Reference

The BPnd (Ichise MRTM2 Ref) reference model is a further developed version of Ichise's multi-linear reference tissue model which is less prone to bias due to noise in the data. In the abstract, Ichise, et al. [24] write:

"We developed and applied two new linearized reference tissue models for parametric images of binding potential (BP) and relative delivery (R1) for [11C]DASB PET imaging of 5-HT transporters in human brain. The original multilinear reference tissue model (MRTM0) was modified (MRTM) and used to estimate a clearance rate (k'₂) from the cerebellum (reference). Then, the number of parameters was reduced from three (MRTM) to two (MRTM₂) by fixing k₂' . The resulting BP and R₁ estimates were compared with the corresponding nonlinear reference tissue models, SRTM and SRTM₂, and one-tissue kinetic analysis (1TKA), for simulated and actual [11C]DASB data. MRTM gave k'₂ estimates with little bias (<1%) and small variability (<6%). MRTM2 was effectively identical to SRTM2 and 1TKA, reducing BP bias markedly over MRTMO from 12-70% to 1-4% at the expense of somewhat increased variability. MRTM2 substantially reduced BP variability by a factor of 2-3 over MRTM or SRTM. MRTM₂, SRTM₂ and 1TKA had R₁ bias < 0.3% and variability at least a factor of 2 lower than MRTM or SRTM. MRTM₂ allowed rapid generation of parametric images with the noise reductions consistent with the simulations. Rapid parametric imaging by MRTM₂ should be a useful method for human [11C]DASB PET studies.