Grayscale contrast enhancement based on greyscale-based contrast-to-noise ratio

2021 ◽  
Author(s):  
Wei Zhou ◽  
Yi Tian ◽  
Xiaolu Cai ◽  
Zhenyu Fei
Keyword(s):  
Contrast Enhancement ◽  
Noise Ratio

Image Quality Enhancing by Efficient Histogram Equalization

2014 ◽  
Vol 2 (2) ◽  
pp. 47-58
Author(s):  
Ismail Sh. Baqer
Keyword(s):  
Image Quality ◽  
Contrast Enhancement ◽  
Mean Squared Error ◽  
Signal To Noise Ratio ◽  
Histogram Equalization ◽  
Gray Level ◽  
Signal To Noise ◽  
Squared Error ◽  
Noise Ratio

A two Level Image Quality enhancement is proposed in this paper. In the first level, Dualistic Sub-Image Histogram Equalization DSIHE method decomposes the original image into two sub-images based on median of original images. The second level deals with spikes shaped noise that may appear in the image after processing. We presents three methods of image enhancement GHE, LHE and proposed DSIHE that improve the visual quality of images. A comparative calculations is being carried out on above mentioned techniques to examine objective and subjective image quality parameters e.g. Peak Signal-to-Noise Ratio PSNR values, entropy H and mean squared error MSE to measure the quality of gray scale enhanced images. For handling gray-level images, convenient Histogram Equalization methods e.g. GHE and LHE tend to change the mean brightness of an image to middle level of the gray-level range limiting their appropriateness for contrast enhancement in consumer electronics such as TV monitors. The DSIHE methods seem to overcome this disadvantage as they tend to preserve both, the brightness and contrast enhancement. Experimental results show that the proposed technique gives better results in terms of Discrete Entropy, Signal to Noise ratio and Mean Squared Error values than the Global and Local histogram-based equalization methods

The Nth‐root stack: Theory, applications, and examples

Geophysics ◽  
1986 ◽  
Vol 51 (10) ◽  
pp. 1879-1892 ◽  
Author(s):  
P. L. McFadden ◽  
B. J. Drummond ◽  
S. Kravis
Keyword(s):  
Contrast Enhancement ◽  
Signal To Noise Ratio ◽  
Beam Steering ◽  
Seismic Refraction ◽  
Signal Distortion ◽  
Signal Attenuation ◽  
Signal To Noise ◽  
Zero Crossing ◽  
Array Data ◽  
Noise Ratio

Multichannel geophysical data are usually stacked by calculating the average of the observations on all channels. In the Nth‐root stack, the average of the Nth root of each observation is raised to the Nth power, with the signs of the observations and average maintained. When N = 1, the process is identical to conventional linear stacking or averaging. Nth‐root stacking has been applied in the processing of seismic refraction and teleseismic array data. In some experiments and certain applications it is inferior to linear stacking, but in others it is superior. Although the variance for an Nth‐root stack is typically less than for a linear stack, the mean square error is larger, because of signal attenuation. The fractional amount by which the signal is attenuated depends in a complicated way on the number of data channels, the order (N) of the stack, the signal‐to‐noise ratio, and the noise distribution. Because the signal‐to‐noise ratio varies across a wavelet, peaking where the signal is greatest and approaching zero at the zero‐crossing points, the attenuation of the signal varies across a wavelet, thereby producing signal distortion. The main visual effect of the distortion is a sharpening of the legs of the wavelet. However, the attenuation of the signal is accompanied by a much greater attenuation of the background noise, leading to a significant contrast enhancement. It is this sharpening of the signal, accompanied by the contrast enhancement, that makes the technique powerful in beam‐steering applications of array data. For large values of N, the attenuation of the signal with low signal‐to‐noise ratios ultimately leads to its destruction. Nth‐root stacking is therefore particularly powerful in applications where signal sharpening and contrast enhancement are important but signal distortion is not.

