1. A method of estimating blood perfusion and permeability indices, for a region of interest (ROI) by operating a computer program on intensity data input to a computer comprising: a. providing a contrast agent to an artery, wherein said artery is upstream from a region of interest (ROI), wherein said ROI comprises tissue; b. measuring intensity data to provide a tissue contrast agent curve C(t) in said tissue, wherein said C(t) is a known intensity profile measured against time; c. measuring an arterial input function AIF a (t) in said artery at a position that is upstream from said tissue, wherein said AIF a (t) is a known intensity profile measured against time; d. simulating a tissue input function AIF t (t) using a first model for a vascular transport function h a (t) taking into account delay and dispersion effect, wherein AIF t (t)=AIF a (t){circle around (×)}h a (t) , where {circle around (×)} is the convolution operator; e. simulating a tissue contrast agent concentration curve C s (t) using a blood flow F t and a second model for a tissue transport function h s (t), wherein C s (t)=(F t /k H )AIF t (t){circle around (×)}R s (t) and R s ⁡ ( t ) = 1 - ∫ 0 t ⁢ h s ⁡ ( τ ) ⁢ ⁢ ⅆ τ + E ⁢ ⁢ ⅇ - kt ⁢ ∫ 0 t ⁢ h s ⁡ ( τ ) ⁢ ⁢ ⅆ τⅇ kt ⁢ ⅆ τ , wherein k H is a hematocrit correction constant having a known value, E is an extraction fraction of said contrast agent that leaks out of blood vessels into said tissue space, wherein k is a clearance rate at which said leaked contrast agent leaves said tissue space, wherein said k=E*F t /V e , wherein V e is a volume fraction of extravascular space and extracellular space in said tissue; wherein E and V e have a value between 0 and 1 respectively; f. using a least squares method to fit the said simulated C s (t) to said measured tissue curve C(t) by optimizing the values of adjustable parameters of said first and second models including E and V e ; g. using a model-free deconvolution method to estimate initial values of said adjustable parameters for said least squares fitting process in order to derive optimized values of said adjustable parameters; and h. calculating perfusion and permeability indices from said optimized values of adjustable parameters by taking into account delay and dispersion effects.