2015 Volume 4 Issue 2 Pages 45-52
As digital image equipment for X-ray, computed radiography (CR) systems and flat-panel detector (FPD) systems have become the mainstream. Additionally, newer FPD systems have been developed that offer high-resolution irradiation side sampling (ISS-FPD), and reduction of each patient incident skin dose is expected. Accordingly, we measured image qualities of an ISS-FPD system and a CR system and compared them for the purpose of reducing radiation exposure. In comparing a lying-position X-ray photographing table-integrated ISS-FPD and a CR system, pre-sampled modulation transfer functions (pre-sampled MTFs), normalized noise power spectrums (NNPSs), and detective quantum efficiencies (DQEs) were measured. Furthermore, visual evaluations by the use of image quality figures (IQFs) were carried out by photographing Burger phantoms. As a result, DQEs of the ISS-FPD were higher and suggested the reduction of radiation exposure by approximately 50%. Also, in the visual evaluation, IQFs of the ISS-FPD system were lower than those of the CR system, suggesting that radiation exposure can be reduced. Our results indicate that this method does not evaluate performance of an image receptor as a single unit but can compare reduction of radiation exposure by calculating the DQE even in image equipment with an integrated grid.
