An adult and pediatric size-based contrast administration reduction phantom study for single and dual-energy CT through preservation of contrast-to-noise ratio.

BACKGROUND: Global shortages of iodinated contrast media (ICM) during COVID-19 pandemic forced the imaging community to use ICM more strategically in CT exams. PURPOSE: The purpose of this work is to provide a quantitative framework for preserving iodine CNR while reducing ICM dosage by either lowering kV in single-energy CT (SECT) or using lower energy virtual monochromatic images (VMI) from dual-energy CT (DECT) in a phantom study. MATERIALS AND METHODS: In SECT study, phantoms with effective diameters of 9.7, 15.9, 21.1, and 28.5 cm were scanned on SECT scanners of two different manufacturers at a range of tube voltages. Statistical based iterative reconstruction and deep learning reconstruction were used. In DECT study, phantoms with effective diameters of 20, 29.5, 34.6, and 39.7 cm were scanned on DECT scanners from three different manufacturers. VMIs were created from 40 to 140 keV. ICM reduction by lowering kV levels for SECT or switching from SECT to DECT was calculated based on the linear relationship between iodine CNR and its concentration under different scanning conditions. RESULTS: On SECT scanner A, while matching CNR at 120 kV, ICM reductions of 21%, 58%, and 72% were achieved at 100, 80, and 70 kV, respectively. On SECT scanner B, 27% and 80% ICM reduction was obtained at 80 and 100 kV. On the Fast-kV switch DECT, with CNR matched at 120 kV, ICM reductions were 35%, 30%, 23%, and 15% with VMIs at 40, 50, 60, and 68 keV, respectively. On the dual-source DECT, ICM reductions were 52%, 48%, 42%, 33%, and 22% with VMIs at 40, 50, 60, 70, and 80 keV. On the dual-layer DECT, ICM reductions were 74%, 62%, 45%, and 22% with VMIs at 40, 50, 60, and 70 keV. CONCLUSIONS: Our work provided a quantitative baseline for other institutions to further optimize their scanning protocols to reduce the use of ICM.

Patient Radiation Doses in IR Procedures: The American College of Radiology Dose Index Registry-Fluoroscopy Pilot.

PURPOSE: To update normative data on fluoroscopy dose indices in the United States for the first time since the Radiation Doses in Interventional Radiology study in the late 1990s. MATERIALS AND METHODS: The Dose Index Registry-Fluoroscopy pilot study collected data from March 2018 through December 2019, with 50 fluoroscopes from 10 sites submitting data. Primary radiation dose indices including fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA) were collected for interventional radiology fluoroscopically guided interventional (FGI) procedures. Clinical facility procedure names were mapped to the American College of Radiology (ACR) common procedure lexicon. Distribution parameters including the 10th, 25th, 50th, 75th, 95th, and 99th percentiles were computed. RESULTS: Dose indices were collected for 70,377 FGI procedures, with 50,501 ultimately eligible for analysis. Distribution parameters are reported for 100 ACR Common IDs. FT in minutes, Ka,r in mGy, and PKA in Gy-cm2 are reported in this study as (n; median) for select ACR Common IDs: inferior vena cava filter insertion (1,726; FT: 2.9; Ka,r: 55.8; PKA: 14.19); inferior vena cava filter removal (464; FT: 5.7; Ka,r: 178.6; PKA: 34.73); nephrostomy placement (2,037; FT: 4.1; Ka,r: 39.2; PKA: 6.61); percutaneous biliary drainage (952; FT: 12.4; Ka,r: 160.5; PKA: 21.32); gastrostomy placement (1,643; FT: 3.2; Ka,r: 29.1; PKA: 7.29); and transjugular intrahepatic portosystemic shunt placement (327; FT: 34.8; Ka,r: 813.0; PKA: 181.47). CONCLUSIONS: The ACR DIR-Fluoro pilot has provided state-of-the-practice statistics for radiation dose indices from IR FGI procedures. These data can be used to prioritize procedures for radiation optimization, as demonstrated in this work.

