Off-line Image Analysis Research Articles

Correlation of Aspergillus niger broth rheological properties with biomass concentration and the shape of mycelial aggregates

Aspergillus niger was grown in a 7-L chemostat at biomass levels of 7 to 9 gL(-1); dilution rates of 0.03, 0.05, 0.075, and 0.009 h(-1); and dissolved oxygen tensions of 7%, 12%, and 40% of air saturation. Broth rheological measurements were made on-line, while off-line image analysis was used to measure mycelial morphology, including characterization of mycelial aggregates (clumps). Under all conditions, more than 87% of the hyphase were in clumps, the shape of which determined the rheological characteristics of the broth. In particular, the power law consistency index could be correlated with the biomass concentration and the roughness factor of the clumps, which describes their hairiness. A decrease in specific growth rate decreased roughness, possibly due to changes in the amount of clump breakup. However, decreases of roughness with increasing dissolved oxygen tension might rather imply some effect on hyphal-hyphal interactions within the clumps.

Three-dimensional distribution of damaged cells in cryopreserved pancreatic islets as determined by laser scanning confocal microscopy.

The technique of serial optical sectioning by confocal microscopy, in conjunction with off-line digital image analysis, was used to quantify the radial distribution of damaged cells in rat pancreatic islets following cryopreservation. The process consists of imaging frozen-thawed islets of Langerhans using laser scanning confocal microscopy (LSCM). The three-dimensional (3-D) distribution and analysis of the two populations of viable and damaged cells was visualized via acridine orange/propidium iodide (AO/PI) fluorescent staining. In preparation for cryopreservation, isolated and cultured rat pancreatic islets were brought to a 2 M concentration of dimethyl sulphoxide (DMSO) by serial addition at decreasing temperatures. Ice was nucleated in the islet suspension at -10 degrees C, and individual specimens were frozen to -70 degrees C at cooling rates of 1, 3, 10 and 30 degrees C/min in a programmable bulk freezer and subsequently stored in liquid nitrogen. After rapid thawing and serial dilution to remove DMSO, individual islets were prepared with AO/PI stains for imaging on the LSCM. Serial sections of the islets, 2-7 microns in thickness, were obtained and processed to obtain high-contrast images. Analysis algorithms consisted of template masking, grey-level thresholding, median filtering and 3-D blob colouring. The radial distribution of damaged cells in the islets was determined by isolating the cell and computing its distance from the centroid of the 3-D islet volume. An increase in the number of blobs corresponding to single and/or aggregates of damaged cells was observed progressively with distance from the centre towards the periphery of the islet. This pattern of freeze-induced killing of cells within the islet was found to occur consistently in the numerous individual specimens processed.

Myocardial contrast echocardiography and the transmural distribution of flow: A critical appraisal during myocardial ischemia not associated with infarction

Objectives. This study was undertaken to determine whether myocardial contrast echocardiography can be used to estimate the transmural distribution of flow.Background. Myocardial contrast echocardiography has been shown to reliably measure average transmural blood flow during myocardial ischemia. However, there is controversy regarding its ability to determine the transmural distribution of flow.Methods. The transmural distribution of flow was measured in 21 open chest anesthetized dogs with use of radiolabeled microspheres and sonicated albumin microbubbles (mean size 4.5 μm). In the 11 Group I dogs, myocardial contrast echocardiography was performed at baseline and during left anterior descending artery stenosis. In five of these dogs, it was also performed during left circumflex artery stenosis. In these dogs large (mean 12 μm) hand-agitated bubbles were also used. In the five Group II dogs, myocardial contrast echocardiography was performed before and 45 s after intracoronary injection of 6 mg of papaverine in the presence of a critical left circumflex artery stenosis. The five Group III dogs were studied during cardiopulmonary bypass at baseline and during left anterior descending artery stenosis. Off-line image analysis of the echocardiographic images was performed and timeintensity curves obtained from thess images were correlated with radiolabeled microsphere-derived flows.Results. The ratios of the parameters derived from the endocardium and epicardium during myocardial contrast echocardiography were found to correlate poorly (ranging from R2= 0 to R2= 0.35) with radiolabeled microsphere-derived endocardial/ epicardial flow ratios over a wide range of flow ratios (0.01 to 2.58). These results were not influenced either by the location of the regions of interest (left anterior descending vs. left circumflex artery bed) or by the size of the bubbles (4.5 vs. 12 μm).Conclusions. Myocardial contrast echocardiography cannot be used to assess the transmural distribution of flow during myocardial ischemia not associated with infarction.

Automatic real-time endocardial edge detection in two-dimensional echocardiography.

Previous approaches to automatic border recognition in two-dimensional echocardiography have utilized off-line computer image analysis. In this paper, we describe a hardware technique for real-time endocardial edge detection during the echocardiographic examination. This technique is based on a new method of line-by-line compensation for ultrasound attenuation. The detected edges and composite edge images can be displayed alone or superimposed upon the usual echocardiographic display. To test the accuracy of our real-time technique, we obtained echocardiograms of excised hearts and compared real-time edges with edges manually traced by an experienced observer. Left ventricular cavity areas and endocardial perimeters derived from real-time edges correlated well with those derived from observer-defined edges.

A simple off-line automatic image analysis system with application to drop sizing in two-phase flows

An automatic image analysis system has been developed, and used initially for obtaining size distributions of droplets in two-phase flows from multiple photographs with sub-microsecond exposure. It requires only a conventional, relatively cheap television camera and computing facilities likely to be available in any laboratory undertaking such work, avoiding the need for expensive purpose-built equipment. Image recognition and subsequent processing, e.g., rejection of unfocused images, are dealt with by software, based on detection at eight grey levels. The system and its calibration are described, and a typical analysis is presented and compared with a manual sizing.