Aortic 4D flow: Quantification of signal-to-noise ratio as a function of field strength and contrast enhancement for 1.5T, 3T, and 7T

2014 ◽  
Vol 73 (5) ◽  
pp. 1864-1871 ◽  
Author(s):  
Aaron T. Hess ◽  
Malenka M. Bissell ◽  
Ntobeko A.B. Ntusi ◽  
Andrew J.M. Lewis ◽  
Elizabeth M. Tunnicliffe ◽  
...  
Keyword(s):  
Field Strength ◽  
Contrast Enhancement ◽  
Signal To Noise Ratio ◽  
Flow Quantification ◽  
Signal To Noise ◽  
4D Flow ◽  
Noise Ratio

scholarly journals Optimal CT Contrast Enhancement Protocol for the Fontan Pathway: An Analysis Based on a 15-year Single-center Experience

2021 ◽  
Author(s):  
Hyun Woo Goo
Keyword(s):  
Standard Deviation ◽  
Contrast Agent ◽  
Contrast Enhancement ◽  
Quantitative Evaluation ◽  
Characteristic Curve ◽  
Low Contrast ◽  
Group 3 ◽  
Heterogeneous Enhancement ◽  
Standard Deviations ◽  
Noise Ratio

Abstract This retrospective study was performed to systemically compare several candidates for optimal contrast enhancement protocols of cardiothoracic CT dedicated for evaluating the Fontan pathway. Of 115 CT examinations from 89 patients, simultaneous injection of contrast agent via the arm and leg veins with 50% diluted contrast agent (group 1, n = 38), 60-second scan delay after leg vein injection (group 2, n = 41) or 3-minute scan delay (group 3, n = 36) was used to obtain optimal contrast enhancement. The degree and heterogeneity of cardiovascular enhancement, image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) were quantitatively evaluated. Histogram-assisted semi-quantitative evaluation was performed for heterogeneous enhancement, and a cut-off value indicating heterogeneous enhancement was determined by comparing the standard deviations between the cases showing homogeneous and heterogeneous enhancement. Contrast enhancement of the Fontan pathway, the standard deviation measured in the Fontan pathway, SNR, and CNR were more frequently lower in group 3 compared to groups 1 and 2 (p < 0.001). Homogeneous enhancement of the Fontan pathway based on the histogram-assisted semi-quantitative evaluation was more frequently seen in group 3 compared to groups 1 and 2 (p < 0.043‒0.001). Receiver operating characteristic curve analysis demonstrated that the standard deviation was an excellent diagnostic test in determining the homogeneity of contrast enhancement (area under the curve = 0.991; 95% confidence interval, 0.988‒0.994; p < 0.001). Standard deviations > 105.1 HU could be considered to indicate heterogeneous enhancement with 73.2% sensitivity and 100.0% specificity. The protocol using a 3-minute scan delay best achieved homogeneous contrast enhancement in the Fontan pathway on cardiothoracic CT among the tested protocols. However, low contrast enhancement, SNR, and, CNR need to be improved.

scholarly journals Perbandingan Metode Contrast Enhancement pada Citra CT-Scan Kanker Paru-paru

Gravitasi ◽  
2020 ◽  
Vol 19 (2) ◽  
pp. 24-28
Author(s):  
Nurhidayah ◽  
Bannu Abdul Samad ◽  
Bualkar Abdullah
Keyword(s):  
Ct Scan ◽  
Contrast Enhancement ◽  
Mean Square Error ◽  
Signal To Noise Ratio ◽  
Median Filter ◽  
Histogram Equalization ◽  
Mean Square ◽  
Signal To Noise ◽  
Adaptive Histogram Equalization ◽  
Noise Ratio

Abstrak: Di Indonesia kanker paru menjadi penyebab kematian kedua setelah kanker payudara. Angka mortalitas yang cukup tinggi, maka penentuan diagnosis lebih awal memegang peranan yang sangat penting dalam manajemen terapi. Kelemahan CT-Scan dalam mendiagnosa kanker paru-paru disebabkan oleh kontras citra yang rendah dan derau pada citra. Pada penelitian ini akan membandingkan metode contrast enhancement berbasis histogram equalization dan contrast limited adaptive histogram equalization untuk meningkatkan kualitas citra dengan menggunakan software Matlab. Namun, sebelumnya dilakukan reduksi noise dengan menggunakan metode median filter. Kinerja dari setiap metode dihitung dengan mencari nilai MSE (Mean Square Error) dan PSNR (Peak Signal to Noise Ratio) citra. Dari nilai MSE dan PSNR yang di dapatkan diperoleh nilai MSE dan PSNR terbaik pada metode contrast limited adaptive histogram equalization dengan nilai 653,434 dB dan 245,547 dB.

