@article{Mei2023,

title = {Design and fabrication of 3D-printed patient-specific soft tissue and bone phantoms for CT imaging},

author = {Kai Mei and Pouyan Pasyar and Michael Geagan and Leening Liu and Nadav Shapira and Grace Gang and J. Webster Stayman and Peter Noël},

url = {https://www.nature.com/articles/s41598-023-44602-9

https://pubmed.ncbi.nlm.nih.gov/37840044/

},

doi = {10.1038/s41598-023-44602-9},

year  = {2023},

date = {2023-10-15},

urldate = {2023-10-15},

journal = {Scientific Reports},

volume = {13},

pages = {17495 },

keywords = {Phantoms, System Assessment},

pubstate = {published},

tppubtype = {article}

}

@article{Shapira2023,

title = {Three-dimensional printing of patient-specific computed tomography lung phantoms: a reader study},

author = {Nadav Shapira and Kevin Donovan and Kai Mei and Michael Geagan and Leonid Roshkovan and Grace Gang and Mohammed Abed and Nathaniel Linna and Coulter Cranston and Cathal O'Leary and Ali Dhanaliwala and Despina Kontos and Harold I Litt and J. Webster Stayman and Russell Shinohara and Peter Noël},

url = {https://academic.oup.com/pnasnexus/article/2/3/pgad026/7019413

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9992761/},

doi = {10.1093/pnasnexus/pgad026},

year  = {2023},

date = {2023-03-01},

journal = {PNAS Nexus},

volume = {2},

issue = {3},

pages = {pgad026},

keywords = {Lungs, Phantoms, System Assessment},

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{Mei2021,

title = {Three-dimensional printing of patient-specific lung phantoms for CT imaging: emulating lung tissue with accurate attenuation profiles and textures},

author = {Kai Mei and Michael Geagan and Leonid Roshkovan and Harold I Litt and Grace Gang and Nadav Shapira and J. Webster Stayman and Peter Noël},

url = {https://www.medrxiv.org/content/10.1101/2021.07.30.21261292v1.full-text},

doi = {10.1101/2021.07.30.21261292 },

year  = {2021},

date = {2021-08-01},

urldate = {2021-08-01},

journal = {Medical Physics},

pages = {Submitted},

keywords = {Lungs, System Assessment},

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{Chen2019,

title = {Precise measurement of coronary stenosis diameter with CCTA using CT number calibration},

author = {Z Chen and Francisco Contijoch and A Schluchter and L Grady and M Schaap and J. Webster Stayman and Jed Pack and Elliot McVeigh},

url = {https://pubmed.ncbi.nlm.nih.gov/31603567/},

doi = {10.1002/mp.13862},

year  = {2019},

date = {2019-12-01},

journal = {Medical Physics},

volume = {46},

number = {12},

pages = {5514-5527},

abstract = {Purpose: Coronary x-ray computed tomography angiography (CCTA) continues to develop as a noninvasive method for the assessment of coronary vessel geometry and the identification of physiologically significant lesions. The uncertainty of quantitative lesion diameter measurement due to limited spatial resolution and vessel motion reduces the accuracy of CCTA diagnoses. In this paper, we introduce a new technique called computed tomography (CT)-number-Calibrated Diameter to improve the accuracy of the vessel and stenosis diameter measurements with CCTA.



Methods: A calibration phantom containing cylindrical holes (diameters spanning from 0.8 mm through 4.0 mm) capturing the range of diameters found in human coronary vessels was three-dimensional printed. We also printed a human stenosis phantom with 17 tubular channels having the geometry of lesions derived from patient data. We acquired CT scans of the two phantoms with seven different imaging protocols. Calibration curves relating vessel intraluminal maximum voxel value (maximum CT number of a voxel, described in Hounsfield Units, HU) to true diameter, and full-width-at-half maximum (FWHM) to true diameter were constructed for each CCTA protocol. In addition, we acquired scans with a small constant motion (15 mm/s) and used a motion correction reconstruction (Snapshot Freeze) algorithm to correct motion artifacts. We applied our technique to measure the lesion diameter in the 17 lesions in the stenosis phantom and compared the performance of CT-number-Calibrated Diameter to the ground truth diameter and a FWHM estimate.



