Measurements of the Modulation Transfer Function, Normalized Noise
Power Spectrum and Detective Quantum Efficiency for two flat panel detectors: A
Fluoroscopic and a Cone Beam Computer Tomography Flat Panel Detectors
Affiliations: Department of Imaging Sciences, University of
Rochester Medical Center, Rochester, NY, USA | Department of Physics and Astronomy, University of
Rochester, Rochester, NY, USA
Abstract: The physical performance of two Flat Panel Detectors has been
evaluated. The first Flat Panel Detector is for Fluoroscopic applications,
Varian PaxScan 2520, and the second is for Cone Beam Computer Tomography
applications, Varian PaxScan 4030CB. First, the spectrum of the X-ray source
was measured. Second, the linearity of the detectors was investigated by using
an ionization chamber and the average ADU values of the detectors. Third, the
temporal resolution was characterized by evaluating their image lag. Fourth,
their spatial resolution was characterized by the pre-sampling Modulation
Transfer Function. Fifth, the Normalized Noise Power Spectrum was calculated
for various exposures levels. Finally, the Detective Quantum Efficiency was
obtained as a function of spatial frequency and entrance exposure. The results
illustrate that the physical performance in Detective Quantum Efficiency and
Normalized Noise Power Spectrum of the Cone Beam Computer Tomography detector
is superior to that of the fluoroscopic detector whereas the latter detector
has a higher spatial resolution as demonstrated by larger values of its
Modulation Transfer Function at large spatial frequencies.
