Dr. Qian Cao Profile

Dr. Qian Cao

at US Food and Drug Administration

SPIE Involvement:

Author

Publications (15)

Proceedings Article | 3 April 2024 Presentation

An in silico generative trabecular bone model for radiomic analysis of bone health

Qian Cao, Gengxin Shi, Andrew Wang, Sriharsha Marupudi, Ravi Samala, Wojciech Zbijewski, Nicholas Petrick

Proceedings Volume 12930, 1293005 (2024) https://doi.org/10.1117/12.3009699

KEYWORDS: Bone, Radiomics, Data modeling, 3D microstructuring, 3D modeling, Computed tomography, Random forests, Modeling, Mahalanobis distance, Image resolution

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Proceedings Article | 5 May 2023 Presentation + Paper

Deep learning texture analysis for the assessment of trabecular bone stiffness in CT

Ran Yan, Qian Cao, Sriharsha Marupudi, Ravi Samala, Nicholas Petrick

Proceedings Volume 12468, 1246807 (2023) https://doi.org/10.1117/12.2654474

KEYWORDS: Bone, Radiomics, Education and training, 3D modeling, Performance modeling, Feature extraction, Image segmentation, Data modeling, Deep learning, X-ray computed tomography

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Evaluation of bone fracture risk is important for the diagnosis and treatment of osteoporosis. Bone stiffness is a major factor in determining overall bone strength and fracture risk. With recent improvements in the spatial resolution of CT systems, it is possible to visualize bone microstructure and extract texture features. It is hypothesized that bone texture can be used to improve the assessment of bone strength compared to using bone mineral density (BMD) alone. In this work, we develop image analysis models for bone stiffness estimation utilizing deep learning (DL) features, radiomics features, and gradient structure tensors (GSTs) to estimate trabecular bone stiffness for high-resolution CT. We base our analysis on a dataset containing micro-CT images of 70 individual lumbar vertebrae. Ten trabecular bone ROIs were extracted from each vertebral body and their bone structure was segmented. The mechanical stiffness of each ROI was estimated using micro-finite element (μFE) analysis. Blur and correlated noise derived from clinical high-resolution CT systems were then added to the trabecular bone ROIs to generate simulated high-resolution CT images. A 3D residual network (ResNet) was trained to extract DL features to predict μFE-derived bone stiffness from the simulated CT images. Radiomics and GST features of bone ROIs were also computed for the same task. The prediction results for DL, radiomics, and GST features combined showed the best performance with a root mean square error (RMSE) of 2.646 N/μm and an R2 of 0.881. The performance of DL features alone was better than using BMD alone or using radiomic features alone. Additionally, incorporating orientation information from GST into the models resulted in improved accuracy. We demonstrate that μFEestimated mechanical properties of lumbar vertebral trabecular bone can be inferred from high-resolution CT images and that a combination of DL, radiomic, and GST features provides the highest prediction performance.

Proceedings Article | 15 February 2021 Presentation

Assessment of bone fragility in projection images using radiomic features

Qian Cao, Nicholas Petrick, Stephanie Coquia, Kenny Cha, Rongping Zeng, Keith Wear, Berkman Sahiner, Qin Li

Proceedings Volume 11597, 1159713 (2021) https://doi.org/10.1117/12.2581489

KEYWORDS: Bone, Finite element methods, X-rays, X-ray imaging, Minerals, Computer simulations

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Proceedings Article | 16 March 2020 Paper

Model-based material decomposition with system blur modeling

Wenying Wang, Matthew Tivnan, Grace Gang, Yiqun Ma, Qian Cao, Minghui Lu, Josh Star-Lack, Richard Colbeth, Wojciech Zbijewski, J. Webster Stayman

Proceedings Volume 11312, 113123Q (2020) https://doi.org/10.1117/12.2549549

KEYWORDS: Systems modeling, Iodine, Scintillators, Imaging systems, X-rays, Computed tomography, Dual energy imaging

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Proceedings Article | 5 March 2020 Presentation + Paper

Application of a novel ultra-high resolution multi-detector CT in quantitative imaging of trabecular microstructure

