title: An improved tissue-mimicking polyacrylamide hydrogel phantom for visualizing thermal lesions with high-intensity focused ultrasound.
abstract: A recipe was created to improve the tissue-mimicking (TM) bovine serum albumin (BSA) polyacrylamide hydrogel (PAG) reported in our previous study (Choi MJ, Guntur SR, Lee KI, Paeng DG, Coleman AJ. Ultrasound Med Biol 2013; 29:439-448). In that work, the concentration of acrylamide in TM BSA PAG was increased to make its attenuation coefficient the same as that of a tissue. However, this increase made the PAG stiffer and less homogeneous. In addition, the increase in acrylamide caused a significant increase in temperature over the denaturation threshold of BSA during polymerization, which required forced cooling so that the PAG did not become opaque at room temperature after polymerization. To eliminate those shortcomings, we substituted the increased acrylamide with a viscous polysaccharide liquid (corn syrup). The concentration of corn syrup was optimized to 20% (w/v, tested in the volume of 50 mL), so that the acoustic properties of the PAG would be close to those of human liver. The improved TM (iTM) BSA PAG constructed in this study had a speed of sound of 1588 ± 9 m/s, an attenuation coefficient of 0.51 ± 0.06 dB cm(-1) at 1 MHz and a backscattering coefficient of 0.22 ± 0.09 × 10(-3) sr(-1) cm(-1) MHz(-1). The density and acoustic impedance were 1057 kg/m(3) and 1.68 MRayl, respectively, and the non-linear parameter (B/A) was 5.9 ± 0.3. The thermal, optical and mechanical properties were almost the same as those of the BSA PAG (Lafon et al.2005). Experimental verification indicated that the thermal lesions visualized in the proposed iTM BSA PAG by high-intensity focused ultrasound were highly reproducible. In conclusion, iTM BSA PAG was proven to eliminate TM BSA PAG shortcomings effectively and is expected to be a promising test phantom for clinical high-intensity focused ultrasound device.
authors.affiliation: Interdisciplinary Postgraduate Program of Biomedical Engineering, Jeju National University, Jeju, Republic of Korea; Rajiv Gandhi Institute of Technology, Visvesvaraya Technological University, Bangalore, India.
authors.forename: Sitaramanjaneya Reddy
authors.initials: SR
authors.lastname: Guntur
authors.affiliation: Interdisciplinary Postgraduate Program of Biomedical Engineering, Jeju National University, Jeju, Republic of Korea; Department of Medicine, School of Medicine, Jeju National University, Jeju, Republic of Korea. Electronic address: mjchoi@jejunu.ac.kr.
authors.forename: Min Joo
authors.initials: MJ
authors.lastname: Choi
mesh_terms: D000180:Acrylic Resins; D057086:High-Intensity Focused Ultrasound Ablation / Q000379:methods*; D006358:Hot Temperature; D006801:Humans; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D008954:Models, Biological; D019047:Phantoms, Imaging
chemical_list: D000180:Acrylic Resins; C016680:polyacrylamide gels; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate
keywords: Bovine serum albumin; Corn syrup; High intensity focused ultrasound; Phantom; Polyacrylamide hydrogel; Polysaccharide; Thermal lesion; Tissue mimicking; Visualization