Microbubbles as a scattering contrast agent for grating-based x-ray dark-field imaging

• Published in: Physics in medicine & biology 2013-02, Vol.58 (4), p.N37-N46
• Main Authors: Velroyen, A, Bech, M, Malecki, A, Tapfer, A, Yaroshenko, A, Ingrisch, M, Cyran, C C, Auweter, S D, Nikolaou, K, Reiser, M, Pfeiffer, F
• Format: Article
• Language: English
• Subjects: Absorption; Clinical Medicine; Computer Simulation; Contrast Media - pharmacology; Diagnostic Imaging - methods; Equipment Design; grating interferometer; Humans; Interferometry - methods; Kidney Diseases - pathology; Klinisk medicin; Medical and Health Sciences; Medicin och hälsovetenskap; Microbubbles; Radiologi och bildbehandling; Radiology, Nuclear Medicine and Medical Imaging; Scattering, Radiation; Ultrasonography - methods; ultrasound contrast agent; x-ray contrast agent; x-ray dark-field imaging; x-ray imaging; x-ray phase-contrast imaging; x-ray scattering; X-Rays
• ISSN: 0031-9155; 1361-6560; 1361-6560
• DOI: 10.1088/0031-9155/58/4/N37

In clinically established-absorption-based-biomedical x-ray imaging, contrast agents with high atomic numbers (e.g. iodine) are commonly used for contrast enhancement. The development of novel x-ray contrast modalities such as phase contrast and dark-field contrast opens up the possible use of alternative contrast media in x-ray imaging. We investigate using ultrasound contrast agents, which unlike iodine-based contrast agents can also be administered to patients with renal impairment and thyroid dysfunction, for application with a recently developed novel x-ray dark-field imaging modality. To produce contrast from these microbubble-based contrast agents, our method exploits ultra-small-angle coherent x-ray scattering. Such scattering dark-field x-ray images can be obtained with a grating-based x-ray imaging setup, together with refraction-based differential phase-contrast and the conventional attenuation contrast images. In this work we specifically show that ultrasound contrast agents based on microbubbles can be used to produce strongly enhanced dark-field contrast, with superior contrast-to-noise ratio compared to the attenuation signal. We also demonstrate that this method works well with an x-ray tube-based setup and that the relative contrast gain even increases when the pixel size is increased from tenths of microns to clinically compatible detector resolutions about up to a millimetre.