AbstractID: 7157 Title: Evaluation of a new technique for the measurement of the two dimensional
MTF of digital radiographic systems
In this work we evaluate a new method for determining the two-dimensional
modulation transfer function (MTF) of digital radiography systems using an
attenuating disk. Traditional methods such as the edge and slit methods
only measure the MTF in one direction. With these methods, the edge or
slit must be re-oriented and other images acquired to measure the MTF at
more than one direction. In the disk method, the MTF can be obtained at
any direction using a single acquisition. The method relies on the image
data from a precise disk test object. The ideal Fourier transform of the
disk object is deconvolved with the acquired image resulting in the MTF.
The application of this method was tested on a digital radiography system
(GE XQ/i) using a standard beam quality and the results were compared
with those obtained using an established edge method. The disk test
object was constructed from a 1.2 cm diameter, 0.25 mm thick circular
lead foil laminated between two 1 mm slabs of acrylic. The results
show excellent agreement between the edge and disk methods in low and
mid frequency ranges, but at high frequencies the disk results were
slightly elevated due possibly to aliasing. The results indicate that
the disk method can be employed to easily measure the two-dimensional
MTF of digital radiography imaging systems for both quality assurance and
comparative analysis among systems, especially those with an asymmetric
point spread function.