G. Shi, S. Subramanian, Q. Cao, S. Demehri, J. Siewerdsen, W. Zbijewski

Proceedings Volume 11317, 113171E (2020) https://doi.org/10.1117/12.2552385

KEYWORDS: Bone, Computed tomography, X-ray computed tomography, Image resolution, Spatial resolution, Scanners, Current controlled current source, Visualization, Error analysis, Diagnostics

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Purpose: To evaluate the performance of a novel ultra-high resolution multi-detector CT scanner (Canon Aquilion Precision UHR CT), capable of visualizing ~150 μm details, in quantitative assessment of bone microarchitecture. Compared to conventional CT, the spatial resolution of UHR CT begins to approach the size of the trabeculae. This might enable measurements of microstructural correlates of osteoporosis, osteoarthritis, and other bone disease. Methods: The UHR CT system features a 160-row x-ray detector with 250x250 μm pixels (measured at isocenter) and a custom-designed x-ray source with a 0.4x0.5 mm focal spot. Visualization of high contrast details down to ~150 μm has been achieved on this device, which is now commercially available for clinical use. To evaluate the performance of UHR CT in quantification of bone microstructure, we imaged a variety of human bone samples (including ulna, hamate, radius, and vertebrae) embedded in a ~16 cm diameter plastic cylinder and in an anthropomorphic thorax phantom (QRM-Thorax, QRM Gmbh). Helical UHR CT acquisitions (120 kVp tube voltage) were acquired at scan exposures of 375 mAs - 5 mAs. For comparison, the samples were also imaged using a Normal Resolution (NR) mode available on the scanner, involving 500 μm slice thickness, exposure of 50 mAs, and a focal spot of 0.6x1.3 mm. We obtained micro-CT (μCT) of the bone samples at ~28 μm voxel size as a gold-standard reference. Geometric measurements of bone microstructure were performed in 17 regions-of-interests (ROIs) distributed throughout the bones of the phantoms; image registration was used to place the ROIs at corresponding locations in the UHR CT and NR CT. Trabecular thickness Tb.Th, spacing Tb.Sp, and Bone Volume fraction BvTv were obtained. The UHR and NR imaging protocols were compared terms of correlations to μCT and error of trabecular measurements. The effect of dose on trabecular morphometry was also studied for the UHR CT. Furthermore, we evaluated the sensitivity of texture features of trabecular bone (recently proposed as an alternative to geometric indices of microstructure) to imaging protocol. Image texture evaluation was performed using ~150 regions of interest (ROIs) across all bone samples. Three-dimensional Gray Level Co-occurrence Matrix (GLCM) and Gray Level Run Length Matrix (GLRM) features were extracted for each ROI. We analyzed correlation and concordance correlation coefficient (CCC) of the mean ROI values of texture features obtained using the UHR and NR modes. Results: UHR CT reconstructions of bone samples clearly demonstrated improved visualization of the trabeculae compared to NR CT. UHR CT achieved substantially better correlations for all three metrics of bone microstructure, in particular for BvTv (correlation coefficient of 0.91 for UHR CT compared to 0.84 for NR CT) and TbSp (correlation of 0.74 for UHR CT and 0.047 for NR CT). The error obtained with UHR CT was generally smaller than that of NR CT. For TbSp, the mean deviation from CT (averaged across all bone samples) was only ~0.07 for UHR CT, compared to 0.25 for NR CT. Analysis of reproducibility of texture features of trabecular bone between UHR CT and NR CT revealed fair correlations (<0.7) for the majority of GLCM features, but relatively poor CCC (e.g. 0.02 for Energy and 0.04 for Entropy). The magnitude of texture metrics is particularly affected by the enhanced spatial resolution of UHR CT. Conclusion: The recently introduced UHR CT achieves improved correlation and reduced error in measurements of trabecular bone microstructure compared to conventional resolution CT. Future development of diagnostic strategies based on textural biomarkers derived from UHR CT will need to account for potential sensitivity of texture features to image resolution.

