Fat‐referenced MR thermometry in the breast and prostate using IDEAL

Abstract

Purpose: To demonstrate a three-echo fat-referenced MR thermometry technique that estimates and corrects for time-varying phase disturbances in heterogeneous tissues. Materials and Methods:Fat protons do not exhibit a temperature-dependent frequency shift. Fat-referenced thermometry methods exploit this insensitivity and use the signal from fat to measure and correct for magnetic field disturbances. In this study, we present a fat-referenced method that uses interpolation of the fat signal to correct for phase disturbances in fat free regions. Phantom and ex vivo tissue cool-down experiments were performed to evaluate the accuracy of this method in the absence of motion. Non-heated in vivo imaging of the breast and prostate was performed to demonstrate measurement robustness in the presence of systemic and motioninduced field disturbances. Measurement accuracy of the method was compared to conventional proton resonance frequency shift MR thermometry.Results: In the ex vivo porcine tissue experiment, maximum measurement error of the fat-referenced method was reduced 42% from 3.3 to 1.9C when compared to conventional MR thermometry. In the breasts, measurement errors were reduced by up to 70% from 6.4 to 1.9 C.Conclusion: Ex vivo and in vivo results show that the proposed method reduces measurement errors in the heterogeneous tissue experiments when compared to conventional MR thermometry.

Validation of MR thermometry: Method for temperature probe sensor registration accuracy in head and neck phantoms

“…For data presented here, a phase-based fatreferenced technique was used to correct for the static B 0 drift [30]. Fat-referenced PRFS maps [25,[31][32][33] are computed as in Equation 2:…”

Influence of water and fat heterogeneity on fat‐referenced MR thermometry

“…Because of this, the nuclear field experienced by hydrogen nuclei in water and fat may be different. Notably, Hofstetter et al measured a larger difference between the fat‐referenced temperature change and temperature probe readings in pork tissue and mayonnaise. These findings suggest that the spatial distribution of water and fat and the degree of homogeneity in that distribution play a role here.…”

Dual‐step iterative temperature estimation method for accurate and precise fat‐referenced PRFS temperature imaging

“…Many studies have noted that fat‐referenced MR thermometry might have a larger error in tissues with a heterogeneous fat/water distribution, as there is a different magnetic susceptibility distribution between water and fat. However, other studies have shown that this technique works well in tissues with homogeneous fat/water distributions . In the present study, the fat/water phantom was constructed with a uniform mixture of water and peanut oil, and BAT is a fatty tissue with lipid and water protons that reside in the same cell compartment.…”