Methods and Tools for Image and Video Quality Assessment

Disertační práce se zabývá metodami a prostředky pro hodnocení kvality obrazu ve videosekvencích, což je velmi aktuální téma, zažívající velký rozmach zejména v souvislosti s digitálním zpracováním videosignálů. Přestože již existuje relativně velké množství metod a metrik pro objektivní, tedy automatizované měření kvality videosekvencí, jsou tyto metody zpravidla založeny na porovnání zpracované (poškozené, například komprimací) a originální videosekvence. Metod pro hodnocení kvality videosekvení bez reference, tedy pouze na základě analýzy zpracovaného materiálu, je velmi málo. Navíc se takové metody převážně zaměřují na analýzu hodnot signálu (typicky jasu) v jednotlivých obrazových bodech dekódovaného signálu, což je jen těžko aplikovatelné pro moderní komprimační algoritmy jako je H.264/AVC, který používá sofistikovené techniky pro odstranění komprimačních artefaktů. V práci je nejprve podán stučný přehled dostupných metod pro objektivní hodnocení komprimovaných videosekvencí se zdůrazněním rozdílného principu metod využívajících referenční materiál a metod pracujících bez reference. Na základě analýzy možných přístupů pro hodnocení video sekvencí komprimovaných moderními komprimačními algoritmy je v dalším textu práce popsán návrh nové metody určené pro hodnocení kvality obrazu ve videosekvencích komprimovaných s využitím algoritmu H.264/AVC. Nová metoda je založena na sledování hodnot parametrů, které jsou obsaženy v transportním toku komprimovaného videa, a přímo souvisí s procesem kódování. Nejprve je provedena úvaha nad vlivem některých takových parametrů na kvalitu výsledného videa. Následně je navržen algoritmus, který s využitím umělé neuronové sítě určuje špičkový poměr signálu a šumu (peak signal-to-noise ratio -- PSNR) v komprimované videosekvenci -- plně referenční metrika je tedy nahrazována metrikou bez reference. Je ověřeno několik konfigurací umělých neuronových sítí od těch nejjednodušších až po třívrstvé dopředné sítě. Pro učení sítí a následnou analýzu jejich výkonnosti a věrnosti určení PSNR jsou vytvořeny dva soubory nekomprimovaných videosekvencí, které jsou následně komprimovány algoritmem H.264/AVC s proměnným nastavením kodéru. V závěrečné části práce je proveden rozbor chování nově navrženého algoritmu v případě, že se změní vlastnosti zpracovávaného videa (rozlišení, střih), případně kodéru (formát skupiny současně kódovaných snímků). Chování algoritmu je analyzováno až do plného vysokého rozlišení zdrojového signálu (full HD -1920 x 1080 obrazových bodů).The doctoral thesis is focused on methods and tools for image quality assessment in video sequences, which is a very up-to-date theme, undergoing a rapid evolution with respect to digital video signal processing, in particular. Although a variety of metrics for objective (automated) video sequence quality measurement has been developed recently, these methods are mostly based on comparison of the processed (damaged, e.g. with compression) and original video sequences. There are very few methods operating without reference, i.e. only on the processed video material. Moreover, such methods are usually analyzing signal values (typically luminance) in picture elements of the decoded signal, which is hardly applicable for modern compression algorithms such as the H.264/AVC as they use sophisticated techniques to remove compression artifacts. The thesis first gives a brief overview of the available metrics for objective quality measurements of compressed video sequences, emphasizing the different approach of full-reference and no-reference methods. Based on an analysis of possible ideas for measuring quality of video sequences compressed using modern compression algorithms, the thesis describes the design process of a new quality metric for video sequences compressed with the H.264/AVC algorithm. The new method is based on monitoring of several parameters, present in the transport stream of the compressed video and directly related to the encoding process. The impact of bitstream parameters on the video quality is considered first. Consequently, an algorithm is designed, employing an artificial neural network to estimate the peak signal-to-noise ratios (PSNR) of the compressed video sequences -- a full-reference metric is thus replaced by a no--reference metric. Several neural network configurations are verified, reaching from the simplest to three-layer feedforward networks. Two sets of video sequences are constructed to train the networks and analyze their performance and fidelity of estimated PSNRs. The sequences are compressed using the H.264/AVC algorithm with variable encoder configuration. The final part of the thesis deals with an analysis of behavior of the newly designed algorithm, provided the properties of the processed video are changed (resolution, cut) or encoder configuration is altered (format of group of pictures coded together). The analysis is done on video sequences with resolution up to full HD (1920 x 1080 pixels, progressive)

