@article{nokey,

title = {Design Optimization of Spatial-Spectral Filters for Cone-Beam CT Material Decomposition},

author = {Matt Tivnan and Wenying Wang and Grace Gang and J. Webster Stayman },

url = {https://pubmed.ncbi.nlm.nih.gov/35377842/, https://ieeexplore.ieee.org/abstract/document/9748122},

doi = {10.1109/TMI.2022.3164568},

year  = {2022},

date = {2022-04-04},

journal = {IEEE Transactions on Medical Imaging},

volume = {41},

issue = {9},

pages = {2399-2413},

keywords = {MBIR, Spectral X-ray/CT, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Tivnan2021b,

title = {A prototype spatial–spectral CT system for material decomposition with energy‐integrating detectors},

author = {Matt Tivnan and Wenying Wang and J. Webster Stayman },

url = {https://pubmed.ncbi.nlm.nih.gov/33964021/, https://aapm.onlinelibrary.wiley.com/doi/full/10.1002/mp.14930},

doi = {10.1002/mp.14930 },

year  = {2021},

date = {2021-10-01},

journal = {Medical Physics},

volume = {48},

issue = {10},

pages = {6401-6411},

keywords = {Sparse Sampling, Spectral X-ray/CT, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Taguchi2020,

title = {Three-dimensional regions-of-interest-based intra-operative 4-dimensional soft tissue perfusion imaging using a standard x-ray system with no gantry rotation: A simulation study for a proof of concept},

author = {Katsuyuki Taguchi and Thomas J. Sauer and W. Paul Segars and Eric Frey and Jingyan Xu and Eleni Liapi and J. Webster Stayman and Kelvin Hong and Ferdinand Hui and Mathias Unberath and Yong Du},

url = {https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7796930/},

doi = {10.1002/mp.14514},

year  = {2020},

date = {2020-12-01},

journal = {Medical Physics},

volume = {47},

number = {12},

pages = {6087-6102},

keywords = {Image Guided Surgery, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Wu2020,

title = {Cone-beam CT for imaging of the head/brain: Development and assessment of scanner prototype and reconstruction algorithms },

author = {Pengwei Wu and Alejandro Sisniega and J. Webster Stayman and Wojciech Zbijewski and David H. Foos and Xiaohui Wang and Nishanth Khanna and Nafi Aygun and R. Stevens and Jeffrey H. Siewerdsen},

url = {https://pubmed.ncbi.nlm.nih.gov/32145076/},

doi = {10.1002/mp.14124},

year  = {2020},

date = {2020-06-01},

journal = {Medical Physics},

volume = {47},

number = {6},

pages = {2392-2407},

keywords = {CBCT, Head/Neck, MBIR, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Gang2019b,

title = {Dynamic fluence field modulation in computed tomography using multiple aperture devices},

author = {Grace Gang and Andrew Mao and Wenying Wang and Jeffrey H. Siewerdsen and Aswin Mathews and Satomi Kawamoto and Reuven Levinson and J. Webster Stayman},

url = {https://iopscience.iop.org/article/10.1088/1361-6560/ab155e/meta},

doi = {10.1088/1361-6560/ab155e},

year  = {2019},

date = {2019-05-21},

journal = {Physics in Medicine and Biology},

volume = {64},

pages = {105024},

keywords = {Customized Acquisition, Dynamic Bowtie, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Sisniega2018,

title = {Image quality, scatter, dose in compact CBCT systems with flat and curved detectors},

author = {Alejandro Sisniega and Wojciech Zbijewski and Pengwei Wu and J. Webster Stayman and Vassilis Koliatsos and Nafi Aygun and R. Stevens and Xiaohui Wang and David H. Foos and Jeffrey H. Siewerdsen },

url = {https://www.spiedigitallibrary.org/conference-proceedings-of-spie/10573/2293872/Image-quality-scatter-and-dose-in-compact-CBCT-systems-with/10.1117/12.2293872.full},

doi = {10.1117/12.2293872},

year  = {2018},

date = {2018-02-15},

journal = {Proc. SPIE Medical Imaging},

volume = {10573},

pages = {1015734E-1-7},

keywords = {Artifact Correction, Head/Neck, Scatter Estimation, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Cao2018,

