title: Magnetically-coated silica nanospheres for dual-mode imaging at low ultrasound frequency.
abstract: OBJECTIVE
  To experimentally investigate the acoustical behavior of different dual-mode nanosized contrast agents (NPCAs) for echographic medical imaging at low ultrasound (US) frequency.
  
  
  METHODS
  We synthesized three different nanosized structures: (1) Pure silica nanospheres (SiNSs); (2) FePt-iron oxide (FePt-IO)-coated SiNSs; and (3) IO-coated SiNSs, employing three different diameter of SiNS-core (160, 330 and 660 nm). Tissue mimicking phantoms made of agarose gel solution containing 5 mg of different NPCAs in 2 mL-Eppendorf tubes, were insonified by a commercial echographic system at three different low US pulse values (2.5, 3.5 and 4.5 MHz). The raw radiofrequency signal, backscattered from each considered NPCA containing sample, has been processed in order to calculate the US average backscatter intensity and compare the acoustic behavior of the different NPCA types.
  
  
  RESULTS
  The highest US contrast was exhibited by pure SiNSs; FePt-IO-coated SiNSs acoustical behavior followed a similar trend of pure SiNSs with a slight difference in terms of brightness values. The acoustic response of the examined NPCAs resulted function of both SiNS diameter and US frequency. Specifically, higher US frequencies determined higher value of the backscatter for a given SiNS diameter. Frequency-dependent enhancement was marked for pure SiNSs and became less remarkable for FePt-IO-coated SiNSs, whereas IO-coated SiNSs resulted almost unaffected by such frequency variations. Pure and FePt-IO-coated SiNSs evidenced an image backscatter increasing with the diameter up to 330 nm. Conversely, among the types of NPCA tested, IO-coated SiNSs showed the lowest acoustical response for each synthesized diameter and employed US frequency, although a diameter-dependent raising trend was evidenced.
  
  
  CONCLUSIONS
  The US characterization of magnetically covered SiNS shows that FePt-IO, rather than IO, was the best magnetic coating for realizing NPCAs suitable for dual mode imaging of deep organs, combining US and magnetic resonance imaging.
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Fernanda
authors.initials: F
authors.lastname: Chiriacò
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Giulia
authors.initials: G
authors.lastname: Soloperto
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Greco
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Conversano
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Ragusa
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Menichetti
authors.affiliation: Fernanda Chiriacò, Giulia Soloperto, Antonio Greco, Francesco Conversano, Sergio Casciaro, Consiglio Nazionale delle Ricerche, Istituto di Fisiologia Clinica (CNR-IFC) c/o Campus Ecotekne, via per Monteroni, 73100 Lecce, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Casciaro
keywords: Contrast agent; Diagnostic imaging; Dual-mode Imaging; Magnetic resonance; Nanocomposite; Ultrasound