Effect of nonlinear three-dimensional optimized reconstruction algorithm filter on image quality and radiation dose: Validation on phantoms

• Published in: Medical physics (Lancaster) 2009-01, Vol.36 (1), p.95-97
• Main Authors: Bai, Mei, Chen, Jiuhong, Raupach, Rainer, Suess, Christoph, Tao, Ying, Peng, Mingchen
• Format: Article
• Language: English
• Subjects: ALGORITHMS; Body Burden; bone; CAT SCANNING; COMPARATIVE EVALUATIONS; Computed radiography; Computed tomography; computerised tomography; FILTERS; Humans; image denoising; IMAGE PROCESSING; image quality; image reconstruction; Imaging, Three-Dimensional - methods; LIVER; Medical image contrast; Medical image noise; medical image processing; Medical image quality; Medical image reconstruction; Medical image smoothing; Medical imaging; Modulation transfer functions; Noise; Nonlinear Dynamics; PHANTOMS; Phantoms, Imaging; Radiation Dosage; radiation dose; RADIATION DOSES; Radiographic Image Enhancement - methods; Radiographic Image Interpretation, Computer-Assisted - methods; RADIOLOGY AND NUCLEAR MEDICINE; Radiometry - methods; Reconstruction; Reproducibility of Results; Sensitivity and Specificity; SKELETON; spatial filtering; spiral CT; THREE-DIMENSIONAL CALCULATIONS; Tomography, X-Ray Computed - instrumentation; Tomography, X-Ray Computed - methods; TRANSFER FUNCTIONS; VALIDATION
• ISSN: 0094-2405; 2473-4209
• DOI: 10.1118/1.3030953

A new technique called the nonlinear three-dimensional optimized reconstruction algorithm filter (3D ORA filter) is currently used to improve CT image quality and reduce radiation dose. This technical note describes the comparison of image noise, slice sensitivity profile (SSP), contrast-to-noise ratio, and modulation transfer function (MTF) on phantom images processed with and without the 3D ORA filter, and the effect of the 3D ORA filter on CT images at a reduced dose. For CT head scans the noise reduction was up to 54% with typical bone reconstruction algorithms (H70) and a 0.6 mm slice thickness; for liver CT scans the noise reduction was up to 30% with typical high-resolution reconstruction algorithms (B70) and a 0.6 mm slice thickness. MTF and SSP did not change significantly with the application of 3D ORA filtering ( P > 0.05 ) , whereas noise was reduced ( P < 0.05 ) . The low contrast detectability and MTF of images obtained at a reduced dose and filtered by the 3D ORA were equivalent to those of standard dose CT images; there was no significant difference in image noise of scans taken at a reduced dose, filtered using 3D ORA and standard dose CT ( P > 0.05 ) . The 3D ORA filter shows good potential for reducing image noise without affecting image quality attributes such as sharpness. By applying this approach, the same image quality can be achieved whilst gaining a marked dose reduction.