Collimated superfine x-ray beam based x-ray luminescence computed tomography

Abstract

X-ray luminescence computed tomography (XLCT) is a hybrid imaging modality with the potential to achieve a spatial resolution up to several hundred micrometers for targets embedded in turbid media with a depth larger than several millimeters. In this paper, we report a high spatial resolution XLCT imaging system with a collimated superfine x-ray beam in imaging the deeply embedded targets. A collimator with a 100 micrometer pinhole was mounted in the front of a powerful x-ray tube to generate a superfine x-ray pencil beam with a beam diameter of 0.175 mm. For the phantom experiment of four capillary targets with an edge-to-edge distance of 400 micrometers, we were able to reconstruct the targets in a depth of 5 mm successfully, which were validated with microCT images. We have further investigated the effect of different x-ray beam diameters on the reconstructed XLCT images with numerical simulations. Our results indicate that XLCT has the ability to image successfully multiple deeply embedded targets when the collimated x-ray beam diameter is less than or equal to the target edge-to-edge distance. Our numerical simulations also demonstrate that XLCT can achieve a spatial resolution of 200 micrometers for targets embedded at a depth of 5 mm if the scanning beam has a diameter of 100 micrometers.

Method for improving the spatial resolution of narrow x-ray beam-based x-ray luminescence computed tomography imaging

“…According to previous studies, the spatial resolution limit of XLCT is generally believed to be determined by the beam aperture size. Therefore, generation of superfine x-ray beams, such as superfine collimated x-ray beams imaging 11 and focused x-ray beams imaging, 12 is generally thought to be the only way to improve the spatial resolution of XLCT imaging. However, both methods for generating superfine beams have their own shortcomings.…”

“…Since Pratx et al. reported for the first time that narrow-beam selective excitation-based XLCT imaging could image the distribution of phosphor particles, 1 – 3 various institutions have made many attempts to further develop and improve XLCT imaging by developing new imaging systems, 1 , 4 – 12 building robust reconstruction algorithms, 13 – 15 and designing efficient imaging probes. 16 – 20 …”

“…Another scanning mode is the narrow beam-based XLCT imaging, in which a collimated or focused x-ray beam is used to scan an object sequentially. 1 , 11 , 12 The narrow beam-based XLCT imaging can have a spatial resolution up to a fraction of a millimeter because the fine beam size can be applied for anatomical guidance in the XLCT reconstruction algorithm. 23 The disadvantage is its relatively long scanning time due to the small excitation region, although this can be addressed by using a higher sensitivity optical detector.…”

“…Zhang et al. 11 have reported that the spatial resolution of a narrow beam-based XLCT imaging is double the size of the scanning beam diameter. Thus, current efforts to improve the spatial resolution focus on how to obtain a small x-ray beam.…”

“…Another approach is to collimate a conical x-ray beam into a fine pencil beam with a small aperture size. 11 The advantage of this approach is that it is straightforward to implement at a very low cost. However, most x-ray photons are absorbed by the collimator leading to a low x-ray utilization efficiency, which contributes to a long measurement time.…”