Results: In all cases, vessel intraluminal maximum voxel value vs diameter was found to have a simple functional form based on the two-dimensional point spread function yielding a constant maximum voxel value region above a cutoff diameter, and a decreasing maximum voxel value vs decreasing diameter below a cutoff diameter. After normalization, focal spot size and reconstruction kernel were the principal determinants of cutoff diameter and the rate of maximum voxel value reduction vs decreasing diameter. The small constant motion had a significant effect on the CT number calibration; however, the motion-correction algorithm returned the maximum voxel value vs diameter curve to that of stationary vessels. The CT number Calibration technique showed better performance than FWHM estimation of diameter, yielding a high accuracy in the tested range (0.8 mm through 2.5 mm). We found a strong linear correlation between the smallest diameter in each of 17 lesions measured by CT-number-Calibrated Diameter (DC ) and ground truth diameter (Dgt ), (DC = 0.951 × Dgt + 0.023 mm, r = 0.998 with a slope very close to 1.0 and intercept very close to 0 mm.



Conclusions: Computed tomography-number-Calibrated Diameter is an effective method to enhance the accuracy of the estimate of small vessel diameters and degree of coronary stenosis in CCTA.



Keywords: coronary CT angiography; coronary stenosis quantification; vessel motion.},

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

pubstate = {published},

tppubtype = {article}

}

@article{Uneri2018c,

title = {Image quality and dose characteristics for an O‐arm intraoperative imaging system with model‐based image reconstruction},

author = {Ali Uneri and Xiaoxuan Zhang and T. Yi and J. Webster Stayman and Patrick Helm and Nick Theodore and Jeffrey H. Siewerdsen},

url = {https://aapm.onlinelibrary.wiley.com/doi/full/10.1002/mp.13167},

doi = {10.1002/mp.13167},

year  = {2018},

date = {2018-09-04},

journal = {Medical Physics},

volume = {45},

number = {11},

pages = {4857-4868},

keywords = {CBCT, MBIR, Spine, System Assessment},

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{Demehri2015,

title = {Assessment of image quality in soft tissue and bone visualization tasks for a dedicated extremity cone-beam CT system.},

author = {Shadpour Demehri and Abdullah Al Muhit and Wojciech Zbijewski and J. Webster Stayman and John Yorkston and Nathan Packard and Robert Senn and Dong Yang and David H. Foos and Gaurav K. Thawait and L. M. Fayad and A. Chabra and John A. Carrino and Jeffrey H. Siewerdsen},

url = {http://www.ncbi.nlm.nih.gov/pubmed/25599933},

doi = {10.1007/s00330-014-3546-6},

issn = {1432-1084},

year  = {2015},

date = {2015-06-01},

journal = {European radiology},

volume = {25},

number = {6},

pages = {1742--51},

abstract = {OBJECTIVE To assess visualization tasks using cone-beam CT (CBCT) compared to multi-detector CT (MDCT) for musculoskeletal extremity imaging. METHODS Ten cadaveric hands and ten knees were examined using a dedicated CBCT prototype and a clinical multi-detector CT using nominal protocols (80 kVp-108mAs for CBCT; 120 kVp- 300 mAs for MDCT). Soft tissue and bone visualization tasks were assessed by four radiologists using five-point satisfaction (for CBCT and MDCT individually) and five-point preference (side-by-side CBCT versus MDCT image quality comparison) rating tests. Ratings were analyzed using Kruskal-Wallis and Wilcoxon signed-rank tests, and observer agreement was assessed using the Kappa-statistic. RESULTS Knee CBCT images were rated "excellent" or "good" (median scores 5 and 4) for "bone" and "soft tissue" visualization tasks. Hand CBCT images were rated "excellent" or "adequate" (median scores 5 and 3) for "bone" and "soft tissue" visualization tasks. Preference tests rated CBCT equivalent or superior to MDCT for bone visualization and favoured the MDCT for soft tissue visualization tasks. Intraobserver agreement for CBCT satisfaction tests was fair to almost perfect ($kappa$ ~ 0.26-0.92), and interobserver agreement was fair to moderate ($kappa$ ~ 0.27-0.54). CONCLUSION CBCT provided excellent image quality for bone visualization and adequate image quality for soft tissue visualization tasks. KEY POINTS • CBCT provided adequate image quality for diagnostic tasks in extremity imaging. • CBCT images were "excellent" for "bone" and "good/adequate" for "soft tissue" visualization tasks. • CBCT image quality was equivalent/superior to MDCT for bone visualization tasks.},

