Molly Donovan

University of Oklahoma, Norman, Oklahoma, United States

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Publications (4)6.58 Total impact

  • Source
    Molly Donovan · Da Zhang · Hong Liu
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    ABSTRACT: Comprehensive research focus on the use of an edge test device for accurate determination of the modulation transfer function (MTF) in x-ray imaging has resulted in the development of numerous edge processing algorithms. While the overall results of the relative algorithms have been compared, the individual steps within the algorithms have not previously been evaluated for similarities and differences that could significantly affect the resultant MTF. Therefore a step by step investigation to evaluate the alternative methods for each step separately holds the potential to provide insight into improving the overall algorithm by optimizing the method employed for each step. Thus this research study focused on comparing methods applicable for each step comprising the edge algorithm and providing a step by step guide for implementing the optimal algorithm based on given experimental conditions. In addition, new methods and combinations of methods were investigated in several of the algorithm steps, and were determined to provide comparable, if not superior, results to the existing methods. This included the use of different numbers of rows and columns in the region of interest (ROI) for determining the edge spread function (ESF), implementing a new three-step ESF filtering approach, and applying a median filter in both the ESF and line spread function (LSF) smoothing steps.
    Full-text · Article · Feb 2009 · Journal of X-Ray Science and Technology
  • Source
    Zhang Da · Molly Donovan · Xizeng Wu · Hong Liu
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    ABSTRACT: This study presents a two-laser alignment approach for facilitating the precise alignment of various imaging and measuring components with respect to the x-ray beam. The first laser constantly pointed to the output window of the source, in a direction parallel to the path along which the components are placed. The second laser beam, originating from the opposite direction, was calibrated to coincide with the first laser beam. Thus, a visible indicator of the direction of the incident x-ray beam was established, and the various components could then be aligned conveniently and accurately with its help.
    Full-text · Article · Dec 2008 · Medical Physics
  • Da Zhang · Molly Donovan · Laurie L Fajardo · Ann Archer · Xizeng Wu · Hong Liu
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    ABSTRACT: In this study, a series of imaging experiments on biological specimens, including human breast core biopsies, lumpectomy, and chicken tissues, as well as standard phantoms, were performed in an effort to investigate the feasibility of an in-line phase contrast X-ray imaging prototype. The prototype system employed in the study consists of a microfocus X-ray source with tungsten target and a digital flat panel detector, and it can be operated in both conventional attenuation-based imaging mode and in-line phase contrast imaging mode. Biological specimens were imaged in the conventional mode and phase contrast mode with the same source-to-image-detector distance (SID), and phase contrast images exhibited both improved image quality compared with conventional images, and the overshooting patterns along the boundaries in the specimens, which revealed the occurrence of the edge enhancement effect provided by the phase contrast technique. In addition, the performance of the phase contrast mode and conventional mode was compared based on the American College of Radiology (ACR) phantom imaging and contrast detail mammography (CDMAM) phantom-based contrast detail analysis with two experimental settings: one with the same SID and the other with the same object entrance exposure. In both pairs of comparison under our experimental conditions, the phase contrast imaging mode exhibited improved image quality as compared to the conventional mode, which further supported the feasibility of the prototype.
    No preview · Article · Oct 2008 · IEEE transactions on bio-medical engineering
  • Molly Donovan · Da Zhang · Wei R. Chen · Hong Liu
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    ABSTRACT: Conventional x-ray imaging presents challenges for early detection and diagnosis, especially in areas such as mammography, where similar attenuation characteristics between malignant and normal breast tissue result in low contrast between them. An emerging technology called phase-contrast x-ray imaging has the potential to overcome this challenge by also incorporating phase shift effects, which contain more information than attenuation alone. The goal of this study was to verify through the accepted technique of contrast-detail analysis that the image quality provided by a phase-contrast prototype system is superior to that provided by a conventional imaging system. The use of a CDMAM phantom further reinforces the validity of the results, as this method has been proven to increase the accuracy, because it employs a four-alternative fixed choice method for the test objects instead of known locations. In the study, phasecontrast and conventional images of a CDMAM phantom were acquired and presented to observers for analysis. The corresponding contrast-detail curves comparing the systems demonstrate higher image quality produced by the phase-contrast system, an encouraging indication of the future of phase-contrast technology and a step forward in proving the feasibility of its introduction into a clinical environment.
    No preview · Article · Mar 2007 · Proceedings of SPIE - The International Society for Optical Engineering