Proceedings Article | 2 March 2020 Presentation + Paper

Quantitative assessment of weight-bearing fracture biomechanics using extremity cone-beam CT

S. Liu, Q. Cao, G. Osgood, J. Siewerdsen, J. W. Stayman, W. Zbijewski

Proceedings Volume 11317, 113170I (2020) https://doi.org/10.1117/12.2549768

KEYWORDS: 3D modeling, Clouds, Image registration, Model-based design, Computed tomography, Metals, Scanners, Calcium, Surgery, Bone

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Purpose: We investigate an application of multisource extremity Cone-Beam CT (CBCT) with capability of weight-bearing tomographic imaging to obtain quantitative measurements of load-induced deformation of metal internal fixation hardware (e.g. tibial plate). Such measurements are desirable to improve the detection of delayed fusion or non-union of fractures, potentially facilitating earlier return to weight-bearing activities. Methods: To measure the deformation, we perform a deformable 3D-2D registration of a prior model of the implant to its CBCT projections under load-bearing. This Known-Component Registration (KC-Reg) framework avoids potential errors that emerge when the deformation is estimated directly from 3D reconstructions with metal artifacts. The 3D-2D registration involves a free-form deformable (FFD) point cloud model of the implant and a 3D cubic B-spline representation of the deformation. Gradient correlation is used as the optimization metric for the registration. The proposed approach was tested in experimental studies on the extremity CBCT system. A custom jig was designed to apply controlled axial loads to a fracture model, emulating weight-bearing imaging scenarios. Performance evaluation involved a Sawbone tibia phantom with an ~4 mm fracture gap. The model was fixed with a locking plate and imaged under five loading conditions. To investigate performance in the presence of confounding background gradients, additional experiments were performed with a pre-deformed femoral plate placed in a water bath with Ca bone mineral density inserts. Errors were measured using eight reference BBs for the tibial plate, and surface point distances for the femoral plate, where a prior model of deformed implant was available for comparison. Results: Both in the loaded tibial plate case and for the femoral plate with confounding background gradients, the proposed KC-Reg framework estimated implant deformations with errors of <0.2 mm for the majority of the investigated deformation magnitudes (error range 0.14 - 0.25 mm). The accuracy was comparable between 3D-2D registrations performed from 12 x-ray views and registrations obtained from as few as 3 views. This was likely enabled by the unique three-source x-ray unit on the extremity CBCT scanner, which implements two off-central-plane focal spots that provided oblique views of the field-of-view to aid implant pose estimation. Conclusion: Accurate measurements of fracture hardware deformations under physiological weight-bearing are feasible using an extremity CBCT scanner and FFD 3D-2D registration. The resulting deformed implant models can be incorporated into tomographic reconstructions to reduce metal artifacts and improve quantification of the mineral content of fracture callus in CBCT volumes.

Proceedings Article | 28 May 2019 Paper

Known-component model-based material decomposition for dual energy imaging of bone compositions in the presence of metal implant

S. Liu, S. Tilley, Q. Cao, J. Siewerdsen, J. Stayman, W. Zbijewski

Proceedings Volume 11072, 1107213 (2019) https://doi.org/10.1117/12.2534725

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Dual energy computed tomography (DE CT) is a promising technology for the assessment of bone compositions. One of potential applications involves evaluations of fracture healing using longitudinal measurements of callus mineralization. However, imaging of fractures is often challenged by the presence of metal fixation hardware. In this work, we report on a new simultaneous DE reconstruction-decomposition algorithm that integrates the previously introduced Model-Based Material Decomposition (MBMD) with a Known-Component (KC) framework to mitigate metal artifacts. The algorithm was applied to the DE data obtained on a dedicated extremity cone-beam CT (CBCT) with capability for weight-bearing imaging. To acquire DE projections in a single gantry rotation, we exploited a unique multisource design of the system, where three X-ray sources were mounted parallel to the axis of rotation. The central source provided high energy (HE) data at 120 kVp, while the two remaining sources were operated at a low energy (LE) of 60 kVp. This novel acquisition trajectory further motivates the use of MBMD to accommodate this complex DE sampling pattern. The algorithm was validated in a simulation study using a digital extremity phantom. The phantom consisted of a water background with an insert containing varying concentrations of calcium (50 – 175 mg/mL). Two configurations of titanium implants were considered: a fixation plate and an intramedullary nail. The accuracy of calcium-water decompositions obtained with the proposed KC-MBMD algorithm was compared to MBMD without metal component model. Metal artifacts were almost completely removed by KC-MBMD. Relative absolute errors of calcium concentration in the vicinity of metal were 6% - 31% for KC-MBMD (depending on the calcium insert and implant configuration), compared favorably to 48% - 273% for MBMD. Moreover, accuracy of concentration estimates for KC-MBMD in the presence of metal implant approached that of MBMD in a configuration without implant (6%-23%). The proposed algorithm achieved accurate DE material decomposition in the presence of metal implants using a non-conventional, axial multisource DE acquisition pattern.

