Gas content dependence in Magnetic Resonance Elastography of the lungs
نویسندگان
چکیده
MR-elastography (MRE) was devised in 1995 through magnetic resonance of the proton to detect the motion of tissues and to follow their response to an acoustic stress, generally applied by a mechanical vibrator at the surface of the body. By implementing this technique on a tracer gas hyperpolarized helium-3, we circumvent the SNR limitations of MRE in the airways. However, the gas contained in the lung is a source of elasticity and therefore its effect must be considered in MRE measurements. Previous experiments of wave propagation in dog lungs suggested that the elastic moduli of lungs are essentially a function of pressure and that gas inertia does not affect the viscoelastic properties of the lung parenchyma, however that method was able to measure only longitudinal waves and global elastic constants. MRE is able to record both shear and longitudinal waves regionally throughout the lung. Here we perform MRE measurements in excised pig lungs inflated with three different gases of widely varying density, air, helium-4 (4He), and sulphur hexafluoride (SF6), in a phantom designed to make pixel by pixel comparison possible.
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