Measuring MTF with wedges: pitfalls and best practices

Koren, Norman L.; Sumner, R. H.; Koren, H. W.

doi:10.2352/issn.2470-1173.2017.19.avm-451

Cited by 3 publications

(4 citation statements)

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“…MTF10 is the frequency at which the MTF curve crosses 0.1. This approximates to the Rayleigh criterion for maximal resolution, at which frequency it is just possible to discern two lines 17 , 18 . MTF10 would correlate to counting television lines.…”

Section: Methodsmentioning

confidence: 85%

“…When the level of edge enhancement is increased, the step response shows an undershoot and overshoot that should not be clipped. 17 The step response was used to determine the level of edge enhancement and modulation transfer function (MTF) as described in the following paragraphs.…”

Section: Methodsmentioning

confidence: 99%

“…This way the other gray patches were available for measuring the optoelectronic conversion function (OECF) and the measured step response on the soft contrast slanted edge is within the dynamic range of the system. When the level of edge enhancement is increased, the step response shows an undershoot and overshoot that should not be clipped 17 . The step response was used to determine the level of edge enhancement and modulation transfer function (MTF) as described in the following paragraphs.…”

Section: Methodsmentioning

confidence: 99%

“…This approximates to the Rayleigh criterion for maximal resolution, at which frequency it is just possible to discern two lines. 17,18 MTF10 would correlate to counting television lines. However, MTF10 is not robustly to measure since the signal is relatively close to the noise floor and the slope of the MTF curve is small.…”

Section: Sharpness (Mtf50 and Mtf50p)mentioning

confidence: 99%

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Influence of edge enhancement applied in endoscopic systems on sharpness and noise

Geleijnse

Rieger

2022

J. Biomed. Opt.

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. Significance Flexible endoscopes are essential for medical internal examinations. Digital endoscopes are connected to a video processor that can apply various operations to enhance the image. One of those operations is edge enhancement, which has a major impact on the perceived image quality by medical professionals. However, the specific methods and parameters of this operation are undisclosed and the arbitrary units to express the level of edge enhancement differ per video processor. Aim Objectively quantify the level of edge enhancement from the recorded images alone, and measure the effect on sharpness and noise. Approach Edge enhancement was studied in four types of flexible digital ear nose and throat endoscopes. Measurements were performed using slanted edges and gray patches. The level of edge enhancement was determined by subtracting the step response of an image without edge enhancement from images with selected settings of edge enhancement and measuring the resulting peak-to-peak differences. These values were then normalized by the step size. Sharpness was characterized by observing the normalized modulation transfer function (MTF) and computing the spatial frequency at 50% MTF. The noise was measured on the gray patches and computed as a weighted sum of variances from the luminance and two chrominance channels of the pixel values. Results The measured levels were consistent with the level set via the user interface on the video processor and varied typically from 0 to 1.3. Both sharpness and noise increase with larger levels of edge enhancement with factors of 3 and 4 respectively. Conclusions The presented method overcomes the issue of vendors expressing the level of edge enhancement each differently in arbitrary units. This allows us to compare the effects, and we can start exploring the relationship with the subjectively perceived image quality by medical professionals to find substantiated optimal settings.

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Section: Methodsmentioning

confidence: 85%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Sharpness (Mtf50 and Mtf50p)mentioning

confidence: 99%

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