Proceedings Article | 15 March 2019 Presentation + Paper

Quantitative evaluation of bone microstructure using high-resolution extremity cone-beam CT with a CMOS detector

S. Subramanian, M. Brehler, Q. Cao, F. Quevedo Gonzalez, R. Breighner, J. Carrino, T. Wright, J. Yorkston, J. Siewerdsen, W. Zbijewski

Proceedings Volume 10953, 1095317 (2019) https://doi.org/10.1117/12.2515504

KEYWORDS: Bone, Image segmentation, Spatial resolution, Imaging systems, CMOS sensors, Sensors, Prototyping, Scintillators, X-ray detectors, Scanners

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Purpose: A high-resolution cone-beam CT (CBCT) system for extremity imaging has been developed using a custom complementary metal–oxide–semiconductor (CMOS) x-ray detector. The system has spatial resolution capability beyond that of recently introduced clinical orthopedic CBCT. We evaluate performance of this new scanner in quantifying trabecular microstructure in subchondral bone of the knee. Methods: The high-resolution scanner uses the same mechanical platform as the commercially available Carestream OnSight 3D extremity CBCT, but replaces the conventional amorphous silicon flat-panel detector (a-Si:H FPD with 0.137 mm pixels and a ~0.7 mm thick scintillator) with a Dalsa Xineos3030 CMOS detector (0.1 mm pixels and a custom 0.4 mm scintillator). The CMOS system demonstrates ~40% improved spatial resolution (FWHM of a ~0.1 mm tungsten wire) and ~4x faster scan time than FPD-based extremity CBCT (FPD-CBCT). To investigate potential benefits of this enhanced spatial resolution in quantitative assessment of bone microstructure, 26 trabecular core samples were obtained from four cadaveric tibias and imaged using FPD-CBCT (75 μm voxels), CMOS-CBCT (75 μm voxels), and reference micro-CT (μCT, 15 μm voxels). CBCT bone segmentations were obtained using local Bernsen’s thresholding combined with global histogram-based pre-thresholding; μCT segmentation involved Otsu’s method. Measurements of trabecular thickness (Tb.Th), spacing (Tb.Sp), number (Tb.N) and bone volume (BV/TV) were performed in registered regions of interest in the segmented CBCT and μCT reconstructions. Results: CMOS-CBCT achieved noticeably improved delineation of trabecular detail compared to FPD-CBCT. Correlations with reference μCT for metrics of bone microstructure were better for CMOS-CBCT than FPD-CBCT, in particular for Tb.Th (increase in Pearson correlation from 0.84 with FPD-CBCT to 0.96 with CMOS-CBCT) and Tb.Sp (increase from 0.80 to 0.85). This improved quantitative performance of CMOS-CBCT is accompanied by a reduction in scan time, from ~60 sec for a clinical high resolution protocol on FPD-CBCT to ~17 sec for CMOS-CBCT. Conclusion: The CMOS-based extremity CBCT prototype achieves improved performance in quantification of bone microstructure, while retaining other diagnostic capabilities of its FPD-based precursor, including weight-bearing imaging. The new system offers a promising platform for quantitative imaging of skeletal health in osteoporosis and osteoarthritis.

