Stability of heterogeneous elastography phantoms made from oil dispersions in aqueous gels - PubMed (original) (raw)

Stability of heterogeneous elastography phantoms made from oil dispersions in aqueous gels

Ernest L Madsen et al. Ultrasound Med Biol. 2006 Feb.

Abstract

A set of five tissue-mimicking phantoms with cylindrical inclusions were produced for assessing long-term stability of geometry and elastic properties and assessing accuracy of determination of elastic properties. The base aqueous materials were either gelatin or a mixture of agar and gelatin. Stiffness was controlled by selection of the volume percent consisting of microscopic safflower oil droplets. Cylinder diameters remained unchanged within 1% or 2% over many months. Strain ratios from elastograms of the phantoms were stable over many months, implying that elastic contrasts were also stable. Test samples, called production samples, for measurement of Young's moduli were made at the time of manufacture of each phantom and were stored separately from one another. Each production sample was homogeneous and consisted of either inclusion material or background material. For all five phantoms, it was found that the elastic contrast computed using Young's modulus values determined using the production samples accurately represented the true elastic contrasts in the corresponding phantom. This finding was established by the fact that the (true) elastic contrasts determined using samples excised from the phantoms themselves agreed with the elastic contrasts obtained using the homogeneous production samples.

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Figures

Fig. 1

Heterogeneous phantom geometry corresponding to phantoms A to C; (a) view with axis of cylindrical inclusion perpendicular to figure, (b) view with axis parallel to plane of figure.

Fig. 2

Structure of phantom D; (a) side view of constraining apparatus in the cubic container, (b) top view of constraining apparatus.

Fig. 3

Schematic of the EnduraTEC 3200 ELF system used to measure dynamic Young’s moduli of test samples.

Fig. 4

Photograph of a slice of a phantom and machinist’s calipers used for direct measurement of cylinder diameter.

Fig. 5

Diagram showing areas on elastograms for computation of strain ratios.

Fig. 6

Strain ratios of phantoms A, B and C as a function of time. P = time of production of each phantom. Mean strain ratios with standard error bars are shown.

Fig. 7

Values of inclusion cylinder diameters measured with US or with calipers on excised phantom slabs (brackets). Uncertainties correspond to SDs.

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Stability of heterogeneous elastography phantoms made from oil dispersions in aqueous gels - PubMed (original) (raw)