AbstractID: 8085 Title: NEQ Description of 3-D Imaging Performance in Flat-Panel Cone-Beam CT
Measurement and theoretical description of the 3-D noise transfer characteristics of a
system for flat-panel imager (FPI) cone-beam CT (CBCT) are presented for conditions
relevant to diagnostic imaging and image-guided procedures. The approach is generalized
to describe the performance of direct and indirect-detection FPI-CBCT systems, giving
quantitative insight to system design for specific imaging tasks. Measurements of the 3-D
noise-power spectrum (NPS) and noise-equivalent quanta (NEQ) are performed using a
large-area (41x41 cm2) FPI incorporating a thick CsI:Tl converter. A number of findings
are revealed regarding 3-D noise that are distinct from classical stacked-slice CT: 1.)
Classical relationships between noise and voxel size area found to hold only under
special cases, and 3-D noise characterististics depend on the 3-D modulation transfer
function (MTF) characteristics of the system; 2.) For fully 3-D FPI-CBCT, the notion of
“slice thickness” is somewhat obsolete, and the transfer characteristics depend on
correlation in all 3 domains; 3.) Detector “efficiency” in the classical sense is properly
interpreted as the low-frequency detective quantum efficiency (DQE), with sources of
Swank noise, electronics noise, etc. included therein; 4.) A description of the 3-D NEQ is
derived that accounts for a generalized detector MTF and NPS; and 5.) Aliasing is a
significant factor in the 3-D NEQ, occurring in both the 2-D projection space and again in
the 3-D reconstruction space. The prominence of NPS aliasing necessitates careful
examination of the interplay between components of the imaging chain (e.g., detector
blur, reconstruction filter, etc.) in describing 3-D imaging performance.