Optimization of tube voltage in X-ray dark-field chest radiography

Andreas P Sauter,Konstantin Willer,Julia Herzen,Lukas B Gromann,Fabian Kriner,Christian Braun,Thomas Koehler,Daniela Pfeiffer,Ernst Rummeny,Wolfgang Noichl,Franz Pfeiffer,Felix Meurer,Florian Fischer,Alexander A Fingerle,Jana Andrejewski,Fabio De Marco

doi:10.1038/s41598-019-45256-2

Andreas P Sauter, Konstantin Willer + Show 14 more

Open Access

https://doi.org/10.1038/s41598-019-45256-2

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Abstract

Grating-based X-ray dark-field imaging is a novel imaging modality which has been refined during the last decade. It exploits the wave-like behaviour of X-radiation and can nowadays be implemented with existing X-ray tubes used in clinical applications. The method is based on the detection of small-angle X-ray scattering, which occurs e.g. at air-tissue-interfaces in the lung or bone-fat interfaces in spongy bone. In contrast to attenuation-based chest X-ray imaging, the optimal tube voltage for dark-field imaging of the thorax has not yet been examined. In this work, dark-field scans with tube voltages ranging from 60 to 120 kVp were performed on a deceased human body. We analyzed the resulting images with respect to subjective and objective image quality, and found that the optimum tube voltage for dark-field thorax imaging at the used setup is at rather low energies of around 60 to 70 kVp. Furthermore, we found that at these tube voltages, the transmission radiographs still exhibit sufficient image quality to correlate dark-field information. Therefore, this study may serve as an important guideline for the development of clinical dark-field chest X-ray imaging devices for future routine use.

Highlights

Grating-based X-ray imaging is able to retrieve a differential-phase and a dark-field image, which visualize the magnitude of X-ray refraction and small-angle scatter, respectively[1]
Structural lung diseases reduce the signal and can be detected in early stages with clearly higher sensitivities compared to conventional radiographs in mice[10,11,12]
For both attenuation-based and dark-field X-ray imaging, the range of suitable tube voltages is limited by the requirement that a reasonably high detector dose is achieved, while the dose delivered to the patient is limited to an acceptably low level

Summary

Introduction

Grating-based X-ray imaging is able to retrieve a differential-phase and a dark-field image, which visualize the magnitude of X-ray refraction and small-angle scatter, respectively[1]. Multiple other applications of dark-field imaging were developed in experimental setups Those include diagnosis of lung cancer, the examination of the breast and of atherosclerotic vessel changes as well as the detection of osteoporosis[5,13,14,15]. Conventional projection radiographs of the lung are performed with 120 to 130 kVp, whereas radiographs of bones are typically obtained with 70 to 80 kVp21,22 At these tube voltages, contrast due to absorption characteristics of the examined tissues is ideal, resulting in an optimal diagnostic value of the examination[23]. An increase of photon energy E leads to a decrease of ξ, where the autocorrelation function will typically achieve a higher value (if ξ is smaller than the characteristic length scale of the imaged sample) This results in further decrease of dark-field signal strength for higher photon energies. For photon energies just below its K-edge energy (80.7 keV), it is nearly transparent, which leads to very poor visibility in this energy range

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