A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique

Abstract

Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT) device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned twice with the high and low energy X-ray, respectively. The data were decomposed into projections of the two basis material coefficients according to the model set up earlier. The two sets of decomposed projections were used to reconstruct CBCT images of the basis material coefficients. Then, the images of electron densities were calculated with these CBCT images. Results. The difference between the calculated and theoretical values was within 2% and the correlation coefficient of them was about 1.0. The dual energy imaging method obtained more accurate electron density values and reduced the beam hardening artifacts obviously. Conclusion. A novel dual energy CBCT imaging method to calculate the electron densities was developed. It can acquire more accurate values and provide a platform potentially for dose calculation.

Fast-switching dual energy cone beam computed tomography using the on-board imager of a commercial linear accelerator

“…Compared to the reference values provided by the vendor, our method obtained a mean percent error of 0.0 ± 1.8%. The largest uncertainties were observed for the bone inserts, which are known to be a problematic region for correct RED and RSP measurement(Matsufuji et al 1998, Kanematsu et al 2012, Peng et al 2016.Nevertheless, the results for the other inserts compare well to the 2% maximum error observed in the Men et al(Men et al 2015) study. The mean error measured for our RED estimation method was 0.00 ± 0.02 which compares well with Schyns et al(Schyns et al 2017) who observed a mean error of 0.01 ± 0.03.…”

“…Additionally, RED images were produced by replacing the attenuation coefficient of Al and PMMA by their corresponding RED values in the decomposed projections (Men et al 2015).…”

Dual-energy imaging method to improve the image quality and the accuracy of dose calculation for cone-beam computed tomography

“…The implementation procedure of DE-CBCT imaging for the RED calculation and treatment planning is shown in Fig 2. The detailed steps to calculate the RED could be found in our previous work 35 . The corresponding high and low X-ray projections acquired under the same imaging angle were registered using the Insight…”

“…Previously, we proposed a projection-based (not image-based) dual-energy decomposition 35 to calculate the RED of a head-like CIRS phantom using high-and low-kV CBCT projections. Here, we describe the implementation of a dual-energy imaging and processing method to improve the image quality and accuracy of the dose calculation based on CBCT images in radiotherapy planning based on a Synergy™ (Elekta, Stockholm, Sweden) system.…”

Image quality of dual-energy cone-beam CT with total nuclear variation regularization

“…To increase the benefit of dual-energy imaging, the overlap should be minimized [12]. Previous research on DE imaging has focused on the linear mixing of the low and high energy acquisitions using conventional filtered back-projection (FBP) [13], but no clear benefit has been shown yet. A common alternative to the FBP based algorithms are the iterative reconstruction algorithms.…”