Proceedings Article | 1 March 2019 Presentation + Paper

Quantitative cone-beam CT of bone mineral density using model-based reconstruction

Q. Cao, A. Sisniega, J. W. Stayman, J. Yorkston, J. H. Siewerdsen, W. Zbijewski

Proceedings Volume 10948, 109480Y (2019) https://doi.org/10.1117/12.2513216

KEYWORDS: Calcium, Bone, Model-based design, Minerals, Monte Carlo methods, X-ray computed tomography, Sensors, Tissues, Metals, Calibration

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Purpose: We develop and validate a model-based framework for artifact correction and image reconstruction to enable application of Cone-Beam CT (CBCT) in quantitative assessment of bone mineral density (BMD). Compared to conventional quantitative CT, this approach does not require a BMD calibration phantom in the field-of-view during an object scan. Methods: The quantitative CBCT (qCBCT) imaging framework combined fast Monte Carlo (MC) scatter estimation, accurate models of detector response, and polyenergetic Poisson likelihood (PolyPL, Elbakri et al 2003). The underlying object model assumed that the tissues were ideal mixtures of water and calcium carbonate (CaCO3). Accuracy and reproducibility of qCBCT was evaluated in benchtop test-retest studies emulating a compact extremity CBCT system (axis-detector distance=56 cm, 90 kVp x-ray beam, ~16 mGy central dose). Various arrangements of Ca inserts (50 – 500 mg/mL) were placed in water cylinders of ~11 cm to ~15 cm diameter and scanned at multiple positions inside the fieldof- view for a total of 20 configurations. In addition, a cadaveric ankle was imaged in five configurations (with and without Ca inserts and water bath). Coefficient of variation (CV) of BMD values across different experimental configurations was used to assess reproducibility under varying imaging conditions. The performance of the model-based qCBCT framework (MC + PolyPL) was compared to FDK with water beam hardening correction and MC scatter correction. Results: The PolyPL framework achieved accuracy of 20 mg/mL or better across all insert densities and experimental configurations. By comparison, the accuracy of the FDK-based BMD estimates deteriorated with higher mineralization, resulting in ~120 mg/mL error for a 500 mg/mL Ca insert. Additionally, the model-based approach mitigated residual streaks that were present in FDK reconstructions. The CV of both methods was ~15% at 50 mg/mL Ca and less than ~8% for higher density inserts, where the PolyPL framework achieved 20-25% lower CV than the FDK-based approach. Conclusion: Accurate and reproducible BMD measurements can be achieved in extremity CBCT, supporting clinical applications in quantitative monitoring of fracture risk, osteoporosis treatment, and early osteoarthritis.

Proceedings Article | 12 March 2018 Paper

Robust quantitative assessment of trabecular microarchitecture in extremity cone-beam CT using optimized segmentation algorithms

M. Brehler, Q. Cao, K. Moseley, G. Osgood, C. Morris, S. Demehri, J. Yorkston, J. Siewerdsen, W. Zbijewski

Proceedings Volume 10578, 105781J (2018) https://doi.org/10.1117/12.2293346

KEYWORDS: Image segmentation, Bone, Image processing algorithms and systems, Image enhancement, Detection and tracking algorithms, In vivo imaging, Algorithm development

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Purpose: In-vivo evaluation of bone microarchitecture remains challenging because of limited resolution of conventional orthopaedic imaging modalities. We investigate the performance of flat-panel detector extremity Cone-Beam CT (CBCT) in quantitative analysis of trabecular bone. To enable accurate morphometry of fine trabecular bone architecture, advanced CBCT pre-processing and segmentation algorithms are developed.

Methods: The study involved 35 transilliac bone biopsy samples imaged on extremity CBCT (voxel size 75 μm, imaging dose ~13 mGy) and gold standard μCT (voxel size 7.67 μm). CBCT image segmentation was performed using (i) global Otsu’s thresholding, (ii) Bernsen’s local thresholding, (iii) Bernsen’s local thresholding with additional histogram-based global pre-thresholding, and (iv) the same as (iii) but combined with contrast enhancement using a Laplacian Pyramid. Correlations between extremity CBCT with the different segmentation algorithms and gold standard μCT were investigated for measurements of Bone Volume over Total Volume (BV/TV), Trabecular Thickness (Tb.Th), Trabecular Spacing (Tb.Sp), and Trabecular Number (Tb.N).