Patient Radiation Doses in Interventional Radiology Procedures: Comparison of Fluoroscopy Dose Indices between the American College of Radiology Dose Index Registry-Fluoroscopy Pilot and the Radiation Doses in Interventional Radiology Study.

PURPOSE: To compare radiation dose index distributions for fluoroscopically guided interventions in interventional radiology from the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR-Fluoro) pilot to those from the Radiation Doses in Interventional Radiology (RAD-IR) study. MATERIALS AND METHODS: Individual and grouped ACR Common identification numbers (procedure types) from the DIR-Fluoro pilot were matched to procedure types in the RAD-IR study. Fifteen comparisons were made. Distribution parameters, including the 10th, 25th, 50th, 75th, and 95th percentiles, were compared for fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA). Two derived indices were computed using median dose indices. The procedure-averaged reference air kerma rate (Ka,r¯) was computed as Ka,r / FT. The procedure-averaged x-ray field size at the reference point (Ar) was computed as PKA / (Ka,r × 1,000). RESULTS: The median FT was equally likely to be higher or lower in the DIR-Fluoro pilot as it was in the RAD-IR study, whereas the maximum FT was almost twice as likely to be higher in the DIR-Fluoro pilot than it was in the RAD-IR study. The median Ka,r was lower in the DIR-Fluoro pilot for all procedures, as was median PKA. The maximum Ka,r and PKA were more often higher in the DIR-Fluoro pilot than in the RAD-IR study. Ka,r¯ followed the same pattern as Ka,r, whereas Ar was often greater in DIR-Fluoro. CONCLUSIONS: The median dose indices have decreased since the RAD-IR study. The typical Ka,r rates are lower, a result of the use of lower default dose rates. However, opportunities for quality improvement exist, including renewed focus on tight collimation of the imaging field of view.

Degradation of bisphenol A by persulfate activation of MoS2 composite iron tailings.

In this paper, molybdenum disulfide was grown on the surface of iron-containing tailings by hydrothermal method, and a series of highly efficient activated persulfate (PMS) iron-based catalysts were successfully prepared. The results show that in the CTM 1-200/PMS system, the additional ratio of tailings and the hydrothermal temperature have important effects on the catalyst. The catalyst prepared under the conditions of CT:MoS2 (molar ratio 1:1) and hydrothermal temperature of 200 °C (CTM 1-200) had the best degradation effect on BPA, and the degradation effect was increased by four times. The reason for the improvement of degradation efficiency is that the introduction of MoS2 accelerates the REDOX cycle between Fe(II)/Fe(III), and the reduction of Fe(III) is mainly related to Mo(IV), while the reduction capacity of S is relatively weak. Molybdenum disulfide/iron tailing composite material provides a way for tailings to solve the problem of water pollution.

Recycling iron from pickling sludge to activate peroxydisulfate for the degradation of phenol.

In this work, iron was recovered from a kind of iron-rich pickling sludge by an acid leaching process, and the recycled iron was used as a catalyst to activate peroxydisulfate (PS) for the degradation of phenol. Different kinds of sludge catalysts were prepared by different drying methods such as ordinary drying (Ods), freeze drying (Fds) and vacuum drying (Vds). The degradation performance of the different catalysts/PS system under different conditions was explored, the vacuum drying sludge catalyst (Vds) has the best activity in a wide pH range (pH = 3-10) and a wide temperature range (0-40 °C). At the same time, the effect of a series of chelating agents (Oxalic acid (OA), Citric acid (CA), Tartaric acid (TA), Malic acid (DL-MA) and Ethylenediaminetetraacetic acid (EDTA)) on Vds/PS system was verified, and TA was selected as the best chelating agent to promote the degradation of the second stage where the degradation rate is limited. The quenching experiment and electron paramagnetic resonance (EPR) analysis indicated that hydroxyl radical (·OH) and sulfate radical (SO4̇-) were responsible for the abatement of the organic contaminant with ·OH playing a more important role. In summary, this study proposed an environmentally-friendly approach for the application of iron-rich pickling sludge in the remediation of phenol-contaminated water.

