Imaging Regional Lung Structure and Function in Small Animals Using Synchrotron Radiation Phase-Contrast and K-Edge Subtraction Computed Tomography.

Sam Bayat,Gaetano Perchiazzi,José Luis Cercos-Pita,Alberto Bravin,Luca Fardin

doi:10.3389/fphys.2022.825433

Abstract

Synchrotron radiation offers unique properties of coherence, utilized in phase-contrast imaging, and high flux as well as a wide energy spectrum which allow the selection of very narrow energy bands of radiation, used in K-edge subtraction imaging (KES) imaging. These properties extend X-ray computed tomography (CT) capabilities to quantitatively assess lung morphology, and to map regional lung ventilation, perfusion, inflammation, aerosol particle distribution and biomechanical properties, with microscopic spatial resolution. Four-dimensional imaging, allows the investigation of the dynamics of regional lung functional parameters simultaneously with structural deformation of the lung as a function of time. These techniques have proven to be very useful for revealing the regional differences in both lung structure and function which is crucial for better understanding of disease mechanisms as well as for evaluating treatment in small animal models of lung diseases. Here, synchrotron radiation imaging methods are described and examples of their application to the study of disease mechanisms in preclinical animal models are presented.

Highlights

An ideal technique for imaging regional lung function should provide both high spatial and temporal resolution, allow for quantitative measurements of functional parameters and provide the ability to image the underlying lung morphology
Conventional computed tomography (CT) is limited by the low radiation flux available in standard X-ray imaging systems, which reduces the spatial and temporal resolution, in in vivo imaging
Four-dimensional (4D) CT imaging, in which highresolution mapping of lung functional parameters is recorded simultaneously with structural deformation of tissue morphology as a function of time, provides the basis for comprehensive modeling of the dynamics of lung function, at spatial resolutions allowing the visualization of alveoli

Summary

INTRODUCTION

An ideal technique for imaging regional lung function should provide both high spatial and temporal resolution, allow for quantitative measurements of functional parameters and provide the ability to image the underlying lung morphology. A multitude of interesting methods and algorithms have been developed for conventional micro-CT of the lung, with prospective and retrospective gating, motion compensation, and radiation dose reduction via sophisticated reconstruction algorithms These have been extensively reviewed previously (Ashton et al, 2015; Clark and Badea, 2021). Four-dimensional (4D) CT imaging, in which highresolution mapping of lung functional parameters is recorded simultaneously with structural deformation of tissue morphology as a function of time, provides the basis for comprehensive modeling of the dynamics of lung function, at spatial resolutions allowing the visualization of alveoli. In this mini-review, methodological aspects of KES-CT and propagation-based 4D-CT lung microscopy are summarized

ANIMAL PREPARATION

Findings

FUTURE PERSPECTIVES AND CHALLENGES