An Easily Made, Low-Cost, Tissue-Like Ultrasound Phantom Material

Ultrasound phantoms are generally of two types. One mimics the acoustic properties of tissue (with regard to the speed of sound, average attenuation, etc.). The main purpose of the other is to approx-imate the sonographic appearance of tissue. The latter is often used as a biopsy training aid. Those which mimic the acoustic properties of tissue have been constructed of agar with suspended graphite, ’ polyurethane foam,2 and magnesium silicate gels,3 and are used chiefly as test phan-toms for assessing diagnostic ultrasound imaging equipment or for studying the interaction of sound with tissue. They are generally not used for biopsy phantoms as they are either expensive or time-consuming to produce. Biopsy phantoms are simpler in construction, contain simulated cysts or masses, and are either echogenic or sonolucent. Echogenic media have consisted of a flour4 or cornstarch5 in gelatin suspension, a silicium car-bide powder in agar suspension,6 or agar.7 When properly made, their echogenicity simulates pa-renchymal tissue (except agar, which is only weakly echogenic and does not simulate paren-chymal echo texture well); however, they can be laborious to produce, requiring stirring or rota-tion during cooling to insure that the scatterers or biopsy targets remain suspended and may require materials that are not widely available (agar, si-licium carbide). Sonolucent media, on the other hand, consist of gelatin ’ without suspended scat-terers and are very easy and inexpensive to pre-pare. Unfortunately, they are also transparent (unless deeply colored), which allows the biopsy needle and biopsy target to be seen from the ex-terior. This does not mimic the in vivo situation, and makes the procedure artificially easy to per-form. Additionally, the biopsy needle is artifi