The **Card. Rb82(1 Compartment)** model has been developed by Lortie et al. [1] for cardiac PET studies using ^{82}Rb bolus injection. It is based on a 1-tissue compartment model with plasma activity C_{P}(t) and total uptake in myocardium C_{myo}(t).

Operational Model Curve

The differential equation is given by

The model uses the activity in the left ventricular cavity C_{lv}(t) is used as the input curve (C_{P}(t)=C_{LV}(t)). 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

This expression is inserted for K_{1} into the differential equation, so that F becomes a fit parameter, and K_{1} is derived from it. The values of the extraction parameters reported by Lortie et al. [1] are

A = 0.77

B = 0.63 [ml/min/g]

They can be entered as input parameters into the model for changing the form of the extraction function. The model curve incorporates a cardiac dual spillover correction, resulting in the operational equation

where

V_{LV} = spill-over fraction of the blood activity in the left ventricular cavity C_{LV}(t),

V_{RV} = spill-over fraction of the blood activity in the right ventricular cavity C_{RV}(t)

Implementation

When using the model from the PCARD module, the data are transferred appropriately. When using it in PKIN the blood data have to be loaded as follows:

- The left ventricle curve must be loaded as the
**Plasma activity**curve. - The right ventricle curve must be loaded as the
**Whole blood**curve.

The following automatic adjustment is performed within the model:

- 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 a region. 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.

Parameter Fitting

The model includes the 4 fitable parameters **F**, **vRV**, **vLV **and **k2**. Please inspect the %SE standard error to get information about the reliability of the parameter estimates. The scale factor A (**EF scale**) and the exponent B (**EF exp**) of the extraction function can be entered as input parameters.

Reference

1. Lortie M, Beanlands RS, Yoshinaga K, Klein R, Dasilva JN, DeKemp RA: Quantification of myocardial blood flow with 82Rb dynamic PET imaging. Eur J Nucl Med Mol Imaging 2007, 34(11):1765-1774.