Measurement of the Lag Correction Factor in Low-Dose Fluoroscopic Imaging

Kim, Dong Sik; Lee, Eunae

doi:10.1109/tmi.2021.3063350

Cited by 6 publications

(17 citation statements)

References 40 publications

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“…The signal-to-noise ratio,

, is very high in practical fluoroscopic imaging. Hence, this NTG can be ignored in the mean-based LCF measurement methods [ 13 , 17 , 18 ]. However, the PSD or correlation-based methods can be very sensitive to NTG even though its strength is quite weak [ 21 ].…”

Section: Nonuniform Temporal Gain Modelmentioning

confidence: 99%

“…For indirect detectors, trapping charges in the amorphous structure of the thin-film-transistor (TFT) panel and incomplete reads are the main causes of lag signals [ 3 , 4 , 5 , 6 ]. The lag artifacts appear in the form of temporal blurring and ghosting in fluoroscopic imaging [ 7 , 8 , 9 , 10 , 11 , 12 , 13 ].…”

Section: Introductionmentioning

confidence: 99%

“…In measuring the noise power spectrum (NPS) for a dynamic detector [ 14 , 15 , 16 ], the lag signal lowers the NPS curve. Conventional approaches for correcting the measured NPS are based on using the lag correction factor (LCF) [ 13 , 17 , 18 , 19 , 20 , 21 ]. Busse et al [ 19 , 20 ] used a temporal power spectral density (PSD) method to measure LCF using steady-state images based on a moving average model of order L (MA( L )) for the lag signals.…”

Section: Introductionmentioning

confidence: 99%

“…Based on an autoregressive model of order 1 (AR(1)), Matsunaga et al [ 17 ] considered LCF measurements. Granfors and Aufrichtig [ 18 ], as well as Kim and Lee [ 13 ], considered the means of transient decaying images after the X-ray turns off.…”

Section: Introductionmentioning

confidence: 99%

“…Compared to the PSD case, the correlation method [ 21 ] is less sensitive to NTG even though a gain correction is required. On the other hand, the mean-based methods are generally insensitive to NTG [ 13 , 18 ].…”

Section: Introductionmentioning

confidence: 99%

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Conditional Covariances for the Signal Lag Measurements in Fluoroscopic Imaging

Lee

Kim

2021

Diagnostics

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In fluoroscopic imaging, we can acquire X-ray image sequences using a flat-panel dynamic detector. However, lag signals from previous frames are added to the subsequently acquired images and produce lag artifacts. The lag signals also inflate the measured noise power spectrum (NPS) of a detector. In order to correct the measured NPS, the lag correction factor (LCF) is generally used. However, the nonuniform temporal gain (NTG), which is from inconsistent X-ray sources and readout circuits, can significantly distort the LCF measurements. In this paper, we propose a simple scheme to alleviate the NTG problem in order to accurately and efficiently measure the detector LCF. We first theoretically analyze the effects of NTG, especially on the correlation-based LCF measurement methods, where calculating the correlation coefficients are required. In order to remove the biases due to NTG, a notion of conditional covariance is considered for unbiased estimates of the correlation coefficients. Experiments using practical X-ray images acquired from a dynamic detector were conducted. The proposed approach could yield accurate LCF values similarly to the current approaches of the direct and U-L corrections with a low computational complexity. By calculating the correlation coefficients based on conditional covariance, we could obtain accurate LCF values even under the NTG environment. This approach does not require any preprocessing scheme of the direct or U-L correction and can provide further accurate LCF values than the method of IEC62220-1-3 does.

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“…The signal-to-noise ratio,

Section: Nonuniform Temporal Gain Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Conditional Covariances for the Signal Lag Measurements in Fluoroscopic Imaging

Lee

Kim

2021

Diagnostics

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Measurements of the noise power spectrum for digital x-ray imaging devices

Kim

2024

Phys. Med. Biol.

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Objective. The noise characteristics of digital X-ray imaging devices are determined by contributions such as photon noise, electronic noise, and fixed pattern noise, and can be evaluated from measuring the noise power spectrum (NPS), which is the power spectral density of the noise. Hence, accurately measuring NPS is important in developing detectors for acquiring low-noise digital X-ray images. To make accurate measurements, it is necessary to understand NPS, identify problems that may arise, and know how to process the obtained X-ray images. Approach. The primitive concept of NPS is first introduced with a periodogram-based estimate and its bias and variance are discussed. In measuring NPS based on the IEC62220 standards, various issues, such as the fixed pattern noise, high-precision estimates, and lag corrections, are summarized with simulation examples. Main results. High-precision estimates can be provided for an appropriate number of samples extracted from X-ray images while compromising spectral resolution. Depending on medical imaging systems, by eliminating the influence of fixed pattern noise, NPS, which represents only photon and electronic noise, can be efficiently measured. For NPS measurements in dynamic detectors, an appropriate lag correction technique can be selected depending on the emitted X-rays and image acquisition process. Significance. Various issues in measuring NPS are reviewed and summarized for accurately evaluating the noise performance of digital X-ray imaging devices.

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Linear Lag Models and Measurements of the Lag Correction Factors

Lee

Kim

2022

IEEE Access

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Measurement of the Lag Correction Factor in Low-Dose Fluoroscopic Imaging

Cited by 6 publications

References 40 publications

Conditional Covariances for the Signal Lag Measurements in Fluoroscopic Imaging

Conditional Covariances for the Signal Lag Measurements in Fluoroscopic Imaging

Measurements of the noise power spectrum for digital x-ray imaging devices

Linear Lag Models and Measurements of the Lag Correction Factors

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