Tissue mimicking materials for a multi‐imaging modality prostate phantom

Abstract

Materials that simultaneously mimic soft tissue in vivo for magnetic resonance imaging ͑MRI͒, ultrasound ͑US͒, and computed tomography ͑CT͒ for use in a prostate phantom have been developed. Prostate and muscle mimicking materials contain water, agarose, lipid particles, protein, Cu ϩϩ , EDTA, glass beads, and thimerosal ͑preservative͒. Fat was mimicked with safflower oil suffusing a random mesh ͑network͒ of polyurethane. Phantom material properties were measured at 22°C. ͑22°C is a typical room temperature at which phantoms are used.͒ The values of material properties should match, as well as possible, the values for tissues at body temperature, 37°C. For MRI, the primary properties of interest are T1 and T2 relaxations times, for US they are the attenuation coefficient, propagation speed, and backscatter, and for CT, the x-ray attenuation. Considering the large number of parameters to be mimicked, rather good agreement was found with actual tissue values obtained from the literature. Using published values for prostate parenchyma, T1 and T2 at 37°C and 40 MHz are estimated to be about 1100 and 98 ms, respectively. The CT number for in vivo prostate is estimated to be 45 HU ͑Hounsfield units͒. The prostate mimicking material has a T1 of 937 ms and a T2 of 88 ms at 22°C and 40 MHz; the propagation speed and attenuation coefficient slope are 1540 m/s and 0.36 dB/cm/MHz, respectively, and the CT number of tissue mimicking prostate is 43 HU. Tissue mimicking ͑TM͒ muscle differs from TM prostate in the amount of dry weight agarose, Cu ϩϩ , EDTA, and the quality and quantity of glass beads. The 18 m glass beads used in TM muscle increase US backscatter and US attenuation; the presence of the beads also has some effect on T1 but no effect on T2. The composition of tissue-mimicking materials developed is such that different versions can be placed in direct contact with one another in a phantom with no long term change in US, MRI, or CT properties. Thus, anthropomorphic phantoms can be constructed.

Construction of a Preclinical Multimodality Phantom Using Tissue-mimicking Materials for Quality Assurance in Tumor Size Measurement

“…TM materials were made of several chemicals for the following reasons 7,11,12 : Milk has the same properties as human tissue; Thimerosal prevents bacterial invasion in milk; Mesh filters remove any impurities that may have been introduced during the prior concentrating and commercial packaging of milk; Agarose is a bonding material and MR T2 relaxation time modifier; Deionized water doesn't include metal ions which lower the relaxation times unlike tap water; Propanol increases the speed of sound for water (1,484 m/sec) to that for soft tissues (1,540 m/sec); BaSO 4 is for CT contrast enhancement; Cu 2+ /EDTA decreases MR T1 relaxation time; Glass beads are for US contrast enhancement.…”

“…The protocols for preparing the TM materials are modified from those developed in Dr. Ernest L. Madsen's laboratory at the University of Wisconsin Madison and more details are in Lee et al 8,11 .…”

System Development of Microwave Induced Thermo-Acoustic Tomography and Experiments on Breast Tumor

“…More details can be referred in [15]. The phantom, which has the similar electromagnetic parameters with tumor, is a good choice for thermo-acoustic imaging experiment [21] to test the imaging ability of the MITAT system. Pictures of the phantom and the achieved thermo-acoustic image are 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.…”

“…[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. Anderson et al 32 have also shown the effect of graphite concentration on shear wave speed in gelatine based phantoms.…”