Pulsatile Flow Phantom for Ultrasound Image-Guided HIFU Treatment of Vascular Injuries

Abstract

A pulsatile flow phantom was developed for studies of ultrasound image-guided High Intensity Focused Ultrasound (HIFU) application in transcutaneous hemostasis of injured blood vessels. The flow phantom consisted of a pulsatile pump system with instrumented excised porcine carotid artery, which was imbedded in a transparent agarose gel to model structural configuration of in-vivo tissues. Heparinized porcine blood was circulated through the phantom. The artery was injured using an 18 Gauge needle to model a penetrating injury in human peripheral vasculature. A HIFU transducer with the diameter of 7 cm, focal length of 6.3 cm and frequency of 3.4 MHz was used to seal the puncture. Ultrasound imaging was used to localize and target the puncture site, and monitor the HIFU treatment. Triphasic blood flows present in the human arteries were reproduced, with flow rates of 50-500 ml/min, pulse rates of 62-138 beats/min, and peak pressures of 100-250 mmHg. The penetrating injury of an artery was mimicked successfully in the flow phantom setting, and was easily visualized both optically through the transparent gel and with Power Doppler ultrasound imaging. Hemostasis was achieved in 55 ± 31 s (n=9) of HIFU application. Histological observations showed that a HIFU-sealed puncture was filled with clotted blood and covered with a fibrin cap. The pulsatile flow phantom provides a controlled and repeatable environment for studies of transcutaneous imageguided HIFU application in hemostasis of a variety of blood vessel injuries.

Multiparametric Evaluation of the Acoustic Behavior of Halloysite Nanotubes for Medical Echographic Image Enhancement

“…HNTs were dispersed in agarose-based gel samples, characterized by minimal echogenicity that makes such gels suitable for in vitro studies of ultrasound (US)-based techniques and of signal enhancement produced by solid nanoparticles, as reported in the literature [13], [14]. In our case, the employment of agarose gel was particularly appropriate to identify the specific HNT contribution to the backscatter signal amplitude with different operative conditions with respect to the surrounding tissue-mimicking material.…”

“…The acoustical behavior of the medium constituting the phantom is assumed as comparable with that of human soft tissues [14], thus the adopted conservative attenuation coefficient for PNP was 0.3 dB/cm/MHz [18] according to the standard for real-time display of thermal and mechanical acoustic output indices on diagnostic US equipment [19]. For any combination of setup parameters, 850 frames, consisting each of 152 tracks × 2980 points/track) were recorded with a constant scansion speed of 12.5 mm/min.…”

Assessment of the enhancement potential of Halloysite Nanotubes for echographic imaging

“…HNTs were dispersed in agarose-based gel samples, whose employment has been already reported in literature as a suitable phantom configuration for "in vitro" studies of ultrasound signal enhancement produced by solid nanoparticles [9], [10]. In our case, the employment of an agarose gel was particularly suited to identify the specific HNT contribution to the backscatter amplitude with respect to control gel samples.…”

Optimal Enhancement Configuration of Silica Nanoparticles for Ultrasound Imaging and Automatic Detection at Conventional Diagnostic Frequencies

“…9 In fact, agarose gels, thanks to their low cost, inertness, ease of preparation, and minimal echogenicity, have been previously used also for experimental investigations of different ultrasound-based diagnostic methods. 21,22 In our case, the employment of an agarose gel was particularly suited to identify the specific modifications introduced by SiNPs in both backscatter amplitude and spectral content with respect to "blank" gel samples. On the other hand, we are aware that results obtained through the present work will need to be confirmed through further studies involving the echogenicity of real biologic tissues.…”