Improved Detectability with Blocked Element Compensation

1994 ◽  
Vol 16 (1) ◽  
pp. 1-18 ◽  
Author(s):  
Pai-chi Li ◽  
M. O'Donnell
Keyword(s):  
Cancer Diagnosis ◽  
Performance Measure ◽  
The Body ◽  
Two Dimensional ◽  
Contrast Resolution ◽  
Low Contrast ◽  
Performance Improvements ◽  
Point Spread ◽  
Spread Function ◽  
And Performance

The inability of diagnostic ultrasound to detect low contrast lesions deep inside the body has limited its success in cancer diagnosis. To enhance low contrast detectability, two-dimensional, very large arrays (VLA's) providing greatly improved spatial resolution have been proposed. Due to discontinuous acoustic windows into the body, however, a significant fraction of such an array might be blocked resulting in degraded detectability in clinical situations. To compensate for this degradation, an object dependent method utilizing multiple receive beams has been proposed and shown to effectively reduce un-desired beamforming artifacts. To further explore the method's capabilities, simulations have been done quantifying improvements in contrast resolution. Using the contrast-to-noise ratio (CNR) as a performance measure, results show that low contrast detectability is determined by sidelobe energy in the point spread function if the total aperture size is not reduced. Moreover, contrast resolution can be restored using the object dependent method if the number of blocked elements is not very significant. If the number of blocked elements is large, however, the method breaks down and performance improvements are minimal.

scholarly journals Expected performances of the Characterising Exoplanet Satellite (CHEOPS)

2020 ◽  
Vol 635 ◽  
pp. A24 ◽  
Author(s):  
S. Hoyer ◽  
P. Guterman ◽  
O. Demangeon ◽  
S. G. Sousa ◽  
M. Deleuil ◽  
...  
Keyword(s):  
Light Curves ◽  
Field Of View ◽  
Current Status ◽  
Point Spread ◽  
Single Target ◽  
Science Operations ◽  
Spread Function ◽  
And Performance ◽  
Irregular Point

The CHaracterizing ExOPlanet Satellite (CHEOPS) is set to be launched in December 2019 and will detect and characterize small size exoplanets via ultra high precision photometry during transits. CHEOPS is designed as a follow-up telescope and therefore it will monitor a single target at a time. The scientific users will retrieve science-ready light curves of the target that will be automatically generated by the CHEOPS data reduction pipeline of the Science Operations Centre. This paper describes how the pipeline processes the series of raw images and, in particular, how it handles the specificities of CHEOPS data, such as the rotating field of view, the extended irregular point spread function, and the data temporal gaps in the context of the strict photometric requirements of the mission. The current status and performance of the main processing stages of the pipeline, that is the calibration, correction, and photometry, are presented to allow the users to understand how the science-ready data have been derived. Finally, the general performance of the pipeline is illustrated via the processing of representative scientific cases generated by the mission simulator.

Vernier Image Processing: Model and Experiments

Perception ◽  
1997 ◽  
Vol 26 (1_suppl) ◽  
pp. 110-110
Author(s):  
A V Chihman ◽  
V N Chihman ◽  
Y E Shelepin
Keyword(s):  
Fourier Analysis ◽  
Visual Processing ◽  
Fourier Spectrum ◽  
Field Size ◽  
Two Dimensional ◽  
Frequency Range ◽  
Additional Line ◽  
Point Spread ◽  
Model Predictions ◽  
Spread Function

Earlier we proposed a model for visual processing of the optical image of Vernier targets (1996 Perception25 Supplement, 115 – 116) based on Fourier analysis of the image. Our model comprises blurring of the thin Vernier bars by the optical point-spread function followed by calculation of the two-dimensional Fourier spectrum. In our model the processing area for Fourier analysis (the receptive field size) is 5 min arc. For a Vernier target, the contrast energy in the low-spatial-frequency range is different in different orientations, and magnification of the Vernier shift changes the orientation of the oblique Fourier components. To test the model, we carried out experiments in which the stimuli were Vernier lines with additional line distractors orthogonal to the orientation of the oblique Fourier components. Thresholds for detecting Vernier displacements were determined by a 2AFC paradigm and compared with model predictions. The results are consistent with our modelling of Vernier performance as a measurement of oblique components of the 2-D Fourier spectrum.

Benefits of Point-Spread Function and Time of Flight for PET/CT Image Quality in Relation to the Body Mass Index and Injected Dose

2013 ◽  
Vol 38 (6) ◽  
pp. 407-412 ◽  
Author(s):  
Go Akamatsu ◽  
Katsuhiko Mitsumoto ◽  
Kaori Ishikawa ◽  
Takafumi Taniguchi ◽  
Nobuyoshi Ohya ◽  
...  
Keyword(s):  
Body Mass Index ◽  
Image Quality ◽  
Body Mass ◽  
Point Spread Function ◽  
The Body ◽  
Ct Image ◽  
Point Spread ◽  
Pet Ct ◽  
Spread Function ◽  
Ct Image Quality

Deconvolution of the two-dimensional point-spread function of area detectors using the maximum-entropy algorithm

