Computer-aided analyses of mouse retinal OCT images - an actual application report.

PURPOSE: There is a need for automated retinal optical coherence tomography (OCT) image analysis tools for quantitative measurements in small animals. Some image processing techniques for retinal layer analysis have been developed, but reports about how useful those techniques are in actual animal studies are rare. This paper presents the use of a retinal layer detection method we developed in an actual mouse study that involves wild type and mutated mice carrying photoreceptor degeneration. METHODS: Spectral domain OCT scanning was performed by four experimenters over 12 months on 45 mouse eyes that were wild-type, deficient for ephrin-A2 and ephrin-A3, deficient for rhodopsin, or deficient for rhodopsin, ephrin-A2 and ephrin-A3. The thickness of photoreceptor complex between the outer plexiform layer and retinal pigment epithelium was measured on two sides of the optic disc as the biomarker of retinal degeneration. All the layer detection results were visually confirmed. RESULTS: Overall, 96% (8519 out of 9000) of the half-side images were successfully processed using our technique in a semi-automatic manner. There was no significant difference in success rate between mouse lines (p = 0.91). Based on a human observer's rating of image quality for images successfully and unsuccessfully processed, the odds ratios for 'easily visible' images and 'not clear' images to be successfully processed is 62 and 4, respectively, against 'indistinguishable' images. Thickness of photoreceptor complex was significantly different across the quadrants compared (p < 0.001). It was also found that the average thickness based on 4-point sparse sampling was not significantly different from the full analysis, while the range of differences between the two methods could be up to about 6 µm or 16% for individual eyes. Differences between mouse lines and progressive thickness reduction were revealed by both sampling measures. CONCLUSIONS: Although the thickness of the photoreceptor complex layer is not even, manual sparse sampling may be as sufficiently accurate as full analysis in some studies such as ours, where the error of sparse sampling was much smaller than the effect size of rhodopsin deficiency. It is also suggested that the image processing method can be useful in actual animal studies. Even for images poorly visible to human eyes the image processing method still has a good chance to extract the complex layer.

[Lesion Extraction from B-type Ultrasound Image Using Subordinate Degree Region Level Set Method].

B-type ultrasound images have important applications in medical diagnosis. However, the widely spread intensity inhomogeneity, low-scale contrast, constructed defect, noise and blurred edges all make it difficult to implement automatic segmentation of lesion in the images. Based on region level set method, a subordinate degree region level set model was proposed, in which subordinate degree probability of each pixel was defined to reflect the pixel subjection grade to target and background respectively. Pixels were classified to either target or background by calculation of their subordinate degree probabilities, and edge contour was obtained by region level set iterations. In this paper, lesion segmentation is regarded as local segmentation of specific area, and the calculation is restrained to the local sphere abide by the contour, which greatly reduce the calculation complexity. Experiments on B-type ultrasound images showed improved results of the proposed method compared to those of some popular level set methods.

VeryGene: linking tissue-specific genes to diseases, drugs, and beyond for knowledge discovery.

In addition to many other genes, tissue-specific genes (TSGs) represent a set of genes of great importance for human physiology. However, the links among TSGs, diseases, and potential therapeutic agents are often missing, hidden, or too scattered to find. There is a need to establish a knowledgebase for researchers to share this and additional information in order to speed up discovery and clinical practice. As an initiative toward systems biology, the VeryGene web server was developed to fill this gap. A significant effort has been made to integrate TSGs from two large-scale data analyses with respective information on subcellular localization, Gene Ontology, Reactome, KEGG pathway, Mouse Genome Informatics (MGI) Mammalian Phenotype, disease association, and targeting drugs. The current release carefully selected 3,960 annotated TSGs derived from 127 normal human tissues and cell types, including 5,672 gene-disease and 2,171 drug-target relationships. In addition to being a specialized source for TSGs, VeryGene can be used as a discovery tool by generating novel inferences. Some inherently useful but hidden relations among genes, diseases, drugs, and other important aspects can be inferred to form testable hypotheses. VeryGene is available online at http://www.verygene.com.