keywords = {CBCT, Extremities, System Assessment},

pubstate = {published},

tppubtype = {article}

}

@article{wang2014low,

title = {Low-dose preview for patient-specific, task-specific technique selection in cone-beam CT.},

author = {Adam S. Wang and J. Webster Stayman and Yoshito Otake and Sebastian Vogt and Gerhard Kleinszig and A. Jay Khanna and Gary L. Gallia and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC4106458},

doi = {10.1118/1.4884039},

issn = {0094-2405},

year  = {2014},

date = {2014-07-01},

journal = {Medical physics},

volume = {41},

number = {7},

pages = {071915},

publisher = {American Association of Physicists in Medicine},

abstract = {PURPOSE A method is presented for generating simulated low-dose cone-beam CT (CBCT) preview images from which patient- and task-specific minimum-dose protocols can be confidently selected prospectively in clinical scenarios involving repeat scans. METHODS In clinical scenarios involving a series of CBCT images, the low-dose preview (LDP) method operates upon the first scan to create a projection dataset that accurately simulates the effects of dose reduction in subsequent scans by injecting noise of proper magnitude and correlation, including both quantum and electronic readout noise as important components of image noise in flat-panel detector CBCT. Experiments were conducted to validate the LDP method in both a head phantom and a cadaveric torso by performing CBCT acquisitions spanning a wide dose range (head: 0.8-13.2 mGy, body: 0.8-12.4 mGy) with a prototype mobile C-arm system. After injecting correlated noise to simulate dose reduction, the projections were reconstructed using both conventional filtered backprojection (FBP) and an iterative, model-based image reconstruction method (MBIR). The LDP images were then compared to real CBCT images in terms of noise magnitude, noise-power spectrum (NPS), spatial resolution, contrast, and artifacts. RESULTS For both FBP and MBIR, the LDP images exhibited accurate levels of spatial resolution and contrast that were unaffected by the correlated noise injection, as expected. Furthermore, the LDP image noise magnitude and NPS were in strong agreement with real CBCT images acquired at the corresponding, reduced dose level across the entire dose range considered. The noise magnitude agreed within 7% for both the head phantom and cadaveric torso, and the NPS showed a similar level of agreement up to the Nyquist frequency. Therefore, the LDP images were highly representative of real image quality across a broad range of dose and reconstruction methods. On the other hand, naïve injection ofuncorrelated noise resulted in strong underestimation of the true noise, which would lead to overly optimistic predictions of dose reduction. CONCLUSIONS Correlated noise injection is essential to accurate simulation of CBCT image quality at reduced dose. With the proposed LDP method, the user can prospectively select patient-specific, minimum-dose protocols (viz., acquisition technique and reconstruction method) suitable to a particular imaging task and to the user's own observer preferences for CBCT scans following the first acquisition. The method could provide dose reduction in common clinical scenarios involving multiple CBCT scans, such as image-guided surgery and radiotherapy.},

