The ability to correctly quantify activity concentration with single photon emission computed tomography （SPECT） is limited by its spatial resolution. Blurring of data between adjacent structures, which is known as ...The ability to correctly quantify activity concentration with single photon emission computed tomography （SPECT） is limited by its spatial resolution. Blurring of data between adjacent structures, which is known as partial volume effects, can be compensated for by utilizing high resolution structural information from other imaging modalities such as CT or MRI. Previously developed partial volume correction （PVC） methods normally assume a spatially invariant point spread function. In SPECT this is not a good approximation, since the resolution varies with the distance from the collimator. A new method, p-PVC, was developed in this paper, which takes into account the distance dependent blurring. The method operates in projection space and is combined with filtered back-projection （FBP） reconstruction. Results from simulations show that similar quantitative results could be obtained with p-PVC＋FBP as with OSEM with resolution recovery, although with better structural definition and an order of magnitude faster.展开更多
Voidage(porosity or void fraction)in packed particles(or pebbles)is of fundamental importance in calculating the pressure drop,obtaining the drag,predicting the bed permeability,estimating the neutron streaming,etc.Fo...Voidage(porosity or void fraction)in packed particles(or pebbles)is of fundamental importance in calculating the pressure drop,obtaining the drag,predicting the bed permeability,estimating the neutron streaming,etc.For the case when particles are deformed,a method of voidage correction during the packing state is proposed using a Discrete Element Method(DEM)simulation of 3D pebble flow inside a bed of cycloidal base.A function to evaluate the remaining volume of a pebble intercepted by horizontal and vertical planes is proposed for voidage calculation.After that,the process of solving voidage distribution is provided in detail.Using this method,the voidage inside the cycloidal-base pebble bed is obtained to refer to reported similar data for validation.This method can be potentially used for dynamical voidage calculation in CFD-DEM simulation which can get suitable voidage distribution after the correction.展开更多
文摘The ability to correctly quantify activity concentration with single photon emission computed tomography （SPECT） is limited by its spatial resolution. Blurring of data between adjacent structures, which is known as partial volume effects, can be compensated for by utilizing high resolution structural information from other imaging modalities such as CT or MRI. Previously developed partial volume correction （PVC） methods normally assume a spatially invariant point spread function. In SPECT this is not a good approximation, since the resolution varies with the distance from the collimator. A new method, p-PVC, was developed in this paper, which takes into account the distance dependent blurring. The method operates in projection space and is combined with filtered back-projection （FBP） reconstruction. Results from simulations show that similar quantitative results could be obtained with p-PVC＋FBP as with OSEM with resolution recovery, although with better structural definition and an order of magnitude faster.
基金support by the National Science and Technology Major Project(grant No.2011zx06901-003)the fund of the Nuclear Power Technology Innovation Centre(grant No.HDLCXZX-2021-ZH-024).
文摘Voidage(porosity or void fraction)in packed particles(or pebbles)is of fundamental importance in calculating the pressure drop,obtaining the drag,predicting the bed permeability,estimating the neutron streaming,etc.For the case when particles are deformed,a method of voidage correction during the packing state is proposed using a Discrete Element Method(DEM)simulation of 3D pebble flow inside a bed of cycloidal base.A function to evaluate the remaining volume of a pebble intercepted by horizontal and vertical planes is proposed for voidage calculation.After that,the process of solving voidage distribution is provided in detail.Using this method,the voidage inside the cycloidal-base pebble bed is obtained to refer to reported similar data for validation.This method can be potentially used for dynamical voidage calculation in CFD-DEM simulation which can get suitable voidage distribution after the correction.
