In:
The Journal of the Acoustical Society of America, Acoustical Society of America (ASA), Vol. 120, No. 5_Supplement ( 2006-11-01), p. 3327-3328
Abstract:
Ultrasound contrast agents were originally designed for use at low MHz frequencies; however, recent experimental evidence suggests that many of these agents may also be useful for contrast imaging at frequencies above 20 MHz. Three polymer shelled agents (mean diameters of 0.56, 1.1, and 3.4 μm) from POINT Biomedical were investigated to determine their optimal high-frequency responses. A flow phantom was constructed to restrict the flow of a dilute contrast agent solution to a small volume. The focus of a 40-MHz single-element transducer from a Visual Sonics V770 was positioned within the flow phantom. Radio-frequency backscatter data from individual contrast agents were digitized under a variety of pulse durations (1–15 cycles) and pressure levels (1.4–7.6 MPa). Echo signals from individual bubbles were windowed, and spectra were calculated. Each of the POINT agents reflected energy at the 40-MHz fundamental; however, only the 1.1-μm-diameter agent displayed characteristics of a harmonic response under longer excitations (15 cycle) and medium pressure settings (2.5 to 5 MPa). Experimental results were compared to theoretical calculations for the case of the polymer shell remaining intact during excitation and for free gas nuclei that result from a ruptured shell.
Type of Medium:
Online Resource
ISSN:
0001-4966
,
1520-8524
Language:
English
Publisher:
Acoustical Society of America (ASA)
Publication Date:
2006
detail.hit.zdb_id:
1461063-2
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