Changes In Pixel Values Research Articles

Development of a cardiac evaluation method using a dynamic flat-panel detector (FPD) system: a feasibility study using a cardiac motion phantom

The purpose of this study is to investigate the feasibility of cardiac evaluation with a dynamic flat-panel detector (FPD), based on changes in pixel values during cardiac pumping. To investigate the feasibility of cardiac evaluation with a dynamic flat-panel detector (FPD), based on changes in pixel values during cardiac pumping. Sequential radiographs of a cardiac motion phantom and water-equivalent material step were obtained with an FPD system. Various combinations of cardiac output and heart rate were evaluated with and without contrast medium. The ventricular area and summation of pixel values in the ventricles were measured. The ejection fraction (EF) was calculated based on the rate of changes and then compared to EF obtained from computed tomography images. In addition, slight changes in pixel values were visualized by use of inter-frame subtraction and color-mapping. The result of a clinical case was examined according to cardiac physiology. There were strong correlations between EF and our results. There was no significant difference between the findings with and without contrast medium. When the heart rate was greater than 60 bpm, EF obtained with our method were underestimated. It is necessary for a patient to be examined at an imaging rate between 7.5 and 10 fps at least. In addition, a +/-1.2% change in pixel value was equivalent to a +/-10 mm change in the thickness of water. Color-mapping images were supported by cardiac physiology. Evaluating changes in pixel values on dynamic chest radiography with FPD has the potential to demonstrate cardiac function without contrast medium. Inter-frame subtraction and color-mapping are very useful for interpreting changes in pixel value as velocities of blood flow.

SU-FF-I-05: Evolution of Adrenal Gland Perfusion with Anti-Angiogenic Therapy: A CT-Based Study

Purpose: In radiological diagnoses, it is important to understand and interpret anatomical changes, specifically those observed in CT scans, which correlate with treatment plans. There are currently many anticancer agents, which affect tumor vasculature growth as well as normal organ vessel growth. Monitoring these effects with imaging may be useful to guide selection and dosing of different treatments. By observing perfusion of certain organs, it is possible to monitor vessel competency. In cases where perfusion is constant over time, it can be assumed that there is no significant change in vasculature, and thus no damage as an effect of chemotherapeutic agents. In contrast, significant changes in perfusion over time, may suggest decease in normal vessel growth as a result of therapy. Methods & Materials: Patients receiving the VEGF inhibitor sorafenib, underwent CT imaging every six weeks, beginning with a baseline study prior to treatment. A “jog scan” was used to track perfusion through the adrenal glands (chosen due to their significant fenestration). Sixteen pairs of adrenal images were obtained per jog scan, and manually contoured using a contouring program. Each of the sixteen scans represents different perfusion time intervals from 0–150 seconds. The mean pixel values of each gland were obtained, and these values were compared over time for any significant changes in pixel value, and thus change in vasculature perfusion over time. Results: The average change in maximum pixel values from baseline to six weeks after treatment initiation shows a change of 4.58% increase in peak pixel value for both adrenal glands. Conclusion: The manual contouring of adrenal glands in conjunction with calculated maximum pixels values shows changes in adrenal perfusion between baseline and beginning therapy. The continued monitoring of perfusion could prove beneficial to the radiologic diagnosis of significant anatomical changes as a result of continuous chemotherapy.

Detectability of Regional Lung Ventilation with Flat-panel Detector-based Dynamic Radiography

This study was performed to investigate the ability of breathing chest radiography using flat-panel detector (FPD) to quantify relative local ventilation. Dynamic chest radiographs during respiration were obtained using a modified FPD system. Imaging was performed in three different positions, ie, standing and right and left decubitus positions, to change the distribution of local ventilation. We measured the average pixel value in the local lung area. Subsequently, the interframe differences, as well as difference values between maximum inspiratory and expiratory phases, were calculated. The results were visualized as images in the form of a color display to show more or less x-ray translucency. Temporal changes and spatial distribution of the results were then compared to lung physiology. In the results, the average pixel value in each lung was associated with respiratory phase. In all positions, respiratory changes of pixel value in the lower area were greater than those in the upper area (P < 0.01), which was the same tendency as the regional differences in ventilation determined by respiratory physiology. In addition, in the decubitus position, it was observed that areas with large respiratory changes in pixel value moved up in the vertical direction during expiration, which was considered to be airway closure. In conclusion, breathing chest radiography using FPD was shown to be capable of quantifying relative ventilation in local lung area and detecting regional differences in ventilation and timing of airway closure. This method is expected to be useful as a new diagnostic imaging modality for evaluating relative local ventilation.

