A practical exposure-equivalent metric for instrumentation noise in x-ray imaging systems

Yadava, G; Kuhls-Gilcrist, Andrew; Rudin, Stephen; Patel, Vikas; Hoffmann, K; Bednarek, Daniel R.

doi:10.1088/0031-9155/53/18/017

Cited by 25 publications

(27 citation statements)

References 36 publications

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“…5 B), and because of this, adjacent detection events are spatially correlated. Blurring degrades spatial resolution, but the spatial correlation it produces filters noise (56)(57)(58)(59). Thus, the grayscale S/N may be greater than that expected from Poisson statistics, despite the added noise of the gain process, as our data show.…”

Section: Cellular Measurements Of Tb(iii)-mediated Fretmentioning

confidence: 47%

Evaluating the Performance of Time-Gated Live-Cell Microscopy with Lanthanide Probes

Rajendran

Miller

2015

Biophysical Journal

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Probes and biosensors that incorporate luminescent Tb(III) or Eu(III) complexes are promising for cellular imaging because time-gated microscopes can detect their long-lifetime (approximately milliseconds) emission without interference from short-lifetime (approximately nanoseconds) fluorescence background. Moreover, the discrete, narrow emission bands of Tb(III) complexes make them uniquely suited for multiplexed imaging applications because they can serve as Förster resonance energy transfer (FRET) donors to two or more differently colored acceptors. However, lanthanide complexes have low photon emission rates that can limit the image signal/noise ratio, which has a square-root dependence on photon counts. This work describes the performance of a wide-field, time-gated microscope with respect to its ability to image Tb(III) luminescence and Tb(III)-mediated FRET in cultured mammalian cells. The system employed a UV-emitting LED for low-power, pulsed excitation and an intensified CCD camera for gated detection. Exposure times of ∼1 s were needed to collect 5-25 photons per pixel from cells that contained micromolar concentrations of a Tb(III) complex. The observed photon counts matched those predicted by a theoretical model that incorporated the photophysical properties of the Tb(III) probe and the instrument's light-collection characteristics. Despite low photon counts, images of Tb(III)/green fluorescent protein FRET with a signal/noise ratio ≥ 7 were acquired, and a 90% change in the ratiometric FRET signal was measured. This study shows that the sensitivity and precision of lanthanide-based cellular microscopy can approach that of conventional FRET microscopy with fluorescent proteins. The results should encourage further development of lanthanide biosensors that can measure analyte concentration, enzyme activation, and protein-protein interactions in live cells.

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Section: Cellular Measurements Of Tb(iii)-mediated Fretmentioning

confidence: 47%

Evaluating the Performance of Time-Gated Live-Cell Microscopy with Lanthanide Probes

Rajendran

Miller

2015

Biophysical Journal

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“…We present a historical overview of the methods used by Varian 9,15,16 , as well as an introduction and discussion of alternate methods introduced by Yadav and Rudin, et al 8,10 to determine the quantum-limited dose. The QLD and NED metrics are based on fundamentally similar principles.…”

Section: Theory Of Methodsmentioning

confidence: 99%

“…In the absence of a formal standard, we found that Yadav, et al 8 provides an excellent overview of previous works [9][10][11][12][13][14] to determine the quantum-limited operation range, while at the same time proposing a new metric 10 . The metric describes a new total-noise formalism to determine the lower end-point of the quantum-limited operation range which is named the instrumentation-noise-equivalent-exposure (INEE).…”

Section: Introductionmentioning

confidence: 92%

“…Several methods for determining the quantum-limited dose range were reviewed by Yadav 8 . In this work we focus on comparing three methods used by our group 9, 15, 16 : 1) Plot Signal-to-noise (SNR) & Signal-to-electronic-noise (SENR) vs. exposure -find intersection of curves, (Method1); 2) Plot total Noise-variance vs. exposure -find least squares fit and calculate intercept and slope, (Method2); and 3) Plot Quantum Noise Variance and Electronic Noise Variance vs. exposure -find intersection of curves, (Method3).…”