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

pubstate = {published},

tppubtype = {article}

}

@article{carrino2013dedicated,

title = {Dedicated cone-beam CT system for extremity imaging.},

author = {John A. Carrino and Abdullah Al Muhit and Wojciech Zbijewski and Gaurav K. Thawait and J. Webster Stayman and Nathan Packard and Robert Senn and Dong Yang and David H. Foos and John Yorkston and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC4263642},

doi = {10.1148/radiol.13130225},

issn = {1527-1315},

year  = {2014},

date = {2014-03-01},

journal = {Radiology},

volume = {270},

number = {3},

pages = {816--24},

publisher = {Radiological Society of North America},

abstract = {PURPOSE To provide initial assessment of image quality and dose for a cone-beam computed tomographic (CT) scanner dedicated to extremity imaging. MATERIALS AND METHODS A prototype cone-beam CT scanner has been developed for imaging the extremities, including the weight-bearing lower extremities. Initial technical assessment included evaluation of radiation dose measured as a function of kilovolt peak and tube output (in milliampere seconds), contrast resolution assessed in terms of the signal difference-to-noise ratio (SDNR), spatial resolution semiquantitatively assessed by using a line-pair module from a phantom, and qualitative evaluation of cadaver images for potential diagnostic value and image artifacts by an expert CT observer (musculoskeletal radiologist). RESULTS The dose for a nominal scan protocol (80 kVp, 108 mAs) was 9 mGy (absolute dose measured at the center of a CT dose index phantom). SDNR was maximized with the 80-kVp scan technique, and contrast resolution was sufficient for visualization of muscle, fat, ligaments and/or tendons, cartilage joint space, and bone. Spatial resolution in the axial plane exceeded 15 line pairs per centimeter. Streaks associated with x-ray scatter (in thicker regions of the patient--eg, the knee), beam hardening (about cortical bone--eg, the femoral shaft), and cone-beam artifacts (at joint space surfaces oriented along the scanning plane--eg, the interphalangeal joints) presented a slight impediment to visualization. Cadaver images (elbow, hand, knee, and foot) demonstrated excellent visibility of bone detail and good soft-tissue visibility suitable to a broad spectrum of musculoskeletal indications. CONCLUSION A dedicated extremity cone-beam CT scanner capable of imaging upper and lower extremities (including weight-bearing examinations) provides sufficient image quality and favorable dose characteristics to warrant further evaluation for clinical use.},

keywords = {CBCT, Extremities, System Assessment},

pubstate = {published},

tppubtype = {article}

}

@article{wang2014soft,

title = {Soft-tissue imaging with C-arm cone-beam CT using statistical reconstruction.},

author = {Adam S. Wang and J. Webster Stayman and Yoshito Otake and Gerhard Kleinszig and Sebastian Vogt and Gary L. Gallia and A. Jay Khanna and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC4046706},

doi = {10.1088/0031-9155/59/4/1005},

issn = {1361-6560},

year  = {2014},

date = {2014-02-01},

journal = {Physics in medicine and biology},

volume = {59},

number = {4},

pages = {1005--26},

publisher = {IOP Publishing},

abstract = {The potential for statistical image reconstruction methods such as penalized-likelihood (PL) to improve C-arm cone-beam CT (CBCT) soft-tissue visualization for intraoperative imaging over conventional filtered backprojection (FBP) is assessed in this work by making a fair comparison in relation to soft-tissue performance. A prototype mobile C-arm was used to scan anthropomorphic head and abdomen phantoms as well as a cadaveric torso at doses substantially lower than typical values in diagnostic CT, and the effects of dose reduction via tube current reduction and sparse sampling were also compared. Matched spatial resolution between PL and FBP was determined by the edge spread function of low-contrast (∼ 40-80 HU) spheres in the phantoms, which were representative of soft-tissue imaging tasks. PL using the non-quadratic Huber penalty was found to substantially reduce noise relative to FBP, especially at lower spatial resolution where PL provides a contrast-to-noise ratio increase up to 1.4-2.2 × over FBP at 50% dose reduction across all objects. Comparison of sampling strategies indicates that soft-tissue imaging benefits from fully sampled acquisitions at dose above ∼ 1.7 mGy and benefits from 50% sparsity at dose below ∼ 1.0 mGy. Therefore, an appropriate sampling strategy along with the improved low-contrast visualization offered by statistical reconstruction demonstrates the potential for extending intraoperative C-arm CBCT to applications in soft-tissue interventions in neurosurgery as well as thoracic and abdominal surgeries by overcoming conventional tradeoffs in noise, spatial resolution, and dose.},

