Ultrasound-mediation of self-illuminating reporters improves imaging resolution in optically scattering media

Research output: Contribution to journalArticle

Authors

  • Junaid Ahmad
  • Baptiste Jayet
  • Philip J. Hill
  • Melissa L. Mather
  • Stephen P. Morgan

External organisations

  • Optics and Photonics Research Group, Faculty of Engineering, University of Nottingham
  • Department of Electrical Engineering, University of Engineering and Technology Lahore
  • School of Biosciences, University of Nottingham
  • Keele University

Abstract

In vivo imaging of self-illuminating bio-and chemiluminescent reporters is used to observe the physiology of small animals. However, strong light scattering by biological tissues results in poor spatial resolution of the optical imaging, which also degrades quantitative accuracy. To overcome this challenging problem, focused ultrasound is used to modulate the light from the reporter at the ultrasound frequency. This produces an ultrasound switchable light ‘beacon’ that reduces the influence of light scattering in order to improve spatial resolution. The experimental results demonstrate that apart from light modulation at the ultrasound frequency (AC signal at 3.5 MHz), ultrasound also increases the DC intensity of the reporters. This is shown to be due to a temperature rise caused by insonification which was minimized to be within acceptable mammalian tissue safety thresholds by adjusting the duty cycle of the ultrasound. Line scans of bio-and chemiluminescent objects embedded within a scattering medium were obtained using ultrasound modulated (AC) and ultrasound enhanced (DC) signals. Lateral resolution is improved by a factor of 12 and 7 respectively, as compared to conventional CCD imaging. Two chemiluminescent sources separated by ~10 mm at ~20 mm deep inside a 50 mm thick chicken breast have been successfully resolved with an average signal-to-noise ratio of approximately 8-10 dB.

Details

Original languageEnglish
Pages (from-to)1664-1679
Number of pages16
JournalBiomedical Optics Express
Volume9
Issue number4
Publication statusPublished - 13 Mar 2018