title = {Modeling and evaluation of a high-resolution CMOS detector for cone-beam CT of the extremities},

author = {Qian Cao and Alejandro Sisniega and Michael Brehler and J. Webster Stayman and John Yorkston and Jeffrey H. Siewerdsen and Wojciech Zbijewski},

url = {https://aapm.onlinelibrary.wiley.com/doi/full/10.1002/mp.12654},

doi = {10.1002/mp.12654},

year  = {2018},

date = {2018-01-01},

journal = {Medical Physics},

volume = {45},

number = {1},

pages = {114-130},

keywords = {Extremities, High-Resolution CT, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{Xu2016b,

title = {Technical assessment of a prototype cone-beam CT system for imaging of acute intracranial hemorrhage},

author = {Jennifer Xu and Alejandro Sisniega and Wojciech Zbijewski and Hao Dang and J. Webster Stayman and Michael Mow and Xiaohui Wang and David H. Foos and Vassilis Koliatsos and Nafi Aygun and Jeffrey H. Siewerdsen},

url = {http://doi.wiley.com/10.1118/1.4963220},

doi = {10.1118/1.4963220},

issn = {00942405},

year  = {2016},

date = {2016-09-29},

journal = {Medical Physics},

volume = {43},

number = {10},

pages = {5745-5757},

keywords = {Head/Neck, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{xu2016evaluation,

title = {Evaluation of detector readout gain mode and bowtie filters for cone-beam CT imaging of the head.},

author = {Jennifer Xu and Alejandro Sisniega and Wojciech Zbijewski and Hao Dang and J. Webster Stayman and Xiaohui Wang and David H. Foos and Nafi Aygun and Vassilis Koliatsos and Jeffrey H. Siewerdsen},

url = {http://www.ncbi.nlm.nih.gov/pubmed/27435162},

doi = {10.1088/0031-9155/61/16/5973},

issn = {1361-6560},

year  = {2016},

date = {2016-08-01},

journal = {Physics in medicine and biology},

volume = {61},

number = {16},

pages = {5973--92},

publisher = {IOP Publishing},

abstract = {The effects of detector readout gain mode and bowtie filters on cone-beam CT (CBCT) image quality and dose were characterized for a new CBCT system developed for point-of-care imaging of the head, with potential application to diagnosis of traumatic brain injury, intracranial hemorrhage (ICH), and stroke. A detector performance model was extended to include the effects of detector readout gain on electronic digitization noise. The noise performance for high-gain (HG), low-gain (LG), and dual-gain (DG) detector readout was evaluated, and the benefit associated with HG mode in regions free from detector saturation was quantified. Such benefit could be realized (without detector saturation) either via DG mode or by incorporation of a bowtie filter. Therefore, three bowtie filters were investigated that varied in thickness and curvature. A polyenergetic gain correction method was developed to equalize the detector response between the flood-field and projection data in the presence of a bowtie. The effect of bowtie filters on dose, scatter-to-primary ratio, contrast, and noise was quantified in phantom studies, and results were compared to a high-speed Monte Carlo (MC) simulation to characterize x-ray scatter and dose distributions in the head. Imaging in DG mode improved the contrast-to-noise ratio (CNR) by ~15% compared to LG mode at a dose (D 0, measured at the center of a 16 cm CTDI phantom) of 19 mGy. MC dose calculations agreed with CTDI measurements and showed that bowtie filters reduce peripheral dose by as much as 50% at the same central dose. Bowtie filters were found to increase the CNR per unit square-root dose near the center of the image by ~5-20% depending on bowtie thickness, but reduced CNR in the periphery by ~10-40%. Images acquired at equal CTDIw with and without a bowtie demonstrated a 24% increase in CNR at the center of an anthropomorphic head phantom. Combining a thick bowtie filter with a short arc (180° + fan angle) scan centered on the posterior of the head reduced dose to the eye lens by up to 90%. Acquisition in DG mode (without a bowtie filter) was beneficial to the detection of small, low contrast lesions (e.g. subtle ICH) in CBCT. While bowtie filters were found to reduce dose, mitigate sensor saturation at the periphery in HG mode, and improve CNR at the center of the image, the image quality at the periphery was slightly reduced compared to DG mode, and the use of a bowtie required careful implementation of the polyenergetic flood-field correction to avoid artifacts.},

