Electron Density Reconstruction Research Articles

Electron density dual-energy CT can improve the detection of lumbar disc herniation with higher image quality than standard and virtual non-calcium images.

To compare the diagnostic performance and image quality of dual-energy computed tomography (DECT) with electron density (ED) image reconstruction with those of DECT with standard CT (SC) and virtual non-calcium (VNCa) image reconstructions, for diagnosing lumbar disc herniation (L-HIVD). A total of 59 patients (354 intervertebral discs from T12/L1 to L5/S1; mean age, 60 years; 30 women and 29 men) who underwent DECT with spectral reconstruction and 3-T MRI within 2 weeks were enrolled between March 2021 and February 2022. Four radiologists independently assessed three image sets of randomized ED, SC, and VNCa images to detect L-HIVD at 8-week intervals. The coefficient of variance (CV) and the Weber contrast of the ROIs in the normal and diseased disc to cerebrospinal fluid space (NCR-normal/-diseased, respectively) were calculated to compare the image qualities of the noiseless ED and other series. Overall, 129 L-HIVDs were noted on MRI. In the detection of L-HIVD, ED showed a higher AUC and sensitivity than SC and VNCa; 0.871 vs 0.807 vs 833 (p = 0.002) and 81% vs 70% vs 74% (p = 0.006 for SC), respectively. CV was much lower in all measurements of ED than those for SC and VNCa (p < 0.001). Furthermore, NCR-normal and NCR-diseased were the highest in ED (ED vs SC in NCR-normal and NCR-diseased, p = 0.001 and p = 0.004, respectively; ED vs VNCa in NCR-diseased, p = 0.044). Compared to SC and VNCa images, DECT with ED reconstruction can enhance the AUC and sensitivity of L-HIVD detection with a lower CV and higher NCR. To our knowledge, this is the first study to quantify the image quality of noiseless ED images. ED imaging may be helpful for detecting L-HIVD in patients who cannot undergo MRI. ED images have diagnostic potential, but relevant quantitative analyses of image quality are limited. ED images detect disc herniation, with a better coefficient of variance and normalized contrast ratio values. ED images could detect L-HIVD when MRI is not an option.

Characterization of mRNA Lipid Nanoparticles by Electron Density Mapping Reconstruction: X-ray Scattering with Density from Solution Scattering (DENSS) Algorithm.

This study aimed to test the feasibility of using Small Angle X-ray Scattering (SAXS) coupled with Density from Solution Scattering (DENSS) algorithm to characterize the internal architecture of messenger RNA-containing lipid nanoparticles (mRNA-LNPs). The DENSS algorithm was employed to construct a three-dimensional model of average individual mRNA-LNP. The reconstructed models were cross validated with cryogenic transmission electron microscopy (cryo-TEM), and dynamic light scattering (DLS) to assess size, morphology, and internal structure. Cryo-TEM and DLS complemented SAXS, revealed a core-shell mRNA-LNP structure with electron-rich mRNA-rich region at the core, surrounded by lipids. The reconstructed model, utilizing the DENSS algorithm, effectively distinguishes mRNA and lipids via electron density mapping. Notably, DENSS accurately models the morphology of the mRNA-LNPs as an ellipsoidal shape with a "bleb" architecture or a two-compartment structure with contrasting electron densities, corresponding to mRNA-filled and empty lipid compartments, respectively. Finally, subtle changes in the LNP structure after three freeze-thaw cycles were detected by SAXS, demonstrating an increase in radius of gyration (Rg) associated with mRNA leakage. Analyzing SAXS profiles based on DENSS algorithm to yield a reconstructed electron density based three-dimensional model can be a useful physicochemical characterization method in the toolbox to study mRNA-LNPs and facilitate their development.

MV-based relative electron density estimation (iMREDe) for MR-LINAC dose calculation.

