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Coronary artery calcium scoring with photon-counting CT: first in vivo human experience
摘要： To evaluate the performance of photon-counting detector (PCD) computed tomography (CT) for coronary artery calcium (CAC) score imaging at standard and reduced radiation doses compared to conventional energy-integrating detector (EID) CT. A dedicated cardiac CT phantom, ten ex vivo human hearts, and ten asymptomatic volunteers underwent matched EID and PCD CT scans at different dose settings without ECG gating. CAC score, contrast, and contrast-to-noise ratio (CNR) were calculated in the cardiac CT phantom. CAC score accuracy and reproducibility was assessed in the ex vivo hearts. Standard radiation dose (120 kVp, reference mAs = 80) in vivo CAC scans were compared against dose-reduced CAC scans (75% dose reduction; reference mAs = 20) for image quality and CAC score reproducibility. Interstudy agreement was assessed by using intraclass correlation (ICC), linear regression, and Bland–Altman analysis with 95% confidence interval limits of agreement (LOA). Calcium-soft tissue contrast and CNR were significantly higher for the PCD CAC scans in the cardiac CT phantom (all P < 0.01). Ex vivo hearts: CAC score reproducibility was significantly higher for the PCD scans at the lowest dose setting (50 mAs) (P = 0.002); score accuracy was similar for both detector systems at all dose settings. In vivo scans: the agreement between standard dose and low dose CAC score was significantly better for the PCD than for the EID with narrower LOA in Bland–Altman analysis, linear regression slopes closer to 1 (0.96 vs. 0.84), and higher ICC values (0.98 vs. 0.93, respectively). Phantom and in vivo human studies showed PCD may significantly improve CAC score image quality and/or reduce CAC score radiation dose while maintaining diagnostic image quality.
关键词： Radiation dose reduction,Photon-counting CT,Coronary artery calcium score
更新于2025-09-23 15:23:52
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A correction method for range walk error in time-correlated single-photon counting using photomultiplier tube
摘要： Time-correlated single-photon counting (TCSPC) is one of the most active technologies for optical time-of-flight ranging and three-dimensional (3D) imaging. It has attracted much attention because of its high sensitivity, high ranging accuracy and excellent resolution. TCSPC is applicable for the cases of detecting weak signals, usually for the cases when the detection probability is not higher than 0.01 to 0.1 photons per signal period. However, the reflectivity of the targets to be measured varies greatly in practical applications. Usually the energy of the retuned signal from targets varies over two orders of magnitude. It is unrealistic to dynamically regulate the energy of the laser source at a high frequency to match the reflectivity of targets. A phenomenon of photon pile-up will occur in detecting strong signals, which will lead to a range walk error. The error is particular serious if the pulse width of the laser is relatively wide, such as a nanosecond laser which is extensively used in practical applications. Therefore, investigation of TCSPC under strong returned signal conditions has important significance to extend the application domains of the TCSPC lidar systems. In this paper, ranging accuracy under conditions of different signal intensities using PMT and one-stop TDC is focused on. The photon pile-up caused by the change of amplitude and distortion of reconstructed laser waveform are theoretically analyzed. A correction method for the range walk errors under strong signal situations is proposed and validated in a laser ranging experiment. The results show that, using the correction method, ranging errors can be reduced from 183 mm to 6 mm for the case when the average number of photon is 9.6. The applicable returned signal domain of the TCSPC technique is extended by two orders of magnitude compared to the conventional weak signals. The accuracy and flexibility of TCSPC ranging system will be greatly improved using the proposed error correction method under strong signal conditions.
关键词： Three-dimensional imaging,Lidar,Laser ranging,Photon counting
更新于2025-09-23 15:22:29
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Simulation of photon-counting detectors for conversion of dual-energy-subtracted computed tomography number to electron density
摘要： For accurate tissue-inhomogeneity correction in radiotherapy treatment planning, the author previously proposed a conversion of the energy-subtracted computed tomography (CT) number to electron density (ΔHU–ρe conversion). The purpose of the present study was to provide a method for investigating the accuracy of a photon-counting detector (PCD) used in the ΔHU–ρe conversion by performing dual-energy CT image simulations of a PCD system with two energy bins. To optimize the tube voltage and threshold energy, the image noise and errors in ρe calibration were evaluated using three types of virtual phantoms: a 35-cm-diameter pure water phantom, 33-cm-diameter solid water surrogate phantom equipped with 16 inserts, and another solid water surrogate phantom with a 25-cm diameter. The third phantom was used to investigate the effect of the object’s size on the ρe-calibration accuracy of PCDs. Two different scenarios for the PCD energy response were considered, corresponding to the ideal and realistic cases. In addition, a simple correction method for improving the spectral separation of the dual energies in a realistic PCD was proposed to compensate for its performance loss. In the realistic PCD case, there exists a trade-off between the image noise and ρe-calibration errors. Furthermore, the weakest image noise was nearly twice that for the ideal case, and the ρe-calibration error did not reach practical levels for any threshold energy. Nevertheless, the proposed correction method is likely to decrease the ρe-calibration errors of a realistic PCD to the level of the ideal case, yielding more accurate ρe values that are less affected by object size variation.
