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

Kuo Men,Jian-Rong Dai,Ying-Jie Xu,Ming-Hui Li,Yuan Tian,Peng Huang,Ke Zhang,Xin-Yuan Chen

doi:10.1155/2015/858907

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.

Highlights

Radiotherapy aims to deliver sufficient dose to the tumor target and spare the organ at risk (OAR) around target to achieve the goal, that is, killing the tumor cell with minimum toxicity to the normal tissues. Advanced irradiation techniques such as intensity modulated radiotherapy (IMRT) [1], volumetric modulated arc therapy (VMAT) [2], and stereotactic radiation therapy (SRT) [3] can generate complex dose distribution with high dose areas firmly conformed to the target
To address this problem, imaging is quite necessary in procedures of radiotherapy treatment in the image guided radiation therapy (IGRT) and the adaptive radiation therapy (ART)
Compared with the theoretical values of the phantom, the dual energy imaging method can obtain more accurate electron density values than the conventional Cone-beam computed tomography (CBCT), and the difference with the theoretical values was within 2%

Summary

Introduction

Radiotherapy aims to deliver sufficient dose to the tumor target and spare the organ at risk (OAR) around target to achieve the goal, that is, killing the tumor cell with minimum toxicity to the normal tissues. Because of the high dose gradients at the boundary of target, the anatomical change due to weight loss, tumor shrinkage, and growth during the treatment will lead to inaccurate dose delivered to patient with respect to the initial planning. To address this problem, imaging is quite necessary in procedures of radiotherapy treatment in the image guided radiation therapy (IGRT) and the adaptive radiation therapy (ART). The accuracy of patient dose calculations is largely dependent on the accuracy of the electron density

Objectives

Methods

Results

Conclusion