Ultralow Dose CT Imaging for Navigated Skull Base Surgery Using ASIR and MBIR-2D and 3D Image Quality

Abstract

Objective: To evaluate 2D and 3D image quality of ultralow dose computed tomography images for navigated skull base surgery using adaptive statistical iterative reconstruction (ASIR) and model-based iterative reconstruction (MBIR) compared with standard filtered back projection (FBP). Study Design: Cadaver study. Material and Methods: A human cadaver head was scanned using a high resolution reference protocol for navigated skull base surgery (CTDIvol 30.48 mGy) and a series of five ultralow dose protocols (3.48, 2.19, 0.82, 0.44, and 0.22 mGy). Subjective image quality of blinded 2D axial and 3D images using FBP and ASIR-50, ASIR-100, and MBIR was evaluated by three observers using top-down scoring. Statistical analyze was performed per protocol and reconstruction including multiple Bonferoni testing (p = 0.05). Results: 2D images: There was no significant difference between the FBP reference 30.48 mGy and the ultralow dose protocol ASIR-50 and 100 at 3.48 mGy, ASIR-100 and MBIR at 2.19, ASIR-100 and MBIR at 0.82, and MBIR at 0.44 mGy. MBIR at 3.48 mGy scored significantly better than the FBP reference (p = 0.004). 3D images: There was no significant difference between the FBP reference and the ultralow dose protocols except FBP and ASIR-50 at 0.44 mGy (p = 0.007, p = 0.013) and ASIR-50 at 0.22 mGy (p = 0.019). Conclusions: ASIR-100 and MBIR significantly improve subjective image quality of ultralow dose imaging and may allow dose reductions of more than 90%.