A feasibility study of time of flight cone beam computed tomography imaging

Article type: Research Article

Authors: Romero, Ignacio O. | Li, Changqing^{; *}

Affiliations: Department of Bioengineering, University of California Merced, Merced, CA, USA

Correspondence: [*] Corresponding author: Changqing Li, Department of Bioengineering, University of California Merced, Merced, CA 95343, USA. E-mail: cli32@ucmerced.edu.

Abstract: BACKGROUND:The time of flight (TOF) cone beam computed tomography (CBCT) was recently shown to reduce the X-ray scattering effects by 95% and improve the image CNR by 110% for large volume objects. The advancements in X-ray sources like in compact Free Electron Lasers (FEL) and advancements in detector technology show potential for the TOF method to be feasible in CBCT when imaging large objects. OBJECTIVE:To investigate the feasibility and efficacy of TOF CBCT in imaging smaller objects with different targets such as bones and tumors embedded inside the background. METHODS:The TOF method used in this work was verified using a 24 cm phantom. Then, the GATE software was used to simulate the CBCT imaging of an 8 cm diameter cylindrical water phantom with two bone targets using a modeled 20 keV quasi-energetic FEL source and various TOF resolutions ranging from 1 to 1000 ps. An inhomogeneous breast phantom of similar size with tumor targets was also imaged using the same system setup. RESULTS:The same results were obtained in the 24 cm phantom, which validated the applied CBCT simulation approach. For the case of 8 cm cylindrical phantom and bone target, a TOF resolution of 10 ps improved the image contrast-to-noise ratio (CNR) by 57% and reduced the scatter-to-primary ratio (SPR) by 8.63. For the case of breast phantom and tumor target, image CNR was enhanced by 12% and SPR was reduced by 1.35 at 5 ps temporal resolution. CONCLUSIONS:This study indicates that a TOF resolution below 10 ps is required to observe notable enhancements in the image quality and scatter reduction for small objects around 8 cm in diameter. The strong scattering targets such as bone can result in substantial improvements by using TOF CBCT.

Keywords: Time of flight (TOF), cone beam computed tomography (CBCT), Monte-Carlo Simulation, GATE software

DOI: 10.3233/XST-210918

Journal: Journal of X-Ray Science and Technology, vol. 29, no. 5, pp. 867-880, 2021