keywords = {CBCT, Head/Neck, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{xu2016modeling,

title = {Modeling and design of a cone-beam CT head scanner using task-based imaging performance optimization.},

author = {Jennifer Xu and Alejandro Sisniega and Wojciech Zbijewski and Hao Dang and J. Webster Stayman and Xiaohui Wang and David H. Foos and Nafi Aygun and Vassilis Koliatsos and Jeffrey H. Siewerdsen},

url = {http://www.ncbi.nlm.nih.gov/pubmed/27025783},

doi = {10.1088/0031-9155/61/8/3180},

issn = {1361-6560},

year  = {2016},

date = {2016-04-01},

journal = {Physics in medicine and biology},

volume = {61},

number = {8},

pages = {3180--207},

publisher = {IOP Publishing},

abstract = {Detection of acute intracranial hemorrhage (ICH) is important for diagnosis and treatment of traumatic brain injury, stroke, postoperative bleeding, and other head and neck injuries. This paper details the design and development of a cone-beam CT (CBCT) system developed specifically for the detection of low-contrast ICH in a form suitable for application at the point of care. Recognizing such a low-contrast imaging task to be a major challenge in CBCT, the system design began with a rigorous analysis of task-based detectability including critical aspects of system geometry, hardware configuration, and artifact correction. The imaging performance model described the three-dimensional (3D) noise-equivalent quanta using a cascaded systems model that included the effects of scatter, scatter correction, hardware considerations of complementary metal-oxide semiconductor (CMOS) and flat-panel detectors (FPDs), and digitization bit depth. The performance was analyzed with respect to a low-contrast (40-80 HU), medium-frequency task representing acute ICH detection. The task-based detectability index was computed using a non-prewhitening observer model. The optimization was performed with respect to four major design considerations: (1) system geometry (including source-to-detector distance (SDD) and source-to-axis distance (SAD)); (2) factors related to the x-ray source (including focal spot size, kVp, dose, and tube power); (3) scatter correction and selection of an antiscatter grid; and (4) x-ray detector configuration (including pixel size, additive electronics noise, field of view (FOV), and frame rate, including both CMOS and a-Si:H FPDs). Optimal design choices were also considered with respect to practical constraints and available hardware components. The model was verified in comparison to measurements on a CBCT imaging bench as a function of the numerous design parameters mentioned above. An extended geometry (SAD = 750 mm},

keywords = {CBCT, Head/Neck, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{sisniega2015volumetric,

title = {Volumetric CT with sparse detector arrays (and application to Si-strip photon counters).},

author = {Alejandro Sisniega and Wojciech Zbijewski and J. Webster Stayman and Jennifer Xu and Katsuyuki Taguchi and Erik Fredenberg and Mats Lundqvist and Jeffrey H. Siewerdsen },