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

pubstate = {published},

tppubtype = {article}

}

@article{Sisniega2013,

title = {Monte Carlo study of the effects of system geometry and antiscatter grids on cone-beam CT scatter distributions.},

author = {Alejandro Sisniega and Wojciech Zbijewski and Andreu Badal and Iacovos S. Kyprianou and J. Webster Stayman and Juan J. Vaquero and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC3651212},

doi = {10.1118/1.4801895},

issn = {0094-2405},

year  = {2013},

date = {2013-05-01},

journal = {Medical physics},

volume = {40},

number = {5},

pages = {051915},

publisher = {American Association of Physicists in Medicine},

abstract = {PURPOSE The proliferation of cone-beam CT (CBCT) has created interest in performance optimization, with x-ray scatter identified among the main limitations to image quality. CBCT often contends with elevated scatter, but the wide variety of imaging geometry in different CBCT configurations suggests that not all configurations are affected to the same extent. Graphics processing unit (GPU) accelerated Monte Carlo (MC) simulations are employed over a range of imaging geometries to elucidate the factors governing scatter characteristics, efficacy of antiscatter grids, guide system design, and augment development of scatter correction. METHODS A MC x-ray simulator implemented on GPU was accelerated by inclusion of variance reduction techniques (interaction splitting, forced scattering, and forced detection) and extended to include x-ray spectra and analytical models of antiscatter grids and flat-panel detectors. The simulator was applied to small animal (SA), musculoskeletal (MSK) extremity, otolaryngology (Head), breast, interventional C-arm, and on-board (kilovoltage) linear accelerator (Linac) imaging, with an axis-to-detector distance (ADD) of 5, 12, 22, 32, 60, and 50 cm, respectively. Each configuration was modeled with and without an antiscatter grid and with (i) an elliptical cylinder varying 70-280 mm in major axis; and (ii) digital murine and anthropomorphic models. The effects of scatter were evaluated in terms of the angular distribution of scatter incident upon the detector, scatter-to-primary ratio (SPR), artifact magnitude, contrast, contrast-to-noise ratio (CNR), and visual assessment. RESULTS Variance reduction yielded improvements in MC simulation efficiency ranging from ∼17-fold (for SA CBCT) to ∼35-fold (for Head and C-arm), with the most significant acceleration due to interaction splitting (∼6 to ∼10-fold increase in efficiency). The benefit of a more extended geometry was evident by virtue of a larger air gap-e.g., for a 16 cm diameter object, the SPR reduced from 1.5 for ADD = 12 cm (MSK geometry) to 1.1 for ADD = 22 cm (Head) and to 0.5 for ADD = 60 cm (C-arm). Grid efficiency was higher for configurations with shorter air gap due to a broader angular distribution of scattered photons-e.g., scatter rejection factor ∼0.8 for MSK geometry versus ∼0.65 for C-arm. Grids reduced cupping for all configurations but had limited improvement on scatter-induced streaks and resulted in a loss of CNR for the SA, Breast, and C-arm. Relative contribution of forward-directed scatter increased with a grid (e.g., Rayleigh scatter fraction increasing from ∼0.15 without a grid to ∼0.25 with a grid for the MSK configuration), resulting in scatter distributions with greater spatial variation (the form of which depended on grid orientation). CONCLUSIONS A fast MC simulator combining GPU acceleration with variance reduction provided a systematic examination of a range of CBCT configurations in relation to scatter, highlighting the magnitude and spatial uniformity of individual scatter components, illustrating tradeoffs in CNR and artifacts and identifying the system geometries for which grids are more beneficial (e.g., MSK) from those in which an extended geometry is the better defense (e.g., C-arm head imaging). Compact geometries with an antiscatter grid challenge assumptions of slowly varying scatter distributions due to increased contribution of Rayleigh scatter.},

