How does the injection protocol influence the attenuation-time curve in CT perfusion measurements: comparison of measured and simulated data.

In this study the authors compared a computer simulation that models bolus dispersion during the first pass to patient PCT data acquired with three different types of injection protocols. PCT was performed in 27 patients with one of the three injection protocols: (1) Monophasic bolus injection with saline flush, (2) monophasic bolus injection without saline flush, and (3) biphasic bolus injection with saline flush. They performed computer simulation to model bolus dispersion in the three injection protocols. Finally, they compared the simulated attenuation-time curves to the measured ones. The simulated attenuation-time curves corresponded well to the measured data for protocol 1. With protocol 2 they found that simulation predicts bolus kinetics correctly but overestimates the concentration by about 31%. They attributed this to the missing saline flush. By comparing the simulated and measured data, they could show that without saline flush about 1/3 of the contrast agent does not contribute to the first pass. For the biphasic injection (protocol 3), they found that the first part of the attenuation-time curve can be modeled by simulating the bolus dispersion of only the high-flow portion of the injected bolus. Although the simulation model does only take into account of the first pass of the bolus, it is a useful tool to analyze and predict effects of modified injection protocols.

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