Development and characterization of a tissue-mimicking material for high-intensity focused ultrasound

Abstract

A tissue-mimicking material (TMM) for the acoustic and thermal characterization of high-intensity focused ultrasound (HIFU) devices has been developed. The material is a high-temperature hydrogel matrix (gellan gum) combined with different sizes of aluminum oxide particles and other chemicals. The ultrasonic properties (attenuation coefficient, speed of sound, acoustical impedance, and the thermal conductivity and diffusivity) were characterized as a function of temperature from 20 to 70°C. The backscatter coefficient and nonlinearity parameter B/A were measured at room temperature. Importantly, the attenuation coefficient has essentially linear frequency dependence, as is the case for most mammalian tissues at 37°C. The mean value is 0.64f(0.95) dB·cm(-1) at 20°C, based on measurements from 2 to 8 MHz. Most of the other relevant physical parameters are also close to the reported values, although backscatter signals are low compared with typical human soft tissues. Repeatable and consistent temperature elevations of 40°C were produced under 20-s HIFU exposures in the TMM. This TMM is appropriate for developing standardized dosimetry techniques, validating numerical models, and determining the safety and efficacy of HIFU devices.

5th International Symposium on Focused Ultrasound

“…Phase change due to displacement was separated from that due to temperature by complex subtraction of an interleaved volume acquired with no FUS applied. Temperature was obtained using the proton resonance frequency method with a referenceless background phase subtraction [6]. Experiments were performed in a gelatin phantom and excised pig brain on 3 T MRI scanners (Siemens Tim Trio and PrismaFit).…”

“…For each cycle, six in total, patients will receive a combination of ThermoDox and HIFU-induced hyperthermia followed by cyclophosphamide. All MR-HIFU experiments will be performed on a dedicated breast MR-HIFU system (Philips Healthcare, Vantaa, Finland) integrated with a clinical 1.5 T MRI scanner (Achieva, Philips Healthcare, Best, The Netherlands) [6,7]. Four to six weeks after finishing the last cycle of chemotherapy the patients will undergo surgery.…”

“…[5] The muscle tissue will be mimicked by a hightemperature hydrogel matrix (gellan gum) combined with different sizes of aluminum oxide particles and other chemicals. [6] Experiment: MR-HIFU experiment will be performed using a clinical HIFU system (InSightec, Ltd., Israel) installed in a 1.5 Tesla MRI scanner (GE Healthcare, USA). HIFU beam will be applied as shown in Fig.…”

Tissue mimicking materials for the detection of prostate cancer using shear wave elastography: A validation study

“…[26][27][28][29] TMM phantoms bridge the gap in translational research without the need of direct experimentation on humans or animals. The phantoms designed with TMMS are essential for assessing different technologies, and for training and research.…”

“…Various kinds of TMMs have already been used in ultrasound research, such as gelatine, agar, silicone, and polyacrylamide (PAA) gel. [26][27][28][29] The key parameters in material characterization for ultrasound imaging include the acoustic velocity, the acoustic impedance, and the acoustical attenuation, while Young's modulus is an important parameter for elastography phantoms. Madsen et al 30 have demonstrated the use of TM phantoms for standardization of both ultrasound imaging of the prostate 26 and for elastographic imaging 18, 31 using agar and gelatine materials.…”