Ultrasonographic image attributes of non-ovulatory follicles and follicles with different luteal outcomes in gonadotropin-releasing hormone (GnRH)-treated anestrous ewes

Ultrasonographic images are composed of multiple square picture elements called pixels. Quantitative changes in numerical pixel values (echotexture) determined by computer-assisted analysis of digital images reflect discrete changes in the microscopic structure and physiological status of ovarian antral follicles. The objective of the present study was to determine and compare the ultrasonographic attributes of non-ovulatory antral follicles that grew to an ostensibly ovulatory diameter (≥5 mm) and follicles with different luteal outcomes in response to gonadotropin-releasing hormone (GnRH) in anestrous Western White Face ewes ( n = 34). All animals received GnRH injections (250 ng i.v. every 2 h for 24 h) followed by a bolus injection of 125 μg of GnRH i.v. Ovarian images obtained by repeated transrectal ultrasonography were digitized and subjected to computerized analyses to determine the changes in follicular size and echotexture of the follicular antrum and wall. At the beginning of GnRH treatment, follicles that formed inadequate corpora lutea following ovulation (ICL; n = 22) had higher ( P < 0.001) pixel intensity of the central and peripheral antrum compared with non-ovulatory follicles ( n = 40). Pixel intensity of the central follicular antrum was greater ( P < 0.01) in follicles that formed ICL compared with follicles that formed normal (full-lifespan) CL post-treatment (NCL; n = 20) and mean pixel heterogeneity of the follicular wall was greater ( P < 0.05) in non-ovulatory follicles compared with follicles that gave rise to NCL. At the time of GnRH bolus injection (i.e., induction of a synchronous LH surge), the mean diameter of non-ovulatory follicles was greater ( P < 0.01) than that of all ovulating follicles, and pixel heterogeneity of the central follicular antrum was lowest ( P < 0.05) in non-ovulatory follicles. The mean diameter of luteinized unovulated follicles ( n = 9) tended to be greater ( P < 0.10) at 2.5 and 3 days after emergence, and pixel intensity of the follicular wall was lower ( P < 0.05) compared with non-luteinized follicles ( n = 8) at 1.5 and 2.5 days after emergence (beginning of the growth from ∼3 mm onwards). In conclusion, ovarian antral follicles with different outcomes after GnRH treatment (in seasonally anestrous ewes) had distinctive ultrasonographic characteristics.

The role of structural facial asymmetry in asymmetry of peak facial expressions

Asymmetric facial expression is generally attributed to asymmetry in movement, but structural asymmetry in the face may also affect asymmetry of expression. Asymmetry in posed expressions was measured using image-based approaches in digitised sequences of facial expression in 55 individuals, N=16 men, N=39 women. Structural asymmetry (at neutral expression) was higher in men than women and accounted for .54, .62, and .66 of the variance in asymmetry at peak expression for joy, anger, and disgust expressions, respectively. Movement asymmetry (measured by change in pixel values over time) was found, but was unrelated to peak asymmetry in joy or anger expressions over the whole face and in facial subregions relevant to the expression. Movement asymmetry was negatively related to peak asymmetry in disgust expressions. Sidedness of movement asymmetry (defined as the ratio of summed movement on the left to movement on the right) was consistent across emotions within individuals. Sidedness was found only for joy expressions, which had significantly more movement on the left. The significant role of structural asymmetry in asymmetry of emotion expression and the exploration of facial expression asymmetry have important implications for evolutionary interpretations of facial signalling and facial expressions in general.

New semi-fragile image authentication watermarking techniques using random bias and nonuniform quantization

Semi-fragile watermarking techniques aim at detecting malicious manipulations on an image, while allowing acceptable manipulations such as lossy compression. Although both of these manipulations are considered to be pixel value changes, semi-fragile watermarks should be sensitive to malicious manipulations but robust to the degradation introduced by lossy compression and other defined acceptable manipulations. In this paper, after studying the characteristics of both natural images and malicious manipulations, we propose two new semi-fragile authentication techniques robust against lossy compression, using random bias and nonuniform quantization, to improve the performance of the methods proposed by Lin and Chang.

SU-FF-T-365: Measurement of Radiation Induced Lung Damage in the Rat by CT Image Analysis

Purpose: To design a method to quantify morphological changes in irradiated lung tissue, assessed by CT. Method and Materials: CT images were made at different time points after administration of varying doses to different regions of the rat lung. The experiment included irradiation of 100%, 50% (6 different regions) and 25% (2 regions) of the total lung volume. The applied doses were: 9,10,11 and 12 Gy for the 100% lung volume, 16,18,20 and 22 Gy for the 50% volumes and 27,30,33 and 36 Gy for the 25% volumes. A computerized contouring method was developed to automatically delineate the lungs in the CT images. For each irradiated region the average CT-value (ACV) of its pixels and its standard deviation (SD) were determined. The changes in ACV and its SD with respect to the same region in controls were combined in a vector M. The length and orientation of M was used to characterize the changes in the CT image pattern, i.e. the morphology of the lung tissue. The total lung volume of all animals and M were measured at 8, 26 and 38 weeks for all irradiated regions, averaged over all dose values. After normalization, M was also measured as a function of dose. Results: About 13.000 contours in lung volume studies of 374 rats were automatically drawn. With respect to the controls, a decrease in total lung volume in time was observed. Significant changes in radiation responses M were found in all irradiated regions. The largest radiation response was found for lateral lung volumes. Conclusion: The auto-contouring method is very robust and can easily be applied to process large amounts of CT-slices of irradiated rat lung. The method showed significant changes in average lung CT pixel values and their variation for sub volumes of irradiated lung tissue.

