A liver-mimicking MRI phantom for thermal ablation experiments
The cuvette consisting of two calcium fluoride windows and a spacer (a) was placed in the cuvette holder using two apertures behind and in front of it [(b) and (c)] and then in the spectrometer (d).
A transverse MR image of ex vivo porcine liver tissue: two ROIs were defined on the image, inside the tissue and in an empty region for recording the signal intensity of the tissue and quantifying the noise. The image was acquired using a 1.5-T MR scanner.
A transverse MR image of the gel phantoms: a ROI was defined inside each phantom and another one in an empty region outside the phantoms for recording the signal intensities of the phantoms and quantifying the noise. The image was acquired using a 1.5-T MR scanner. The phantoms feature the same CM but different CL values whose increase from left to right affects the signal intensity.
Optical absorption behavior of porcine liver tissue as a function of temperature at 1064 nm.
Measurement of the MR relaxation times, T1 (a) and T2 (b), in the ex vivo porcine liver using an IRTF and a MSE sequence, respectively.
The change of the relaxation times, T1 (a) and T2 (b), with temperature in the ex vivo porcine liver.
Comparison of the optical absorption behavior of the ex vivo porcine liver and the gel material at 1064 nm: the samples were experimented in the nonheated state and six heated states at temperatures 35 ≤ T ≤ 80 °C. Gel samples contained different hemoglobin amounts.
Optical absorption of the gel samples as a function of the hemoglobin concentration. The absorption does not show a remarkable variation at different temperatures.
Temperature-dependent change of T1 (a) and T2 (b) of the phantom at different contrast agent concentrations compared to the ex vivo porcine liver tissue.
MR relaxation times of the gel samples featuring various contrast agent concentrations at different temperatures: (a) T1 as a function of CM, (b)–(f) T2 as a function of CL for different CM values.
Dependence of T2 on both CL and CM gives rise to several CL values, which can give a liver-mimicking T2 in the phantom. From a linear fit, the CL value related to the preobtained CM can be determined.
Validation of the phantom absorption compared to the ex vivo porcine liver: up to ∼50 °C, the phantom and liver show an almost similar trend.
Comparison of the absorption spectra of the porcine liver tissue and the constructed gel phantom, measured in the wavelength range from 750 to 2500 nm.
Change of the phantom T1 relaxation time with temperature compared to the ex vivo porcine liver: (a) the linear fit slope of the phantom data differs slightly from that of liver, (b) Bland–Altman plot, showing the difference between the phantom and liver data.
Change of the phantom T2 relaxation time with temperature compared to the ex vivo porcine liver: (a) the linear fit slope of the phantom data differs slightly from that of liver, (b) Bland–Altman plot, showing the difference between the phantom and liver data.
The concentrations of the phantom ingredients.
Comparison of the relaxation times of ex vivo porcine liver and the gel material at different temperatures.
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