关键词： Energy-selective CT,Dual-energy CT,Electron density,Photon-counting detector
更新于2025-09-23 15:22:29
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Tomodensitométrie spectrale?: de la double énergie à la multiénergie
摘要： Standard computed tomography imaging allows the differentiation between anatomic structures based on their X-ray global attenuation difference. This difference, due to the Compton and photoelectric effects, depends essentially on the effective atomic number and electronic density of the elements evaluated. Spectral dual energy CT expends the capabilities of standard CT by distinguishing elements of same attenuation by their difference of Compton and photoelectric effects. The purpose of this didactic content is to introduce principles and explain the technology of spectral CT imaging, based on the attenuation difference at two different energies. Moreover, evolutions towards spectral multienergy CT will be introduced.
关键词： K-edge,Dual energy CT,Spectral CT,Spectral photon-counting CT,Contrast agents,Virtual monoenergetic image
更新于2025-09-23 15:22:29
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Generalized Likelihood Block Detection for SPAD-based Underwater VLC System
摘要： In the underwater visible light communication (VLC) system, the single photon avalanche diode (SPAD) can expand communication distance. However, the output signals from practical SPADs under dead time limit are not Poisson distributed. In this paper, the generalized likelihood block detection (GLBD) receiver is developed for practical SPAD-based underwater VLC system with on-off keying (OOK) modulation. The proposed receiver can detect the data sequence without any prior knowledge of the channel and the background radiation. Correspondingly, a fast search algorithm for GLBD receiver is also proposed. In addition, a block coding scheme is utilized to solve the error floor problem. Simulation results show that the bit error rate (BER) performance of the proposed receiver is closer to the BER low bound compared to the existing receiver. Moreover, the fast search algorithm reduces the computational complexity without any performance loss.
关键词： Underwater visible light communication,photon counting,blind detection
更新于2025-09-23 15:22:29
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Distance-Resolving Raman Radar Based on a Time-Correlated CMOS Single-Photon Avalanche Diode Line Sensor
摘要： Remote Raman spectroscopy is widely used to detect minerals, explosives and air pollution, for example. One of its main problems, however, is background radiation that is caused by ambient light and sample fluorescence. We present here, to the best of our knowledge, the first time a distance-resolving Raman radar device that is based on an adjustable, time-correlated complementary metal-oxide-semiconductor (CMOS) single-photon avalanche diode line sensor which can measure the location of the target sample simultaneously with the normal stand-off spectrometer operation and suppress the background radiation dramatically by means of sub-nanosecond time gating. A distance resolution of 3.75 cm could be verified simultaneously during normal spectrometer operation and Raman spectra of titanium dioxide were distinguished by this system at distances of 250 cm and 100 cm with illumination intensities of the background of 250 lux and 7600 lux, respectively. In addition, the major Raman peaks of olive oil, which has a fluorescence-to-Raman signal ratio of 33 and a fluorescence lifetime of 2.5 ns, were distinguished at a distance of 30 cm with a 250 lux background illumination intensity. We believe that this kind of time-correlated CMOS single-photon avalanche diode sensor could pave the way for new compact distance-resolving Raman radars for application where distance information within a range of several metres is needed at the same time as a Raman spectrum.
关键词： time-correlated single photon counting (TCSPC),remote Raman spectroscopy,CMOS single-photon avalanche diode (SPAD),time interval measurement,distance-resolving Raman radar,stand-off Raman spectrometer
更新于2025-09-23 15:21:21
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Pixel-to-pixel variation on a calibrated PILATUS3-based multi-energy soft x-ray detector
摘要： A multi-energy soft x-ray pin-hole camera based on the PILATUS3 100 K x-ray detector has recently been installed on the Madison Symmetric Torus. This photon-counting detector consists of a two-dimensional array of ～100 000 pixels for which the photon lower-threshold cutoff energy Ec can be independently set for each pixel. This capability allows the measurement of plasma x-ray emissivity in multiple energy ranges with a unique combination of spatial and spectral resolution and the inference of a variety of important plasma properties (e.g., T e, nZ, Z eff). The energy dependence of each pixel is calibrated for the 1.6–6 keV range by scanning individual trimbit settings, while the detector is exposed to ?uorescence emission from Ag, In, Mo, Ti, V, and Zr targets. The resulting data for each line are then ?t to a characteristic "S-curve" which determines the mapping between the 64 possible trimbit settings for each pixel. The statistical variation of this calibration from pixel-to-pixel was explored, and it was found that the discreteness of trimbit settings results in an effective threshold resolution of ?E < 100 eV. A separate calibration was performed for the 4–14 keV range, with a resolution of ?E < 200 eV.