MR-LINAC systems have been increasingly utilized for real-time imaging in adaptive treatments worldwide. Challenges in MR representation of air cavities and subsequent estimation of electron density maps impede planning efficiency and may lead to dose calculation uncertainties. To demonstrate the generation of accurate electron density maps using the primary MV beam with a flat-panel imager. The ViewRay MRIdian MR-LINAC system was modeled digitally for Monte Carlo simulations. Iron shimming, the magnetic field, and the proposed flat panel detector were included in the model. The effect of the magnetic field on the detector response was investigated. Acquisition of projections over 360 degrees was simulated for digital phantoms of the Catphan 505 phantom and a patient treated for Head and Neck cancer. Shim patterns on the projections were removed and detector noise linearity was assessed. Electron density maps were generated for the digital patient phantom using the flat-panel detector and compared with actual treatment planning CT generated electron density maps of the same patient. The effect of the magnetic field on the detector point-spread function (PSF) was found to be substantial for field strengths above 50 mT. Shims correction in the projection images using air normalization and in-painting effectively removed reconstruction artifacts without affecting noise linearity. The relative difference between reconstructed electron density maps from the proposed method and electron density maps generated from the treatment planning CT was 11% on average along all slices included in the iMREDe reconstruction. The proposed iMREDe technique demonstrated the feasibility of generating accurate electron densities for the ViewRay MRIdian MR-LINAC system with a flat-panel imager and the primary MV beam. This work is a step towards reducing the time and effort required for adaptive radiotherapy in the current ViewRay MR-LINAC systems.

A storm-time global electron density reconstruction model in three-dimensions based on artificial neural networks

We present results of a dedicated global storm-time model for the reconstruction of ionospheric electron density in three-dimensions. Using the storm criterion of |Dst|⩾50 nT and Kp⩾4, the model is constructed using a combination of radio occultation and ionosonde data during the periods of 2006–2021 and 2000–2020, respectively. From the ionosonde data, only the bottomside electron density profiles up to the maximum height of the F2 layer (hmF2) are considered. In addition to the selection of storm-time data only for the model development, we have investigated the inclusion of time history for the geomagnetic storm indicator Kp at 9 and 33 h in an attempt to take into account the delay of physical processes related to atmospheric gravity waves or traveling ionospheric disturbances and thermospheric composition changes which drive varying ionospheric storm effects during storm conditions. Based on incoherent scatter radar data and in comparison with the IRI 2020 model, the developed storm-time model provides foF2 modelling improvement of above 50% during the storm main phase over Millstone Hill (42.6°N, 71.5°W) and Tromsø (69.6°N, 19.2°E) for the storm periods of 3–6 November 2021 and 23–25 March 2023, respectively. Modelled results for Jicamarca (11.8°S, 77.2°W) show that the storm-time model estimates foF2 by an improvement of over 20% during the main phase of the 07–10 September 2017 storm period. As the ionospheric conditions return to quiet time levels, the IRI 2020 model perform better than the constructed storm -time model

A full reconstruction of two galaxy clusters intra-cluster medium with strong gravitational lensing

ABSTRACT Whilst X-rays and Sunyaev–Zel’dovich observations allow to study the properties of the intra-cluster medium (ICM) of galaxy clusters, their gravitational potential may be constrained using strong gravitational lensing. Although being physically related, these two components are often described with different physical models. Here, we present a unified technique to derive the ICM properties from strong lensing for clusters in hydrostatic equilibrium. In order to derive this model, we present a new universal and self-similar polytropic temperature profile, which we fit using the X-COP sample of clusters. We subsequently derive an analytical model for the electron density, which we apply to strong lensing clusters MACS J0242.5-2132 and MACS J0949.8+1708. We confront the inferred ICM reconstructions to XMM-Newton and ACT observations. We contrast our analytical electron density reconstructions with the best canonical β-model. The ICM reconstructions obtained prove to be compatible with observations. However they appear to be very sensitive to various dark matter halo parameters constrained through strong lensing (such as the core radius), and to the halo scale radius (fixed in the lensing optimizations). With respect to the important baryonic effects, we make the sensitivity on the scale radius of the reconstruction an asset, and use the inferred potential to constrain the dark matter density profile using ICM observations. The technique here developed should allow to take a new, and more holistic path to constrain the content of galaxy clusters.

An Extended Simultaneous Algebraic Reconstruction Technique for Imaging the Ionosphere Using GNSS Data and Its Preliminary Results

