Symbol	Meaning
*2	Two‐dimensional convolution operator
α	Polar angle (defined in Figs. 3 and 6)
Γ	Azimuthal angle of ray (Fig. 1)
δ	Delta function
θ	Incidence angle (Figs. 1, 2).
μ	Linear attenuation coefficient of selenium
ξ 1, ξ 2	Coordinates of point B relative to point S (Fig. 1)
ω 1, ω 2	Dummy variables in the evaluation of a convolution [Eq. (19)].
a x , a y	Del dimensions; if a x  = a y , the dimension is abbreviated a
C I	Normalization term for P I [Eq. (18)]
C Net	Normalization term for P Net [Eq. (24)]
CE‐DBT	Contrast‐enhanced digital breast tomosynthesis
CE‐DM	Contrast‐enhanced digital mammography.
d	Distance between focal spot and origin in Fig. 1
DBT	Digital breast tomosynthesis
Del	Detector element
DM	Digital mammography
FS	Focal spot
h i,k	Left‐hand endpoint of rect function [i = case number, k = ordering based on Eq. (32)]
$h_{i,k}^{\prime }$	Left‐hand endpoint of rect function [i = case number, k = ordering by positioning of left‐hand endpoints]
j i,k	Right‐hand endpoint of rect function [i = case number, k = ordering based on Eq. (32)]
$j_{i,k}^{\prime }$	Right‐hand endpoint of rect function [i = case number, k = ordering by positioning of left‐hand endpoints]
l	Selenium thickness
m x , m y	Del indices [Eqs. (50), (51)]
MTF	Modulation transfer function
N	Relative number of x‐ray quanta at depth z [Eq. (15)]
P I	PSF associated with arbitrary ionization point in x‐ray converter
P Net	Net PSF (additional subscripts denote case number)
P TFT	PSF of TFT array
P z	Depth‐dependent PSF (combined effect of P I and P TFT)
PSF	Point spread function
r	Distance between points B and S in Fig. 1
t i,k	Lower (k = 1) or upper (k = 2) limit of overlap of rect functions (i = case number)
TFT	Thin‐film transistor
v 1, v 2	Coordinate transformation for point B [Eqs. (48), (49)]
$v_1^{\prime }$	Position (relative to point Q) measured along x ′ direction in Fig. 2
$v_2^{\prime }$	Position (relative to point Q) measured along y ′ direction
VCT	Virtual clinical trial
x ′	Position along ray incidence direction
x ′′	Position measured along polar angle α in Figs. 3 and 6
x FS, y FS	Focal spot coordinates (Fig. 1)
y ′	Position perpendicular to ray incidence direction
y ′′	Position measured perpendicular to polar angle α in Figs. 3 and 6
Z	Atomic number