The model has the standard 1-compartment form

with the differential equation

The equation assumes that the activity in the left ventricle C_{lv}(t) is used as the input curve.

Rb is known to have a flow-dependent extraction fraction, so that K_{1} , which is the product of flow F times extraction fraction E, is described by the expression

The values of the correction factors reported by Lortie et al. [44] are

A = 0.77

B = 0.63 [ml/min/g]

The model implements a geometric double spillover correction for activity from the left and right ventricle in the form

where

V_{lv} = spill-over fraction of the blood activity in the left ventricle C_{lv}(t),

V_{rv} = spill-over fraction of the blood activity in the right ventricle C_{rv}(t) .

Implementation Notes:

- The right ventricle curve is only used for spillover correction of septal TACs. It must be loaded as the
**Total blood**curve. - The left ventricle curve serves two purposes: (1) as the input curve, (2) it is used for spillover correction of all myocardial TACs. It must be loaded as the
**Input curve**. - In practice, the expression for K
_{1}is inserted into the differential equation, so that F becomes a fit parameter, and K_{1}is a derived parameter. - To allow the user to change the form of the extraction function the scale factor A and the exponent B an be entered as input parameters.
- The spill-over fraction from the right ventricle V
_{rv}is automatically fixed to zero if the string "Sep" is*not*contained in the name of the regional TAC. The assumption is that such a TAC is not from septal tissue and should thus be modeled with spill-over from the left ventricle only. The reason for this automatism is usage of the model in the**PCARD**tool. - To set V
_{rv}= 0 in all regional models proceed as follows: in one region, set V_{rv}=0 and disable the fit checkbox; fit the region; configure the button below**Copy to all regions**to**Model and Par.**and activate it.

This model is also usable in the cardiac modeling tool **PCARD**.