Visibility of objects in computer simulations of noisy micrographs

Bright, David S.; Newbury, Dale E.; Steel, Eric B.

doi:10.1046/j.1365-2818.1998.00249.x

Cited by 30 publications

(20 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The MDAs of 131 I and 124 I were therefore determined for the different reconstruction methods. The MDA of 131 I was higher for SC 6i8s reconstruction than for no-SC 6i8s reconstruction for some sphere sizes (10,22, and 28 mm). MDAs were not necessarily lower for images obtained with scatter correction, possibly because of the additional noise introduced in the reconstruction by the scatter projections.…”

Section: Discussionmentioning

confidence: 84%

See 1 more Smart Citation

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

et al. 2015

View full text Add to dashboard Cite

Radioiodine therapy with 131 I is used for treatment of suspected recurrence of differentiated thyroid carcinoma. Pretherapeutic 124 I PET/CT with a low activity (∼1% of 131 I activity) can be performed to determine whether uptake of 131 I, and thereby the desired therapeutic effect, may be expected. However, false-negative 124 I PET/CT results as compared with posttherapeutic 131 I SPECT/CT have been reported by several groups. The purpose of this study was to investigate whether the reported discrepancies may be ascribed to a difference in lesion detectability between 124 I PET/CT and 131 I SPECT/CT and, hence, whether the administered 124 I activity is sufficient to achieve equal detectability. Methods: Phantom measurements were performed using the National Electrical Manufacturers Association 2007 image-quality phantom. As a measure of detectability, the contrast-to-noise ratio was calculated. The 124 I activity was expressed as the percentage of 131 I activity required to achieve the same contrast-to-noise ratio. This metric was defined as the detectability equivalence percentage (DEP). Results: Because lower DEPs were obtained for smaller spheres, a relatively low 124 I activity was sufficient to achieve similar lesion detectability between 124 I PET/CT and 131 I SPECT/CT. DEP was 1.5%, 1.9%, 1.9%, 4.4%, 9.0%, and 16.2% for spheres with diameters of 10, 13, 17, 18, 25, and 37 mm, respectively, for attenuation-and scatter-corrected SPECT versus point-spread function (PSF) model-based and time-of-flight (TOF) PET. For no-PSF no-TOF PET, DEP was 3.6%, 2.1%, 3.5%, 7.8%, 15.1%, and 23.3%, respectively. Conclusion: A relatively low 124 I activity of 74 MBq (∼1% of 131 I activity) is sufficient to achieve similar lesion detectability between 124 I PSF TOF PET/CT and 131 I SPECT/CT for small spheres (#10 mm), since the reported DEPs are close to 1%. False-negative 124 I PET/CT results as compared with posttherapeutic 131 I SPECT/CT may be ascribed to differences in detectability for large lesions (.10 mm) and for no-PSF no-TOF PET, since DEPs are greater than 1%. On the basis of DEPs of 3.5% for lesion diameters of up to 17 mm on no-PSF no-TOF PET, 124 I activities as high as 170 MBq may be warranted to obtain equal detectability.

show abstract

Section: Discussionmentioning

confidence: 84%

“…A K 2D threshold of 8 was used to determine MDA (22,23). MDA was defined as the activity at which the K 2D -versus-activity curve intersected with the threshold.…”

Section: Quantitative Analysismentioning

confidence: 99%

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Moreover, the autoscaling may be applied with no record kept of the actual scaling factor. While such an autoscaling operation for compositional mapping may be expedient, the loss of true intensity information clearly eliminates any possibility of determining a k-value map or of performing any other mathematical operations that require true counts, such as analyzing the signal-to-noise ratio (Bright et al, 1998). With arbitrarily ap-plied scaling, there is simply no direct way to know if a certain gray level corresponds to a major, minor, or trace constituent in a single map.…”

Section: Scalingmentioning

confidence: 99%

Logarithmic 3-Band Color Encoding: Robust Method for Display and Comparison of Compositional Maps in Electron Probe X-ray Microanalysis