Enlarging field of view by a two-step method in a near-eye 3D holographic display.

The narrow field of view (FOV) has always been one of the most with limitations that drag the development of holographic three-dimensional (3D) near-eye display (NED). The complex amplitude modulation (CAM) technique is one way to realize holographic 3D display in real time with the advantage of high image quality. Previously, we applied the CAM technique on the design and integration of a compact colorful 3D-NED system. In this paper, a viewing angle enlarged CAM based 3D-NED system using a Abbe-Porter scheme and curved reflective structure is proposed. The viewing angle is increased in two steps. An Abbe-Porter filter system, composed of a lens and a grating, is used to enlarge the FOV for the first step and, meanwhile, realize complex amplitude modulation. A curved reflective structure is used to realize the FOV enlargement for the second step. Besides, the system retains the ability of colorful 3D display with high image quality. Optical experiments are performed, and the results show the system could present a 45.2° diagonal viewing angle. The system is able to present dynamic display as well. A compact prototype is fabricated and integrated for wearable and lightweight design.

Full-color see-through near-eye holographic display with 80° field of view and an expanded eye-box.

A full-color see-through near-eye holographic display is proposed with 80° field of view (FOV) and an expanded eye-box. The system is based on a holographic optical element (HOE) to achieve a large FOV while the image light is focused at the entrance to human pupil and the image of entire field enters human eye. As we know, one of the major limitations of the large FOV holographic display system is the small eye-box that needs to be expanded. We design a double layer diffraction structure for HOE to realize eye-box expansion. The HOE consists of two non-uniform volume holographic gratings and a transparent substrate. Two fabricated holographic gratings are attached to front and back surfaces of the substrate to multiplex image light and achieve eye-box expansion. Simultaneously, the HOE is also manufactured for RGB colors to realize full-color display. The experiment results show that our proposed display system develops 80° round FOV and an enlarged eye-box of 7.5 mm (H) ×5 mm (V) at the same time. The dynamic display ability is also tested in the experiments. The proposed system provides a new solution for the practical application of augmented reality display.

Fast method for calculating a curved hologram in a holographic display.

A curved hologram can increase the view angle in a holographic display. The huge data processing and curved computer-generated hologram (CCGH) computation time is still a challenge for real-time display. Here, we propose two fast methods to accelerate the computation. The first one is a diffraction compensation (DC) method where the diffraction calculation is from the wave-front recording plane (WRP) to a CCGH. The other is an approximate compensation (AC) method that adds a phase difference distribution to the WRP to obtain the CCGH. Numerical simulations and optical experiments are performed, which demonstrate that the two methods are feasible and the computation time is dramatically reduced. The AC method can further reduce time significantly compared with the DC method. And the image quality for proposed methods is similar. It is expected that these fast methods can be combined with curved display screen and flexible display materials in the future.

The American College of Radiology Fluoroscopy Dose Index Registry Pilot: Technical Considerations and Dosimetric Performance of the Interventional Fluoroscopes.

PURPOSE: To characterize the accuracy and consistency of fluoroscope dose index reporting and report rates of occupational radiation safety hardware availability and use, trainee participation in procedures, and optional hardware availability at pilot sites for the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR). MATERIALS AND METHODS: Nine institutions participated in the registry pilot, providing fluoroscopic technical and clinical practice data from 38 angiographic C-arm-type fluoroscopes. These data included measurements of the procedure table and mattress transmission factors and accuracy measurements of the reference-point air kerma (Ka,r) and air kerma-area product (PKA). The accuracy of the radiation dose indices were analyzed for variation over time by 1-way analysis of variance (ANOVA). Sites also self-reported information on availability and use of radiation safety hardware, hardware configuration of fluoroscopes, and trainee participation in procedures. RESULTS: All Ka,r and PKA measurements were within the ±35% regulatory limit on accuracy. The mean absolute difference between correction factors for a given system in fluoroscopic and acquisition mode was 0.03 (95% confidence interval, 0.03-0.03). For the 28 fluoroscopic imaging planes that provided data for 3 time points, ANOVA yielded an F value of 0.134 with an F-critical value of 3.109 (P = .875). CONCLUSIONS: This publication provides the technical and clinical framework pertaining to the ACR Fluoroscopy DIR pilot and offers necessary context for future analysis of the clinical procedure radiation-dose data collected.

