón, Chile. High-speed, visible-wavelength images were taken at all sites, in addition to simultaneous K-band images at the IRTF. Solid-body occultations were observed from two sites. Post-event reconstruction suggested an occultation of two different stars observed from two different sites. Follow-up, speckle imaging revealed a second star, which verified that the occulting body in both cases was Orcus’ satellite, Vanth. The two single-chord detections, with an anomalously large timing delay in one chord, have lengths of 291 ± 125 km and 434.4 ± 2.4 km. The observations, combined with a non-detection at a nearby site, allow a tight constraint of 443 ± 10 km to be placed on Vanth's size (assuming it is spherical). A 3-σ upper limit of 1–4 μbar (depending on constituent) is found for a global Vanth atmosphere. The immersion and emersion profiles are slightly different, with atmospheric constraints 40% higher on immersion than on emersion. No rings or other material were detected within ten thousand kms of Vanth, and beyond 8010 km from Orcus, to the tightest optical depth limit of ∼0.1 at ∼5 km scale. The occultation probed as close as 5040 km from Orcus, placing an optical depth limit of ∼0.3 at ∼5 km scale on any encircling material at that distance.

Interferometric out-of-focus imaging of freezing droplets

Abstract Interferometric out-of-focus images of freezing droplets are presented, and compared to simultaneous in-focus images. In these experiments, the freezing process is characterized by a breaking of the initial droplet’s glare points into a wide number of neighbor bright spots. The 2D-Fourier transforms of the interferometric patterns show an elliptical contour, with a central spot and eventually symmetric spread spots more or less intense, located around the position of the initial glare points of the liquid droplet (depending on the degree of freezing).

Unsupervised TOF Image Segmentation through Spectral Clustering and Region Merging

Time of Flight (TOF) cameras generate two simultaneous images, one of intensity and one of range. This allows to tackle segmentation problems in which the separate use of intensity or range information is not enough to extract objects of interest from the 3D scene. In turn, range information allows to obtain a normal vector estimation of each point of the captured surfaces. This article presents a semi-supervised spectral clustering method which combines intensity and range information as well as normal vector orientations to improve segmentation results. The main contribution of this article consists in the use of a statistical region merging as a final step of the segmentation method. The region merging process combines adjacent regions which satisfy a similarity criterion. The performance of the proposed method was evaluated over real images. The use of this final step presents preliminary improvements in the metrics evaluated.

Imaging of Discharge Plasma Channel Evolution Process of Microsecond Wire Explosion in Air

The discharge plasma channel (DPC) evolution process is observed by taking time-series self-emission intensified charge-coupled device (iCCD) photos and simultaneous shadow images. By adding neutral density filters before iCCD, the subtle structure of the DPC self-emission is observed. It is interesting that a treelike structure is observed soon after the voltage breakdown. Long exposure time photos demonstrate that this structure existed for hundreds of nanoseconds. An inner homogeneously luminous column arises latterly, forming a two-layer self-emission structure. Then, this column gradually occupies the whole DPC. Shadow images show that the expanding DPC maintains good axial uniformity, manifesting the long-standing uneven treelike structure only has limited impact on the energy distribution and the expansion process. The calculated expansion rate reaches its maximum value (4.75 km/s) not at the power peak, but 0.24 $\mu \text{s}$ after that. Then, the expansion rate undergoes fast drop and slow decline. In addition, it seems that the distributions of related plasma parameters experience an evolution from nonuniform to uniform.

Short-term Efficacy of Micropulse Yellow Laser in Non-center-involving Diabetic Macular Edema: Preliminary Results.

Objectives:The aim of this study was to evaluate the efficacy of micropulse yellow laser (MPL) on best corrected visual acuity (BCVA) and retinal thickness in patients with non-center-involving diabetic macular edema (DME).Materials and Methods:We retrospectively reviewed 9 eyes of 8 patients with non-center-involving DME who underwent MPL treatment between January 2015 and December 2016. BCVA (logMAR) and retinal thickness were evaluated before and 3 months after treatment. Maximum retinal thickness was determined manually from simultaneous spectral-domain optical coherence tomography images and recorded. The change in the measurements from before to after treatment was analyzed statistically.Results:Of the 8 patients, 3 were female and 5 were male. The mean age was 52.8 years. Two of the 9 eyes had received previous intravitreal anti-vascular endothelial growth factor injection(s). Median BCVA was improved 3 months after treatment, although the difference was not statistically significant (0.34 logMAR before and 0.29 logMAR after treatment). BCVA was improved in 4 eyes while it showed no change in the remaining 5 eyes. The mean retinal thickness was 470.6 μm at baseline and 416 μm at 3 months after MPL treatment (p=0.01). Retinal thickness decreased in all eyes after treatment.Conclusion:In this study, parafoveal retinal thickness showed significant decrease after MPL treatment in patients with DME. The limited increase in BCVA may be due to the inclusion of a low number of patients and only those with non-center-involving macular edema. MPL may be used as an alternative to conventional argon laser in non-center-involving DME.

