Quantitative Functional Imaging and Kinetic Studies With High‐z Contrast Agents Using Synchrotron Radiation Computed Tomography

Abstract

1. There is an increasing demand in diagnostic radiology for extracting additional morphological and functional quantitative parameters from three-dimensional computed tomography (CT) images. Synchrotron radiation computed tomography (SRCT) is the state-of-the-art method in preclinical X-ray CT, because its performance is close to the theoretical limits in terms of accuracy and precision. 2. The SRCT method with monochromatic X-ray beams yields absolute high-Z element contrast agent concentrations, without errors arising from beam hardening or scatter artefacts, by using digital subtraction techniques of the sinograms. Each pixel of the reconstructed difference images provides a quantitative concentration versus time curve of inhaled or injected high-Z contrast agents (xenon or iodine) with a high sensitivity. This is the key point of two functional imaging techniques that were developed at the European Synchrotron Radiation Facility: brain perfusion and lung function (ventilation and perfusion). 3. These two imaging techniques provide parametric images expressed in absolute perfusion parameters (blood volume, blood flow, mean transit time and capillary permeability) or ventilation parameters (lung volume, regional lung ventilation, bronchial lumen size, regional airway and lung compliance) with a high accuracy and precision. 4. The aim of the present brief review is to give a snapshot of the status and perspectives of these two imaging techniques, with emphasis on the performances and interests for functional imaging. Two separate sections will then describe the results obtained so far using SRCT as an in vivo functional imaging tool for measuring changes in haemodynamics and ventilation, in the investigation of experimental pathophysiology and in the effects of therapeutic intervention.

Altered Lung Motion is a Sensitive Indicator of Regional Lung Disease

“…35 We direct the reader to a number of topical examples of the use of PCXI 49,54 as well as some excellent review articles. 1,53 In this study, we demonstrate that the combination of PCXI and velocimetry can produce quantitative measures of regional lung motion, which can be used to differentiate between normal and abnormal lung tissue. Furthermore, we demonstrate that this technology is more sensitive and provides richer quantitative information for disease detection than other conventional measures such as global lung function tests and non-biased histological sampling.…”

Synchrotron Radiation Imaging for Advancing Our Understanding of Cardiovascular Function

“…85 Dynamic SR micro-CT with less motion artefacts 86 now can be acquired in relatively rapid times 84 at much higher spatial resolution than conventional CT scanners at speeds that are dependent on the size of the imaging area. 84,87 In the immediate future, it should be possible to perform fast SR micro-CT angiography in rodents selective for arterial vessels faster than is possible with conventional devices.…”

Introduction

“…In contrast, temporal subtraction is ideal for high-resolution imaging of organ systems with small fields of view (i.e. microangiography), as reviewed in this series by Shirai et al 4 and the recent investigations described in the first part of the review by Adam et al 7 In the former, the authors demonstrate that the high-intensity synchrotron radiation available now at third-generation synchrotrons enables dynamic tracking of vascular responses even in moving organ systems, such as the heart and lungs, in small animal models, with typical 2-5 msec shutter open times. In larger animals, increased tissue thickness will increase X-ray attenuation and, therefore, necessarily increase shutter exposure times to achieve adequate vessel detection.…”

“…Nevertheless, rapid imaging may yet be achieved with the higher photon fluxes that are expected to be achieved with new superconducting multipole wiggler X-ray sources planned for synchrotron facilities in Canada and Australia. In the latter review, 7 the research teams at the European Synchrotron Radiation Facility briefly describe some of their highly successful studies using dual-energy and temporal subtraction (two-dimensional) absorption imaging in rodents, pigs, primates and recently concluded clinical trials. However, in this series, the authors focus solely on temporal K-edge subtraction, which they now use with computed tomography (CT) to achieve three-dimensional image reconstructions and quantitative measurements of tracer concentration over time.…”