Quantification of [18F]UCB-H Binding in the Rat Brain: From Kinetic Modelling to Standardised Uptake Value

Purpose: [18F]UCB-H is a specific positron emission tomography (PET) biomarker for the
Synaptic Vesicle protein 2A (SV2A), the binding site of the antiepileptic drug levetiracetam. With
a view to optimising acquisition time and simplifying data analysis with this radiotracer, we
compared two parameters: the distribution volume (Vt) obtained from Logan graphical analysis
using a Population-Based Input Function, and the Standardised Uptake Value (SUV).
Procedures: Twelve Sprague Dawley male rats, pre-treated with three different doses of
levetiracetam were employed to develop the methodology. Three additional kainic acid (KA)
treated rats (temporal lobe epilepsy model) were also used to test the procedure. Image
analyses focused on: (i) length of the dynamic acquisition (90 versus 60 min); (ii) correlations
between Vt and SUV over 20-min consecutive time-frames; (iii) and (iv) evaluation of differences
between groups using the Vt and the SUV; and (v) preliminary evaluation of the methodology in
the KA epilepsy model.
Results: A large correlation between the Vt issued from 60 to 90-min acquisitions was observed.
Further analyses highlighted a large correlation (r 9 0.8) between the Vt and the SUV. Equivalent
differences between groups were detected for both parameters, especially in the 20–40 and 40–
60-min time-frames. The same results were also obtained with the epilepsy model.
Conclusions: Our results enable the acquisition setting to be changed from a 90-min dynamic to
a 20-min static PET acquisition. According to a better image quality, the 20–40-min time-frame
appears optimal. Due to its equivalence to the Vt, the SUV parameter can be considered in order
to quantify [18F]UCB-H uptake in the rat brain. This work, therefore, establishes a starting point
for the simplification of SV2A in vivo quantification with [18F]UCB-H, and represents a step
forward to the clinical application of this PET radiotracer.