Abstract
BackgroundA multimodal polymer-shelled contrast agent (CA) with target specific potential was recently developed and tested for its acoustic properties in a single element transducer setup. Since the developed polymeric CA has different chemical composition than the commercially available CAs, there is an interest to study its acoustic response when using clinical ultrasound systems. The aim of this study was therefore to investigate the acoustic response by studying the visualization capability and shadowing effect of three polymer-shelled CAs when using optimized sequences for contrast imaging.MethodsThe acoustic response of three types of the multimodal CA was evaluated in a tissue mimicking flow phantom setup by measuring contrast to tissue ratio (CTR) and acoustic shadowing using five image sequences optimized for contrast imaging. The measurements were performed over a mechanical index (MI) range of 0.2-1.2 at three CA concentrations (106, 105, 104 microbubbles/ml).ResultsThe CTR-values were found to vary with the applied contrast sequence, MI and CA. The highest CTR-values were obtained when a contrast sequence optimized for higher MI imaging was used. At a CA concentration of 106 microbubbles/ml, acoustic shadowing was observed for all contrast sequences and CAs.ConclusionsThe CAs showed the potential to enhance ultrasound images generated by available contrast sequences. A CA concentration of 106 MBs/ml implies a non-linear relation between MB concentration and image intensity.
Highlights
A multimodal polymer-shelled contrast agent (CA) with target specific potential was recently developed and tested for its acoustic properties in a single element transducer setup
As can be seen, using the pulse inversion (PI) and power modulation (PM) sequences, the highest contrast to tissue ratio (CTR)-values were obtained at a lower mechanical index (MI) (0.4), whereas with power pulse inversion (PPI) sequence, the highest CTR-values appeared at higher MI (1.2)
A high dependency of the highest CTR values produced with different contrast sequences on the applied MI was apparent in this study, a higher MI being optimal for use with PPI and contrast pulse sequence (CPS) and a lower MI optimal for use with PI and PM sequences
Summary
A multimodal polymer-shelled contrast agent (CA) with target specific potential was recently developed and tested for its acoustic properties in a single element transducer setup. Since the developed polymeric CA has different chemical composition than the commercially available CAs, there is an interest to study its acoustic response when using clinical ultrasound systems. The CAs might be employed as a carrier of drugs that could be released locally at chosen target sites by disruption of the MBs with high-energy ultrasound. Other advantages of these CAs are a long shelf life as well as a narrow size distribution that increases the image sensitivity, which is of primary importance during targeting imaging [7,8,9]
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