Barium sulfate and pigment admixture for photoacoustic and x-ray contrast imaging of the gut

• Published in: Journal of biomedical optics 2023-08, Vol.28 (8), p.082803-082803
• Main Authors: Kilian, Hailey I, Zhang, Huijuan, Shiraz Bhurwani, Mohammad Mahdi, Nilam, Anoop M, Seong, Daewoon, Jeon, Mansik, Ionita, Ciprian N, Xia, Jun, Lovell, Jonathan F
• Format: Article
• Language: English
• Subjects: Admixtures; Animals; Barite; Barium; Barium Sulfate; Contrast agents; Contrast Media; Dyes; Gastrointestinal system; Gastrointestinal tract; Intestine; Mice; Nanoparticles; Near infrared radiation; Neodymium lasers; Photoacoustic Techniques - methods; Pigments; Radiography; Semiconductor lasers; Special Section on Seeing Inside Tissue with Optical Molecular Probes; Spectrum Analysis; Sulfates; X ray imagery; X-Rays; YAG lasers
• ISSN: 1083-3668; 1560-2281
• DOI: 10.1117/1.JBO.28.8.082803

X-ray imaging is frequently used for gastrointestinal imaging. Photoacoustic imaging (PAI) of the gastrointestinal tract is an emerging approach that has been demonstrated for preclinical imaging of small animals. A contrast agent active in both modalities could be useful for imaging applications. We aimed to develop a dual-modality contrast agent comprising an admixture of barium sulfate with pigments that absorb light in the second near-infrared region (NIR-II), for preclinical imaging with both x-ray and PAI modalities. Eleven different NIR-II dyes were evaluated after admixture with a 40% w/v barium sulfate mixture. The resulting NIR-II absorption in the soluble fraction and in the total mixture was characterized. Proof-of-principle imaging studies in mice were carried out. Pigments that produced more uniform suspensions were assessed further for photoacoustic contrast signal at a wavelength of 1064 nm that corresponds to the output of the Nd:YAG laser used. Phantom imaging studies demonstrated that the pigment-barium sulfate mixture generated imaging contrast in both x-ray and PAI modalities. The optimal pigment selected for further study was a cyanine tetrafluoroborate salt. and whole-body mouse imaging demonstrated that photoacoustic and x-ray contrast signals co-localized in the intestines for both imaging modalities. These data demonstrate that commercially-available NIR-II pigments can simply be admixed with barium sulfate to generate a dual-modality contrast agent appropriate for small animal gastrointestinal imaging.