To generate high-quality reconstructions of ionospheric electron density (IED), we propose an extended simultaneous algebraic reconstruction technique (ESART). The ESART method distributes the discrepancy between the actual GNSS TEC and the calculated TEC among the ray–voxels based on the contribution of voxels to GNSS TEC, rather than the ratio of the length of ray–voxel intersection to the sum of the lengths of all ray–voxel intersections, as is adopted by conventional methods. The feasibility of the ESART method for reconstructing the IED under different levels of geomagnetic activities is addressed. Additionally, a preliminary experiment is performed using the reconstructed IED profiles and comparing them with ionosonde measurements, which provide direct observations of electron density. The root mean square errors (RMSE) and absolute errors of the ESART method, the simultaneous algebraic reconstruction technique (SART) method, and the International Reference Ionosphere (IRI) 2016 model are calculated to evaluate the effectiveness of the proposed method. Compared to the conventional SART method of ionospheric tomography and the IRI-2016 model, the reconstructed IED profiles obtained using the ESART method are in better agreement with the electron density obtained from the ionosondes, especially for the peak electron densities (NmF2). In addition, a case study of an intense geomagnetic storm on 17–19 March 2015 shows that the spatial and temporal features of storm-related ionospheric disturbances can be more clearly depicted using the ESART method than with the SART method.

Cones and spirals: Multi-axis acquisition for scalar and vector electron tomography

Electron tomography (ET) has become an important tool for understanding the 3D nature of nanomaterials, with recent developments enabling not only scalar reconstructions of electron density, but also vector reconstructions of magnetic fields. However, whilst new signals have been incorporated into the ET toolkit, the acquisition schemes have largely kept to conventional single-axis tilt series for scalar ET, and dual-axis schemes for magnetic vector ET. In this work, we explore the potential of using multi-axis tilt schemes including conical and spiral tilt schemes to improve reconstruction fidelity in scalar and magnetic vector ET. Through a combination of systematic simulations and a proof-of-concept experiment, we show that spiral and conical tilt schemes have the potential to produce substantially improved reconstructions, laying the foundations of a new approach to electron tomography acquisition and reconstruction.

A New Algorithm for Ill-Posed Problem of GNSS-Based Ionospheric Tomography

Ill-posedness of GNSS-based ionospheric tomography affects the stability and the accuracy of the inversion results. Truncated singular value decomposition (TSVD) is a common algorithm of ionospheric tomography reconstruction. However, the TSVD method usually has low inversion accuracy and reconstruction efficiency. To resolve the above problem, a truncated mapping singular value decomposition (TMSVD) algorithm is presented to improve the reconstructed accuracy and computational efficiency. To authenticate the effectiveness and the advantages of the TMSVD algorithm, a numerical test scheme is devised. Finally, ionospheric temporal–spatial variations of the selected reconstructed region are studied using the GNSS observations under different geomagnetic conditions. The reconstructed results of TMSVD can accurately reflect semiannual anomalies, diurnal variations, and geomagnetic storm effects. In contrast with the ionosonde data, it is found that the reconstructed profiles of the TMSVD method are more consistent with than those of the IRI 2016. The study suggests that TMSVD is an efficient algorithm for the tomographic reconstruction of ionospheric electron density (IED).

Mineral quantitative characterization method based on basis material decomposition model by dual-energy computed tomography.

Dual-energy computed tomography (DECT) can reconstruct electron density ρe and effective atomic number Zeff distribution for material discrimination. Image-domain basis material decomposition (IBMD) method is a widely used DECT method. However, IBMD method cannot be used for mineral identification directly due to limitations of complex basis material determination, beam hardening artifacts, and inherent errors caused by approximate empirical formulas. This study proposes an improved IBMD (IIBMD) method to overcome the above limitations. In IIBMD method, the composition of basis material is optimized to obtain accurate decomposition coefficients, which enables accurate ρe and Zeff distribution. Moreover, the thickness of basis material is optimized to reduce the effect of beam hardening. Furthermore, two formulas in place of empirical formulas are proposed to calculate ρe and Zeff. Finally, a threshold technique is applied to separate different mineral phases. Numerical simulations and practical experiments using a photon-counting detector CT system are implemented to verify IIBMD method. Results show that the relative errors of ρe and Zeff for seven common minerals are down to 5%, lower than most of the existing DECT methods for rocks. Reasonable volume fraction results of mineral phases are thus obtained through threshold segmentation. This study demonstrates that the proposed IIBMD method has high practical value in mineralogical identification.

Electron Density Changes and Ultrafast Carrier Dynamics of the Antiferromagnetic Semiconductor MnPS3 through Magnetic Phase Transition.

Studying ultrafast dynamics provides us with a way to modify materials from the timescale of particle interaction, and the related research on antiferromagnetic semiconductors is still inadequate. Based on the electron density reconstruction, we achieve the visualization of magnetic interactions of bulk antiferromagnetic MnPS3 in the ground state, reveal the role of two atomic site occupations of S atoms in different magnetic phase transitions, and provide the theoretical and experimental support for modifying magnetic properties by selectively replacing the S atom. The ultrafast carrier dynamics can provide information from the excited state to the ground state. Based on time-resolved transmittance measurements, ultrafast carrier dynamics of MnPS3 are reported. The phonon-assisted gap transition driven by the electronic structure is characterized. The coupling relationship among electrons, spin, and phonons is established. Furthermore, the spin orientations within different phases are confirmed.

