Factor Analysis (H2O, Lung TAC)

The Factor Analysis (H2O, Lung TAC) model performs a factor analysis (FA) on dynamic cardiac H₂¹⁵O PET data to obtain anatomical images of the heart. Please refer to the guide of the cardiac modeling tool PCARD for details.

Principle

One TAC must be specified which is assumed to represent H₂¹⁵O activity in the lung. The model then proceeds as follows:

During model preprocessing three TACs are mathematically derived from the Lung TAC

Blood activity in the right ventricle (negative time shift of lung TAC)
Blood activity in the left ventricle (positive time shift of lung TAC)
Activity in myocardium: it is calculated using a 1-tissue compartment model and pre-defined values for myocardial perfusion, partition coefficient, and the shifted lung TAC as the input curve.

During pixel-wise processing myocardium and blood pool images are calculated by a factor analyis:

Myocardium: variate is TAC_myocardium; covariates are TAC_LV, TAC_RV
Blood Pool: variate is TAC_lung; covariates are TAC_myocardium

Acquisition and Data Requirements

Image Data	Dynamic cardiac H₂¹⁵O PET study (decay corrected).
TAC 1	Time-activity curve representing blood activity in the lungs.

Model Preprocessing

The lung TAC must be specified as a VOI or a file. It is then used together with the input parameters to calculate the expected TACs in the left ventricle (LV), the right ventricle (RV), and the myocardium.

PXMOD FA H2O Model Pre-processing Result

Delay Lung-RV	Left shift of the lung TAC to the time when the bolus arrived in the RV.
Delay Lung-LV	Right shift of the lung TAC to the time when the bolus arrived in the LV.
Delay Lung-Myo	Right shift of the lung TAC to the time when the bolus arrived in the myocardium.
Mean Perfusion	Expected mean perfusion of the myocardium.
Partition Coefficient	Partition coefficient of water in myocardium

The results of preprocessing is shown in the Results panel.

PXMOD FA H2O Model Pre-processing Result

Model Configuration

PXMOD FA H2O Model Parameters

Myo	The myocardium factor images which should represent an anatomical image of myocardium.
BV	Blood volume factor images which should show the blood volume.