Influence of the phase effect on gradient-based and statistics-based focus measures in bright field microscopy.

Autofocusing is essential to high throughput microscopy and live cell imaging and requires reliable focus measures. Phase objects such as separated single Chinese hamster ovary cells are almost invisible at the optical focus position in bright field microscopy images. Because of the phase effect, defocused images of phase objects have more contrast. In this paper, we show that widely used focus measures exhibit an untypical behaviour for such images. In the case of homogeneous cells, that is, when most cells tend to lie in the same focal plane, both gradient-based and statistics-based focus measures tend to have a local minimum instead of a global maximum at the optical focus position. On the other hand, if images show inhomogeneous cells, gradient-based focus measures tend to yield typical focus curves, whereas statistics-based focus measures deliver curves similar to the case of homogeneous cells. These results were interpreted using the equation describing the phase effect and patch-wise analysis of the focus curves. Bioprocess engineering experts are also influenced by the phase effect. Forty-four focus positions selected by them led to the conclusion that they prefer to look at defocused images instead of those at the optical focus.

Toward automatic detection of vessel stenoses in cerebral 3D DSA volumes.

Vessel diseases are a very common reason for permanent organ damage, disability and death. This fact necessitates further research for extracting meaningful and reliable medical information from the 3D DSA volumes. Murray's law states that at each branch point of a lumen-based system, the sum of the minor branch diameters each raised to the power x, is equal to the main branch diameter raised to the power x. The principle of minimum work and other factors like the vessel type, impose typical values for the junction exponent x. Therefore, deviations from these typical values may signal pathological cases. In this paper, we state the necessary and the sufficient conditions for the existence and the uniqueness of the solution for x. The second contribution is a scale- and orientation- independent set of features for stenosis classification. A support vector machine classifier was trained in the space of these features. Only one branch was misclassified in a cross validation on 23 branches. The two contributions fit into a pipeline for the automatic detection of the cerebral vessel stenoses.

Infective endocarditis: a prospective study of 60 consecutive cases.

Sixty cases of infective endocarditis were studied prospectively between May, 1985 and December, 1988. There were 40 males and 20 females with a mean age of 28 years. Endocarditis was found on normal valves in 13 patients, on rheumatic valves in 30, on congenital lesions in 8, on prosthetic valves in 4 and on mitral valve prolapse in 5 cases. Positive blood cultures were detected in 35 patients (58%). In addition bone marrow culture was positive in 1 and valves removed on surgery grew causative organisms in eight. Thus the total culture positive cases were 44 (73%). The commonest infective organism was Streptococcus viridans. Uncommon organisms accounted for 10 cases (17%). Two dimensional echocardiography (2D-Echo) was done in all cases and vegetations were detected in 48 patients (80%). 2 D-Echo was helpful not only in the detection of vegetations but also in the demonstration of other complications of endocarditis like ring abscesses, ruptured chordae, ulceration of aortic root, interventricular septum abscess, and mitral xenograft obstruction. Early surgery was performed in 31 patients. In this group of patients severe heart failure was present in 21, embolization in 10, persistence of fever in 15 and large vegetations in 19. Of the 29 patients treated medically, 2 died. The mortality in the surgical group was seen in 5 (16%) with a mean follow-up of 15 months. The major reason for a large number of our patients undergoing surgery is the fact that this is a referral Center and patients were sent later or when there was a failure of medical treatment.