Software | Parameters | Parameter abbreviation | Parameter name | Unit | Definition | Significance | References |
---|---|---|---|---|---|---|---|
Qontraxt software to analyze ultrasonography time–intensity curve parameters | Time parameters | AT | Arrival time | s | Time after injection when ROI signal start to enhance | Determined by the blood flow velocity in renal cortical microvessels | |
TTP | Time to peak | s | Time after injection when ROI signal intensity reaches its maximum | It is the time from zero intensity to maximum intensity. This parameter is calculated from the fitted mathematical model and often is supplied in a closed form analytical expression | |||
AS | Ascending slope | dB/s | Slope of ascending part of TIC | Representing the perfusion speed of the ROI | |||
DT/2 | Descending time/2 | s | Half of descending time | Time needed after injection for intensity to decrease to half of PI | |||
DS | Descending slope | dB/s | Slope of descending part of the TIC, representing the dilution speed of the ROI | Reflecting the total number of microbubbles clearing the vessels within the ROI, in response to renal perfusion | |||
Intensity parameters | PI | Peak intensity | dB | The peak intensity is the difference between the maximum and minimum intensity | Reflecting the total number of microbubbles entering the vessels within the ROI, in response to renal perfusion | ||
AUC | Area under the curve | dB/s | Area under the TIC curve | Influenced by blood flow velocity and blood distribution volume, it is proportional to the mean blood flow at the ROI, which reflects changes in intravascular blood flow volume | |||
Sonotumor software analyses contrast time–intensity curve parameters | Time parameters | RT | Rise time | s | The time from injection until the peak of enhancement | Referring to the time interval between the first arrival of contrast and TTP | Schneider et at. [76]; Harrois et al. [10]; Liu et al. [78]; Nylund et al. [79] |
MTT | Mean transit time | s | Describe the average time it takes for a microbubble to pass through the ROI | It is a measure of the time to recharge after contrast destruction, with shorter times indicating higher levels of perfusion | |||
FT | Fall time | s | Referring to the duration of contrast wash-out | – | |||
WIS | Wash in slope | dB/s | The speed from the beginning of enhancement to the peak of enhancement | Maximum of wash in slope of contrast agent | |||
WIT | Wash-in time | dB/s | It is time from 5% intensity to 95% intensity | It is proportional to the time to peak but it is sometimes used with mathematical models that do not have closed form analytical expressions of TTP | |||
WOT | Wash-out time | dB/s | It is the time from the peak of the TIC curve to the zero value again | The latter timepoint (zero enhancement) is rarely seen in the raw data as it may take a long time for the ROI to become completely black again. It is easily calculated from the fitted mathematical model (curve) | |||
WiPI | Wash-in perfusion index | dB/s | Calculated as WiAUC divided by RT | – | |||
Intensity parameters | RBV | Relative blood volume | a.u | Measure of maximum intensity of ROI after full recharge | RBV is proportional to the concentration of contrast agent within the ROI and increases with increasing perfusion levels | ||
PI | Perfusion index | a.u | RBV/MTT | A measure of maximum CEUS signal intensity that is more variable than time to replenishment | |||
PE | Peak enhancement | a.u | The maximum intensity of the TIC | Â | |||
WiWoAUC | Wash-in and wash-out area under the curve | dB/s | The total area under the curve of TIC | - | |||
WiAUC | Wash-in area under the curve | dB/s | The area under the TIC from time of arrival to the PE | - | |||
WoAUC | Wash-out area under the curve | dB/s | The area under the TIC from the PE to the end of the curve | – |