关键词： energy calibration,x-ray detector,photon-counting,multi-energy soft x-ray,plasma x-ray emissivity,PILATUS3
更新于2025-09-23 15:21:21
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0.16 μm–BCD Silicon Photomultipliers with Sharp Timing Response and Reduced Correlated Noise
摘要： Silicon photomultipliers (SiPMs) have improved significantly over the last years and now are widely employed in many different applications. However, the custom fabrication technologies exploited for commercial SiPMs do not allow the integration of any additional electronics, e.g., on-chip readout and analog (or digital) processing circuitry. In this paper, we present the design and characterization of two microelectronics-compatible SiPMs fabricated in a 0.16 μm–BCD (Bipolar-CMOS-DMOS) technology, with 0.67 mm × 0.67 mm total area, 10 × 10 square pixels and 53% fill-factor (FF). The photon detection efficiency (PDE) surpasses 33% (FF included), with a dark-count rate (DCR) of 330 kcps. Although DCR density is worse than that of state-of-the-art SiPMs, the proposed fabrication technology enables the development of cost-effective systems-on-chip (SoC) based on SiPM detectors. Furthermore, correlated noise components, i.e., afterpulsing and optical crosstalk, and photon timing response are comparable to those of best-in-class commercial SiPMs.
关键词： Silicon photomultiplier (SiPM),photon counting,photon number resolution,optical crosstalk,time-correlated single-photon counting (TCSPC),afterpulsing
更新于2025-09-23 15:21:01
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Characterization of a Time-Resolved Diffuse Optical Spectroscopy Prototype Using Low-Cost, Compact Single Photon Avalanche Detectors for Tissue Optics Applications
摘要： Time-resolved diffuse optical spectroscopy (TR-DOS) is an increasingly used method to determine the optical properties of diffusive media, particularly for medical applications including functional brain, breast and muscle measurements. For medical imaging applications, important features of new generation TR-DOS systems are low-cost, small size and efficient inverse modeling. To address the issues of low-cost, compact size and high integration capabilities, we have developed free-running (FR) single-photon avalanche diodes (SPADs) using 130 nm silicon complementary metal-oxide-semiconductor (CMOS) technology and used it in a TR-DOS prototype. This prototype was validated using assessments from two known protocols for evaluating TR-DOS systems for tissue optics applications. Following the basic instrumental performance protocol, our prototype had sub-nanosecond total instrument response function and low differential non-linearity of a few percent. Also, using light with optical power lower than the maximum permissible exposure for human skin, this prototype can acquire raw data in reflectance geometry for phantoms with optical properties similar to human tissues. Following the MEDPHOT protocol, the absolute values of the optical properties for several homogeneous phantoms were retrieved with good accuracy and linearity using a best-fitting model based on the Levenberg-Marquardt method. Overall, the results of this study show that our silicon CMOS-based SPAD detectors can be used to build a multichannel TR-DOS prototype. Also, real-time functional monitoring of human tissue such as muscles, breasts and newborn heads will be possible by integrating this detector with a time-to-digital converter (TDC).
关键词： diffuse optical spectroscopy,time-resolved spectroscopy,tissue optics,single-photon avalanche diode,silicon photodetectors,time-correlated single-photon counting
更新于2025-09-23 15:21:01
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Photoresponse of current-biased superconductor/normal metal strip with large ratio of resistivities
摘要： Detection of electromagnetic radiation by superconductor is based on destruction of superconductivity by photons and corresponding change of resistance of superconducting sample. For example in the superconducting bolometer or transition edge sensor (TES) the superconductor is biased near the resistive transition, at temperature below the critical temperature Tc of superconductor [1, 2]. The absorbed photons heat up electrons in the detector, electron temperature increases and it leads to the increase of the temperature dependent resistance of superconductor R(T ). In such a detector the sharper the dependence R(T ) the higher sensitivity the superconducting detector has.
关键词： single photon counting,bolometric regime,photoresponse,superconductor,normal metal
更新于2025-09-23 15:21:01