Fully spherical stretchable silicon photodiodes array for simultaneous 360 imaging

Imaging is one of the important wonders of today's world. While everyday millions of snaps are taken, new advances like panoramic imaging have become increasingly popular. However, as of today an imaging system which can simultaneously capture images from all 360° viewpoints with a single sensor has not been achieved. Here, we show a physically flexible and stretchable version of arrayed silicon photodiodes made from low-cost bulk monocrystalline silicon (100) that can capture simultaneous omnidirectional images. The present report, with multiple wavelength detection, fast photoresponsivity, a wide viewing angle, selective aberration, and dynamic focusing enabled by 3D printed pneumatic actuators (note, today millions of image sensors can be integrated in mm2 area), overcomes previous demonstrations of only hemispherical photodetection capability. Such imaging capability will make unmanned air vehicles or self-driven cars safer, affordable augmented and virtual reality and more importantly, in-vivo biomedical imaging will be more effective.

Reconstructing Solar Wind Inhomogeneous Structures From Stereoscopic Observations in White Light: Small Transients Along the Sun‐Earth Line

AbstractThe Heliospheric Imagers (HI) onboard the two spacecraft of the Solar Terrestrial Relations Observatory (STEREO) provided white‐light images of transients in the solar wind from dual perspectives from 2007 to 2014. In this paper, we develop a new method to identify and locate the transients automatically from simultaneous images from the two inner telescopes, known as HI‐1, based on a correlation analysis. Correlation coefficient (cc) maps along the Sun‐Earth line are constructed for the period from 1 January 2010 to 28 February 2011. From the maps, transients propagating along the Sun‐Earth line are identified, and a 27‐day periodic pattern is revealed, especially for small‐scale transients. Such a periodicity in the transient pattern is consistent with the rotation of the Sun's global magnetic structure and the periodic crossing of the streamer structures and slow solar wind across the Sun‐Earth line, and this substantiates the reliability of our method and the high degree of association between the small‐scale transients of the slow solar wind and the coronal streamers. Besides, it is suggested by the cc map that small‐scale transients along the Sun‐Earth line are more frequent than large‐scale transients by a factor of at least 2, and that they quickly diffused into background solar wind within about 40 Rs in terms of the signal‐to‐noise ratio of white‐light emissions. The method provides a new tool to reconstruct inhomogeneous structures in the heliosphere from multiple perspectives.

Multi-beam scan analysis with a clinical LINAC for high resolution Cherenkov-excited molecular luminescence imaging in tissue.

Cherenkov-excited luminescence scanned imaging (CELSI) is achieved with external beam radiotherapy to map out molecular luminescence intensity or lifetime in tissue. Just as in fluorescence microscopy, the choice of excitation geometry can affect the imaging time, spatial resolution and contrast recovered. In this study, the use of spatially patterned illumination was systematically studied comparing scan shapes, starting with line scan and block patterns and increasing from single beams to multiple parallel beams and then to clinically used treatment plans for radiation therapy. The image recovery was improved by a spatial-temporal modulation-demodulation method, which used the ability to capture simultaneous images of the excitation Cherenkov beam shape to deconvolve the CELSI images. Experimental studies used the multi-leaf collimator on a clinical linear accelerator (LINAC) to create the scanning patterns, and image resolution and contrast recovery were tested at different depths of tissue phantom material. As hypothesized, the smallest illumination squares achieved optimal resolution, but at the cost of lower signal and slower imaging time. Having larger excitation blocks provided superior signal but at the cost of increased radiation dose and lower resolution. Increasing the scan beams to multiple block patterns improved the performance in terms of image fidelity, lower radiation dose and faster acquisition. The spatial resolution was mostly dependent upon pixel area with an optimized side length near 38mm and a beam scan pitch of P = 0.33, and the achievable imaging depth was increased from 14mm to 18mm with sufficient resolving power for 1mm sized test objects. As a proof-of-concept, in-vivo tumor mouse imaging was performed to show 3D rendering and quantification of tissue pO2 with values of 5.6mmHg in a tumor and 77mmHg in normal tissue.