Dual-Energy CT: Lower Limits of Iodine Detection and Quantification.

Background Assessments of the quantitative limitations among the six commercially available dual-energy (DE) CT acquisition schemes used by major CT manufacturers could aid researchers looking to use iodine quantification as an imaging biomarker. Purpose To determine the limits of detection and quantification of DE CT in phantoms by comparing rapid peak kilovoltage switching, dual-source, split-filter, and dual-layer detector systems in six different scanners. Materials and Methods Seven 50-mL iohexol solutions were used, with concentrations of 0.03-2.0 mg iodine per milliliter. The solutions and water sample were scanned five times each in two phantoms (small, 20-cm diameter; large, 30 × 40-cm diameter) with six DE CT systems and a total of 10 peak kilovoltage settings or combinations. Iodine maps were created, and the mean iodine signal in each sample was recorded. The limit of blank (LOB) was defined as the upper limit of the 95% confidence interval of the water sample. The limit of detection (LOD) was defined as the concentration with a 95% chance of having a signal above the LOB. The limit of quantification (LOQ) was defined as the lowest concentration where the coefficient of variation was less than 20%. Results The LOD range was 0.021-0.26 mg/mL in the small phantom and 0.026-0.55 mg/mL in the large phantom. The LOQ range was 0.07-0.50 mg/mL in the small phantom and 0.20-1.0 mg/mL in the large phantom. The dual-source and rapid peak kilovoltage switching systems had the lowest LODs, and the dual-layer detector systems had the highest LODs. Conclusion The iodine limit of detection using dual-energy CT systems varied with scanner and phantom size, but all systems depicted iodine in the small and large phantoms at or below 0.3 and 0.5 mg/mL, respectively, and enabled quantification at concentrations of 0.5 and 1.0 mg/mL, respectively. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Hindman in this issue.

Novel computer-generated hologram encoding method based on partially temporal coherent light.

Partially temporal coherent light (PTCL) has been applied to holographic reconstruction to reduce speckle noise in display systems, while the encoding methods of computer-generated hologram (CGH), based on PTCL, have not been reported. We propose a novel method to encoding CGH, in which a PTCL with a broadband continuous spectrum is used to illuminate the object image. The continuous spectrum is discretized into different wavelengths and a weight value associated with PTCL power spectrum is assigned to each wavelength. The diffractive transmission is based on Fresnel diffraction theory. The phase distribution of the encoded CGH is obtained using the sum of multiplying the different CGH phase distributions of corresponding discrete wavelengths by the corresponding weight values. The modulation results without iteration are performed to verify the feasibility of the proposed method and the iterative algorithm is introduced to improve the quality of the modulation. The reconstructed images from the proposed encoding method exhibit high quality as compared with that obtained from the encoding method based on ideal temporal coherent light. Numerical simulations and optical experiments are good consistent with each other. The proposed method can provide a reference for various wave-front modulations.

A full-color compact 3D see-through near-eye display system based on complex amplitude modulation.

