1. FREQUENCY RESPONSE AND DISTORTION PROPERTIES OF RECONSTRUCTION ALGORITHMS IN COMPUTED TOMOGRAPHY
- Author
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Joel Larsson, Magnus Båth, and Anne Thilander-Klang
- Subjects
Paper ,Frequency response ,Computer science ,Context (language use) ,Iterative reconstruction ,Radiation Dosage ,030218 nuclear medicine & medical imaging ,Amplitude modulation ,03 medical and health sciences ,0302 clinical medicine ,Distortion ,Image Processing, Computer-Assisted ,Median filter ,Radiology, Nuclear Medicine and imaging ,AcademicSubjects/SCI00180 ,Radiation ,Radiological and Ultrasound Technology ,Radon transform ,Phantoms, Imaging ,Public Health, Environmental and Occupational Health ,General Medicine ,Nonlinear system ,030220 oncology & carcinogenesis ,Radiographic Image Interpretation, Computer-Assisted ,Tomography, X-Ray Computed ,Algorithm ,Algorithms - Abstract
Denoising reconstruction techniques can introduce nonlinear properties into computed tomography (CT) systems. These nonlinear algorithms introduce distortion which affects the assessment of the resolution of the system. The purpose of the present study was to decouple and investigate amplitude modulation and waveform distortion in reconstruction algorithms in CT. The methodology developed by Wells, J. R. and Dobbins, J. T. III [Frequency response and distortion properties of nonlinear image processing algorithms and the importance of imaging context. Med. Phys. 40, 091906 (2013)] was adapted to CT reconstruction algorithms. The CT simulating program ASTRA Toolbox© for MATLAB™ was used for the reconstruction of the sinusoidal wave functions. Filtered back projection and the simultaneous iterative reconstruction technique were investigated with simple nonlinear mechanisms: a median filter and a non-negative constraint, respectively. The native reconstruction algorithms were not free from nonlinear waveform distortion, however, none of the metrics showed any dependence on the contrast-to-noise ratio (CNR). Furthermore, the algorithms including nonlinear mechanisms showed a clear and specific CNR dependence, indicating the necessity for distortion analysis in nonlinear CT reconstruction.
- Published
- 2021