Towards task-based assessment of CT performance: System and object MTF across different reconstruction algorithms
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- 11 June 2012
- journal article
- Published by Wiley in Medical Physics
- Vol. 39 (7Part1), 4115-4122
- https://doi.org/10.1118/1.4725171
Abstract
To investigate a measurement method for evaluating the resolution properties of CT imaging systems across reconstruction algorithms, dose, and contrast. An algorithm was developed to extract the task-based modulation transfer function (MTF) from disk images generated from the rod inserts in the ACR phantom (model 464 Gammex, WI). These inserts are conventionally employed for HU accuracy assessment. The edge of the disk objects was analyzed to determine the edge-spread function, which was differentiated to yield the line-spread function and Fourier-transformed to generate the object-specific MTF for task-based assessment, denoted MTF(Task). The proposed MTF measurement method was validated against the conventional wire technique and further applied to measure the MTF of CT images reconstructed with an adaptive statistical iterative algorithm (ASIR) and a model-based iterative (MBIR) algorithm. Results were further compared to the standard filtered back projection (FBP) algorithm. Measurements were performed and compared across different doses and contrast levels to ascertain the MTF(Task) dependencies on those factors. For the FBP reconstructed images, the MTF(Task) measured with the inserts were the same as the MTF measured from the wire-based method. For the ASIR and MBIR data, the MTF(Task) using the high contrast insert was similar to the wire-based MTF and equal or superior to that of FBP. However, results for the MTF(Task) measured using the low-contrast inserts, the MTF(Task) for ASIR and MBIR data was lower than for the FBP, which was constant throughout all measurements. Similarly, as a function of mA, the MTF(Task) for ASIR and MBIR varied as a function of noise--with MTF(Task) being proportional to mA. Overall greater variability of MTF(Task) across dose and contrast was observed for MBIR than for ASIR. This approach provides a method for assessing the task-based MTF of a CT system using conventional and iterative reconstructions. Results demonstrated that the object-specific MTF can vary as a function of dose and contrast. The analysis highlighted the paradigm shift for iterative reconstructions when compared to FBP, where iterative reconstructions generally offer superior noise performance but with varying resolution as a function of dose and contrast. The MTF(Task) generated by this method is expected to provide a more comprehensive assessment of image resolution across different reconstruction algorithms and imaging tasks.Keywords
This publication has 16 references indexed in Scilit:
- Deriving the modulation transfer function of CT from extremely noisy edge profilesRadiological Physics and Technology, 2009
- Cascaded systems analysis of noise reduction algorithms in dual-energy imagingMedical Physics, 2008
- Modulation transfer function of digitally reconstructed radiographs using helical computed tomographyMedical Physics, 2001
- A method for measuring the presampled MTF of digital radiographic systems using an edge test deviceMedical Physics, 1998
- Signal and noise in modulation transfer function determinations using the slit, wire, and edge techniquesMedical Physics, 1992
- A simple method for determining the modulation transfer function in digital radiographyIEEE Transactions on Medical Imaging, 1992
- A simplified approach for modulation transfer function determinations in computed tomographyMedical Physics, 1985
- A practical method to measure the MTF of CT scannersMedical Physics, 1982
- Transfer function analysis of radiographic imaging systemsPhysics in Medicine & Biology, 1979
- Modulation transfer function of the EMI CT head scannerMedical Physics, 1977