Analysis of Beam Hardening of Modulation Layers for Dual Energy Cone-beam CT

Sohyun Ahn; Sam Ju Cho; Ki Chang Keum; Sang Gyu Choi; Rena Lee

Article

Original Article

Korean Journal of Medical Physics 2016; 27(1): 8-13

Published online March 31, 2016

Analysis of Beam Hardening of Modulation Layers for Dual Energy Cone-beam CT

Sohyun Ahn^*, Sam Ju Cho^*, Ki Chang Keum^*, Sang Gyu Choi^†, Rena Lee^‡

Author Info ⁺

^*Department of Radiation Oncology, College of Medicine, Yonsei University, Seoul, ^†Department of Radiation Oncology, Colledge of Medicine, Dankook University, Cheonan, ^‡Department of Radiation Oncology, School of Medicine, Ewha Womans University, Seoul, Korea

Received: March 14, 2016; Revised: March 25, 2016; Accepted: March 28, 2016

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Abstract

Dual energy cone-beam CT can distinguish two materials with different atomic compositions. The principle of dual energy cone-beam CT based on modulation layer is that higher energy spectrum can be acquired at blocked x-ray window. To evaluate the possibility of modulation layer based dual energy cone-beam CT, we analyzed x-ray spectrum for various thicknesses of modulation layers by Monte Carlo simulation. To compare with the results of simulation, the experiment was performed on prototype cone-beam CT for 50∼100 kVp with CdTe XR-100T detector. As the result of comparing, the mean energy of energy spectrum for 80 kVp are well matched with that of simulation. The mean energy of energy spectrum for 80 and 120 kVp were increased as 1.67 and 1.52 times by 2.0 mm modulation layer, respectively. We realized that the virtual dual energy x-ray source can be generated by modulation layer.

KeywordsDual energy cone-beam CT, Beam hardening effect, Modulation layer, Monte Carlo simulation