Results: The combination of local thresholding with global pre-thresholding and Laplacian contrast enhancement outperformed other CBCT segmentation methods. Using this optimal segmentation scheme, strong correlation between extremity CBCT and μCT was achieved, with Pearson coefficients of 0.93 for BV/TV, 0.89 for Tb.Th, 0.91 for Tb.Sp, and 0.88 for Tb.N (all results statistically significant). Compared to a simple global CBCT segmentation using Otsu’s algorithm, the advanced segmentation method achieved ~20% improvement in the correlation coefficient for Tb.Th and ~50% improvement for Tb.Sp.

Conclusions: Extremity CBCT combined with advanced image pre-processing and segmentation achieves high correlation with gold standard μCT in measurements of trabecular microstructure. This motivates ongoing development of clinical applications of extremity CBCT in in-vivo evaluation of bone health e.g. in early osteoarthritis and osteoporosis.

Proceedings Article | 9 March 2018 Presentation + Paper

High-resolution extremity cone-beam CT with a CMOS detector: evaluation of a clinical prototype in quantitative assessment of bone microarchitecture

Q. Cao, M. Brehler, A. Sisniega, S. Tilley, M. Shiraz Bhurwani, J. Stayman, J. Yorkston, J. Siewerdsen, W. Zbijewski

Proceedings Volume 10573, 105730R (2018) https://doi.org/10.1117/12.2293810

KEYWORDS: Bone, CMOS sensors, Image segmentation, Prototyping, Sensors, Scanners, Modulation transfer functions, Imaging systems, Amorphous silicon, Scintillators

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Purpose: A prototype high-resolution extremity cone-beam CT (CBCT) system based on a CMOS detector was developed to support quantitative in vivo assessment of bone microarchitecture. We compare the performance of CMOS CBCT to an amorphous silicon (a-Si:H) FPD extremity CBCT in imaging of trabecular bone.

Methods: The prototype CMOS-based CBCT involves a DALSA Xineos3030 detector (99 μm pixels) with 400 μm-thick CsI scintillator and a compact 0.3 FS rotating anode x-ray source. We compare the performance of CMOS CBCT to an a- Si:H FPD scanner built on a similar gantry, but using a Varian PaxScan2530 detector with 0.137 mm pixels and a 0.5 FS stationary anode x-ray source. Experimental studies include measurements of Modulation Transfer Function (MTF) for the detectors and in 3D image reconstructions. Image quality in clinical scenarios is evaluated in scans of a cadaver ankle. Metrics of trabecular microarchitecture (BV/TV, Bone Volume/Total Volume, TbSp, Trabecular Spacing, and TbTh, trabecular thickness) are obtained in a human ulna using CMOS CBCT and a-Si:H FPD CBCT and compared to gold standard μCT.

Results: The CMOS detector achieves ~40% increase in the f20 value (frequency at which MTF reduces to 0.20) compared to the a-Si:H FPD. In the reconstruction domain, the FWHM of a 127 μm tungsten wire is also improved by ~40%. Reconstructions of a cadaveric ankle reveal enhanced modulation of trabecular structures with the CMOS detector and soft-tissue visibility that is similar to that of the a-Si:H FPD system. Correlations of the metrics of bone microarchitecture with gold-standard μCT are improved with CMOS CBCT: from 0.93 to 0.98 for BV/TV, from 0.49 to 0.74 for TbTh, and from 0.9 to 0.96 for TbSp.

Conclusion: Adoption of a CMOS detector in extremity CBCT improved spatial resolution and enhanced performance in metrics of bone microarchitecture compared to a conventional a-Si:H FPD. The results support development of clinical applications of CMOS CBCT in quantitative imaging of bone health.

