Investigation of calibration-based projection domain dual energy decomposition CBCT technique for brain radiotherapy applications


Conference Paper

© SPIE. Downloading of the abstract is permitted for personal use only. The purpose of the present study was to develop and evaluate a practical dual-energy imaging approach for enhancing on-board cone-beam CT (CBCT) image quality for brain radiotherapy applications. The proposed primary technique involves a projection domain calibration procedure. In-house fabricated aluminum and acrylic step wedges were stacked and oriented orthogonally to each other to produce 72 unique combinations of two-material path lengths, i.e. 8 acrylic steps × 9 aluminum steps. High (120 kV) and low (70 kV) energy projections were acquired of the step wedges and a 3rd order polynomial fit was used to map the log-normalized projection intensities to the known acrylic and aluminum thicknesses. The subsequent model was tested on two phantoms: 1) in-house DE phantom with PMMA background and calcium inserts of different concentrations (5 mg/mL, 200 mg/mL and 400 mg/mL) and 2) a RANDO head phantom. The decomposed projections were reconstructed separately as aluminum-only and acrylic-only reconstructions. In addition, virtual monochromatic projections (VMPs) obtained by combining the aluminum-only and acrylic-only projections were reconstructed at different keVs. A quantitative improvement was observed in the SDNR (signal difference to noise ratios) of the calcium inserts using Aluminum-reconstructions and synthesized VMPs (40 to 100 keV) compared to the single energy reconstructions. A reduction in beam hardening was observed as well. In addition, a qualitative improvement in soft-tissue visualization was observed with the RANDO phantom reconstructions. The findings indicate the potential of dual energy CBCT images: material specific images as well as VMPs for improved CBCT-based image guidance. The present approach can readily be applied on existing commercial systems and a feasibility study on patients is a worthwhile investigation.

Full Text

Duke Authors

Cited Authors

  • Sajja, S; Hashemi, M; Huynh, C; Mainprize, JG; Eriksson, M; Lee, Y; Nordstrom, H; Nico, A; Yin, FF; Sahgal, A; Ruschin, M

Published Date

  • January 1, 2019

Published In

Volume / Issue

  • 10948 /

International Standard Serial Number (ISSN)

  • 1605-7422

International Standard Book Number 13 (ISBN-13)

  • 9781510625433

Digital Object Identifier (DOI)

  • 10.1117/12.2510430

Citation Source

  • Scopus