Section: Introductionmentioning

confidence: 99%

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A comparison of quantum limited dose and noise equivalent dose

et al. 2016

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Quantum-limited-dose (QLD) and noise-equivalent-dose (NED) are performance metrics often used interchangeably. Although the metrics are related, they are not equivalent unless the treatment of electronic noise is carefully considered. These metrics are increasingly important to properly characterize the low-dose performance of flat panel detectors (FPDs). A system can be said to be quantum-limited when the Signal-to-noise-ratio (SNR) is proportional to the square-root of x-ray exposure. Recent experiments utilizing three methods to determine the quantum-limited dose range yielded inconsistent results. To investigate the deviation in results, generalized analytical equations are developed to model the image processing and analysis of each method. We test the generalized expression for both radiographic and fluoroscopic detectors. The resulting analysis shows that total noise content of the images processed by each method are inherently different based on their readout scheme. Finally, it will be shown that the NED is equivalent to the instrumentation-noise-equivalent-exposure (INEE) and furthermore that the NED is derived from the quantum-noise-only method of determining QLD. Future investigations will measure quantum-limited performance of radiographic panels with a modified readout scheme to allow for noise improvements similar to measurements performed with fluoroscopic detectors.Keywords: Flat panel detector (FPD), quantum limited performance range, quantum limited dose (QLD), noise equivalent dose (NED), instrumentation noise equivalent exposure (INEE), radiography, fluoroscopy

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“…The heart of the MAF is the light image intensifier (LII) that enables the MAF to exhibit large variable gain. This large variable gain provides quantum-limited operation with effectively no additive instrumentation noise [12], [13]. The MAF is currently being evaluated as an EI X-ray transmission imager in a local hospital and providing encouraging results [10].…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the Micro-Angiographic Fluoroscope as a High-Resolution, Single-Photon Counting and Energy-Integrating Imager for Transmission and Emission Imaging

Jain

Panse

Bednarek

et al. 2012

IEEE Trans. Nucl. Sci.

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X-ray and radionuclide imaging are widely popular medical imaging modalities. The requirements for each imaging modality are different, and different detectors are normally used. For this paper, we demonstrate our new detector capable of both fluoroscopy and angiography, to be used as an imager for both single-photon and integral-energy imaging and applied to the dual modalities of radionuclide imaging and X-ray imaging. This newly developed micro-angiographic fluoroscope (MAF) has 1024 1024 pixels of 35 m effective size and is capable of real-time imaging at 30 fps. The large variable gain of its light image intensifier (LII) provides quantum-limited operation with essentially no additive instrumentation noise. We demonstrate that the MAF can be operated in single-photon counting (SPC) mode for X-ray imaging with substantially better resolution than in energy integration (EI) mode. We may use high LII gain with very low exposure (less than 1 X-ray photon/pixel) per frame for SPC mode (with X-ray and radionuclide) and higher exposure with lower gain for EI mode (transmission imaging with X-rays). For a demonstration of the operation in both EI and SPC mode, a heavily K-edge filtered X-ray beam (average energy of 31 keV) was used to provide a nearly monochromatic spectrum. The MTF measured using a standard slit method showed a dramatic improvement for the SPC mode over the EI mode at all spatial frequencies. Images of a line-pair phantom also showed improved spatial resolution in SPC mode compared to EI mode. In SPC mode, images of human distal and middle phalanges showed the trabecular structures of the bone with far better contrast and detail. We also show MAF operation in SPC mode for radionuclide imaging using a custom-built phantom filled with I-125. A 1-mm-diameter parallel hole, medium-energy gamma camera collimator was placed between the phantom, and the MAF and was moved multiple times at equal intervals in random directions to eliminate the pattern corresponding to the collimator septa. Data was acquired at 20 fps, and multiple signal-thresholded frames were summed in SPC mode to provide an integrated frame. The sharpness of the emission image is limited by the collimator resolution and could be improved by optimized collimator design. We demonstrate that the same MAF is capable of operating in both SPC and EI modes and can be used in both X-ray transmission imaging and radionuclide emission imaging.

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A practical exposure-equivalent metric for instrumentation noise in x-ray imaging systems

Cited by 25 publications

References 36 publications

Evaluating the Performance of Time-Gated Live-Cell Microscopy with Lanthanide Probes

Evaluating the Performance of Time-Gated Live-Cell Microscopy with Lanthanide Probes

A comparison of quantum limited dose and noise equivalent dose

Evaluation of the Micro-Angiographic Fluoroscope as a High-Resolution, Single-Photon Counting and Energy-Integrating Imager for Transmission and Emission Imaging

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