Image characteristics and effective dose estimation of cone beam CT using video-fluoroscopic system

We describe the image characteristics and effective dose estimation of cone beam CT. This CT is based on video-fluoroscopic system and yields data that is amenable to three-dimensional (3D) image processing. An X-ray tube and a large area detector were mounted on a frame and rotated around an object in 12 seconds. The large area detector consisted of a fluorescent plate and a CCD (charge coupled device) video camera. While the X-ray tube was rotated around the object, X-ray pulses were generated and 360 projected images were collected in a 12-second scan. A 256×256×256 matrix image was reconstructed using a parallel processor with reconstruction time of 6 minutes. Image characteristics such as spatial resolution, image noise and distortion were evaluated by phantoms and compared with those of helical CT. Organ or tissue doses by the scan were determined by in-phantom measurement. The effective dose recommended by ICRP60 was evaluated using the organ or tissue doses. The results showed isotropic resolving power of less than 1.6 mm and no distortion of images though they showed larger image noise and effective dose than helical CT