| 摘要 |
Methods for increasing the imaging accuracy of object density pixel values by forming linear combinations thereof to counteract spatial mixing of object density pixel value information, and by using an estimate of the object density pixel values to correct for the effects of variations in the object density. A measured variable M as a function of time t is related to the actual object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00001"> by M(t)=∫F(<CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00002">(q),q,t) <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00003">(q) dq, where q is the spatial variable. An estimated object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00004">* is related to an actual object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00005"> bywhere E is an approximate inverse of F, and SIGMAtE([<CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00010">],q,t)F(<CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00011">,q',t) is defined as the kernel function A(q,q'). Due to the limited number of time samples, the kernel A only approximates the delta function delta(q-q'), and values of <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00012">(q') away from q=q' contribute to <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00013">*(q). An improved-accuracy object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00014">**(q) is therefore obtained aswhere the kernel matrix B is a discretized version of the kernel function A. For magnetic resonance imaging, the predominant L-dependence of E and F is through the dependence of the transverse relaxation time T2 on the object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00017">. The boundaries of the ischemic- and normal-tissue regions of the myocardium may be determined from the estimated object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00018">*(q) or from the improved-accuracy object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00019">**(q). Based on the locations of these regions, a corrected transform Ec(t), which takes the spatial dependence of the transverse relaxation time into account, may be used to obtain a corrected estimated object density <CUSTOM-CHARACTER FILE="US06351121-20020226-P00900.TIF" ID="CUSTOM-CHARACTER-00020">c*(q) according to
|
