Absorbing and scattering inhomogeneity detection using TPSF conformal

Absorbing and scattering inhomogeneity detection using TPSF conformal mapping Potlov A. Yu. , Abdulkareem S. N. , Frolov S. V. , Proskurin S. G. Biomedical engineering, TSTU, Russia http: //bmt. tstu. ru/ spros@tamb. ru Saratov Fall Meeting 2014

Objectives A time-resolved method of direct optical inhomogeneity detection in turbid media before the image reconstruction is described. The key feature of the method is time point spread functions (TPSF) acquisition followed by their conformal mapping into surfaces in the cylindrical coordinate system. Inhomogeneities’ express detection can be used in optical mammography and premature babies’ brain diagnostics. The described technique can be implemented using the same hardware as for standard time-resolved diffuse optical tomography (TR-DOT). Quantum Electronics (2011) p. 402

Photon density in a cylinder Simulation results (a) (b) Distribution of the photons in homogeneous (a) and inhomogeneous (b) cylindrical objects through 0. 75 ns after light pulse injection (blue arrow)

Numerical simulation of TPSFs were obtained numerically using the model of a drop, i. e. , the radiation pulse containing a fixed initial number of photons that appears in the object near its surface and diffuses within the object, decaying exponentially and moving mainly towards its centre. According to the diffusion equation, photon density is described as follows: Photonics and Lasers in Medicine (2013 ) p. 139

Boundary condition of the third kind (the Robin condition): where, Quantum Electronics (2014) sbm.

Software for numerical TPSF simulation The above model was implemented as dedicated software in Lab. VIEW Quantum Electronics (2014) p. 174

Inhomogeneity localization and size Quantum Electronics (2014) p. 174

Comparison of theoretical and experimental TPSF Quantum Electronics (2014) p. 174

Inhomogeneity detection Cartesian coordinate system We obtain information from the tail of the time point spread function (TPSF) corresponding to the late arriving photons (LAP) and visualize it in three-dimensional surface. in Cartesian frame homogenous case TPSF converge to a plane in the inhomogeneous case, the curves also form a plane, but with a crevasse near position of the inhomogeneity.

Slide 12 Cartesian coordinate system (a) (b) Three-dimensional representation of TPSF for homogeneous (a) and inhomogeneous (b) cases Photonics & Lasers in Medicine (2013) p. 139

Conformal mapping to cylindrical coordinates system To visualize the late arriving photons from all TPSF remove the leading area: where, Cylindrical representation is made using:

Cylindrical coordinate system (a) (b) Three-dimensional conformal mapping of TPFS for homogeneous (a) and inhomogeneous (b) cases Quantum Electronics (2014) p. 174

Normalized function is modified: where K can be any real number except zero. Then standard function is created:

The resulting function is the conformal mapping into cylindrical coordinate system: where, Quantum Electronics (2014) sbm.

Conclusion Using cylindrical system of coordinates in the homogenous case, TPSF are represented by a right cylindrical surface. In the inhomogeneous case, conformal mapping shows a convexity near the angle where absorbing heterogeneity is located. Such 3 D mapping provides quick real time detection of inhomogeneities prior to inverse problem solution.

Future work Photon density in a sphere (a) (b) Distribution of the photons in a homogeneous (a) and inhomogeneous (b) spherical objects through 0. 75 ns after light pulse injection (blue arrow)