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Signal Normalization among Multiple Optical Coherence Tomography Devices

Chen, Chieh-Li (2015) Signal Normalization among Multiple Optical Coherence Tomography Devices. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Optical coherence tomography (OCT) has become a clinical standard in ophthalmology because it has the ability to provide in vivo cross-sectional images of ocular tissues with microscopic resolution in a non-contact and non-invasive manner. More and more manufacturers are getting involved in the race of instrument design and the development of the spectral-domain OCT (SD-OCT). Various light sources, optical designs, and image acquisition settings were employed by different manufacturers to stand out among competitors. This provides a wide variety of options in terms of scanning protocol, image processing, and presentation. However, the diversity also reflects in the variability in the OCT signal characteristics. The variability of OCT signal characteristics not only results in systematic differences in OCT measurement data, such as the retinal nerve fiber layer (RNFL) thickness and total retinal thickness, but also induces discrepancies in OCT image appearance. Those differences cause serious clinical challenges when comparing OCT images from different OCT devices, or recruiting multiple OCT devices in one study.
To solve this problem, a novel signal normalization method was developed in this dissertation. The signal normalization was developed in a stepwise fashion to resolve all factors contributing to the systematic differences among various OCT devices, including axial sampling density, the amount of speckle noise, intensity dynamic range, and image quality. Quantitative analyses and qualitative assessments were conducted to evaluate the proposed signal normalization method. For the quantitative analyses, engineering and clinical validations were performed via measuring the absolute differences in A-scan profile intensity and comparing the systematic RNFL thickness differences before and after signal normalization. For the qualitative assessment, subjective evaluation of the similarity of OCT image appearance through a questionnaire was performed. Statistically significant reduction in both the absolute difference in A-scan profile and the systematic differences among SD-OCT devices were observed after signal normalization. Statistically significant improvements of image similarity between OCT image pairs were also found after the processing. With the proposed signal normalization method, quantitative analysis as well as qualitative assessment among OCT devices will become directly comparable, which would broaden the use of OCT technology in both clinical and research applications.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Chen, Chieh-Lichc154@pitt.eduCHC154
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairIshikawa,
Committee MemberAizenstein, Howard Jaizensteinhj@upmc.eduAIZEN
Committee MemberKagemann, Larrylek19@pitt.eduLEK19
Committee MemberKim,
Committee MemberStetten,
Committee MemberSchuman, Joel
Committee MemberWollstein,
Date: 28 January 2015
Date Type: Publication
Defense Date: 8 September 2014
Approval Date: 28 January 2015
Submission Date: 20 November 2014
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 189
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: Signal normalization, Optical coherence tomography
Date Deposited: 28 Jan 2015 16:42
Last Modified: 19 Dec 2016 14:42


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