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Automated Beam Hardening Correction for Myocardial Perfusion Imaging using Computed Tomography

Levi, Jacob
http://orcid.org/0000-0001-9376-4170
http://rave.ohiolink.edu/etdc/view?acc_num=case1553868329519413

Abstract Details

2019, Doctor of Philosophy, Case Western Reserve University, Physics.
Myocardial perfusion imaging using computed tomography (MPI-CT) and coronary computed tomography angiography (CTA) have the potential to make CT an ideal, non-invasive imaging gatekeeper exam for invasive coronary angiography. However, beam hardening (BH) artifacts prevent accurate blood flow assessment and the reduction of false positive identification of coronary disease in MPI-CT. BH occurs when a poly-energetic x-ray beam passes through an attenuating material. Depending on the source spectrum and the material absorption, the low-energy (soft) photons are attenuated at a higher rate than high-energy (hard) photons, therefore hardening the beam. In the image reconstruction process, BH leads to characteristic streaks and non-uniformities (“cupping”), which can lead to incorrect clinical interpretation or diagnosis. Current BH correction methods require either energy-sensitive CT, not widely available, prior knowledge of physical characteristics of the scanner (i.e., the x-ray source spectrum or calibration against attenuating materials). In this dissertation, I propose an image-based, calibration-free, automated BH correction (ABHC) method suitable for MPI-CT, which is one of the most demanding applications for BH correction. In the heart of ABHC, a tailored cost function is used to evaluate streak and cupping artifacts that originate from BH. ABHC minimizes the cost function and finds optimal correction parameters for an image based BH correction algorithm. Two BH correction algorithms from the literature were incorporated into ABHC and tested: the polynomial BH correction and the newer empirical BH correction (EBHC). With both correction algorithms, ABHC leads to optimal correction parameters that dramatically reduced BH artifacts. The ABHC algorithm is evaluated by measuring BH artifact streaks and cupping on simulated and physical phantom images, and on preclinical porcine and clinical MPI-CT data. For example, we observe a reduction of 86% in cupping artifact in a physical phantom. For another example, flow ratios between two ROI’s in healthy porcine myocardium are 0.56, 0.85 and 0.93 for conventional, ABHC, and 70keV scans, respectively, a result that would change clinical decision-making. Preclinical porcine and phantom scans are obtained on a prototype spectral detector CT (SDCT) scanner and clinical scans are obtained on a Philips iCT (conventional, single-energy). From the SDCT data, virtual mono-energetic (keV) reconstructed images are used as the ground truth. ABHC can be used to reduce BH artifacts in conventional CT and improve blood flow estimation in MPI-CT, particularly by removing false flow deficits which could be interpreted as false positives. This will allow CT to become an ideal noninvasive modality for physiologic and anatomic assessment of cardiovascular disease.
Michael Martens, PhD (Committee Chair)
David Wilson, PhD (Committee Member)
Robert Brown, PhD (Committee Member)
Steven Izen, PhD (Committee Member)
114 p.
Biomedical Engineering; Medical Imaging; Physics
beam hardening; beam hardening correction; BHC; CT; ABHC; myocardial perfusion; MPI-CT; image processing

Recommended Citations

Citations

  • Levi, J. (2019). Automated Beam Hardening Correction for Myocardial Perfusion Imaging using Computed Tomography [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1553868329519413

    APA Style (7th edition)

  • Levi, Jacob. Automated Beam Hardening Correction for Myocardial Perfusion Imaging using Computed Tomography. 2019. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1553868329519413.

    MLA Style (8th edition)

  • Levi, Jacob. "Automated Beam Hardening Correction for Myocardial Perfusion Imaging using Computed Tomography." Doctoral dissertation, Case Western Reserve University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1553868329519413

    Chicago Manual of Style (17th edition)

case1553868329519413
191
© 2019, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.