Low-dose quantitative phase contrast medical CT

Abstract

X-ray computed tomography (CT) is a powerful and routinely used clinical diagnostic technique, which is well tolerated by patients, and which provides high-resolution images and volumetric information about the body. However, two important limitations still affect this examination procedure: (1) its low sensitivity with respect to soft tissues, and (2) the hazards associated with x-ray exposure. Conventional radiology is based on the detection of the different photon absorption properties that characterize biological tissues, and thus the obtainable image contrast from soft and/or similar tissues is intrinsically limited. In this scenario, x-ray phase contrast imaging (XPCI) has been extensively tested and proven to overcome some of the main issues surrounding standard x-ray imaging. In addition to the absorption signal, XPCI relies on detecting the phase shifts induced by an object. Interestingly, as the order of magnitude of the phase contrast is higher than that of absorption, XPCI can, in principle, offer higher sensitivity at lower radiation doses. However, other technical aspects may counterbalance this gain, and an optimized setup and image processing solutions need to be implemented. The work presented here describes the strategies and developments we have realized, with the aim of controlling the radiation dose for the highly sensitive and quantitative XPCI-CT. Different algorithms for the phase retrieval and CT reconstruction of the XPCI data are presented. The CT algorithms we have implemented, namely the equally sloped tomography and the dictionary learning method, allow the image quality to be preserved while reducing the number of angular projections required by a factor of five. The results applied to breast imaging report accurate reconstructions at clinically compatible doses of the 3D distribution of the refractive properties of full human organs obtained by using three different phase retrieval methods. The described methodologies and the presented results have been validated by a team of clinical radiologists and represent an important step in the exploitation of XPCI-CT for in vivo and possible clinical applications.

Multiscale pink-beam microCT imaging at the ESRF-ID17 biomedical beamline

“…Briefly, in the first hutch, intense-filtered X-ray beams are used mainly for microbeam radiation therapy (MRT) programs (Brä uer-Krisch et al, 2005), while, in the second hutch, only monochromatic radiation is available. The latter hutch is used for experiments of X-ray phase-contrast imaging (analyzer based, propagation based and edge illumination) (Bravin et al, 2013;Coan et al, 2013;Gasilov et al, 2013;Mittone et al, 2018), dual energy imaging techniques (Broche et al, 2017), radiobiology (Ceresa et al, 2018) and radiotherapy (Brä uer-Krisch et al, 2015).…”

Optimization of a customized simultaneous algebraic reconstruction technique algorithm for phase-contrast breast computed tomography

“…In addition to conventional x-ray imaging that relies uniquely on the absorption properties of the sample, phase-contrast (PhC) imaging techniques have demonstrated improved visibility of low-contrast features in soft tissues (Wilkins et al 1996, Mittone et al 2018, Brombal 2020a. In this context, programs of phase-contrast bCT (PhC bCT) are under development at Elettra, the Italian synchrotron radiation (SR) facility (Trieste, Italy) (Longo et al 2019), and at the Australian Synchrotron in Melbourne (Gureyev et al 2019).…”

Advanced x-ray tomography: experiment, modeling, and algorithms

“…The issue collects 18 articles on various aspects of advanced x-ray tomography. In [1], a review is given on the development of low-dose phase contrast tomography in the synchrotron, which can be seen as illustrative for the extensive development effort that goes into new tomographic techniques. The remaining articles contain a broad range of novel research results related to various aspects of the tomographic imaging pipeline.…”