An investigation of perceived vehicle speed from a driver's perspective.

PURPOSE: Speed estimation of drivers' own vehicles and other vehicles on the road is an important task for drivers and is also crucial to the roadway safety. The objective of the study was to examine the effects of multiple factors such as image scale, speed, road type, driving experience, and gender on the speed perception of drivers' own vehicles. METHODS: Thirty participants consisted of 17 males and 13 females, including 13 without driving experience. All participants estimated the driving speed of 192 5-second video clips, which were selected from naturalistic driving recordings. The recorded driving speeds were evenly distributed across the entire range from 5mph to 65mph. Half of the selected video clips were recorded on wide roads and another half were recorded on comparatively narrow roads. Video clips were played on a large screen, with each clip shown in one of 4 image scales (100%, 75%, 50%, and 38% of the actual field of view in the real world). RESULTS: Speed estimates were most accurate for the smallest image size (38% of the actual field of view). As the image size increased, the driving speed was increasingly underestimated. Participants with driving experience accurately estimated the driving speed on both wide and narrow roads whereas those without driving experience had greater underestimates on wider roads. Speeds were most accurately estimated within the range 25-35mph, but the speeds slower than the range tend to be overestimated and the speeds faster than the range are more likely to be underestimated. While males and females showed the same pattern across speed groups, females have greater estimation errors at the highest and lowest speed groups. Participants without driving experience showed increasing underestimation of speed as driving speed increased whereas participants with driving experience primarily underestimated the highest speeds. CONCLUSIONS: The present study shows the effect of multidimensional influential factors on perceived vehicle speed from drivers' perspective. The results also have implications for driving simulation scenario design, driving simulator setup, and the assessment of speed control in simulated and naturalistic environments.

[Level set method reconciled with a dynamic weighting factor for B-mode ultrasound image segmentation].

OBJECTIVE: To modify the level set method for precise and fast segmentation of B-type ultrasound image lesions. METHODS: Based on the best of region level set method, entropy in the information theory was introduced into image processing to define a dynamic weighting factor that responded to the gradient change of the local gray levels to evaluate the dynamic degree of driven force on each pixel on the contour to the target and background areas. The dynamic weighting factors were reconciled into the regional level set model and led the contour to deform and move during the iterations. As lesion segmentation was classified as local segmentation of a specific area, the calculation was restrained to the local sphere abide by the contour, which greatly reduced the calculation complex. RESULTS: Experiments on B-type ultrasound images showed improved results of the proposed method with a better accuracy and less time consumption compared with several current level set methods. CONCLUSION: Level set method reconciled with dynamic weighting factor allows a better evaluation of the lesion contour pixels, and the local calculation strategy results in an enhanced segmentation efficiency.

[Study on distribution of cardiac electric field around the isolated heart of guinea pig].

OBJECTIVE: To define the distribution of the cardiac electric field around the isolated heart of guinea pig. METHODS: The hearts of 26 guinea pigs were isolated and immersed in normal saline or distilled water, and the ECGs were recorded in 4 directions of every plane with 4 points deposited in every direction at different distances from the anterior, posterior and the laterals of both the ventricles of the heart. RESULT: In both media, ECGs were composed mainly of upright waves were recorded at all points in the 4 directions at the 3 levels. CONCLUSION: The uniformed outward distribution of the cardiac electric field suggests that it is not dipolar but a sphere-like single source when the interference of different potentials of the reference points over the body surface is excluded.

[Fast elimination of 50-Hz noise in PC-based application system].

The interference by 50-Hz noise arising from the power supply cables is common in PC-based application system, often considerably affecting the detection of useful signals. On the basis of self-adapting correlation method, we attempt to address the problem of fast elimination of 50-Hz noise from the useful signals in PC-based application system such as digital ECG recording system.

Microbead-induced ocular hypertensive mouse model for screening and testing of aqueous production suppressants for glaucoma.