Helium line ratio imaging in the C-2W divertor.

A 2D imaging instrument has been designed and deployed on C-2W ("Norman") [H. Gota et al., Nucl. Fusion 61, 106039 (2021)] to study the plasma in the expander divertor by simultaneously measuring three neutral helium spectral lines. Ratios of these images, in conjunction with a collisional-radiative model, yield 2D maps of electron temperature and density. Almost the entire radial plasma cross-section (∼60cm) can be mapped with a spatial resolution ≲1cm. These data can, in principle, be acquired at 3kHz. The neutral helium target is provided by a custom-built supersonic gas injector located inside the divertor vessel, which injects helium toward the magnetic axis and perpendicular to the camera sight-cone. Images of helium emission and reconstructed electron density and temperature profiles of the plasma produced from an end gun are presented. Voltages applied to concentric annular electrodes located in the divertors are used to stabilize beam-driven field reversed configuration plasmas. Magnetic field expansion is also employed to thermally isolate electrons from the end electrodes. Measurements of electron temperature and density in the divertor are important in order to study the effects of both the electrostatic biasing and the divertor magnetic field on electron confinement, neutral gas transport, and the overall machine performance.

Electron density profile reconstruction with convolutional neural networks

Convolutional neural networks are introduced into reconstructing electron density profiles from line-integrated density measurements of interferometers in the EAST tokamak. Diagnostic data from the polarimeter/interferometer and the hydrogen cyanide interferometer diagnostic systems are integrated to improve the reconstruction performance. By training and optimization with unreliable measurements in the data set, the robustness of this algorithm is enhanced. The established model can predict the probability distribution of density profiles accurately, fast, and robustly to noise and interference. This algorithm is not restricted to specific equilibrium configurations and can be transferred easily between different fusion devices.

SBAS ionospheric grid delay estimation based on ionospheric tomography: a case study on September 7–9, 2017

In Satellite-Based Augmentation Systems (SBASs), e.g., the US Wide-Area Augmentation System (WAAS), the planar method and the kriging method based on the thin-shell model have been used to estimate the ionospheric grid delay (IGD). Generally, the kriging method can achieve higher accuracy than the planar method. In comparison with the thin-shell model, ionospheric tomography overcomes the limitations of the 2D ionospheric delay modeling and can realize 3D or even 4D ionospheric electron density reconstructions, especially suitable over disturbed periods. For the first time by virtue of electron density inversions, a tomographic method and a kriging-combined tomographic method are proposed innovatively to apply for estimating IGDs over part of the WAAS region using 32 ground stations during ionospheric disturbances on September 7–9, 2017. Then, independent dual-frequency Global Positioning System (GPS) data at six stations are applied to validate estimated IGD results from these four methods. It is shown that the overall errors of the planar method, the kriging method, the tomographic method, and the kriging-combined tomographic method over 3 days are decreased one by one, while errors using the latter two methods are quite similar. When focusing on the strong disturbed times, the latter two tomographic methods can obtain more accurate IGD than the former two methods based on the thin shell model. Tomographic total electron content (TEC) maps over the study area are also reconstructed to help analyze the underlying mechanism at different stations. It is also noted that the kriging-combined tomography has little improvement in IGD estimates in comparison with the tomographic method alone during strong ionospheric disturbances.

Ionospheric Reconstruction Using GNSS Signals Around an Anomaly Crest Location in Indian Longitude Sector

