title: Ultrasound imaging and characterization of biofilms based on wavelet de-noised radiofrequency data.
abstract: The ability to non-invasively image and characterize bacterial biofilms in children during nasopharyngeal colonization with potential otopathogens and during acute otitis media would represent a significant advance. We sought to determine if quantitative high-frequency ultrasound techniques could be used to achieve that goal. Systematic time studies of bacterial biofilm formation were performed on three preparations of an isolated Haemophilus influenzae (NTHi) strain, a Streptococcus pneumoniae (Sp) strain and a combination of H. influenzae and S. pneumoniae (NTHi + Sp) in an in vitro environment. The process of characterization included conditioning of the acquired radiofrequency data obtained with a 15-MHz focused, piston transducer by using a seven-level wavelet decomposition scheme to de-noise the individual A-lines acquired. All subsequent spectral parameter estimations were done on the wavelet de-noised radiofrequency data. Various spectral parameters-peak frequency shift, bandwidth reduction and integrated backscatter coefficient-were recorded. These parameters were successfully used to map the progression of the biofilms in time and to differentiate between single- and multiple-species biofilms. Results were compared with those for confocal microscopy and theoretical evaluation of form factor. We conclude that high-frequency ultrasound may prove a useful modality to detect and characterize bacterial biofilms in humans as they form on tissues and plastic materials.
authors.affiliation: Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, New York, USA.
authors.forename: Kunal
authors.initials: K
authors.lastname: Vaidya
authors.affiliation: Biomedical Sciences, Rochester Institute of Technology, Rochester, New York, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Osgood
authors.affiliation: Rochester General Hospital Research Institute, Rochester, New York, USA.
authors.forename: Dabin
authors.initials: D
authors.lastname: Ren
authors.affiliation: Rochester General Hospital Research Institute, Rochester, New York, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Pichichero
authors.affiliation: Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, Rochester, New York, USA. Electronic address: helguera@cis.rit.edu.
authors.forename: María
authors.initials: M
authors.lastname: Helguera
mesh_terms: D018441:Biofilms / Q000254:growth & development*; D049109:Cell Proliferation; D006193:Haemophilus influenzae / Q000166:cytology* / Q000502:physiology*; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D011846:Radio Waves; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D059629:Signal-To-Noise Ratio; D013296:Streptococcus pneumoniae / Q000166:cytology* / Q000502:physiology*; D014463:Ultrasonography / Q000379:methods*; D058067:Wavelet Analysis
keywords: Acute otitis media; Biofilms; Characterization; Haemophilus influenzae; High-frequency ultrasound; Streptococcus pneumoniae; Wavelet de-noising