For complex amplitude modulation (CAM)-based three-dimensional (3D) near-eye systems, it is a challenge to realize colorful 3D display by using spatial light modulator (SLM) and grating. Here, a full-color compact 3D see-through near-eye display (NED) system by CAM is proposed. Computer generated holograms (CGHs) for different wavelengths are calculated separately. Each CGH contains two position-shifted sub-holograms and the separated distance is carefully calibrated to eliminate chromatic aberration. Colorful 3D images are synthesized through time-multiplexing. Color managements are performed and chromatic aberration of the system is analyzed to provide better colorful effect. The system structure is integrated to be compact and a prototype is implemented. Pre-compensation is added on CGHs to offset the system's assembling errors. Optical experiment results show that the proposed system can provide good 3D full-color see-through performance without vergence-accommodation conflict (VAC). Dynamic colorful display ability is also tested, which shows good potential for interactive NED in the future.

Formulas of partially spatial coherent light and design algorithm for computer-generated holograms.

Formulas of partially spatial coherent light are derived and its corresponding design algorithm is proposed for generating computer-generated holograms based on partially spatial coherent light. The partially coherent light is divided into two terms: spatially absolute coherent part and incoherent part. The former is propagated by angular spectrum method, while the latter is based on the optical transfer function. The related formulas are derived where the coherent function (degree of coherence) is related. A modified iterative algorithm is further developed for optimizing the phase distributions. Numerical simulations and optical experiments are both performed to verify the proposed algorithm. The results obtained by the proposed method and the traditional method are compared, and it is clear that the speckle contrasts in optical experiments are improved more than 46%, and the image quality is obviously improved. This method could also provide new applications for three-dimensional holographic display, beam shaping, and other wave-front modulation techniques.

Phantom Validation of Spectral Detector Computed Tomography-Derived Virtual Monoenergetic, Virtual Noncontrast, and Iodine Quantification Images.

PURPOSE: Spectral detector computed tomography (SDCT) is a new CT technology that uses a dual-layer detector to perform energy separation. We aim to assess 3 clinical concepts using a phantom model: noise profile across the virtual monoenergetic (VME) spectrum, accuracy of iodine quantification, and virtual noncontrast (VNC) reconstructions' ability to remove iodine contribution to attenuation. METHODS: Six vials containing varying concentrations of iodinated contrast (0-6 mg/mL) diluted in water were placed in a water bath and scanned on an SDCT scanner. Virtual monoenergetic (40-200 keV at 10-keV increments), iodine-no-water, and VNC reconstructions were created. Attenuation (in Hounsfield units [HU]), VME noise at each energy level, CT-derived iodine concentration, and VNC attenuation were recorded. RESULTS: Virtual monoenergetic noise was improved at all energies compared with conventional images (conventional, 9.8-11.2; VME, 7.5-9.5). Noise profile showed a slightly higher image noise at 40 keV, but was otherwise relatively flat across the energy spectrum. On iodine-no-water reconstructions, measured varied from actual iodine concentration by ±0.1 mg/mL (SD, 0.16-0.36). Virtual noncontrast attenuation was within 5 HU of water attenuation at all iodine concentrations. CONCLUSION: Reconstructions of SDCT show lower VME image noise, accurate iodine quantification, and VNC attenuation values within 5 HU of expected in a phantom model.

Design methods to generate a computer hologram for improving image quality.

In order to suppress the speckle noise on a holographic display, we propose two design methods to initialize the phase to generate a computer hologram illuminating with partially coherent light. We introduce an initial phase of the image in consideration of the relationship of gray value among adjacent pixels when generating the computer hologram. After simulations, we compare these two methods and conclude that one is better than the other in terms of running speed or quality of the reconstructed image. Finally, we perform experiments to verify the theory. It is expected that these methods can greatly enhance the quality of reconstructed images and could be widely applied in the holographic field in the future.

Compact see-through 3D head-mounted display based on wavefront modulation with holographic grating filter.

A compact see-through three-dimensional head-mounted display (3D-HMD) is proposed and investigated in this paper. Two phase holograms are analytically extracted from the object wavefront and uploaded on different zones of the spatial light modulator (SLM). A holographic grating is further used as the frequency filter to couple the separated holograms together for wavefront modulation. The developed preliminary prototype has a simple optical facility and a compact structure (133.8mm × 40.4mm × 35.4mm with a 47.7mm length viewing accessory). Optical experiments demonstrated that the proposed system can present 3D images to the human eye with full depth cues. Therefore, it is free of the accommodation-vergence conflict and visual fatigue problem. The dynamic display ability is also tested in the experiments, which provides a promising potential for the true 3D interactive display.

