An Overview of X-ray Photon Counting Spectral Imaging (x-CSI) with a Focus on Gold Nanoparticle Quantification in Oncology

Abstract

This review article offers an overview of the differences between traditional energy integrating (EI) X-ray imaging and the new technique of X-ray photon counting spectral imaging (x-CSI). The review is motivated by the need to image gold nanoparticles (AuNP) in vivo if they are to be used clinically to deliver a radiotherapy dose-enhancing effect (RDEE). The aim of this work is to familiarise the reader with x-CSI as a technique and to draw attention to how this technique will need to develop to be of clinical use for the described oncological applications. This article covers the conceptual differences between x-CSI and EI approaches, the advantages of x-CSI, constraints on x-CSI system design, and the achievements of x-CSI in AuNP quantification. The results of the review show there are still approximately two orders of magnitude between the AuNP concentrations used in RDEE applications and the demonstrated detection limits of x-CSI. Two approaches to overcome this were suggested: changing AuNP design or changing x-CSI system design. Optimal system parameters for AuNP detection and general spectral performance as determined by simulation studies were different to those used in the current x-CSI systems, indicating potential gains that may be made with this approach.

Demonstrating a Novel, Hidden Source of Spectral Distortion in X-ray Photon Counting Detectors and Assessing Novel Trigger Schemes Proposed to Avoid It

“…This additional information allows for material decomposition tasks to be performed without the need for multiple sources or detectors. This approach is often referred to as spectral-photon-counting-computed tomography (SPCCT) [13,14] or X-ray photon counting spectral imaging (x-CSI) [15]. We will use the term x-CSI in this paper, to refer to the approach as applied more generally to X-ray imaging (e.g., line scanners or planar projection imaging [16]) rather than just to computed tomography.…”

X-ray Digital Radiography and Computed Tomography

“…Interestingly, four review papers illustrate the principles and perspective of radiographic imaging with muons [ 20 ], an overview of photon-counting spectral imaging detectors [ 21 ], a comparison of imaging techniques for biological and biomedical studies [ 22 ] and a review of the use of coherent X-rays, from early synchrotron tests to the most recent brain studies [ 23 ].…”