keywords = {CBCT, Scatter Estimation, System Assessment},

pubstate = {published},

tppubtype = {article}

}

@article{lee2012intraoperative,

title = {Intraoperative C-arm cone-beam computed tomography: quantitative analysis of surgical performance in skull base surgery.},

author = {Stella Lee and Gary L. Gallia and Douglas D. Reh and Sebastian Schafer and Ali Uneri and Daniel J. Mirota and Sajendra Nithiananthan and Yoshito Otake and J. Webster Stayman and Wojciech Zbijewski and Jeffrey H. Siewerdsen },

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC3725328},

doi = {10.1002/lary.23374},

issn = {1531-4995},

year  = {2012},

date = {2012-09-01},

journal = {The Laryngoscope},

volume = {122},

number = {9},

pages = {1925--32},

publisher = {Wiley Subscription Services, Inc., A Wiley Company},

abstract = {OBJECTIVES/HYPOTHESIS To determine whether incorporation of intraoperative imaging via a new cone-beam computed tomography (CBCT) image-guidance system improves accuracy and facilitates resection in sinus and skull-base surgery through quantification of surgical performance. STUDY DESIGN Landmark identification and skull base ablation tasks were performed with a CBCT intraoperative image-guidance system in the experimental group and with image-guided surgery (IGS) alone based on preoperative computed tomography (CT) in the control group. METHODS Six cadaveric heads underwent preoperative CT imaging and surgical planning identifying surgical targets. Three types of surgical tasks were planned: landmark point identification, line contour identification, and volume drill-out. Key anatomic structures (carotid artery and optic nerve) were chosen for landmark identification and line contour tasks. Complete ethmoidectomy, vidian corridor drill-out, and clival resection were performed for volume ablation tasks. The CBCT guidance system was used in the experimental group and performance was assessed by metrics of target registration error, sensitivity, and specificity of excision. RESULTS Significant improvements were seen for point identification and line tracing tasks. Additional resection was performed in 67% of tasks in the CBCT group, and qualitative feedback indicated unequivocal improvement in confidence for all tasks. In review of tasks in the control group, additional resection would have been performed in 35% of tasks if an intraoperative image was available. CONCLUSIONS An experimental prototype C-arm CBCT guidance system was shown to improve surgical precision in the identification of skull base targets and increase accuracy in the ablation of surgical target volumes in comparison to using IGS alone.},

keywords = {CBCT, Head/Neck, Image Guided Surgery, System Assessment},

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}

}

@article{schafer2011mobile,

title = {Mobile C-arm cone-beam CT for guidance of spine surgery: image quality, radiation dose, and integration with interventional guidance.},

author = {Sebastian Schafer and Sajendra Nithiananthan and Daniel J. Mirota and Ali Uneri and J. Webster Stayman and Wojciech Zbijewski and Christian Schmidgunst and Gerhard Kleinszig and A. Jay Khanna and Jeffrey H. Siewerdsen },

url = {http://www.ncbi.nlm.nih.gov/pubmed/21928628 http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC3161502},