Proceedings Article | 9 March 2017 Presentation + Paper

High-resolution extremity cone-beam CT with a CMOS detector: task-based optimization of scintillator thickness

Q. Cao, M. Brehler, A. Sisniega, J. Stayman, J. Yorkston, J. Siewerdsen, W. Zbijewski

Proceedings Volume 10132, 1013210 (2017) https://doi.org/10.1117/12.2255695

KEYWORDS: Modulation transfer functions, Scintillators, CMOS sensors, X-ray computed tomography, Bone, Image resolution, Systems modeling, X-ray detectors

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Purpose: CMOS x-ray detectors offer small pixel sizes and low electronic noise that may support the development of novel high-resolution imaging applications of cone-beam CT (CBCT). We investigate the effects of CsI scintillator thickness on the performance of CMOS detectors in high resolution imaging tasks, in particular in quantitative imaging of bone microstructure in extremity CBCT. Methods: A scintillator thickness-dependent cascaded systems model of CMOS x-ray detectors was developed. Detectability in low-, high- and ultra-high resolution imaging tasks (Gaussian with FWHM of ~250 μm, ~80 𝜇m and ~40 μm, respectively) was studied as a function of scintillator thickness using the theoretical model. Experimental studies were performed on a CBCT test bench equipped with DALSA Xineos3030 CMOS detectors (99 μm pixels) with CsI scintillator thicknesses of 400 μm and 700 𝜇m, and a 0.3 FS compact rotating anode x-ray source. The evaluation involved a radiographic resolution gauge (0.6-5.0 lp/mm), a 127 μm tungsten wire for assessment of 3D resolution, a contrast phantom with tissue-mimicking inserts, and an excised fragment of human tibia for visual assessment of fine trabecular detail. Results: Experimental studies show ~35% improvement in the frequency of 50% MTF modulation when using the 400 μm scintillator compared to the standard nominal CsI thickness of 700 μm. Even though the high-frequency DQE of the two detectors is comparable, theoretical studies show a 14% to 28% increase in detectability index (d’2) of high- and ultra- high resolution tasks, respectively, for the detector with 400 μm CsI compared to 700 μm CsI. Experiments confirm the theoretical findings, showing improvements with the adoption of 400 μm panel in the visibility of the radiographic pattern (2x improvement in peak-to-through distance at 4.6 lp/mm) and a 12.5% decrease in the FWHM of the tungsten wire. Reconstructions of the tibial plateau reveal enhanced visibility of trabecular structures with the CMOS detector with 400 μm scinitllator. Conclusion: Applications on CMOS detectors in high resolution CBCT imaging of trabecular bone will benefit from using a thinner scintillator than the current standard in general radiography. The results support the translation of the CMOS sensor with 400 μm scinitllator.

Proceedings Article | 22 March 2016 Paper

Image-based motion compensation for high-resolution extremities cone-beam CT

A. Sisniega, J. Stayman, Q. Cao, J. Yorkston, J. Siewerdsen, W. Zbijewski

Proceedings Volume 9783, 97830K (2016) https://doi.org/10.1117/12.2217243

KEYWORDS: Computed tomography, Motion estimation, Spatial resolution, Visualization, Motion models, Image restoration, Bone, Tissues, Reconstruction algorithms, Motion measurement, X-ray computed tomography

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SPIE Journal Paper | 12 August 2013 Open Access

Multispectral imaging in the extended near-infrared window based on endogenous chromophores

Qian Cao, Natalia Zhegalova, Steven Wang, Walter Akers, Mikhail Berezin

JBO, Vol. 18, Issue 10, 101318, (August 2013) https://doi.org/10.1117/12.10.1117/1.JBO.18.10.101318

KEYWORDS: Tissues, Absorption, Proteins, Near infrared, Chromophores, Multispectral imaging, Indium gallium arsenide, Imaging systems, Absorbance, Water

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Proceedings Article | 22 February 2013 Paper

Multi-spectral analysis of animal tissues in the second NIR window based on endogenous chromophores

Qian Cao, Steven Wang, Natalia Zhegalova, Walter Akers, Mikhail Berezin

Proceedings Volume 8587, 85870V (2013) https://doi.org/10.1117/12.2008786

KEYWORDS: Tissues, Near infrared, Chromophores, Absorption, Indium gallium arsenide, Scattering, Imaging systems, Optical properties, Spectrophotometry, Tissue optics

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