Affiliations: Division of Medical Physics, Department of Radiology,
University of Kentucky, Lexington, KY, USA | Division of Diagnostic Imaging Physics and Webster
Center for Advanced Research and Education in Radiation, Department of
Radiology, Massachusetts General Hospital, Boston, MA, USA
Note: [] Corresponding author: Jie Zhang, Division of Medical Physics,
Department of Radiology, University of Kentucky, 800 Rose Street, HX311A,
Lexington, KY 40536, USA. Tel.: +1 859 323 2146; Fax: +1 859 257 4457; E-mail:
jnzh222@uky.edu
Abstract: Image performance of a cone beam O-arm system with the use of a
Varian flat panel detector (PaxScan 4030CB) was evaluated. Modulation Transfer
Function (MTF), Noise Power Spectrum (NPS), and tube output characteristics
were measured. Image quality measurements were performed with a CATPHAN 424
phantom using a 120 kVp beam filtered with 1 mm Al and 0.1 mm Cu and three
preset protocols at different exposure levels. The CPT445 Module was used to
measure MTF. Water phantom images were used to calculate NPS. Then the NPS was
normalized by dividing the square of the mean signal. The Photon fluence at
each exposure (q) was estimated using the SpekCalc. The MTF indicates that the
reconstruction filter of the O-arm is overenhancing, meaning that it yields
values greater than unity. The system has a 10% MTF at 0.45 mm. The NPS shows
the low frequency structured noise. The evaluation of image performance of the
O-arm imaging system helps its future improvements and clinical
applications.
Keywords: O-arm, cone-beam computed tomography (CT), modulation transfer function (MTF), noise power spectrum (NPS), performance, flat panel detector (FPD)
