Enhancement and associative restoration of electronic portal images in radiotherapy.

Electronic portal imaging devices use the high energy treatment beam to project the body interior of the patient during radiation onto a fluorescent screen that is scanned by a camera. Because of the imaging physics, the unprocessed images of very poor quality, but they are the only available information during treatment for observation of the patient's organs. This paper presents an approach that combines an associative restoration algorithm with a fuzzy image enhancement technique. By fusion of the electronic portal image (EPI) with a pre-treatment captured simulator image (SI) a higher image quality than by conventional techniques is achieved.

The self-fulfilling prophecy in close relationships: rejection sensitivity and rejection by romantic partners.

The authors hypothesized a self-fulfilling prophecy wherein rejection expectancies lead people to behave in ways that elicit rejection from their dating partners. The hypothesis was tested in 2 studies of conflict in couples: (a) a longitudinal field study where couples provided daily-diary reports and (b) a lab study involving behavioral observations. Results from the field study showed that high rejection-sensitive (HRS) people's relationships were more likely to break up than those of low rejection-sensitive (LRS) people. Conflict processes that contribute to relationship erosion were revealed for HRS women but not for HRS men. Following naturally occurring relationship conflicts, HRS women's partners were more rejecting than were LRS women's partners. The lab study showed that HRS women's negative behavior during conflictual discussions helped explain their partners' more rejecting postconflict responses.

Growing 3D-SOMs with 2D-input layer as a classification tool in a motion detection system.

This paper describes the employment of an 'Adaptive Growing Three-Dimensional Self-Organizing Map' for the classification of images. First a short description of growing SOMs is given and the fundamental advantages are mentioned. Then an extension of the original SOM from two to three dimensions with growing feature is presented. By means of some selected examples the general behavior of the algorithm is illustrated.

Using an artificial neural network to define the planning target volume in radiotherapy.

A neural network for predicting the planning target volume in radiotherapy from the shape of the detected tumor is designed and tested in this research project. The proposed neural network is able to generalize expert medical knowledge and predict the planning target volume from a three-dimensional image of the detected tumor. Initial results for simple shaped brain tumors are presented in this paper.

HIV replication can be blocked by recombinant human interferon beta.

Recombinant human interferon beta (rIFN-beta) reduces replication of HIV in cultured peripheral mononuclear cells. The effect is most pronounced when high levels of the drug are employed. Maintenance of the rIFN-beta in culture is required since removal of the agent generally leads to a return of virus production by the infected cells. Moreover, at low concentrations of the drug, a breakthrough in HIV replication is observed. High concentrations of the rIFN-beta (greater than 100 units/ml) were cytotoxic for transformed T cells. This latter observations suggests that rIFN-beta might be useful in human T-cell malignancies. Beta interferon therefore might be useful for the treatment of HIV infection, particularly since side effects of the drug are limited in treated individuals.

Isolation of AIDS-associated retrovirus from genital secretions of women with antibodies to the virus.

The AIDS-associated retrovirus (ARV) was isolated from vaginal and/or cervical secretions from 4 out of 8 women whose sera contained antibodies to the virus. The quantity of virus recovered initially was so low that identification of ARV was accomplished only after passage of the isolates to cultured mitogen-stimulated normal human peripheral blood mononuclear cells. The results indicate that the vaginal canal under certain conditions could be a source of transmission of ARV.

Herpetic keratitis in inbred mice.

The corneas of four inbred strains of mice (BALB/c, DBA/2, C3H and C57BL/6) were inoculated with the RE strain of herpes simplex virus, type 1. The corneas were examined at frequent intervals and graded on a scale of 0 (clear cornea) to +5 (severe necrotizing stromal keratitis). At 3 weeks postinfection, the mean corneal scores were: DBA/2, 4.0; BALB/c, 2.2; C3H, 0.7; and C57BL/6, 0.15. The differences between the scores are statistically significant (P less than 0.05), except for the C3H and C57BL/6 strains. The order of severity of corneal disease in these mice corresponds to the order of susceptibility to systemic infection found in these same inbred strains. Additional studies of herpetic keratitis in inbred mice should prove helpful in understanding the genetic and immunologic basis of herpetic stromal keratitis.

