Evaluation of three-dimensional iterative image reconstruction in C-arm-based interventional cone-beam CT A phantom study in comparison with customary reconstruction technique

We compared images obtained using a three-dimensional iterative image reconstruction (3D-IIR) algorithm for C-arm-based interventional cone-beam computed tomography (CBCT) with that using the customary reconstruction technique to quantify the effect of reconstruction techniques on image quality. We scanned 2 phantoms using an angiography unit with digital flat-panel system-an elliptical cylinder acrylic phantom to evaluate spatial resolution and a Catphan phantom to evaluate CT number linearity, image noise, and low-contrast resolution. Three-dimensional imaging was calculated using Feldkamp algorithms, and additional image sets were reconstructed using 3D-IIR at 5 settings (Sharp, Default, Soft(+), Soft(++), Soft(+++)). We evaluated quality of images obtained using the 6 reconstruction techniques and analyzed variance to test values of the 10% value of each MTF, mean CT number, and contrast-to-noise ratio (CNR), with P<.05 considered statistically significant. Modulation transfer function curves and CT number linearity among images obtained using the customary technique and the 5 3D-IIR techniques showed excellent agreement. Noise power spectrum curves demonstrated uniform noise reduction across the spatial frequency in the iterative reconstruction, and CNR obtained using all but the Sharp 3D-IIR technique was significantly better than that using the customary reconstruction technique (Sharp, P=.1957; Default, P=.0042; others, P<.0001). Use of 3D-IIR, especially the Soft(++) and Soft(+++) settings, improved visualization of low-contrast targets. Use of a 3D-IIR can significantly improve image noise and low-contrast resolution while maintaining spatial resolution in C-armbased interventional CBCT, yielding higher quality images that may increase safety and efficacy in interventional radiology.