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 approximate 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 phantoms 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 rotation 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 prepare. Unfortunately, they are also transparent (unless deeply colored), which allows the biopsy needle and biopsy target to be seen from the exterior. This does not mimic the in vivo situation, and makes the procedure artificially easy to perform. Additionally, the biopsy needle is artificially easy to demonstrate sonographically in a sonolucent or hypoechoic medium compared to in vivo, as it stands out as a much more brightly echogenic structure in those media than in most tissues, again making the procedure artificially easy to perform. These shortcomings limit their usefulness in training for in vivo biopsy procedures. We describe an easily made, low-cost preparation that possesses the advantages of both types of previously reported biopsy phantoms, with none of the disadvantages. It is visually opaque with an echogenicity which simulates parenchymal echo texture, yet is as easy and inexpensive to produce as clear gelatin phantoms. Ingredients in the following proportions, in the total volume desired, are stirred until completely dissolved, which takes only 1 or 2 minutes: 250 mL (approximately 1 cup) boiling water, 20 g …