A Preliminary Investigation into the Use of Edge Illumination X-ray Phase Contrast Micro-CT for Preclinical Imaging

Charlotte K Hagen,Rebecca Towns,Jeffrey A Meganck,Alessandro Olivo,Marco Endrizzi

doi:10.1007/s11307-019-01396-5

Charlotte K Hagen, Rebecca Towns + Show 3 more

Open Access

https://doi.org/10.1007/s11307-019-01396-5

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Abstract

PurposeTo enable a preliminary assessment of the suitability of edge illumination (EI) x-ray phase contrast (XPC) micro x-ray computed tomography (micro-CT) to preclinical imaging. Specifically, to understand how different acquisition schemes and their combination with dedicated data processing affect contrast-to-noise ratio (CNR) and spatial resolution, while providing control over scan time and radiation dose delivery.ProceduresDeceased mice (n = 3) were scanned with an EI XPC micro-CT setup operated under different settings, leading to scan times between 18 h and 13 min. For the shortest scan, the entrance dose was measured with a calibrated PTW 23344 ion chamber. Different data processing methods were applied, retrieving either separate attenuation and phase images, or hybrid (combined attenuation and phase) images. A quantitative comparison was performed based on CNR and spatial resolution measurements for a soft tissue interface.ResultsAll phase-based images have led to a higher CNR for the considered soft tissue interface than the attenuation image, independent of scan time. The best relative CNR (a sixfold increase) was observed in one of the hybrid images. Spatial resolution was found to be connected to scan time, with a resolution of approximately 20 μm and 60 μm achieved for the longest and shortest scans, respectively. An entrance dose of approximately 300 mGy was estimated for the scan performed within 13 min.ConclusionsDespite their preliminary nature, our results suggest that EI XPC bears potential for enhancing the utility of preclinical micro-CT, and, pending further research and development, could ultimately become a valuable technique in this field.

Highlights

X-ray micro-computed tomography has gained major significance in the area of preclinical imaging of smallHagen C.K. et al.: Edge illumination x-ray phase contrast micro-CT suboptimal for visualising the structures with weak or similar attenuation
We report on the first edge illumination (EI) x-ray phase contrast (XPC) micro-CT images of deceased mice, and evaluate, in a preliminary manner, its suitability to preclinical imaging
We evaluate how key image quality metrics (CNR, spatial resolution) in EI XPC micro-CT are affected by different combinations of acquisition schemes and processing methods, while aiming to minimise scan time and radiation dose

Summary

Introduction

Hagen C.K. et al.: Edge illumination x-ray phase contrast micro-CT suboptimal for visualising the structures with weak or similar attenuation (such as soft tissue). This could be improved by selecting a higher tube current or extending the exposure; both would reduce noise and, increase contrast-to-noise ratio (CNR). The development of x-ray phase contrast (XPC) microCT, which exploits phase effects for image formation, could provide a solution [2, 3] This type of imaging focusses on the fact that x-rays are electromagnetic waves with an amplitude and a phase and takes into account the phase shift that occurs during interaction with matter, rather than, or in addition to the amplitude reduction caused by attenuation. The fact that, within the diagnostic energy window (10–100 keV), differences in δ between weakly attenuating materials (such as soft tissue) can be up to three orders of magnitude larger than in β (see Table 1) is often considered the rationale behind XPC imaging, since, if properly exploited, this can lead to a significant increase in CNR

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