Speaker
Dr
Chang-Woo Seo
(Advanced Medical Device Research Center, KERI)
Description
Recently X-ray based Computed Tomography (CT) technology has a revolution impact on medical diagnosis and also has been successfully used in industrial non-destructive testing of advanced materials. Such a technique takes advantage of the cone-beam CT (CBCT) geometry, to increase the resolution and reduce the acquisition time. CBCT system relies extremely on geometric precision and measurement quality. In CBCT system, it is generally considered that instrumentation effects (misalignment and noise, etc) and physical effects (beam hardening, scattering, etc) produce artifacts and blurring which limit the spatial resolution.
In this work, we have approached to the two-step process for misaligned geometry of CBCT system.
In the first step, the center of the detector was forcibly aligned in order to adjust X-ray focal spot by using metal-hole phantom and physical center of the detector. After setting the focal spot, in the second step, the projection data were acquired at intervals of one degree by putting five pin-hole phantoms on detector for geometric alignment between source part and detector part. The misalignment of gantry was measured by using the difference between reference point (start point) and each rotation point based on the 2D projection. The geometric alignment of CBCT system was implemented through their measured difference.
In this experiment, the X-ray tube (A-132, Varian inc.) having rhenium-tungsten molybdenum target and flat panel amorphous silicon X-ray image sensor (PaxScan 4030CB, Varian inc.) having a 397mm x 298mm active area with 194μm pixel pitch and 2048 x 1536 pixels was used for geometric alignment in our CBCT system. The focal spot alignment was repeatedly carried out by acquiring the X-ray image of 14 x 14 metal-hole phantom. 360 projections with five pin-hole phantoms were used for geometric alignment. The X-ray image results of before and after alignment of CBCT system will be analyzed and compared through the proposed method.
Author
Dr
Chang-Woo Seo
(Advanced Medical Device Research Center, KERI)
