Volume-of-interest imaging with dynamic fluence modulation using multiple aperture devices

Wenying Wang, Grace J. Gang, Jeffrey H. Siewerdsen, Reuven Levinson, Satomi Kawamoto, J. Webster Stayman

Research output: Contribution to journalArticlepeer-review

Abstract

Volume-of-interest (VOI) imaging is a strategy in computed tomography (CT) that restricts x-ray fluence to particular anatomical targets via dynamic beam modulation. This permits dose reduction while retaining image quality within the VOI. VOI-CT implementation has been challenged, in part, by a lack of hardware solutions for tailoring the incident fluence to the patient and anatomical site, as well as difficulties involving interior tomography reconstruction of truncated projection data. We propose a general VOI-CT imaging framework using multiple aperture devices (MADs), an emerging beam filtration scheme based on two binary x-ray filters. Location of the VOI is prescribed using two scout views at anterior-posterior (AP) and lateral perspectives. Based on a calibration of achievable fluence field patterns, MAD motion trajectories were designed using an optimization objective that seeks to maximize the relative fluence in the VOI subject to minimum fluence constraints. A modified penalized-likelihood method is developed for reconstruction of heavily truncated data using the full-field scout views to help solve the interior tomography problem. Physical experiments were conducted to show the feasibility of noncentered and elliptical VOI in two applications-spine and lung imaging. Improved dose utilization and retained image quality are validated with respect to standard full-field protocols. We observe that the contrast-to-noise ratio (CNR) is 40% higher compared with low-dose full-field scans at the same dose. The total dose reduction is 50% for equivalent image quality (CNR) within the VOI.

Original languageEnglish (US)
Article number033504
JournalJournal of Medical Imaging
Volume6
Issue number3
DOIs
StatePublished - Jul 1 2019

Keywords

  • Fluence field modulation
  • Model-based iterative reconstruction
  • Volume-of-interest imaging

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging

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