url = {http://www.ncbi.nlm.nih.gov/pubmed/26611740},

doi = {10.1088/0031-9155/61/1/90},

issn = {1361-6560},

year  = {2016},

date = {2016-01-01},

journal = {Physics in medicine and biology},

volume = {61},

number = {1},

pages = {90--113},

publisher = {IOP Publishing},

abstract = {Novel x-ray medical imaging sensors, such as photon counting detectors (PCDs) and large area CCD and CMOS cameras can involve irregular and/or sparse sampling of the detector plane. Application of such detectors to CT involves undersampling that is markedly different from the commonly considered case of sparse angular sampling. This work investigates volumetric sampling in CT systems incorporating sparsely sampled detectors with axial and helical scan orbits and evaluates performance of model-based image reconstruction (MBIR) with spatially varying regularization in mitigating artifacts due to sparse detector sampling. Volumetric metrics of sampling density and uniformity were introduced. Penalized-likelihood MBIR with a spatially varying penalty that homogenized resolution by accounting for variations in local sampling density (i.e. detector gaps) was evaluated. The proposed methodology was tested in simulations and on an imaging bench based on a Si-strip PCD (total area 5 cm × 25 cm) consisting of an arrangement of line sensors separated by gaps of up to 2.5 mm. The bench was equipped with translation/rotation stages allowing a variety of scanning trajectories, ranging from a simple axial acquisition to helical scans with variable pitch. Statistical (spherical clutter) and anthropomorphic (hand) phantoms were considered. Image quality was compared to that obtained with a conventional uniform penalty in terms of structural similarity index (SSIM), image uniformity, spatial resolution, contrast, and noise. Scan trajectories with intermediate helical width (~10 mm longitudinal distance per 360° rotation) demonstrated optimal tradeoff between the average sampling density and the homogeneity of sampling throughout the volume. For a scan trajectory with 10.8 mm helical width, the spatially varying penalty resulted in significant visual reduction of sampling artifacts, confirmed by a 10% reduction in minimum SSIM (from 0.88 to 0.8) and a 40% reduction in the dispersion of SSIM in the volume compared to the constant penalty (both penalties applied at optimal regularization strength). Images of the spherical clutter and wrist phantoms confirmed the advantages of the spatially varying penalty, showing a 25% improvement in image uniformity and 1.8 × higher CNR (at matched spatial resolution) compared to the constant penalty. The studies elucidate the relationship between sampling in the detector plane, acquisition orbit, sampling of the reconstructed volume, and the resulting image quality. They also demonstrate the benefit of spatially varying regularization in MBIR for scenarios with irregular sampling patterns. Such findings are important and integral to the incorporation of a sparsely sampled Si-strip PCD in CT imaging.},

keywords = {MBIR, Photon Counting, Sparse Sampling, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{prakash2011task,

title = {Task-based modeling and optimization of a cone-beam CT scanner for musculoskeletal imaging.},

author = {Prakhar Prakash and Wojciech Zbijewski and Grace Gang and Yifu Ding and J. Webster Stayman and John Yorkston and John A. Carrino and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC3208412},

doi = {10.1118/1.3633937},

issn = {0094-2405},

year  = {2011},

date = {2011-10-01},

journal = {Medical physics},

volume = {38},

number = {10},

pages = {5612--29},

publisher = {American Association of Physicists in Medicine},

abstract = {PURPOSE This work applies a cascaded systems model for cone-beam CT imaging performance to the design and optimization of a system for musculoskeletal extremity imaging. The model provides a quantitative guide to the selection of system geometry, source and detector components, acquisition techniques, and reconstruction parameters. METHODS The model is based on cascaded systems analysis of the 3D noise-power spectrum (NPS) and noise-equivalent quanta (NEQ) combined with factors of system geometry (magnification, focal spot size, and scatter-to-primary ratio) and anatomical background clutter. The model was extended to task-based analysis of detectability index (d') for tasks ranging in contrast and frequency content, and d' was computed as a function of system magnification, detector pixel size, focal spot size, kVp, dose, electronic noise, voxel size, and reconstruction filter to examine trade-offs and optima among such factors in multivariate analysis. The model was tested quantitatively versus the measured NPS and qualitatively in cadaver images as a function of kVp, dose, pixel size, and reconstruction filter under conditions corresponding to the proposed scanner. RESULTS The analysis quantified trade-offs among factors of spatial resolution, noise, and dose. System magnification (M) was a critical design parameter with strong effect on spatial resolution, dose, and x-ray scatter, and a fairly robust optimum was identified at M ∼ 1.3 for the imaging tasks considered. The results suggested kVp selection in the range of ∼65-90 kVp, the lower end (65 kVp) maximizing subject contrast and the upper end maximizing NEQ (90 kVp). The analysis quantified fairly intuitive results-e.g., ∼0.1-0.2 mm pixel size (and a sharp reconstruction filter) optimal for high-frequency tasks (bone detail) compared to ∼0.4 mm pixel size (and a smooth reconstruction filter) for low-frequency (soft-tissue) tasks. This result suggests a specific protocol for 1 × 1 (full-resolution) projection data acquisition followed by full-resolution reconstruction with a sharp filter for high-frequency tasks along with 2 × 2 binning reconstruction with a smooth filter for low-frequency tasks. The analysis guided selection of specific source and detector components implemented on the proposed scanner. The analysis also quantified the potential benefits and points of diminishing return in focal spot size, reduced electronic noise, finer detector pixels, and low-dose limits of detectability. Theoretical results agreed quantitatively with the measured NPS and qualitatively with evaluation of cadaver images by a musculoskeletal radiologist. CONCLUSIONS A fairly comprehensive model for 3D imaging performance in cone-beam CT combines factors of quantum noise, system geometry, anatomical background, and imaging task. The analysis provided a valuable, quantitative guide to design, optimization, and technique selection for a musculoskeletal extremities imaging system under development.},