AbstractThe present study aims to reconstruct the vertical ionospheric electron density (IED) profile using computerized ionospheric tomography (CIT) techniques, over the northern crest of the equatorial ionization anomaly (EIA) which is one of the most geo‐physically sensitive regions of Indian longitude sector. Total electron content (TEC) measurements obtained from GNSS signals from receivers located at Kolkata (22.57°N, 88.36°E), Purulia (23.33°N, 86.36°E), and Siliguri (26.73°N, 88.39°E) and International GNSS Service (IGS) stations of Port Blair (11.64°N, 92.71°E), Bangalore (13.02°N, 77.57°E), Hyderabad (17.42°N, 78.55°E), Lucknow (26.91°N, 80.96°E) and Lhasa (29.66°N, 91.10°E) have been incorporated into the tomography algorithm for ionospheric reconstructions. Among the different iterative techniques used for retrieving IED profiles on a 2‐dimensional altitude versus latitude plane fixed at a certain longitude, simultaneous iterative reconstruction technique (SIRT) was shown to be the optimum choice based on the representation of the EIA phenomenon and reconstruction accuracy. A comparative assessment between two ionospheric models IRI2016 and PIM1.4 was performed, with PIM based initial guess for inversions resulting in lower reconstruction errors. The 2D CIT algorithm was then used to reconstruct the hourly vertical IED profiles to study the impact of the severe G4‐class St. Patrick's Day storm on 17 March 2015 and reconstructed electron densities showed a large increase over the values obtained from the geomagnetically quiet day of 10 March 2015, indicating a positive ionospheric storm phase. Ionospheric response to the G1‐class geomagnetic disturbance on 5 December 2017 and the average F‐region IED values have also been compared with a geomagnetically quiet day of 3 December 2017.

First Experimental Quantitative Charge Density Studies of Advanced Intermediate of Vitamin D Analogues.

Vitamins D are a group of fat-soluble secosteroids which play a regulatory role in the functioning of most cells. Rational design of new vitamin D analogs, of increased therapeutic potency and lowered calcemic side effects, requires high-resolution initial structures and a deep understanding of interactions with the molecular targets. In this paper, using quantum crystallography, we present the first determination of the experimental quantitative charge density of an advanced intermediate of vitamin D analogues as well as a reconstruction of the theoretical electron density of final vitamin D analogues. Application of these methods allows for topological and electrostatic interaction energy analysis. We showed that the A-ring chair conformation has a significant influence on the topological properties of vitamin D compounds. Moreover, the interactions between the CD-ring and side-chain additionally stabilize the crystal structure. These results are supported by our theoretical calculations and previous biological studies.

Characteristics of the Effective Scale Height in the Topside Ionosphere Extracted From Swarm A and Digisonde Observations: Preliminary Results

AbstractThe ionospheric scale height is a key parameter that defines the shape of the electron density profile. Given that its direct calculation requires knowledge of the physical and chemical state of the plasma, the concept of the effective scale height was proposed to facilitate its application. It is defined as the scale height that fits the electron density profiles with the α‐Chapman function. Its main characteristics, including the diurnal and altitudinal variation are still under investigation. This paper focuses on the specification of its key characteristics at middle latitudes based on coincident Digisonde and Swarm A satellite data. Based on the assumption that the topside electron density profile is approximated with the α‐Chapman model of variable scale height, the effective scale height at the Swarm A altitude is calculated and compared with the effective scale height at . A general conclusion is that the topside effective scale height at ∼450 km exhibits a diurnal variation with highest values in the early morning and evening sectors, while at it gets its maximum values at noon. At night, the effective scale height tends to increase with altitude, however in the daytime, its behavior is more complex. On a local scale, evidence for connection between spread F irregularities and high variability in the topside effective scale height is reported. These preliminary results indicate the potential to further exploit Swarm and Digisonde data for the development of a model for the effective scale height, able to support realistic electron density reconstruction models.

Diagnostic performance of electron-density dual-energy CT in detection of cervical disc herniation in comparison with standard gray-scale CT and virtual non-calcium images.

ObjectivesTo assess the diagnostic performance of dual-energy CT (DECT) with electron-density (ED) image reconstruction compared with standard CT (SC) and virtual non-calcium (VNCa) image CT reconstruction for detecting cervical disc herniation.MethodsThis cross-sectional study was approved by the IRB. We enrolled 64 patients (336 intervertebral discs from C2/3 to C7/T1; mean age, 55 years; 17 women and 47 men) who underwent DECT with spectral reconstruction and 3-T MRI within 2 weeks between January 2018 and June 2020. Four radiologists independently evaluated the first image set of randomized SC, VNCa, and ED images to detect cervical disc herniation. After 8 weeks, the readers re-evaluated the second and the last image sets with an 8-week interval. MRI evaluations performed by two other experienced served as the reference standard. Comparing diagnostic performance between each images set was evaluated by a generalized estimating equation.ResultsA total of 233 cervical disc herniations were noted on MRI. For detecting cervical disc herniation, electron-density images showed higher sensitivity (94% [219/233; 95% CI, 90–97] vs. 76% [177/233; 70–81] vs. 69% [160/233; 62–76]) (p < 0.001) and similar specificity (90% [93/103; 83–95] vs. 89% [92/103; 82–96] vs. 90% [93/103; 83–95]) (p > 0.05) as SC and VNCa images, respectively. Inter-reader agreement for cervical disc herniation calculated among the four readers was moderate for all image sets (κ = 0.558 for ED, κ = 0.422 for SC, and κ = 0.449 for VNCa).ConclusionDECT with ED reconstruction can improve cervical disc herniation detection and diagnostic confidence compared with SC and VNCa images.Key Points• Intervertebral discs with high material density are well visualized on electron-density images obtained from dual-energy CT.• Electron-density images showed much higher sensitivity and diagnostic accuracy than standard CT and virtual non-calcium images for the detection of cervical disc herniation.• Electron-density images can have false-negative results, especially for disc herniation with high signal intensity on T2W images and can show pseudo-disc extrusion at the lower cervical spine.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00330-021-08374-y.

