Table 1.

Summary of terms used in cascaded systems analysis of the proposed extremities CBCT scanner. Nominal values were used in the experiments unless mentioned otherwise.

Term	Definition	Nominal value
MTFFPD(fu,fv)	Modulation transfer function for 2D detector cascade	—
MTFspot(fu,fv)	Modulation transfer function associated with focal spot blur	—
SQ(fu,fv)	NPS associated with x-ray quantum noise in the 2D projection	—
SE(fu,fv)	NPS associated with electronic noise in the 2D projection	—
(fu,fv)	Frequency components of the detector Fourier domain (expressed in the detector plane)	—
(fu′,fv′)	Frequency components of the detector Fourier domain (expressed in the imaging plane)	—
${\stackrel{-}{q}}_o$	Mean fluence incident on the detector for a given projection (nominal beam: 90 kVp + 0.3 mm Cu + 4 mm Al; knee model, detector signal=100 × additive noise)	2200 (x-rays/mm2)
$\stackrel{-}{m}$	Mean detector signal	2 00 000 e/pixel
$\stackrel{-}{g_1}$	Quantum detection efficiency (mean fraction of incident photons interacting in the scintillator, imaging conditions as for ${\stackrel{-}{q}}_o$)	0.78
$\stackrel{-}{g_2}$	Mean number of optical photons generated per x-ray interaction	1905
$\stackrel{-}{g_4}$	Coupling efficiency of optical photons to sensor photodiode	0.6
apix	Detector sampling interval	0.194 mm (full-res)
0.388 mm (half-res)
apd	Detector sensitive aperture	0.16 mm (full-res)
0.32 mm (half-res)
σadd	Additive electronics noise	2000 e/pixel
aspot	Focal spot size	0.5 mm
N	Number of projections acquired across circular orbit	480
SDD	Source-detector distance	550 mm
SAD	Source-isocenter distance	420 mm
M	Magnification factor, SDD/SAD	1.3
τ	X-ray pulse length	30 ms