Breast MRI at very short TE (minTE): image analysis of minTE sequences on non-fat-saturated, subtracted T1-weighted images

2017 ◽  
Vol 14 (03) ◽  
pp. 160-168
Author(s):  
Evelyn Wenkel ◽  
Rolf Janka ◽  
Christian Geppert ◽  
Nadine Kaemmerer ◽  
Arndt Hartmann ◽  
...  
Keyword(s):  
Contrast Enhancement ◽  
Temporal Resolution ◽  
Signal To Noise Ratio ◽  
Breast Mri ◽  
Transverse Diameter ◽  
Final Assessment ◽  
Scan Time ◽  
Noise Ratio ◽  
The Difference ◽  
Lesion Morphology

Purpose The aim was to evaluate a minimum echo time (minTE) protocol for breast magnetic resonance imaging (MRI) in patients with breast lesions compared to a standard TE (nTE) time protocol. Methods Breasts of 144 women were examined with a 1.5 Tesla MRI scanner. Additionally to the standard gradient-echo sequence with nTE (4.8 ms), a variant with minimum TE (1.2 ms) was used in an interleaved fashion which leads to a better temporal resolution and should reduce the scan time by approximately 50 %. Lesion sizes were measured and the signal-to-noise ratio (SNR) as well as the contrast-to-noise ratio (CNR) were calculated. Subjective confidence was evaluated using a 3-point scale before looking at the nTE sequences (1 = very sure that I can identify a lesion and classify it, 2 = quite sure that I can identify a lesion and classify it, 3 = definitely want to see nTE for final assessment) and the subjective image quality of all examinations was evaluated using a four-grade scale (1 = sharp, 2 = slight blur, 3 = moderate blur and 4 = severe blur/not evaluable) for lesion and skin sharpness. Lesion morphology and contrast enhancement were also evaluated. Results With minTE sequences, no lesion was rated with “definitely want to see nTE sequences for final assessment”. The difference of the longitudinal and transverse diameter did not differ significantly (p > 0.05). With minTE, lesions and skin were rated to be significantly more blurry (p < 0.01 for lesions and p < 0.05 for skin). There was no difference between both sequences with respect to SNR, CNR, lesion morphology, contrast enhancement and detection of multifocal disease. Conclusion Dynamic breast MRI with a minTE protocol is feasible without a major loss of information (SNR, CNR, lesion morphology, contrast enhancement and lesion sizes) and the temporal resolution can be increased by a factor of 2 using minTE sequences. Key points 

scholarly journals Lung Mediated Auditory Contrast Enhancement Improves the Signal-to-Noise Ratio for Communication in Frogs

2021 ◽  
Author(s):  
Norman Lee ◽  
Jakob Christensen-Dalsgaard ◽  
Lauren A. White ◽  
Katrina M. Schrode ◽  
Mark A. Bee
Keyword(s):  
Contrast Enhancement ◽  
Signal To Noise Ratio ◽  
Signal To Noise ◽  
Noise Ratio

Entropy based Range Optimized Brightness Preserved Histogram-Equalization for Image Contrast Enhancement

2016 ◽  
Vol 6 (1) ◽  
pp. 59-72 ◽  
Author(s):  
Krishna Gopal Dhal ◽  
Sankhadip Sen ◽  
Kaustav Sarkar ◽  
Sanjoy Das
Keyword(s):  
Contrast Enhancement ◽  
Signal To Noise Ratio ◽  
Histogram Equalization ◽  
Image Contrast ◽  
Experimental Results ◽  
Signal To Noise ◽  
Image Histogram ◽  
Image Contrast Enhancement ◽  
Noise Ratio

In this study the over-enhancement problem of traditional Histogram-Equalization (HE) has been removed to some extent by a variant of HE called Range Optimized Entropy based Bi-Histogram Equalization (ROEBHE). In ROEBHE image histogram has been thresholded into two sub-histograms i.e. histograms corresponding to background and foreground. The threshold is calculated by maximizing the sum of the entropy of these two sub-histograms. The range for equalization has been optimized by maximizing the Peak-Signal to Noise ratio (PSNR). The experimental results prove that ROEBHE has prevailed over existing methods and PSNR is a better range optimizer than Absolute Mean Brightness Error (AMBE).