A Tomographic Method for the Reconstruction of the Plasmasphere Based on COSMIC/ FORMOSAT-3 Data

A tomographic method has been developed for reconstructing the topside ionospheric and plasmaspheric electron density distribution using total electron content (TEC) measurements from global positioning system (GPS) receivers aboard the constellation observing system for meteorology, ionosphere, and climate&#x002F;Formosa Satellite Mission 3 (COSMIC&#x002F;FORMOSAT-3). Since the COSMIC&#x002F;FORMOSAT-3 constellation has an orbit altitude of about 800 km, the integral TEC measurements obtained from the topside GPS navigation data are rather small and imposed relevant challenges to obtaining stable electron density reconstructions. However, the developed method can represent the natural variability of the plasma ambient in terms of latitude, altitude, solar activity, season, and local time when analyzing electron density reconstructions during 2008&#x2013;2013. The method employs independent spatial grids for satellite rising and setting geometries and imposes a set of constraints to stabilize the solution in the presence of noise and ill-conditioned geometry. We further consider background ionosphere and plasmasphere models for electron density initialization and filling data gaps. The quality assessment using TEC and <i>in-situ</i> electron density measurements has shown that the proposed method performs better than the background model, with improvements of about 26&#x0025; in TEC and 20&#x0025; in terms of electron density. Our investigation also reveals the necessity of more accurate background electron density representations and precise TEC measurements in order to have better plasmaspheric specifications at high altitudes.

Three-Step Tomographic Algorithm for Ionospheric Electron Density Reconstruction

In this work, a three-step algorithm for the tomographic reconstruction of ionospheric electron density (IED) is proposed. In the new algorithm, the Taylor series expansion of the multiplicative algebraic reconstruction technique is first introduced to perform an adaptive adjustment for the relaxation parameter vector. Second, the horizontal and vertical constraints are imposed on the tomography system aiming to reduce the dependence on the initial iteration values for those voxels without any rays traversing them. Third, the uniformed voxel size is replaced with the variable voxel size by adopting the unequal grid interval in the altitudinal direction. The feasibility and superiority of the three-step algorithm are validated by devising a numerical simulation scheme. Finally, the new algorithm is successfully used to obtain the 3-D IED distribution under magnetically quiet conditions. The comparisons of IED profiles and the statistics of the reconstruction error of different algorithms further validate the superiority of the three-step algorithm.

A Method for Automatic Scaling of Ionograms and Electron Density Reconstruction

Ionogram scaling is the process of reconstructing electron density with respect to height by using the measurements of a remote sensing instrument known as ionosonde. In this study, a novel two-stage ionogram scaling technique, ionogram scaling and electron density (ISED), is proposed. In the first stage, hidden Markov models (HMMs) are used to identify the actual ionospheric reflections in the ionosonde measurements. In the second stage, an International Reference Ionosphere extended to plasmasphere (IRI-Plas) model-based optimization problem is solved to obtain the vertical profile that generates the best least-squares fit to the reflections identified in the first stage. To show the performance of ISED in a global scale, experiments are conducted on 14812 ionograms recorded at the three different stations that are Pruhonice in Czech Republic, Eielson in USA, and São Luis in Brazil. Application of ISED to raw ionograms indicates 97.6% of the cases, and ISED provides accurate electron density reconstructions, which is an improvement about 8.7% over automatic real-time ionogram scaler with true height (ARTIST), most commonly used ionogram scaling technique.