Flat panel detector-based cone-beam volume CT angiography imaging: System evaluation

Preliminary evaluation of recently developed large-area flat panel detector s (FPDs) indicates that FPDs have some potential advantages: compactness, a bsence of geometric distortion and veiling glare with the benefits of high resolution, high detective quantum efficiency (DQE), high frame rate and hi gh dynamic range, small image lag (<1%), and excellent linearity (similar t o1%). The advantages of the new FPD make it a promising candidate for cone- beam volume computed tomography (CT) angiography (CBVCTA) imaging. The purp ose of this study is to characterize a prototype FPD-based imaging system f or CBVCTA applications. A prototype FPD-based CBVCTA imaging system has bee n designed and constructed around a modified GE 8800 CT scanner. This syste m is evaluated for a CBVCTA imaging task in the head and neck using four ph antoms and a frozen rat. The system is first characterized in terms of line arity and dynamic range of the detector. Then, the optimal selection of kVp s for CBVCTA is determined and the effect of image lag and scatter on the i mage quality of the CBVCTA system is evaluated. Next, low-contrast resoluti on and high-contrast spatial resolution are measured. Finally, the example reconstruction images of a frozen rat are presented. The results indicate t hat the FPD-based CBVCT can achieve 2.75-1p/mm spatial resolution at 0% mod ulation transfer function (MTF) and provide more than enough low-contrast r esolution for intravenous CBVCTA imaging in the head and neck with clinical ly acceptable entrance exposure level. The results also suggest that to use an FPD for large cone-angle applications, such as body angiography, furthe r investigations are required.