Effect of noise on MTF calculations using different phantoms

González‐López, Antonio

doi:10.1002/mp.12847

Cited by 17 publications

(30 citation statements)

References 13 publications

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“…This is because, the noise in the body PMMA phantom is greater (about 6.5‐fold) than that in the head PMMA phantom at the same exposure factor (mAs and kVp), while the CT number in the head PMMA phantom (about 117 HU) is smaller than that in the body PMMA phantom (about 127 HU). Higher noise causes correspondingly higher MTF fluctuations, resulting in an increase in the standard deviation of the measured MTF …”

Section: Discussionmentioning

confidence: 99%

An algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images

Anam

Budi

Haryanto

et al. 2018

J Applied Clin Med Phys

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PurposeThe purpose of this study was to introduce a new algorithm for automated measurement of the modulation transfer function (MTF) using an edge of a readily available phantom and to evaluate the effect of reconstruction filter and field of view (FOV) on the spatial resolution in the CT images.MethodsOur automated MTF measurement consisted of several steps. The center of the image was established and an appropriate region of interest (ROI) designated. The edge spread function (ESF) was determined, and a suitably interpolated ESF curve was differentiated to obtain the line spread function (LSF). The LSF was Fourier transformed to obtain the MTF. All these steps were accomplished automatically without user intervention. The results of the automated MTF from the edge phantom were validated by comparing them with a point image, and the results of the automated calculation were validated by the standard fitting method. The automated MTF calculation was then applied to the images of two polymethyl methacrylate (PMMA) phantoms and a wire phantom which had been scanned by a Toshiba Alexion 4‐slice CT scanner and reconstructed with various filter types and FOVs.ResultsThe difference in the 50% MTF values obtained from the edge and point phantoms were within ±4%. The values from the automated and fitted methods agreed to within ±2%, indicating that the automated MTF calculation was accurate. The automated MTF calculation was able to differentiate MTF curves for various filters. The spatial resolution values were 0.37 ± 0.00, 0.71 ± 0.01, and 0.78 ± 0.01 cycles/mm for FC13, FC30 and FC52 filters, respectively. The spatial resolution of the images decrease linearly (R 2 > 0.98) with increasing FOVs.ConclusionAn automated MTF method was successfully developed using an edge phantom, the PMMA phantom. The method is easy to implement in a clinical environment and is not influenced by user experience.

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Section: Discussionmentioning

confidence: 99%

An algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images

Anam

Budi

Haryanto

et al. 2018

J Applied Clin Med Phys

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“…Energy is distributed between a discrete set of frequencies and not on a continuous set and the SNR of the MTF decays more slowly with frequency than in the case of the edge. 21 The star-bar pattern presented in this work is built in stainless steel, which limits its best performance to low beam qualities like RQA 3, RQA 5 or x-ray beams used for mammography. The reason for this limit is that steel has a much lower attenuation coefficient than tungsten, material used in the edge phantom.…”

Section: Discussionmentioning

confidence: 99%

“…The uncertainty in the MTF determination with star-bar phantoms has been previously studied. 21,22 In these works, theoretical expressions were derived for the MTF standard deviation for several phantoms. In, 22 the squared-SNR of the MTF was expressed as a function of frequency f for five different phantoms as…”

Section: B Predicted and Measured Uncertaintiesmentioning

confidence: 99%

“…It is shown that the standard deviation (SD) of the MTF is proportional to the frequency. [20][21][22] Also, it has been shown that the information of intermediate and high frequencies is encapsulated in a small area of the edge image. 23 A theoretical method for MTF calculations using star-bar phantoms has been presented in Ref.…”

Section: Introductionmentioning

confidence: 99%

“…[23] Some aspects of the theory, like using higher order harmonics or determining its uncertainties have also been developed in Ref. [21,22,24] One important result states that the SD of the MTF determination is proportional to the square root of the frequency, 21,22 a better behavior than that of the edge method.…”

Section: Introductionmentioning

confidence: 99%

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Performance of a new star‐bar phantom designed for MTF calculations in x‐ray imaging systems

et al. 2020

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Purpose: A new phantom, designed and manufactured for modulation transfer function (MTF) calculations is presented in this work. The phantom has a star-bar pattern and is manufactured in stainless steel. Modulation transfer function determinations are carried out with the new phantom and with an edge phantom to compare their performance and to compare them with previous theoretical predictions. Methods: The phantoms are imaged in an x-ray imaging system using different beam qualities and different entrance air KERMA. Methods, previously developed for synthetic images and simulations, are adapted to real measurements, solving practical implementation issues. Results: In the case of the star-bar, in order to obtain optimal MTF determinations it is necessary to accurately determine the center of the pattern. Also, to avoid underestimates in MTF calculations, the length in pixels of each of the scanning circumferences must be an integer multiple of the number of cycles in the pattern. Both methods, star-bar and edge, give similar mean values of the MTF in all cases analyzed. Also, the dependence with frequency of the experimental MTF standard deviation (SD) agrees with the theoretical expressions presented in previous works. In this regard, the precision is better for the star-bar method than for the edge and differences in precision between both methods are higher for the lowest beam quality. Conclusions: The star-bar phantom can be used for MTF determinations with the advantage of having an improved precision. However, precision is reduced when the radiation quality increases. This fact suggests that, for the highest beam qualities, materials with an attenuation coefficient greater than that of steel should be used to manufacture the phantom.

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An approach to evaluation of the point‐spread function for ²³Na magnetic resonance imaging

2021

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Despite the technical challenges that require lengthy acquisitions to overcome poor signal-to-noise ratio (SNR), sodium ( 23 Na) magnetic resonance imaging (MRI) is an intriguing area of research due to its essential role in human metabolism. Low SNR images can impact the measurement of the point-spread function (PSF) by adding uncertainty into the resulting quantities. Here, we present methods to calculate the PSF by using the modulation transfer function (MTF), and a 3D-printed line-pair phantom in the context of 23 Na MRI. A simulation study investigated the effect of noise on the resulting MTF curves, which were derived by direct modulation (DM) and a method utilizing Fourier harmonics (FHs). Experimental data utilized a line-pair phantom with nine spatial frequencies, filled with different concentrations (15, 30, and 60 mM) of sodium in 3% agar. MTF curves were calculated using both methods from data acquired from density-adapted 3D radial projections (DA-3DRP) and Fermat looped orthogonally encoded trajectories (FLORET). Simulations indicated that the DM method increased variability in the MTF curves at all tested noise levels over the FH method. For the experimental data, the FH method resulted in PSFs with a narrower full width half maximum with reduced variability, although the improvement in variability was not as pronounced as predicted by simulations. The DA-3DRP data indicated an improvement in the PSF over FLORET. It was concluded that a 3D-printed line-pair phantom represents a convenient method to measure the PSF experimentally. The MTFs from the noisy images in 23 Na MRI have reduced variability from a FH method over DM.

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Effect of noise on MTF calculations using different phantoms

Cited by 17 publications

References 13 publications

An algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images

An algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images

Performance of a new star‐bar phantom designed for MTF calculations in x‐ray imaging systems

An approach to evaluation of the point‐spread function for ²³Na magnetic resonance imaging

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Effect of noise on MTF calculations using different phantoms

Cited by 17 publications

References 13 publications

An algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images

An algorithm for automated modulation transfer function measurement using an edge of a PMMA phantom: Impact of field of view on spatial resolution of CT images

Performance of a new star‐bar phantom designed for MTF calculations in x‐ray imaging systems

An approach to evaluation of the point‐spread function for 23Na magnetic resonance imaging

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An approach to evaluation of the point‐spread function for ²³Na magnetic resonance imaging