Table 2.

Definition of parameters used to assess renal function

Calyceal transit time (CTT)	The time required for contrast to pass from the renal cortex in the arterial phase to the dependent portions of the calyces on the maximum-intensity projection (MIP) images of the dynamic, contrast enhanced, sequence.
Renal transit time (RTT)	The time required for the contrast agent to pass from the renal cortex in the arterial phase until it is visualized in the ureter below the lower pole of the kidney on the MIP images of the dynamic post-contrast sequences
Mean transit time (MTT)	The time calculated using a tracer kinetic model with two (or more) compartments and corresponds to the average time for the contrast to pass from the glomerulus into the collecting ducts
Volumetric differential function (vDRF)	The relative volume of enhancing (functional) renal parenchyma of each kidney immediately before contrast is excreted into collecting system relative to the total volume of enhancing parenchyma
Patlak slope (number)	Is calculated using a tracer kinetic model with two (or more) compartments and corresponds to rate at which contrast is filtered at the glomerulus and is related to the individual kidney glomerular filtration rate (GFR)
Patlak DRF	The Patlak number of each kidney relative to the sum of both Patlak numbers
Unit Patlak	Is calculated by dividing the Patlak number for each kidney by the functioning renal volume of that kidney
Asymmetry index	Used to compare the unit Patlak values for each kidney and is an indicator of the degree of functional derangement between the two kidneys irrespective of size