keywords = {Analysis, CBCT, Extremities, System Design},

pubstate = {published},

tppubtype = {article}

}

@article{zbijewski2011dedicated,

title = {A dedicated cone-beam CT system for musculoskeletal extremities imaging: design, optimization, and initial performance characterization.},

author = {Wojciech Zbijewski and Paul De Jean and Prakhar Prakash and Yifu Ding and J. Webster Stayman and Nathan Packard and Robert Senn and Dong Yang and John Yorkston and Antonio Machado and John A. Carrino and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC3172864},

doi = {10.1118/1.3611039},

issn = {0094-2405},

year  = {2011},

date = {2011-08-01},

journal = {Medical physics},

volume = {38},

number = {8},

pages = {4700--13},

publisher = {American Association of Physicists in Medicine},

abstract = {PURPOSE This paper reports on the design and initial imaging performance of a dedicated cone-beam CT (CBCT) system for musculoskeletal (MSK) extremities. The system complements conventional CT and MR and offers a variety of potential clinical and logistical advantages that are likely to be of benefit to diagnosis, treatment planning, and assessment of therapy response in MSK radiology, orthopaedic surgery, and rheumatology. METHODS The scanner design incorporated a host of clinical requirements (e.g., ability to scan the weight-bearing knee in a natural stance) and was guided by theoretical and experimental analysis of image quality and dose. Such criteria identified the following basic scanner components and system configuration: a flat-panel detector (FPD, Varian 3030+, 0.194 mm pixels); and a low-power, fixed anode x-ray source with 0.5 mm focal spot (SourceRay XRS-125-7K-P, 0.875 kW) mounted on a retractable C-arm allowing for two scanning orientations with the capability for side entry, viz. a standing configuration for imaging of weight-bearing lower extremities and a sitting configuration for imaging of tensioned upper extremity and unloaded lower extremity. Theoretical modeling employed cascaded systems analysis of modulation transfer function (MTF) and detective quantum efficiency (DQE) computed as a function of system geometry, kVp and filtration, dose, source power, etc. Physical experimentation utilized an imaging bench simulating the scanner geometry for verification of theoretical results and investigation of other factors, such as antiscatter grid selection and 3D image quality in phantom and cadaver, including qualitative comparison to conventional CT. RESULTS Theoretical modeling and benchtop experimentation confirmed the basic suitability of the FPD and x-ray source mentioned above. Clinical requirements combined with analysis of MTF and DQE yielded the following system geometry: a -55 cm source-to-detector distance; 1.3 magnification; a 20 cm diameter bore (20 x 20 x 20 cm3 field of view); total acquisition arc of -240 degrees. The system MTF declines to 50% at -1.3 mm(-1) and to 10% at -2.7 mm(-1), consistent with sub-millimeter spatial resolution. Analysis of DQE suggested a nominal technique of 90 kVp (+0.3 mm Cu added filtration) to provide high imaging performance from -500 projections at less than -0.5 kW power, implying -6.4 mGy (0.064 mSv) for low-dose protocols and -15 mGy (0.15 mSv) for high-quality protocols. The experimental studies show improved image uniformity and contrast-to-noise ratio (without increase in dose) through incorporation of a custom 10:1 GR antiscatter grid. Cadaver images demonstrate exquisite bone detail, visualization of articular morphology, and soft-tissue visibility comparable to diagnostic CT (10-20 HU contrast resolution). CONCLUSIONS The results indicate that the proposed system will deliver volumetric images of the extremities with soft-tissue contrast resolution comparable to diagnostic CT and improved spatial resolution at potentially reduced dose. Cascaded systems analysis provided a useful basis for system design and optimization without costly repeated experimentation. A combined process of design specification, image quality analysis, clinical feedback, and revision yielded a prototype that is now awaiting clinical pilot studies. Potential advantages of the proposed system include reduced space and cost, imaging of load-bearing extremities, and combined volumetric imaging with real-time fluoroscopy and digital radiography.},

keywords = {Analysis, CBCT, Extremities, System Assessment, System Design},

pubstate = {published},

tppubtype = {article}

}