A comparison of x-ray detectors for mouse CT imaging

There is significant interest in using computed tomography (CT) for in vivo imaging applications in mouse models of disease. Most commercially available mouse x-ray CT scanners utilize a charge-coupled device (CCD) detector coupled via fibre optic taper to a phosphor screen. However, there has been little research to determine if this is the optimum detector for the specific task of in vivo mouse imaging. To investigate this issue, we have evaluated four detectors, including an amorphous selenium (a-Se) detector, an amorphous silicon (a-Si) detector with a gadolinium oxysulphide (GOS) screen, a CCD with a 3:1 fibre taper and a GOS screen, and a CCD with a 2:1 fibre taper and both GOS and thallium-doped caesium iodide (CsI:Tl) screens. The detectors were evaluated by measuring the modulation transfer function (MTF), noise power spectrum (NPS), detective quantum efficiency (DQE), stability over multiple exposures, and noise in reconstructed CT images. The a-Se detector had the best MTF and the highest DQE (0.6 at 0 lp mm−1) but had the worst stability (45% reduction after 2000 exposure frames). The a-Si detector and the CCD with the 3:1 fibre, both of which used the GOS screen, had very similar performance with a DQE of approximately 0.30 at 0 lp mm−1. For the CCD with the 2:1 fibre, the CsI:Tl screen resulted in a nearly two-fold improvement in DQE over the GOS screen (0.4 versus 0.24 at 0 lp mm−1). The CCDs both had the best stability, with less than a 1% change in pixel values over multiple exposures. The pixel values of the a-Si detector increased 5% over multiple exposures due to the effects of image lag. Despite the higher DQE of the a-Se detector, the reconstructed CT images acquired with the a-Si detector had lower noise levels, likely due to the blurring effects from the phosphor screen.

Implementation and evaluation of data compression of MR images.

A full-frame bit-allocation technique of data compression has been implemented using the existing computer facilities of an MR imager. Images reconstructed from compressed data files have been compared with the original image and changes in noise and pixel value measured to evaluate any image degradation introduced by the compression process. A 256 x 256 x 8 bit brain image can be compressed in 20 seconds with a compression ratio of greater than 4:1 without significant loss of information.

Pulmonary ventilation and perfusion during graded pulmonary arterial occlusion.

ArticlePulmonary ventilation and perfusion during graded pulmonary arterial occlusion.N R Silverman, M Intaglietta, and W R TompkinsN R Silverman, M Intaglietta, and W R TompkinsPublished Online:01 May 1973https://doi.org/10.1152/jappl.1973.34.5.726MoreSectionsPDF (2 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByDetection of Pulmonary Embolism Based on Reduced Changes in Radiographic Lung Density During Cardiac Beating Using Dynamic Flat-panel Detector: An Animal-based StudyAcademic Radiology, Vol. 26, No. 10Dynamic chest radiography: flat-panel detector (FPD) based functional X-ray imaging13 June 2016 | Radiological Physics and Technology, Vol. 9, No. 2Respiratory and Cardiac Function Analysis on the Basis of Dynamic Chest Radiography31 October 2013Ventilatory impairment detection based on distribution of respiratory-induced changes in pixel values in dynamic chest radiography: a feasibility study13 June 2010 | International Journal of Computer Assisted Radiology and Surgery, Vol. 6, No. 1Development of pulmonary blood flow evaluation method with a dynamic flat-panel detector: quantitative correlation analysis with findings on perfusion scan7 November 2009 | Radiological Physics and Technology, Vol. 3, No. 1Pulmonary blood flow evaluation using a dynamic flat-panel detector: feasibility study with pulmonary diseases4 June 2009 | International Journal of Computer Assisted Radiology and Surgery, Vol. 4, No. 5Development of functional chest imaging with a dynamic flat-panel detector (FPD)1 July 2008 | Radiological Physics and Technology, Vol. 1, No. 2Development of a cardiac evaluation method using a dynamic flat-panel detector (FPD) system: a feasibility study using a cardiac motion phantom1 November 2007 | Radiological Physics and Technology, Vol. 1, No. 1Mammalian Locomotor-Respiratory Integration: Implications for Diaphragmatic and Pulmonary DesignScience, Vol. 262, No. 5131 More from this issue > Volume 34Issue 5May 1973Pages 726-31 https://doi.org/10.1152/jappl.1973.34.5.726PubMed4703753History Published online 1 May 1973 Published in print 1 May 1973 Metrics