PURPOSE: To characterize the microbead-induced ocular hypertension (OHT) mouse model and investigate its potential use for preclinical screening and evaluation of ocular hypotensive agents, we tested the model's responses to major antiglaucoma drugs. METHODS: Adult C57BL/6J mice were induced to develop OHT unilaterally by intracameral injection of microbeads. The effects of the most commonly used ocular hypotensive drugs, including timolol, brimonidine, brinzolamide, pilocarpine, and latanoprost, on IOP and glaucomatous neural damage were evaluated. Degeneration of retinal ganglion cells (RGCs) and optic nerve axons were quantitatively assessed using immunofluorescence labeling and histochemistry. Thickness of the ganglion cell complex (GCC) was also assessed with spectral-domain optical coherence tomography (SD-OCT). RESULTS: A microbead-induced OHT model promptly responded to drugs, such as timolol, brimonidine, and brinzolamide, that lower IOP through suppressing aqueous humor production and showed improved RGC and axon survival as compared to vehicle controls. Accordingly, SD-OCT detected significantly less reduction of GCC thickness in mice treated with all three aqueous production suppressants as compared to the vehicle contol-treated group. In contrast, drugs that increase aqueous outflow, such as pilocarpine and latanoprost, failed to decrease IOP in the microbead-induced OHT mice. CONCLUSIONS: Microbead-induced OHT mice carry dysfunctional aqueous outflow facility and therefore offer a unique model that allows selective screening of aqueous production suppressant antiglaucoma drugs or for studying the mechanisms regulating aqueous humor production. Our data set the stage for using GCC thickness assessed by SD-OCT as an imaging biomarker for noninvasive tracking of neuronal benefits of glaucoma therapy in this model.

[Comparison of head-chest lead electrocardiogram and routine lead electrocardiogram in diagnosis of acute posterior wall myocardial infarction].

OBJECTIVE: To compare the value of head-chest lead electrocardiogram (HCECG) and routine lead electrocardiogram (RLECG) in diagnosis of acute positive posterior myocardial infarction. METHODS: HCECGs and RLECGs were recorded simultaneously in 68 normal individuals and 32 patients with acute posterior wall myocardial infarction confirmed by coronary angiography and echocardiography. Each HCECG and RLECG was analyzed by two senior physicians specialized in clinical electrophysiology who were blinded to the results. The HCECG- and RLECG-based diagnostic results were compared with the results of coronary angiography, and the coincidence rates and false positive rates of diagnosis based on HCECGs and RLECGs were calculated. RESULTS: The coincidence rate was 93.8% (30/32) for RLECGs and 100% (32/32) for HCECGs in the diagnosis of acute posterior wall myocardial infarction, showing no significant difference between them (P>0.05). RLECGs-based diagnosis, however, resulted in a significantly higher false positive rate than HCECGs [13.2% (9/68) vs 0% (0/68), P<0.05]. CONCLUSION: Head-chest lead system is superior to routine lead system for its low false positive rates in the diagnosis of acute posterior wall myocardial infarction.

[An efficient method for simulating ventricular electrical activity based on anatomic structure by incorporating AP model].

Conventional medical experiments can hardly simulate cardiac excitation propagation and observe the evolvement of cardiac electrical activities firsthand as is possible with computer simulation. Based on the anatomic structure of the heart, simulation of cardiac electrical activity mainly consists of the emulation of the excitation process among the cardiac cells and calculation of the electrical activities of individual cardiac cells. In this study we establish a geometric ventricular structure model demonstrating the direction of the cardiac muscle fibers and the layers of the ventricular cells, and endow different action potential models to the ventricular cells of different layers, and observe the activation process of the ventricular parts in view of the three-dimensional anatomy. This method gives attention to both enough calculation amounts and efficiency, which achieves satisfactory simulation results of ventricular electrical activity based on the anatomic structure and cell electrophysiology through an improved algorithm on personal computer.