A novel CT perfusion protocol for quantitative contrast material mapping

In conventional CT-assisted perfusion imaging the quantitative assessment of diagnostically important parameters (e.g. cerebral blood flow and cerebral blood volume for brain perfusion) is based on the CT numbers in the acquired images. These CT numbers are distorted by a number of artifacts, especially by beam hardening. The distortion due to beam hardening can be avoided by acquiring the first images after injection of the contrast agent with a dual kV-scan, and decompose the projections into base component line integrals representing Compton scattering and photo effect. These base component line integrals can be used to estimate the contrast material line integrals from the projections of the following CT scans, done in a conventional manner. The contrast material line integrals can then be reconstructed to get a quantitative iodine map, from which perfusion parameters can be calculated more accurately. Based on simulated data, we show that this technique indeed has the potential to completely eliminate errors in the estimation of perfusion parameters due to beam hardening.