Analysis of Resolution in Aerial Earth Surface Photography

The paper deals with a simplified analysis of subjective resolution of an aerial sensing system for Earth surface photography in the visible light spectrum. The proposed simplified linear method allows approximate estimation of the minimal target size in the image scanned using a camera with CCD sensor

Digital Video Image Quality

Optical physic

Nucleation of a sodium droplet on C60

We investigate theoretically the progressive coating of C60 by several sodium atoms. Density functional calculations using a nonlocal functional are performed for NaC60 and Na2C60 in various configurations. These data are used to construct an empirical atomistic model in order to treat larger sizes in a statistical and dynamical context. Fluctuating charges are incorporated to account for charge transfer between sodium and carbon atoms. By performing systematic global optimization in the size range 1<=n<=30, we find that Na_nC60 is homogeneously coated at small sizes, and that a growing droplet is formed above n=>8. The separate effects of single ionization and thermalization are also considered, as well as the changes due to a strong external electric field. The present results are discussed in the light of various experimental data.Comment: 17 pages, 10 figure

Hepcidin and ferritin levels as markers of immune cell activation during septic shock, severe COVID-19 and sterile inflammation

IntroductionMajor clinically relevant inflammatory events such as septic shock and severe COVID-19 trigger dynamic changes in the host immune system, presenting promising candidates for new biomarkers to improve precision diagnostics and patient stratification. Hepcidin, a master regulator of iron metabolism, has been intensively studied in many pathologies associated with immune system activation, however these data have never been compared to other clinical settings. Thus, we aimed to reveal the dynamics of iron regulation in various clinical settings and to determine the suitability of hepcidin and/or ferritin levels as biomarkers of inflammatory disease severity.CohortsTo investigate the overall predictive ability of hepcidin and ferritin, we enrolled the patients suffering with three different diagnoses – in detail 40 patients with COVID-19, 29 patients in septic shock and eight orthopedic patients who were compared to nine healthy donors and all cohorts to each other.ResultsWe showed that increased hepcidin levels reflect overall immune cell activation driven by intrinsic stimuli, without requiring direct involvement of infection vectors. Contrary to hepcidin, ferritin levels were more strongly boosted by pathogen-induced inflammation – in septic shock more than four-fold and in COVID-19 six-fold in comparison to sterile inflammation. We also defined the predictive capacity of hepcidin-to-ferritin ratio with AUC=0.79 and P = 0.03.DiscussionOur findings confirm that hepcidin is a potent marker of septic shock and other acute inflammation-associated pathologies and demonstrate the utility of the hepcidin-to-ferritin ratio as a predictor of mortality in septic shock, but not in COVID-19