Correlation between Chondroitin Sulfate Iron Colloid-Enhanced MR Imaging and the Histological Grade of Hepatocellular Carcinoma

1995 ◽  
Vol 36 (1) ◽  
pp. 102-105 ◽  
Author(s):  
Y. Suto ◽  
F. Kodama ◽  
M. Kamba ◽  
Y. Ohta
Keyword(s):  
Hepatocellular Carcinoma ◽  
Mr Imaging ◽  
Chondroitin Sulfate ◽  
Contrast Enhancement ◽  
Histological Examination ◽  
Histological Grade ◽  
Poorly Differentiated ◽  
Noise Ratio ◽  
Well Differentiated ◽  
T2 Weighted Images

The association between contrast enhancement by chondroitin sulfate iron colloid (CSIC) and the histological grade of hepatocellular carcinoma (HCC) was evaluated in 24 patients diagnosed by histological examination of surgical specimens (26 nodules: 11 well-differentiated and 15 poorly—moderately-differentiated nodules). In the well-differentiated HCC nodules, the tumor—liver contrast to noise ratio (CNR) was not significantly increased after i.v. CSIC injection on both T1-weighted and T2-weighted images. In the moderately-poorly-differentiated HCC, CNR was significantly increased after CSIC administration on both T1-weighted and T2-weighted images (p<0.01). MR imaging using CSIC may be useful for diagnosing the degree of HCC differentiation.

scholarly journals Image quality, contrast enhancement and radiation dose of ECG-triggered versus non-ECG-triggered imaging of the aorta on a single source 256-slice CT scanner

2021 ◽  
Author(s):  
YM Wong ◽  
CC Ong ◽  
CR Liang ◽  
CA Tan ◽  
LLS Teo
Keyword(s):  
Image Quality ◽  
Radiation Dose ◽  
Contrast Enhancement ◽  
Aortic Root ◽  
Ascending Aorta ◽  
Single Source ◽  
Ct Scanner ◽  
Noise Ratio ◽  
Group 2 ◽  
Group 1

Introduction: Computed tomography angiography of the aorta (CTAA) is the modality of choice for investigating aortic disease. Our aim was to evaluate image quality, contrast enhancement and radiation dose of electrocardiograph (ECG)-triggered and non-ECG-triggered CTAA on a 256-slice single source CT scanner. Knowledge of these will allow requesting clinician and radiologist to balance radiation risk and image quality. Methods: We retrospectively assessed data from 126 patients who had undergone CTAA on a single-source CT scanner using ECG-triggered (group 1, n = 77) or non-ECG-triggered (group 2, n =49) protocols. Radiation doses were compared. Qualitative (4-point scale) and quantitative image quality assessments were performed. Results: The mean volume CT dose index, dose length product and effective dose in group 1 were 12.4 ± 1.9 mGy, 765.8 ± 112.4 mGy x cm and 13.0 ± 1.9 mSv, respectively. These were significantly higher compared with group 2 (9.1 ± 2.6 mGy, 624.1 ± 174.8 mGy x cm and 10.6 ± 3.0 mSv, respectively) ( p < 0.001). Qualitative assessment showed image quality at the aortic root-proximal ascending aorta was significantly higher in group 1 (median = 3) than in group 2 (median = 2, p < 0.001). Quantitative assessment showed significantly better mean arterial attenuation, signal-to-noise ratio and contrast-to-noise ratio in ECG-triggered CTAA compared with non-ECG-triggered CTAA. Conclusion: ECG-triggered CTAA in a single-source scanner has superior image quality and vessel attenuation of aortic root/ascending aorta but a higher radiation dose of approximately 23%. Its use should be considered specifically when assessing aortic root/ascending aorta pathology.

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