Colorectal cancer: Parametric evaluation of morphological, functional and molecular tomographic imaging

Table 2 Main quantitative parameters extracted from perfusion imaging of colorectal cancer

Parameter name	Parameter definition	Parameter significance
Regional blood flow	Blood flow per unit volume or mass of tissue, expressed in mL of blood/min/100 mL tissue	It reflects the rate of the delivery of oxygen and nutrients to a certain tissue
Regional blood volume	Volume of capillary blood contained in a certain volume of tissue, expressed in mL blood/100 mL of tissue	It reflects the functional vascular volume
Mean transit time	Mean time needed for blood to pass through the capillary network, expressed in seconds	It reflects the time required for the contrast agent bolus to pass through tissue
Permeability-surface area product (PS)	Flow of molecules through the capillary membranes in a certain volume of tissue, expressed in mL/min/100 mL tissue	It reflects the vascular leakage rate in the microcirculation
Transfer constant (KTrans)	Rate at which the contrast agent transfers from the blood to the interstitium (rate of contrast extraction)	It reflects the balance between capillary permeability and blood flow in a tissue
Tissue interstitial volume (Ve)	Volume of extravascular and extracellular contrast agent in a certain tissue, expressed as a percentage	It is a measure of cell density
Rate constant (Kep)	Rate at which the contrast agent returns from the extravascular-extracellular space to the vascular compartment: Kep = Ktrans/Ve	It reflects the tissue microcirculation and contrast agent permeability