Antiinflammatory Therapy with Canakinumab for Atherosclerotic Disease

Background: Experimental and clinical data suggest that reducing inflammation without affecting lipid levels may reduce the risk of cardiovascular disease. Yet, the inflammatory hypothesis of atherothrombosis has remained unproved. Methods: We conducted a randomized, double-blind trial of canakinumab, a therapeutic monoclonal antibody targeting interleukin-1β, involving 10,061 patients with previous myocardial infarction and a high-sensitivity C-reactive protein level of 2 mg or more per liter. The trial compared three doses of canakinumab (50 mg, 150 mg, and 300 mg, administered subcutaneously every 3 months) with placebo. The primary efficacy end point was nonfatal myocardial infarction, nonfatal stroke, or cardiovascular death. RESULTS: At 48 months, the median reduction from baseline in the high-sensitivity C-reactive protein level was 26 percentage points greater in the group that received the 50-mg dose of canakinumab, 37 percentage points greater in the 150-mg group, and 41 percentage points greater in the 300-mg group than in the placebo group. Canakinumab did not reduce lipid levels from baseline. At a median follow-up of 3.7 years, the incidence rate for the primary end point was 4.50 events per 100 person-years in the placebo group, 4.11 events per 100 person-years in the 50-mg group, 3.86 events per 100 person-years in the 150-mg group, and 3.90 events per 100 person-years in the 300-mg group. The hazard ratios as compared with placebo were as follows: in the 50-mg group, 0.93 (95% confidence interval [CI], 0.80 to 1.07; P = 0.30); in the 150-mg group, 0.85 (95% CI, 0.74 to 0.98; P = 0.021); and in the 300-mg group, 0.86 (95% CI, 0.75 to 0.99; P = 0.031). The 150-mg dose, but not the other doses, met the prespecified multiplicity-adjusted threshold for statistical significance for the primary end point and the secondary end point that additionally included hospitalization for unstable angina that led to urgent revascularization (hazard ratio vs. placebo, 0.83; 95% CI, 0.73 to 0.95; P = 0.005). Canakinumab was associated with a higher incidence of fatal infection than was placebo. There was no significant difference in all-cause mortality (hazard ratio for all canakinumab doses vs. placebo, 0.94; 95% CI, 0.83 to 1.06; P = 0.31). Conclusions: Antiinflammatory therapy targeting the interleukin-1β innate immunity pathway with canakinumab at a dose of 150 mg every 3 months led to a significantly lower rate of recurrent cardiovascular events than placebo, independent of lipid-level lowering. (Funded by Novartis; CANTOS ClinicalTrials.gov number, NCT01327846.

Systematic Review of Potential Health Risks Posed by Pharmaceutical, Occupational and Consumer Exposures to Metallic and Nanoscale Aluminum, Aluminum Oxides, Aluminum Hydroxide and Its Soluble Salts

Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007). Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of “total Al”assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al+ 3 to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)+ 2 and Al(H2O)6 + 3] that after complexation with O2•−, generate Al superoxides [Al(O2•)](H2O5)]+ 2. Semireduced AlO2• radicals deplete mitochondrial Fe and promote generation of H2O2, O2 • − and OH•. Thus, it is the Al+ 3-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer\u27s disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances

Contrast-enhanced MR angiography utilizing parallel acquisition techniques in renal artery stenosis detection

Contrast-enhanced MR angiography utilizing parallel acquisition techniques in renal artery stenosis detection Objective: The aim of our study was to assess the diagnostic value of contrast- enhanced MR angiography (MRA) utilizing parallel acquisition techniques in the detection of renal artery stenosis (RAS). Material and Methods: 81 hypertensive subjects with suspected RAS were examined on a 1.5 T MR system with body array coil. Bolus tracking was used to monitor the arrival of contrast agent to the abdominal aorta. The MRA sequence parameters were as follows: TR 3.7 ms; TE 1.2 ms; flip angle 25ř; acquisition time 18 s; voxel size 1.1 mm × 1.0 mm × 1.1 mm; centric k-space sampling; parallel acquisition techniques with acceleration factor of 2 (GRAPPA). Renal artery stenosis of 60% and more was considered hemodynamically significant. The results of MRA were compared to digital subtraction angiography serving as a standard of reference. Results: Sensitivity, specificity, positive predictive value and negative predictive value of MRA in the detection of hemodynamically significant RAS were 91%, 96%, 94% and 94%, respectively. Prevalence of RAS was 41% in our study population. Conclusion: Contrast-enhanced MRA with high spatial resolution offers sufficient sensitivity and specificity for screening of..