RESUMO
Objective:To prepare ultrasound-responsive nanodroplets with block polymer PEG-PCL as shell and perfluoropentane (PFP) as core, and study the effects of mechanical index (MI) on contrast-enhanced imaging properties of nanodroplet.Methods:PEG-PCL micelles were first prepared by dialysis, and then the micelles were mixed with PFP for emulsification to obtain nanodroplets. The particle size and zeta potential of nanodroplets were measured, and the morphology of nanodroplets were observed using transmission electron microscope (TEM). The stability of nanodroplets after storage at 25 ℃ and 37 ℃ was investigated. The phase transition and contrast-enhanced imaging of nanodroplets in vitro under a series of mechanical index (MI) were studied using an ultrasound diagnostic instrument.Results:The particle size of the nanodroplets was (356.6±5.6)nm, and the zeta potential was -(7.30±0.14)mV. The nanodroplets were close to spherical under TEM and had a clear core-shell structure. The particle size and dispersion of the nanodroplets increased after storage at 37 ℃ and 25 ℃. For imaging in vitro, no acoustic signal were observed at 25 ℃ when the MI varied from 0.08 to 1.0. At 37 ℃, acoustic signals were observed when MI≥0.4, and the intensity was stronger for higher MIs.Conclusions:The contrast-enhanced imaging of nanodroplets are closely related to the MI, and a higher MI could induce the phase transition of more nanodroplets and produce stronger contrast enhancement. This study could provide basis for the application of polymeric nanodroplets in ultrasound diagnosis and targeted therapy.
RESUMO
Objective:To compare the efficacy and safety of ultrasound-guided percutaneous translumial septal myocardial ablation in dogs using laser and radiofrequency.Methods:Twelve healthy adult Beagle dogs (males or females) were randomly divided into two groups, namely, group laser and group radiofrequency (6 dogs each group). Under ultrasound guidance, laser fiber or radiofrequency ablation needle was respectively inserted into the basal and middle segments of the interventricular septa via the percutaneous transapical approach to perform ablation. The Beagle dogs received radiologic examination, laboratory tests and pathological detection before ablation, immediately after ablation, at 1 week after ablation, and at 1 month after ablation, respectively. The efficacy and safety of the two ablation procedures were compared.Results:All dogs survived after ablation. The peak gradient of LVOT decreased immediately after ablation using either laser or radiofrequency ( P<0.05), but it increased at 1 week after ablation than before ( P<0.05). At 1 month after ablation, no significant differences were found in the peak gradient of LVOT compared with that before surgery ( P<0.05). The interventricular septum thickness was increased immediately after ablation using either laser or radiofrequency than before ( P<0.05), but it decreased at 1 week and at 1 month after surgery than before ( P<0.05). The ablation zone using radiofrequency was slightly larger than that of using laser[(372.50±69.06)mm 3 vs (116.65±20.15)mm 3, P<0.001], and the surgical time of the former was significantly shorter than that of using laser [(56.00±3.22)s vs (260.00±65.39)s, P<0.05)]. Conclusions:Ultrasound-guided percutaneous translumial septal myocardial ablation is feasible, safe and effective using either laser or radiofrequency. Comparatively speaking, radiofrequency ablation is more simple and convenient.