Dr. Emily L. Marshall Profile

Dr. Emily L. Marshall

at Univ of Chicago

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Publications (3)

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Proceedings Article | 4 April 2022 Paper

Task-specific evaluation of clinical pediatric fluoroscopy systems

Emily Marshall, Daniela Olivera Velarde, Natalie Baughan, Nikolaj Reiser, Chao Guo, Juan Pablo Bastida Cruz, Kate Feinstein, Ingrid Reiser

Proceedings Volume 12035, 120351A (2022) https://doi.org/10.1117/12.2613006

KEYWORDS: Fluoroscopy, Imaging systems, Iodine, Image intensifiers, Diagnostics, Signal to noise ratio, Printing

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Fluoroscopic imaging is utilized to dynamically image a patient’s internal anatomy and physiology during an examination. Current methods for the evaluation of fluoroscopic image performance do not challenge systems in real- time or with clinically meaningful tasks. This work presents a methodology for the task-specific quantification of clinical fluoroscopy systems’ imaging performance, through reader assessments of live fluoroscopic images. First, a set of clinically relevant tasks was developed based on the internationally recognized grading scale for kidney-ureter vesicoureteric reflux (VUR) in pediatric patients. Tasks were generated to represent VUR grades from 2 to 5, and were printed using iodine ink 2D printing. Tasks were described by the total number of pages, i.e. total iodine contrast, and the VUR grade of the task itself. In total, 24 combinations of contrast and grade were assessed. Images of each task were taken under three experimental conditions: first, under a high-dose flat panel detector clinical system; second, under a low-dose protocol on the same flat panel detector system; and third, under a comparable high-dose protocol in an image intensifier clinical system. Readers assessed imaging tasks in the clinical environment in two manners: 1) detection (VUR present or absent), and 2) identification of the VUR grade. The results of the reader study indicate that after the application of a scoring scheme, a metric quantifying task-performance of fluoroscopy systems may be obtained. The evaluation process outlined in this work will enable a standard mechanism for the quantitative comparison across fluoroscopic systems, technologies, and protocols.

Proceedings Article | 15 February 2021 Presentation + Paper

Towards the objective assessment of fluoroscopy systems: development of a framework to aid the design of tasks and metrics

Juan P. Cruz-Bastida, Natalie Baughan, Emily Marshall, Kayla Blunt, Kate Feinstein, Ingrid Reiser

Proceedings Volume 11599, 1159908 (2021) https://doi.org/10.1117/12.2581089

KEYWORDS: Fluoroscopy, X-ray imaging, Systems modeling, Radiography, Profiling, Image segmentation, Diagnostics, Computer simulations

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The purpose of this work is to propose a framework that could help to accelerate the development of task models and figures of merit for fluoroscopy applications. Our final goal is to use this framework to establish an imaging task based on pediatric vesicoureteral reflux (VUR) diagnosis, and to assess a reader study design that mimics contrast medium uptake. The proposed framework is based on task and observer study fine-tuning after consecutive virtual trials. Radiographs of neonates were selected by a radiologist for phantom and observer study development. Ureter depictions of five VUR grades were segmented from published references and used as imaging tasks. A tool to simulate patient+task images was developed based on well-known x-ray imaging models. To validate this tool, two quality assurance phantoms were simulated and compared to actual acquisitions, having as result a good agreement in terms of maximum resolvable line-pair frequency and contrast resolution. In addition, the noise texture and magnitude were very similar. To facilitate virtual trials, a web-based application was developed, which displays simulated images and asks the observer to grade them. Preliminary tests have shown that the application is practical, accessible and provides the needed flexibility for testing different study designs. In conclusion, a framework to facilitate phantom profiling and observer study design has been developed. With this framework it has been possible to simulate and score pediatric VUR diagnostic tasks embedded in realistic anatomical backgrounds, with the goal of developing a study design that can be performed in real time.

Proceedings Article | 1 March 2019 Paper

Development of a compact inkjet-printed patient-specific phantom for optimization of fluoroscopic image quality in neonates

Emily Marshall, Claire Joswiak, Lindsay Douglas, Erik Pearson, Zheng-Feng Lu, Hania Al-Hallaq, Ingrid Reiser

Proceedings Volume 10948, 109484W (2019) https://doi.org/10.1117/12.2513118

KEYWORDS: Iodine, Printing, Signal attenuation, Radiography, Image quality, Chest, Fluoroscopy, X-rays

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Flat panel detectors remain a new and emerging technology in under-table fluoroscopy systems. This technology is more susceptible than image intensifiers to electronic noise, which degrades image contrast resolution. Compensation for increased electronic noise is provided through proprietary vendor image processing algorithms. Lacking optimization in pediatrics, these algorithms interfere with patient anatomy particularly in neonate patients with low native anatomic contrast from bony structures, which serve as landmarks during fluoroscopic procedures. Existing phantoms do not adequately mimic the neonate anatomy making assessment and optimization of image quality for these patients difficult if not impossible. This work presents a method to inexpensively print iodine based anthropomorphic phantoms derived from patient radiographs with sufficient anatomic detail to assess system image quality. First, the attenuation of iodine ink densities (μt) was correlated to a standard pixel value grayscale map. Next, for proof-of-principle, radiographs of an anthropomorphic chest phantom were developed into a series of iodine ink printed sheets. Sheets were stacked to build a compact 2D phantom matching the x-ray attenuation of the original radiographs. The iodine ink printed phantom was imaged and attenuation values per anatomical regions of interest were compared. This study provides the fundamentals and techniques of phantom construction, enabling generation of anatomically realistic phantoms for a variety of patient age and size groups by use of clinical radiographs. Future studies will apply these techniques to generate neonatal phantoms from radiographs. These phantoms provide realistic imaging challenges to enable optimization of image quality in fluoroscopy and other projection-based x-ray modalities.

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