Zhiyu Qian

Monitoring the reduced scattering coefficient of bone tissues on the trajectory of pedicle screw placement using near-infrared spectroscopy

Abstract. Pedicle screw (PS) fixation has been widely used for spine diseases. Scientists and clinicians employ several approaches to navigate PS during operation. We have demonstrated the feasibility of monitoring the reduced scattering coefficient (μs′) on the trajectory of PS using near-infrared spectroscopy (NIRS). To perform the in-vitro monitoring, an NIRS measurement system was introduced and the reduced scattering coefficients of different sites in porcine pedicle were accurately deduced from the spectrum. Moreover, the changes of the reduced scattering coefficient along the different paths were studied. The results show reduced scattering coefficients on different regions of bones can be significantly distinguished. Furthermore, monitoring experiments along different paths confirmed that a reduced scattering coefficient would change versus the depth of puncture in pedicles. Thus, the proposed monitoring system based on NIRS provides a potential for guiding PS during operation.

An Optimization Algorithm to Inverse Problem in 2-D Optical Computed Tomography by BP Neural Network

An optimization approach is introduced to inverse model of optical CT, which can reconstruct the optical properties namely scattering coefficients of thick tissue such as brain and breast tissues. A modeling and simulation tool named FEMLAB and based on finite element method has been tested wherein the forward models based on the diffusion equation. Solve the inverse model as an optimization approach, including the optimization methods of optical properties. An improved BP neural network which based on Levenberg-Marquardt optimization algorithm was employed to solve this inverse problem. The simulation results show that the algorithm can reconstruct the optical image quickly and accurately.

Method to improve the performance of reflectance diffuse optical imaging based on polygonal optical fibers arrangement

In order to improve the performance of reflectance diffuse optical imaging (rDOI), a novel polynomial geometry (PG) of optical fibers arrangement is proposed. Polynomial geometry is based on the hexagonal geometry (HG) and multicentered double-density (MD) mode. The overlapping sensitivity matrix, area ratio (AR), reconstruction image, two-absorber model, and contrast-to-noise ratio (CNR) in different depths are used to evaluate the performance of PG. The other three geometries including HG, rectangular geometry (RG), and MD mode are also compared with PG. The deformation of the reconstruction images is evaluted by circular ratio (CR). The results prove that the proposed PG has high performance and minimum deformation in quality of reconstruction image in rDOI.