multilinearReferenceTissueModel: The Multilinear Reference Tissue Model

Description

The multilinear reference tissue model (MRTM) estimates the binding potential from an observed time activity curve without the need for arterial sampling. Instead, a second time activity curve must be provided from a suitable reference region where there is negligible binding.

Usage

multilinearReferenceTissueModel(tac, ref, time, tstar, MRTM2 = TRUE, k2prime = NULL)

Arguments

tac

a vector corresponding to the time activity curve from the tissue (in Bq/mL).

ref

a vector corresponding to the time activity curve from the reference region (in Bq/mL).

time

a vector of average frame times (in minutes).

tstar

the time (in minutes) where the linear relationship between the response and covariates may be assumed to be true.

MRTM2

a logical value that selects the three-parameter model (MRTM) or the two-parameter model (MRTM2), where k2prime is fixed.

k2prime

the value of k2prime that has been fixed.

Value

BPBinding potential
BP.errorApproximate standard error of the binding potential
R1Ratio of the volumes of distrubution for the tissue and reference region (assumes a one-tissue model is valid)
R1.errorApproximate standard error for the ratio
k2Clearance rate constant from the tissue to plasma (assumes a one-tissue model is valid)
k2.errorApproximate standard error for k2
XDesign matrix used in the linear regression
betaRegression coefficients

Details

See the references.

The numeric integration required to construct the design matrix is performed by interpolating the time activity curves, both for the tissue and reference region, to one-second resolution and then performing the cumsum operation on them.

Given the nonlinear relationship between binding potential and the regression parameters, the deltamethod is used to approximate its standard error.

References

Ichise, M., Ballinger, J.R., Golan, H., Vines, D., Luong, A., Tsai, S. and Kung, H.F. (1996) Noninvasive quantification of dopamine D2 receptors with iodine-123-IBF SPECT, Journal of Nuclear Medicine, 37, 513-520.