Image performance evaluation of a cone beam O-arm imaging system

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.