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May 21, 2018 | Author: Manuel Flores | Category: Medical Ultrasound, Agar, Nature


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J Clin Ultrasound 23:271-273, May 19950 1995 by John Wiley & Sons, Inc. CCC 0091-2751/95/040271-03 Technical Note An Easily Made, Low-Cost, Tissue-Like Ultrasound Phantom Material Ronald 0. Bude, MD, and Ronald S. Adler, MD, PhD Ultrasound phantoms are generally of two types. cially easy to demonstrate sonographically in a One mimics the acoustic properties of tissue (with sonolucent or hypoechoic medium compared to in regard to the speed of sound, average attenuation, vivo, as it stands out as a much more brightly etc.). The main purpose of the other is to approx- echogenic structure in those media than in most imate the sonographic appearance of tissue. The tissues, again making the procedure artificially latter is often used as a biopsy training aid. Those easy to perform. These shortcomings limit their which mimic the acoustic properties of tissue usefulness in training for in vivo biopsy proce- have been constructed of agar with suspended dures. graphite,’ polyurethane foam,2 and magnesium We describe an easily made, low-cost prepara- silicate gels,3 and are used chiefly as test phan- tion that possesses the advantages of both types of toms for assessing diagnostic ultrasound imaging previously reported biopsy phantoms, with none equipment o r for studying the interaction of of the disadvantages. It is visually opaque with sound with tissue. They are generally not used for an echogenicity which simulates parenchymal biopsy phantoms as they are either expensive or echo texture, yet is as easy and inexpensive to time-consuming to produce. Biopsy phantoms are produce as clear gelatin phantoms. simpler in construction, contain simulated cysts or masses, and are either echogenic or sonolucent. Echogenic media have consisted of a flour4 or MATERIALS AND METHODS cornstarch5 in gelatin suspension, a silicium car- bide powder in agar suspension,6 or agar.7 When Ingredients in the following proportions, in the properly made, their echogenicity simulates pa- total volume desired, are stirred until completely renchymal tissue (except agar, which is only dissolved, which takes only 1 or 2 minutes: 250 weakly echogenic and does not simulate paren- mL (approximately 1 cup) boiling water, 20 g of chymal echo texture well); however, they can be unflavored gelatin (3 packets of Knox brand gel- laborious to produce, requiring stirring or rota- atin), and 10 g (approximately 1 tablespoon) of tion during cooling to insure that the scatterers or sugar-free psyllium hydrophilic mucilloid fiber biopsy targets remain suspended and may require (brand name: sugar-free Metamucil). If the sugar- materials that are not widely available (agar, si- containing variety is used, approximately three licium carbide). Sonolucent media, on the other times the volume (3 tablespoons) will be required hand, consist of gelatin’ without suspended scat- to obtain the same amount of psyllium fiber. To terers and are very easy and inexpensive to pre- form a phantom without internal inclusions such pare. Unfortunately, they are also transparent as simulated “cysts” or “masses,” this mixture is (unless deeply colored), which allows the biopsy poured into the container selected (plastic bag, needle and biopsy target to be seen from the ex- milk carton, etc.) and cooled until firm. One “unit terior. This does not mimic the in vivo situation, volume” as described above, roughly cubic in and makes the procedure artificially easy to per- shape, takes 1 hour to 2 hours to congeal in a form. Additionally, the biopsy needle is artifi- refrigerator at 6°C. Forming the phantom in stages is the most sat- isfactory method to produce internal “cysts” or From the Department of Radiology, University of Michigan masses. A layer of mixture is poured into the con- Medical School, Ann Arbor, Michigan. For reprints contact Ronald 0. Bude, MD, Department of Radiology, University of tainer of choice and cooled until the surface is Michigan Medical Center, Taubman Center 2910, 1500 E. firm enough t o support the intended inclusion, Medical Center Drive, Ann Arbor, MI 48109-0326. which is placed on it (the remaining mixture has VOL. 23, NO.4, MAY 1995 271 This material is very can be reduced by approximately 50% without a inexpensive. or si- “Cysts” are simulated with water-filled bal.~ or glyc. “Cysts” are water-filled balloons..8 “Masses” are simulated with congealing of the mixture occurs. the phantom will not begin using psyllium hydrophilic mucilloid fiber can be to undergo significant microbial degeneration for prepared much more easily. not required to maintain an even suspension of maining mixture is then poured over the trapped the scattering medium. This is in contrast to inclusion and cooled until firm.^ m a c a r ~ n i . Milpitas. as the scattering water to keep it from congealing). phantom materials using flour.The echo texture of this ma- does not float. mixture is initially prepared. Image of a phantom obtained with a 5-MHZ curvilinear array transducer (Diasonics Corp. cornstarch. not with the naked eye). 272 JOURNAL OF CLINICAL ULTRASOUND . trapping the inclusion. tips of examining g ~ o v e sgrapes.olive^. more quickly. impregnated gauze. and several weeks. CA). The chief advantage that the use of this If the intended inclusion floats. the remainder of the mixture is terial simulates thyroid or testicular paren- poured into the container and allowed to congeal. and is opaque (so that biopsy needles DISCUSSION and targets can only be seen sonographically and We have produced a tissue-like ultrasound phan. A strip of gelatin- tom using a previously unreported material. a process which carrot piece^. uses widely available materials. ported tissue-like is that after the clusion placed within this layer. The re. The layer is al. chyma. further mixing is lowed to congeal. Note the homogeneous ”parenchymal“ echotexture. licium carbide as the scattering medium. Phantoms prepared pieces. (approximately 250 mL). If the inclusion medium (Figure 1). We have found this mixture to be more reproducibly than phantoms made with pre- very “forgiving. a thin layer of material provides. which loons. costing less than $1per unit volume substantial change in firmness. psyl. require intermittent stirring during cooling until erine suppositories. compared with previously re- mixture is poured into the container and the in. BUDE AND ADLER been partially submersed in a container of warm lium hydrophilic mucilloid fiber. The echogenic line immediately superior to the ”cysts” represents the bound- ary between successively poured layers. If refrigerated. with the larger one containing a small pebble.^ ~ or hot dog can take more than 1 hour.” and the gelatin concentration viously reported materials.’ . which simulates skin and FIGURE 1. B r J Radiol tom for learning needle placement for sonographi- 57:1161. TISSUE-LIKE ULTRASOUND PHANTOM helps prevent surface laceration. 23. 134517. NO. J Ultrasound Med 5:295. nique. 7. 4. 1989.6 trasound 17:456. 1982. B r J Radiol sound-guided needle biopsy using the freehand tech- 55:667. MAY 1995 2 73 . Metzger TS. McNamara ME: Preparation of a onto the scanning surface with a small amount of homemade ultrasound biopsy phantom. 1984. Duck FA: Ultrasonic tissue-equivalent 8. Burlew MM. J Ultrasound Med 8:701. 3. Radiology phantom. Bude RO. 1980. Silver B. Fredfeldt KE: An easily made ultrasound biopsy ultrasound tissue-equivalent material. REFERENCES 1991. cally guided biopsy. 1990. et al: Clean and dirty shadowing a t US: a reappraisal. 1. 1986. Fornage B: A simple phantom for training in ultra- materials using inorganic gel mixtures. J Clin U1- gelatin to prolong the life of the phantom. Rubin JM. VOL. Matalon TA: A simple phan- 2. 1989. Zagzebski JA. McNamara MP. Sheppard J. Radiology 181:231. 5. et al: A new 6. Adler RS. Madsen EL. can be coated 4. Ophir J: Ultrasound phantom material. A J R 1542347.
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