1999 ◽  
Vol 32 (4) ◽  
pp. 683-691 ◽  
Author(s):  
H. Graafsma ◽  
R. Y. de Vries
Keyword(s):  
Maximum Entropy ◽  
Point Spread Function ◽  
Contrast Ratio ◽  
Entropy Method ◽  
Protein Crystal ◽  
Two Dimensional ◽  
Two Phase ◽  
X Ray ◽  
Point Spread ◽  
Spread Function

The maximum-entropy method (MEM) has been applied for the deconvolution of the point-spread function (PSF) of two-dimensional X-ray detectors. The method is robust, model and image independent, and only depends on the correct description of the two-dimensional point-spread function and gain factor of the detector. A significant enhancement of both the spatial resolution and the contrast ratio has been obtained for two phase-contrast images recorded with an ultra-high-resolution X-ray imaging detector. The method has also been applied to a Laue diffraction image of a protein crystal, showing an important improvement in both the peak separation of closely spaced diffraction peaks and the signal-to-noise ratio of medium and weak peaks. The principle of the method is explained and examples of its application are presented.

scholarly journals Efficient Two-Dimensional Blocked Element Compensation

1994 ◽  
Vol 16 (3) ◽  
pp. 164-175 ◽  
Author(s):  
Pai-Chi Li ◽  
M. O'Donnell
Keyword(s):  
Image Quality ◽  
Ultrasound Image ◽  
The Body ◽  
Two Dimensional ◽  
Hardware Complexity ◽  
Computationally Efficient ◽  
One Dimensional ◽  
Spread Function ◽  
Computationally Efficient Algorithms ◽  
Beam Characteristics

Very large, two-dimensional, anisotropic arrays have been proposed to improve ultrasound image quality. Due to noncontiguous acoustic windows into the body, however, a significant portion of such an aperture may be blocked. Blocked elements result in high sidelobes in the point spread function, degrading image quality. To compensate for this, an object dependent method using multiple receive beams has been recently proposed. This method is effective in removing undesired sidelobes. However, previous results were for one-dimensional arrays where only lateral beams were used for estimation. With two-dimensional arrays, the distribution of blocked elements can change beam characteristics, both laterally and elevationally. In other words, receive beams must be formed in both directions for better performance. Although straightforward in principle, extension of the algorithm from one dimension to two increases computational complexity dramatically. Furthermore, the restricted elevational steering capability of anisotropic arrays also limits performance. In this paper, several computationally efficient algorithms for two-dimensional blocked element compensation are proposed and evaluated. It is shown that undesired sidelobes can be effectively removed using only a limited number of receive beams. Image quality can therefore be restored in the presence of blocked elements without significantly increasing hardware complexity.

scholarly journals Impact of time of flight and point spread function on quantitative parameters of lung lesions in 18F-FDG PET/CT

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Kemin Huang ◽  
Yanlin Feng ◽  
Weitang Liang ◽  
Lin Li
Keyword(s):  
Fdg Pet ◽  
Standard Uptake Value ◽  
Reconstruction Algorithms ◽  
Lung Lesions ◽  
Low Contrast ◽  
Quantitative Parameters ◽  
Point Spread ◽  
Pet Ct ◽  
Spread Function ◽  
Fdg Pet Ct

Abstract Background Image reconstruction algorithm is one of the important factors affecting the quantitative parameters of PET/CT. The purpose of this study was to investigate the effects of time of flight (TOF) and point spread function (PSF) on quantitative parameters of lung lesions in 18F-FDG PET/CT. Methods This retrospective study evaluated 60 lung lesions in 39 patients who had undergone 18F-fluoro-deoxy-glucose (FDG) PET/CT. All lesions larger than 10 mm in diameter were included in the study. The PET data were reconstructed with a baseline ordered-subsets expectation–maximization (OSEM) algorithm, OSEM + PSF, OSEM + TOF and OSEM + TOF + PSF respectively. The differences of maximum standard uptake value (SUVmax), mean standard uptake value (SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG)and signal to noise ratio (SNR)were compared among different reconstruction algorithms. Results Compared with OSEM reconstruction, using OSEM + TOF + PSF increased SUVmean and SUVmax by 23.73% and 22.71% respectively, and SNR increased by 70.18%, MTV decreased by 23.84% (p < 0.01). The percentage difference was significantly higher in smaller lesions (diameter 10–22 mm) than in larger lesions (diameter 23–44 mm), and significantly higher in low contrast lesions (SNR ≤ 15.31) than in high contrast lesions (SNR > 15.31). The difference of TLG among various reconstruction algorithms is relatively small, the highest value is − 6.48% of OSEM + TOF + PSF, and the lowest value is 0.81% of OSEM + TOF. Conclusion TOF and PSF significantly affected the quantitative parameters of lung lesions in 18F-FDG PET/CT. OSEM + TOF + PSF can significantly increased SUVmax, SUVmean and SNR, and significantly reduce MTV, especially in small lesions and low contrast lesions. TLG can be relatively stable in different reconstruction algorithms.

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