Table 1.

Variable definitions.

Variable	Unit	Description
Ait	–	Attenuation along LOR I at time index t
cijt	mm	Contribution of voxel j to LOR i at time index t (includes geometry, resolution, solid angle, and motion effects)
Δt	s	Duration of each time bin (for direct reconstruction; time interval for discretization of the kinetic model, which can theoretically be as small as 1 ms, the timing resolution of the list mode file)
f	–	Frame index (for indirect reconstruction)
G	–	Number of k2 values used to compute sensitivity images with motion correction (Eqs. 16 and 17)
i	–	LOR index
j	–	Voxel index
k	–	List mode event index
K1,j	mL/min/cm3	Inflow rate constant of 1T model at voxel j
k2,j	1/min	Outflow rate constant of 1T model at voxel j
Lt	–	Decay factor
λj	Bq/mL	Value of emission image at voxel j
$M_{\mathit{ijt}\tau }^{\left(n\right)}$	counts	Conditional expectation of complete data at iteration n
n	–	Iteration number
Ni	(counts/s)/(Bq/mL·mm)	Normalization factor for LOR i (in terms of absolute sensitivity)
Pτ	Bq/mL	Value of input function to 1T model at time index τ
Qj	(counts/s)/(Bq/mL)	Sensitivity of voxel j
Rit	counts/s	Randoms rate for LOR i at time index t
Sit	counts/s	Scatter rate for LOR i at time index t
t	–	Time bin index, relative to injection time
T	s	Duration of an emission time frame (for indirect reconstruction)
τ	–	Time bin index of tracer delivery (for discretization of convolution integral)
Xijtτ	counts	Random variable representing counts detected on LOR i at time t, emitted from voxel j for tracer delivered at time index τ (xijtτ denotes a realization of this random variable)
ξijtτ	1/s	Rate parameter of the Poisson distribution of Xijtτ
Yit	counts	Random variable representing counts detected on LOR i at time index t (yit denotes a realization of this random variable)