Design and fabrication of DOEs on multi- freeform surfaces via complex amplitude modulation.

A non-iterative design and precise fabrication method of diffractive optical elements (DOEs) on multiple freeform surfaces is proposed and investigated in this paper. Complex amplitude modulation (CAM) technology is applied to design complicated DOEs. The wave-front for desired DOEs fabrication is interfered with a plane wave and then be encoded to a pure phase hologram. Simulations for different DOEs (binary and gray scales) on freeform surfaces are performed and the relative errors are 0.56% and 0.78%, respectively. Since the reconstructed optical fields generated by spatial light modulator (SLM) can be recorded into light-sensitive materials (photopolymer), the DOEs fabrication is realized by optical exposure. The results show that the proposed method can design and fabricate DOEs on multi-freeform surfaces at one time with high quality. Since the CAM method ensures precise reconstruction without iterations, the fabrication is accurate as well as the design is fast. It is expected that the proposed method could be applied in the precise 3D optical fabrication and processing in the future.

Multi-region phase calibration of liquid crystal SLM for holographic display.

The liquid crystal spatial light modulator (SLM) is able to provide flexible wavefront control, whereas the initial phase and its response distortions will heavily influence the modulation accuracy. The currently existing calibration methods are tedious and time consuming. A novel multi-region calibration method for minimizing those distortions is proposed. The entire panel is divided into several local regions based on the similarity of phase response characteristic. The nonlinear phase response and static phase distortion of each local region are calibrated in the iterative division procedure. The calibration method is theoretically analyzed and experimentally verified. For the Jasper 4 K SLM panel, when five local regions are built, the root mean error of linear phase shifts is reduced to 0.1 rad and the compensation accuracy of the static phase distortion reaches 0.24 wavelength. The calibrated SLM is applied for the color holographic display and the results show that the reconstructed image quality is improved significantly. The proposed method is simpler and faster because of the reasonable regional division and lower calibration complexity. It could be used for the calibration of various phase only or complex modulators with high space bandwidth product in the future.

Dual-Energy CT for Quantification of Urinary Stone Composition in Mixed Stones: A Phantom Study.

OBJECTIVE: The purpose of this study was to assess the feasibility of using dual-energy CT to accurately quantify uric acid and non-uric acid components in urinary stones of mixed composition. MATERIALS AND METHODS: A total of 24 urinary stones were analyzed with micro CT to serve as the reference standard for uric acid and non-uric acid composition. These stones were placed in water phantoms to simulate body attenuation of slim to obese adults and scanned with a third-generation dual-source CT scanner by use of dual-energy modes adaptively selected on the basis of phantom size. CT number ratio, which is distinct for different materials, was calculated for each pixel of the stones. Each pixel was then classified as uric acid and non-uric acid by comparison of the CT number ratio with preset thresholds ranging from 1.10 to 1.70. Minimal, maximal, and root-mean-square errors were calculated by comparing composition with the reference standard, and the threshold with the minimal root-mean-square error was determined. A paired t test was performed to compare the stone composition determined with dual-energy CT with the reference standard obtained with micro CT. RESULTS: The optimal CT number ratio threshold ranged from 1.27 to 1.55, dependent on phantom size. The root-mean-square error ranged from 9.60% to 12.87% across all phantom sizes. Minimal absolute error ranged from 0.04% to 1.24% and maximal absolute error from 22.05% to 35.46%. Dual-energy CT and the reference micro CT did not differ significantly on uric acid and non-uric acid composition (paired t test, p = 0.20-0.96). CONCLUSION: Accurate quantification of uric acid and non-uric acid composition in mixed stones is possible with dual-energy CT.