Noise Reduction Settings Among Model-based Iterative Reconstruction on Decreasing Radiation Dose in CT Angiography: An Experimental Study / 中国医学影像学杂志

ABSTRACT

[Abstraet] Purpose To explore the application of noise reduction settings among modelbased iterative reconstruction (MBIRn) on decreasing radiation dose in CTA through experimental study.Materials and Methods Spectral CT was used to scan vessel model which could accommodate 8 tubes under static condition under 120 kVp fixed tube voltage at 10 mA,50 mA,150 mA and 600 mA.The tubes were filled with purified water,1,2,5,10,20 and 30 mgI/ml solutions and 30 mgCa/ml solution.Algorithms of FBP (standard),ASIR40 (combined by 40％ ASIR and FBP),MBIRc and MBIRn with optimized spatial resolution setting as MBIRRP20,MBIRstnd (standard setting),and MBIRNR40 (noise reduction setting) were adopted for original scanning data to reconstruct images of 0.625 mm slice thickness for contrastive analysis.Three fixed layers were chosen and regions of interest were placed on central tube and surrounding ester matrix,and CT value and standard variation (SD) were measured to represent noise.Noise reduction setting MBIRNR40 and solution noise of other reconstruction algorithm images were calculated and compared and average value of contrast noise ratio (CNR) was compared.Results Compared to FBP under different tube currents,ASIR40,MBIRc,MBIRRP20,MBIRstnd and MBIRNR40 reduce noise and increase CNR at different levels.Average noise of MBIRNR40 was the lowest (reduced by 78.33％) and CNR the highest (increased by 241.74％),making it superior to other reconstruction algorithm images (P＜0.05).Meanwhile,the lower the radiation dose was,the more obvious its advantage was.Reconstruction image noise of MBIRNR40 at 10 mA was close to that of FBP and ASIR40 at 600 mA.CNR was obvious greater than that of FBP and ASIR40 at other tube voltage.Conclusion Reconstruction algorithms of MBIRc,MBIRn and ASIR can help enhance CTA image quality and reduce radiation dose.Noise reduction setting MBIRNR40 from MBIRn has the lowest noise and greatest CNR.The lower the radiation dose is,the more obvious its advantage is.