Newbury

Bright

1999

Microsc Microanal

View full text Add to dashboard Cite

Electron-excited X-ray maps recorded with the scanning electron microscope (SEM)/electron probe X-ray microanalyzer (EPMA) are a major method of presenting compositional information. Digitally recorded maps are processed in a variety of ways to improve the visibility of features. Scaling of the recorded signal to match the 8-bit gray-scale intensity range of a typical computer display system is almost always necessary.Inherent limitations of gray-scale displays have led to other intensity-encoding methods for X-ray maps, including clipping, histogram normalization, and pseudocolor scales. While feature visibility is improved by applying these scales, comparisons among image sets are difficult. Quantitative comparisons must be based on standardized intensities corrected for background to produce intensity ratio (k-value) maps. We have developed a new logarithmic, multiband color-encoding method to view these k-value maps more effectively. Three color bands are defined, starting with a dark primary color and grading to a bright pastel: blue = trace (0.001 to 0.01); green = minor (0.01 to 0.1); and red = major (0.1 to 1.0). Within each band, the color is assigned according to a logarithmic scale that depends on intensity ratio or compositional measurements. Logarithmic multiband color encoding permits direct comparisons of maps, such as maps of different elements in the same field of view or maps of the same element in different areas, because the color scale is identical for all maps.

show abstract

“…Because the information regarding the image and alteration products is encoded in the top ~100-200 nm of the plate [9,10], and the primary x-ray signal penetrates many micrometers into the Ag coating and Cu bulk, the resultant chemical signal of interest is weak. Poor signal quality, on the order of less than 10 counts per second in the spectral region of interest (ROI), generally results in an unsatisfactorily noisy image [11]. In this case, the signal is dominated by the variance inherent to a Poisson distribution.…”

Section: Introductionmentioning

confidence: 99%

Optimizing compositional images of daguerreotype photographs using post processing methods

Davis

Vicenzi

2016

Herit Sci

View full text Add to dashboard Cite

Microfocused X-ray fluorescence imaging was used to examine two 19th century daguerreotypes. The distribution of Hg-bearing nanoparticles beneath the Au gilding layer gives rise to contrast in the photographs. The sum image for Au + Hg M line X-rays is therefore a compositional image that mimics daguerreotype photograph contrast. Because the thickness of the Au and Hg on the surface represents a small fraction of the X-ray activation depth, the resulting sum images are not of high quality and are dominated by Poisson noise. This is true even for long collection times up to multiple days in length. Achieving superior contrast resolution by increasing the duration of data collection further is impractical. In this study, a new image processing technique based upon the Haar-Fisz algorithm and wavelet theory was used to improve the image quality of compositional maps. The digitally processed images show a reduction in noise without a loss of spatial resolution over the length-scale of photographic features. The Haar-Fisz denoising algorithm decreased the contribution of the Poisson noise in compositional images. Multiple resolution analysis improved image quality further. Features within the portraits are uniformly more recognizable in the final processed images relative to the raw X-ray images. Intensity line profiles that traverse midtone, highlight and shadow regions of the daguerreotype reveal that spatial resolution is not degraded by the image processing routines. Improvement in image quality is quantified by comparing the relative variance of the raw and Haar-Fisz processed imagery. The use of a Haar-Fisz denoising transformation, coupled with multiple resolution analysis was found to improve the quality of low count X-ray images without impacting the spatial resolution at the scale of photograph features. The process can be implemented in freely available open-source software with a minimum of programming effort. Such digital post processing routines offset the need for longer acquisition times to achieve improved X-ray fluorescence image quality. Finally, because the Au + Hg map is insensitive to surface imperfections and tarnishing via atmospheric adsorption of sulfur, digitally processed images may be used to reconstruct photograph features in heavily disfigured daguerreotypes.

show abstract

Visibility of objects in computer simulations of noisy micrographs

Cited by 30 publications

References 15 publications

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

Logarithmic 3-Band Color Encoding: Robust Method for Display and Comparison of Compositional Maps in Electron Probe X-ray Microanalysis

Optimizing compositional images of daguerreotype photographs using post processing methods

Contact Info

Product

Resources

About

Visibility of objects in computer simulations of noisy micrographs

Cited by 30 publications

References 15 publications

Quantitative Comparison of 124I PET/CT and 131I SPECT/CT Detectability

Quantitative Comparison of 124I PET/CT and 131I SPECT/CT Detectability

Logarithmic 3-Band Color Encoding: Robust Method for Display and Comparison of Compositional Maps in Electron Probe X-ray Microanalysis

Optimizing compositional images of daguerreotype photographs using post processing methods

Contact Info

Product

Resources

About

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability

Quantitative Comparison of ¹²⁴I PET/CT and ¹³¹I SPECT/CT Detectability