Measurement of tissue-radiation dosage using a thermal steady-state elastic shear wave

Abstract

A biodosimeter based on thermal-induced elastic shear wave (TIESW) in silicone acellular porcine dermis (SAPD) at thermal steady state has been proposed and demonstrated. A square slab SAPD treated with ionizing radiation was tested. The SAPD becomes a continuous homogeneous and isotropic viscoelastic medium due to the generation of randomly coiled collagen fibers formed from their bundle-like structure in the dermis. A harmonic TIESW then propagates on the surface of the SAPD as measured by a nanometer-scaled strain-stress response under thermal equilibrium conditions at room temperature. TIESW oscillation frequency was noninvasively measured in real time by monitoring the transverse displacement of the TIESW on the SAPD surface. Because the elastic shear modulus is highly sensitive to absorbed doses of ionizing radiation, this proposed biodosimeter can become a highly sensitive and noninvasive method for quantitatively determining tissue-absorbed dosage in terms of TIESW’s oscillation frequency. Detection sensitivity at 1 cGy and dynamic ranges covering 1 to 40 cGy and 80 to 500 cGy were demonstrated.

Characterizing the elastic shear modulus of a soft medium via a thermally induced elastic shear wave in thermodynamic equilibrium

“…However, in the case of an extremely soft medium for shear modulus measurement-by either externally or intrinsically driving force-this becomes very hard to apply. Recently, a noncontact and noninvasive method that enables measurement of the absorbed dose of ion izing radiation in the silicone acellular porcine dermis under thermal equilibrium was proposed and demonstrated [10]. In this study, we propose a novel method based on the thermally induced elastic shear wave (TIESW) in an isotropic, homoge neous and extremely soft medium under thermodynamic equi librium at room temper ature [10,11].…”

“…Recently, a noncontact and noninvasive method that enables measurement of the absorbed dose of ion izing radiation in the silicone acellular porcine dermis under thermal equilibrium was proposed and demonstrated [10]. In this study, we propose a novel method based on the thermally induced elastic shear wave (TIESW) in an isotropic, homoge neous and extremely soft medium under thermodynamic equi librium at room temper ature [10,11]. It is a noninvasive and noncontact method in which only the elastic shear modulus G is considered as opposed to the complex shear modulus G considered in conventional methods [5][6][7][8][9].…”

“…Both beams are recombined together and pass the analyzer (A s ) of its azimuth angle that is set at 45°. Thus the heterodyne signal I s is expressed as (10) where DC 2 is the noninterference term, while I P2 and I S2 are the intensities of the P 2 and S 2 waves in the tested beam, respectively. ∆φ A = φ P1 − φ S1 ∼ = 0 due to the common path propagation of the P 1 and S 1 waves, and ∆φ B is the phase difference between the P 2 and S 2 waves .…”

“…∆φ A = φ P1 − φ S1 ∼ = 0 due to the common path propagation of the P 1 and S 1 waves, and ∆φ B is the phase difference between the P 2 and S 2 waves . To decode ∆φ B , the azimuth angle ϕ r of the analyzer in the first reference beam is adjusted until sin(2ϕ r ) √ I P1 I S1 = √ I P2 I S2 = κ in equations ( 9) and (10), where the DC terms are filtered out by using a band pass filter. Finally, a differential amplifier (DA) subtracts two heterodyne signals from each other, as expressed by [13][14][15].…”

“…The advantage of TFPHI of using twofrequency polarized laser beams is mainly addressed on their highly spatial and temporal correlation between the linear polarization pair of photons in laser beam [20]. As a result, the polarization gating, coherence gating and electronic filtering gating are simultaneously involved in the optical het erodyning to assure high detection sensitivity in analytical phase detection [10][11][12]. The sensitivity of the measurement of the elastic shear modulus is then significantly improved, not only in the oscillation frequency domain of the TIESW, but also in respect of the insensitivity to common background noise in TFPHI.…”