Robust phase-retrieval-based X-ray tomography for morphological assessment of early hepatic echinococcosis infection in rats

Abstract

Propagation-based phase-contrast computed micro-tomography (PPCT) dominates the non-destructive, three-dimensional inner-structure measurement in synchrotron-based biomedical research due to its simple experimental setup. To quantitatively visualize tiny density variations in soft tissues and organs closely related to early pathological morphology, an experimental study of synchrotron-based X-ray PPCT combined with generalized phase and attenuation duality (PAD) phase retrieval was implemented with the hepatic echinococcosis (HE) infection rat model at different stages. We quantitatively analyzed and evaluated the different pathological characterizations of hepatic echinococcosis during the development of this disease via our PAD-based PPCT and especially provided evidence that hepatic alveolar echinococcosis invades the liver tissue and spreads through blood flow systems with abundant blood supply in the early stage. Additionally, the infiltration of tiny vesicles in HE lesions can be clearly observed by our PAD-PPCT technique due to the striking contrast-to-noise ratio (CNR) and mass density resolution, which cannot be found by the medical imaging techniques, such as magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound, in hospitals. The results demonstrated that our PAD-PPCT technique has a great potential for indicating the subtle structural information of pathological changes in soft biomedical specimens, especially helpful for the research of early micro-morphology of diseases.

Fig 1. Hepatic echinococcosis (HE) experimental specimen from the two-month disease rat model (a) and the corresponding MRI examination results: (b) Coronal section image; (c) Transverse section image (T1WI); (d) Transverse section image (T2WI).

The unit of length of the scalebars in (b-d) is 1cm.

Fig 2. Schematic representation of the PPCTexperimental setup at SSRF.

Fig 3. Comparison of reconstructed section imagesof standard material specimens in terms of contrast and histogram.

The tomogram (a) and corresponding histogram (c) based on the direct PPCT technique. The tomogram (b) and correspondinghistogram (d) based on the PAD-PPCT technique. The rectangular region of interests (ROIs), depicted with green dashed linesfor background and red solid lines(I/PS, II/PP, III/PMMA) for different materialsamples in (a) and (b), are used for calculation of the contrast-to-noise ratio (CNR). The length of the scale bar is 300μm.

Fig 4. Relationship between the theoretical phase-shift values and the measuredvalues based on PAD-PPCT.

The calibration factor of our imaging system is 1.5.

Fig 5. Reconstructed results ofthe early HE specimen of the two-week rat model based on PAD-PPCT.

(a), (b)and (c) are,respectively,transversal, sagittal and coronalsection imagesdisplayed on a mass density gray scale. The red arrows in (b) and (c) indicate the early HE lesions. (d) and (e) are the 3D renderings of entire volumetric early HE lesions of different HE specimens in the two-week group with different length scales. The length scalebars are, respectively, 200μm and 100μm in (a)-(d) and (e).

Fig 6. Histopathological examinations of the early HE specimens of the two-week rat modelwith thehematoxylin and eosin (H&E) staining process, corresponding to the light dark area indicated by the red rectangle in Fig 5(b), using 10× and 40× objective lens.

(b) corresponds to the yellow rectangular area in (a). The length scalebars are, respectively,20μm and 5μm in (a) and (b).

Fig 7. Reconstructed results ofthe developed HE specimen of the two-monthrat model based on PAD-PPCT.

(a), (b)and (c) are,respectively,transversal, sagittal and coronal section imagesdisplayed on a mass density gray scale. The green arrows denote HE-induced cysts, white arrows denote micro-calcifications, yellow arrows denote inflammation areas, and red rectangle corresponds to H&E examination. (d) is the 3D rendering of entire volumetric developed HE lesions, and (e) and (f) are the quantitative segmentation resultsof (d). The length scalebars are, respectively, 200μm and 100μm in (a)-(d) and (e)-(f).

Fig 8. Histopathological examinations of the early HE specimen of the two-monthrat model with thehematoxylin and eosin (H&E) staining process, corresponding to the area indicated by the red rectangle in Fig 7(a), using 10× and 40× objective lens.

(b) corresponds to the yellow rectangle area in (a). The length scalebars are, respectively,20μm and 5μm in (a) and (b).

Fig 9. Statistical volumetric results of three types of HE lesions based on quantitative PAD-PPCT segmentation.