Metal artifact reduction by filter-based dual-energy cone-beam computed tomography on a bench-top micro-CBCT system: concept and demonstration

Abstract

We evaluated two dual-energy cone-beam computed tomography (DE-CBCT) methodologies for a bench-top micro-CBCT system to reduce metal artifacts on reconstructed images. Two filter-based DE-CBCT methodologies were tested: (i) alternative spectral switching and (ii) simultaneous beam splitting. We employed filters of 0.6-mm-thick tin and 0.1-mm-thick tungsten to generate high- and low-energy spectra from 120 kVp X-rays, respectively. The spectral switching method was imitated by two half scans with different filters (pseudo-switching). Filters were placed and between the X-ray tube and a phantom (‘1-u,’ ‘2-u’), a phantom and a flat panel detector (‘1-d,’ ‘2-d’), and compared with (iii) two half scans at 80 and 140 kVp [pseudo-(80,140)]. For the splitting method, two half-width filters were aligned along a rotating axis. Projections were separated into halves and merged with corresponding areas of opposed projections after one full rotation. A solid 30-mm-diameter acrylic phantom and an acrylic phantom with four 5-mm-diameter titanium rods were used. DE images were generated by weighted summation of the high- and low-energy images. The blending factor was changed from 0 to +5 in increments of 0.01. Relative errors (REs) of the linear attenuation coefficients of the two phantoms and the contrast-to-noise ratios (CNRs) between the titanium and acrylic regions were compared. All methods showed zero REs except for the method (2-d). CNRs for pseudo-switching with upstream placement were 1.4-fold larger than CNRs for the pseudo-(80,140) method. CNRs for the downstream placements were small. It was concluded that the pseudo-switching method with upstream placement is appropriate for reducing metal artifacts.

Fast-switching dual energy cone beam computed tomography using the on-board imager of a commercial linear accelerator

“…The HU VM and RED values from these images were compared with theoretical values, and showed good overall agreement. Previously, the evaluation of DE-CBCT has been studied mainly on bench-top systems (Li et al 2013a, Iramina et al 2018, Zbijewski et al 2014, and more recently on a Synergy linear accelerator (Elekta, Stockholm, Sweden) (Men et al 2017). Li et al (Li et al 2013a(Li et al , 2012.…”

“…These approaches used a material decomposition approach based on attenuation measurements on scatter-corrected calibrations images of physical step wedges. Iramina et al (Iramina et al 2018) used a filter-based DE separation technique on a bench-top micro-CBCT system. The authors evaluated a split-filter and alternate switching filters during image acquisition for spectral separation, and found the latter to be useful for metal artifact reduction.…”

Challenging Cases of Aortic Prosthesis Dysfunction, the Importance of Multimodality Imaging, a Case Series

“…In case 4, the 3D anatomical model provided by MDCT clarified the stent’s frame’s crumpling morphology, guiding the choice of the right tools for angioplasty. MDCT integrated with metal artifact reduction filters plays an important role in determining the morphology and location of the frame’s misfolding in percutaneous valves [ 20 , 22 , 23 ], caused by native aortic valve/annulus calcifications, valve undersizing or mal-positioning [ 2 ].…”

Cone-Beam Computed Tomography in Dentomaxillofacial Radiology

“…In a study where singleenergy CBCT and dual-energy CBCT were compared, metal artifact with the use of upstream filter on dual energy CT was significantly reduced. This method also resulted in higher signal-to-noise values [53].…”