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

Yueming Zhang,Changqing Li,Michael C Lun,Zhongxing Zhou

doi:10.1117/1.jbo.24.8.086002

Yueming Zhang, Changqing Li + Show 2 more

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.X-ray luminescence computed tomography (XLCT) is an emerging hybrid imaging modality which has the potential for achieving both high sensitivity and spatial resolution simultaneously. For the narrow x-ray beam-based XLCT imaging, based on previous work, a spatial resolution of about double the x-ray beam size can be achieved using a translate/rotate scanning scheme, taking step sizes equal to the x-ray beam width. To break the current spatial resolution limit, we propose a scanning strategy achieved by reducing the scanning step size to be smaller than the x-ray beam size. We performed four sets of numerical simulations and a phantom experiment using cylindrical phantoms and have demonstrated that our proposed scanning method can greatly improve the XLCT-reconstructed image quality compared with the traditional scanning approach. In our simulations, by using a fixed x-ray beam size of 0.8 mm, we were able to successfully reconstruct six embedded targets as small as 0.5 mm in diameter and with the same edge-to-edge distances by using a scanning step as small as 0.2 mm which is a 1.6 times improvement in the spatial resolution compared with the traditional approach. Lastly, the phantom experiment further demonstrated the efficacy of our proposed method in improving the XLCT image quality, with all image quality metrics improving as the step size decreased.

Highlights

X-ray luminescence computed tomography (XLCT) is an emerging hybrid molecular imaging modality with promising potential to have both the high molecular sensitivity of optical imaging and the good spatial resolution of x-ray imaging, which cannot be achieved by either modality alone
Since Pratx et al reported for the first time that narrow-beam selective excitationbased XLCT imaging could image the distribution of phosphor particles,[1,2,3] various institutions have made many attempts to further develop and improve XLCT imaging by developing new imaging systems,[1,4,5,6,7,8,9,10,11,12] building robust reconstruction algorithms,[13,14,15] and designing efficient imaging probes.[16,17,18,19,20]
For the XLCT simulations, the phantom was discretized by a finiteelement mesh (FEM) with 26,638 nodes, 153,053 tetrahedral elements, and 11,456 face elements, and the reconstructed section was interpolated onto a grid of 25 × 25 μm2-pixel size and the system matrix was interpolated onto the grid from the FEM

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Introduction

X-ray luminescence computed tomography (XLCT) is an emerging hybrid molecular imaging modality with promising potential to have both the high molecular sensitivity of optical imaging and the good spatial resolution of x-ray imaging, which cannot be achieved by either modality alone. One is the cone beam-based XLCT imaging,[9,21,22] in which a conical x-ray beam is used to cover the whole object so that the scanning time is as short as a few seconds. The disadvantage of this approach is that the spatial resolution is compromised because the x-ray beam size is larger and cannot be used for anatomical guidance in the image reconstruction. The disadvantage is its relatively long scanning time due to the small excitation region, this can be addressed by using a higher sensitivity optical detector.[10,12]

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