Can time-resolved, high-resolution data as acquired by an intensified gated CCD camera (ICCD) aid in the tomographic reconstruction of fluorescence concentration? Usually it is argued that fluorescence is a linear process and thus does not require non-linear, time-dependent reconstructions algorithms, unless absorption and scattering coefficients need to be determined as well. Furthermore, the acquisition of a number of time frames is usually prohibitive for fluorescence measurements, at least in small animals, due to the increased total measurement time. On the other hand, it is obvious that diffusion is less pronounced in images at early gates, due to selective imaging of photons of lower scatter order. This will be the case also for photons emitted by fluorescent sources. Early-gated imaging might increase the contrast in acquired images and could possibly improve fluorescence localization. Herein, we present early gated fluorescence images obtained from phantoms and compare them to continuously acquired data. Increased contrast between background and signal maximum can be observed in time-gated images as compared to continuous data. To make use of the properties exhibited by early gated frames, it is necessary to use a modified reconstruction algorithm. We propose a variant of the well-known Born approximation to the diffusion equation that allows to take into account single time frames. The system matrix for the time-dependent Born approach is more complex to calculate, however the complexity of the actual inverse problem (and the acquisition times) of single-frame reconstructions remains the same as compared to continuous mode.
Applying time-dependent data for fluorescence tomography
D'ANDREA, COSIMO;VALENTINI, GIANLUCA;CUBEDDU, RINALDO;
2007-01-01
Abstract
Can time-resolved, high-resolution data as acquired by an intensified gated CCD camera (ICCD) aid in the tomographic reconstruction of fluorescence concentration? Usually it is argued that fluorescence is a linear process and thus does not require non-linear, time-dependent reconstructions algorithms, unless absorption and scattering coefficients need to be determined as well. Furthermore, the acquisition of a number of time frames is usually prohibitive for fluorescence measurements, at least in small animals, due to the increased total measurement time. On the other hand, it is obvious that diffusion is less pronounced in images at early gates, due to selective imaging of photons of lower scatter order. This will be the case also for photons emitted by fluorescent sources. Early-gated imaging might increase the contrast in acquired images and could possibly improve fluorescence localization. Herein, we present early gated fluorescence images obtained from phantoms and compare them to continuously acquired data. Increased contrast between background and signal maximum can be observed in time-gated images as compared to continuous data. To make use of the properties exhibited by early gated frames, it is necessary to use a modified reconstruction algorithm. We propose a variant of the well-known Born approximation to the diffusion equation that allows to take into account single time frames. The system matrix for the time-dependent Born approach is more complex to calculate, however the complexity of the actual inverse problem (and the acquisition times) of single-frame reconstructions remains the same as compared to continuous mode.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
