Polychromatic X-ray in computed tomography (CT) can cause metal artifacts and beam hardening artifacts, which are limiting factors in the detection and diagnosis of lesions. Several groups have introduced virtual monochromatic imaging (VMI) techniques using dual-source CT to reduce these artifacts. However, the dual-source system with two exposures can increase the patient dose. The photon-counting detector with one exposure can replace a dual-source system. In this study, we investigated the feasibility of VMI in a photon-counting system. A prototype of the photon-counting CT system, which has 64 line-pixels Cadmium Zinc Telluride (CZT)-based photon-counting detector, was used. The source-to-detector distance and the source-to-center of rotation distance were 1,400 and 1,200 mm, respectively. Energy bins were set at 23 - 32, 33 - 42, 43 - 52, 53 - 62, and 63 - 90 keV. For comparison, the integrating mode was obtained by sum of five energy bins, which is assumed to polychromatic X-ray. Two copper (Cu) rods were inserted into PMMA cylinder phantom. As results, the VMI effectively removed metal artifacts. Noise and Signal-to-noise ratio (SNR) were evaluated and the optimal VMI was measured at 77 keV. Our results indicated that VMI in the prototype of the photon-counting system effectively eliminates the metal artifact and provides better image quality than integrating mode at 23 - 90 keV.

Date Published: 27 March 2019
PDF: 5 pages
Proc. SPIE 11050, International Forum on Medical Imaging in Asia 2019, 1105005 (27 March 2019); doi: 10.1117/12.2521025

Published in SPIE Proceedings Vol. 11050:
International Forum on Medical Imaging in Asia 2019
Feng Lin; Hiroshi Fujita; Jong Hyo Kim, Editor(s)