doi = {10.1118/1.3597566},

issn = {0094-2405},

year  = {2011},

date = {2011-08-01},

journal = {Medical physics},

volume = {38},

number = {8},

pages = {4563--74},

publisher = {American Association of Physicists in Medicine},

abstract = {PURPOSE A flat-panel detector based mobile isocentric C-arm for cone-beam CT (CBCT) has been developed to allow intraoperative 3D imaging with sub-millimeter spatial resolution and soft-tissue visibility. Image quality and radiation dose were evaluated in spinal surgery, commonly relying on lower-performance image intensifier based mobile C-arms. Scan protocols were developed for task-specific imaging at minimum dose, in-room exposure was evaluated, and integration of the imaging system with a surgical guidance system was demonstrated in preclinical studies of minimally invasive spine surgery. METHODS Radiation dose was assessed as a function of kilovolt (peak) (80-120 kVp) and milliampere second using thoracic and lumbar spine dosimetry phantoms. In-room radiation exposure was measured throughout the operating room for various CBCT scan protocols. Image quality was assessed using tissue-equivalent inserts in chest and abdomen phantoms to evaluate bone and soft-tissue contrast-to-noise ratio as a function of dose, and task-specific protocols (i.e., visualization of bone or soft-tissues) were defined. Results were applied in preclinical studies using a cadaveric torso simulating minimally invasive, transpedicular surgery. RESULTS Task-specific CBCT protocols identified include: thoracic bone visualization (100 kVp; 60 mAs; 1.8 mGy); lumbar bone visualization (100 kVp; 130 mAs; 3.2 mGy); thoracic soft-tissue visualization (100 kVp; 230 mAs; 4.3 mGy); and lumbar soft-tissue visualization (120 kVp; 460 mAs; 10.6 mGy)--each at (0.3 x 0.3 x 0.9 mm3) voxel size. Alternative lower-dose, lower-resolution soft-tissue visualization protocols were identified (100 kVp; 230 mAs; 5.1 mGy) for the lumbar region at (0.3 x 0.3 x 1.5 mm3) voxel size. Half-scan orbit of the C-arm (x-ray tube traversing under the table) was dosimetrically advantageous (prepatient attenuation) with a nonuniform dose distribution (-2 x higher at the entrance side than at isocenter, and -3-4 lower at the exit side). The in-room dose (microsievert) per unit scan dose (milligray) ranged from -21 microSv/mGy on average at tableside to -0.1 microSv/mGy at 2.0 m distance to isocenter. All protocols involve surgical staff stepping behind a shield wall for each CBCT scan, therefore imparting -zero dose to staff. Protocol implementation in preclinical cadaveric studies demonstrate integration of the C-arm with a navigation system for spine surgery guidance-specifically, minimally invasive vertebroplasty in which the system provided accurate guidance and visualization of needle placement and bone cement distribution. Cumulative dose including multiple intraoperative scans was -11.5 mGy for CBCT-guided thoracic vertebroplasty and -23.2 mGy for lumbar vertebroplasty, with dose to staff at tableside reduced to -1 min of fluoroscopy time (-4(0-60 microSv), compared to 5-11 min for the conventional approach. CONCLUSIONS Intraoperative CBCT using a high-performance mobile C-arm prototype demonstrates image quality suitable to guidance of spine surgery, with task-specific protocols providing an important basis for minimizing radiation dose, while maintaining image quality sufficient for surgical guidance. Images demonstrate a significant advance in spatial resolution and soft-tissue visibility, and CBCT guidance offers the potential to reduce fluoroscopy reliance, reducing cumulative dose to patient and staff. Integration with a surgical guidance system demonstrates precise tracking and visualization in up-to-date images (alleviating reliance on preoperative images only), including detection of errors or suboptimal surgical outcomes in the operating room.},

keywords = {CBCT, Image Guided Surgery, Spine, System Assessment},

pubstate = {published},

tppubtype = {article}

}

@article{lee2011cone,

title = {Cone Beam CT-Assisted Endoscopic Sinus and Skull Base Surgery: Quantitative Analysis of Surgical Performance Using a Next-Generation C-Arm Prototype},

author = {Stella Lee and Gary L. Gallia and Douglas D. Reh and Sebastian Schafer and Ali Uneri and Daniel J. Mirota and Sajendra Nithiananthan and Yoshito Otake and J. Webster Stayman and Wojciech Zbijewski and Jeffrey H. Siewerdsen},

url = {http://www.thieme-connect.de/DOI/DOI?10.1055/s-2011-1274205},

doi = {10.1055/s-2011-1274205},

issn = {1531-5010},

year  = {2011},

date = {2011-01-01},

journal = {Skull Base},

volume = {21},

number = {S 01},

pages = {A030},

keywords = {CBCT, Head/Neck, Image Guided Surgery, System Assessment},

pubstate = {published},

tppubtype = {article}

}