@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{Sisniega2017,

title = {Motion compensation in extremity cone-beam CT using a penalized image sharpness criterion},

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

url = {http://stacks.iop.org/0031-9155/62/i=9/a=3712?key=crossref.84caaff65ba9b2a3f6da8ee49365aca7},

doi = {10.1088/1361-6560/aa6869},

issn = {0031-9155},

year  = {2017},

date = {2017-04-06},

journal = {Physics in Medicine and Biology},

volume = {62},

number = {9},

pages = {3712-3734},

keywords = {Extremities, Motion Compensation},

pubstate = {published},

tppubtype = {article}

}

@article{Cao2016,

title = {Multiresolution iterative reconstruction in high-resolution extremity cone-beam CT},

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

url = {http://stacks.iop.org/0031-9155/61/i=20/a=7263?key=crossref.3714aec7223f83ec2e527f7be1ae5e4f},

doi = {10.1088/0031-9155/61/20/7263},

issn = {0031-9155},

year  = {2016},

date = {2016-10-03},

journal = {Physics in Medicine and Biology},

volume = {61},

number = {20},

pages = {7263-7281},

keywords = {Artifact Correction, Extremities, Fast Algorithms, High-Resolution CT},

pubstate = {published},

tppubtype = {article}

}

@article{zbijewski2015quantitative,

title = {Quantitative Assessment Of Bone And Joint Health On A Dedicated Extremities Cone-Beam CT System.},

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

url = {http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=PMC4451217},

issn = {1861-6429},

year  = {2015},

date = {2015-06-01},

journal = {International journal of computer assisted radiology and surgery},

volume = {10},

number = {Suppl 1},

pages = {S29--S31},

publisher = {NIH Public Access},

keywords = {CBCT, Extremities, Spectral X-ray/CT},

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{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{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}

}