[Dependence of adaptation behavior of receptor neurons on current intensity]. / Abhängigkeit des Adaptationsverhaltens von der Reizintensität bei Rezeptorneuronen.

The slowly adapting stretch receptor neuron exhibits a marked spike adaptation. In the present paper the dependence of the adaptation time constants and other parameters from the stimulus intensity or the stationary discharge frequency was investigated. In general, the adaptation in response to an intracellular current step is sufficiently approximated by the sum of two exponential terms. A transformation of the parameters measured to a feed back subsystem, which describes the effect of the ionic pump, was performed, too. Proceeding from these data, a generalizing conclusion is that the time constants decrease nearly hyperbolically with increasing stationary impulse frequency. This results in a nearly constant product of carrier frequency and adequate time constant. With regard to the degree of adaptation a marked saturation characteristic appears. In qualitative terms, these effects have to be explained mainly by the properties of the ionic pump and its dependence on the concrete in concentrations.

[Frequency domain analysis of the dynamic properties of the encoder in the slowly adapting crayfish stretch receptor neuron]. / Untersuchung der Enkoder-Ubertragungseigenschaften des langsam adaptierenden Dehnungsrezeptoreurons von Orconectes limosus (RAF.) im Frequenzbereich.

The transfer properties of the slowly adapting stretch receptor neuron can be suitably described in the frequency domain. The measurements are carried out by means of sinusoidally varying intracellular currents. The frequency response at low stimulation frequencies has been calculated from responses to current steps. At very low input frequencies the amplitude-frequency characteristic in the Bode diagram is nearly parallel to the abscissa. With increasing stimulation frequency the gain becomes larger and has a maximum at 1--3 Hz (stimulation frequency/carrier frequency (f/fo approximately 0.2). The amplitude-frequency characteristic decreases then, at first slowly then more rapidly, and reaches in the range of carrier frequency (f/fo approximately 1) small values. The phase-frequency characteristic shows at low input frequencies a small positive magnitude of 8--10(0). With higher stimulation frequencies the phase angle decreases and reaches negative values. In the range of carrier frequency the phase shift runs to -180 degrees. The present findings demonstrate also that the transfer function of the encoder depends on the carrier frequency of the receptor neuron. Larger carrier frequencies cause a decrease of the gain but the peak remains. This maximum shifts with increasing fo in direction to higher stimulation frequencies. The elimination of the encoder adaptation by means of a suitable model results in the frequency response of the real encoder. The above statements hold for higher stimulation frequencies too, but the typical differential behaviour at low frequencies disappears.

[Modelling of biological encoding mechanisms as a system with distributed parameters]. / Modellierung biologischer Kodierer als System mit verteilten Parametern

The encoder region in receptors and neurons is represented by the inhomogeneous origin of the axon. The axon diameter and the excitability are in fact space-dependent. For the analysis the soma is described by a system with concentrated parameters followed by an inhomogeneous axon. The membrane properties are approximated by the slightly modified Hodgkin-Huxley equations. The assumption that the space-dependence of the excitability originates in variations of the conductance value for sodium ions accounts for a number of experimental results. The influence of other membrane parameters upon the mechanism of impulse generation and transmission has also been analysed.

Ion conductance changes associated with spike adaptation in the rapidly adapting stretch receptor of the crayfish.

The time course of the repetitive impulse discharges has been investigated for two high intensities of maintained depolarizing currents, 30 nA and 50 nA, for which the receptor adaptation was complete within 70 msec. The changes in sodium and potassium conductance associated with the decline in spike activity have been analyzed at different instances of time by interrupting in successive experiments the various action potentials in the pulse trains either at the early phase by holding the potential at about -60 mV and recording the inward current (upstroke-gNa) or by evaluating the delayed outward current flowing as the result of a depolarizing voltage pulse which at the end of the action potential re-increased the membrane potential by mV (after potentialgK). At the higher current intensity of 50 nA the discharge frequency was increased, while larger reductions in upstroke-gNa and after potential-gK during receptor adaptation became apparent. The progressive decrease in pulse amplitude from 99 mV to 63 or 55 mV is paralleled by a gradual reduction in upstroke-gNa from 97 mmho/cm-2 to 37 or 27.5 mmho/cm-2 and in after potential-gK from 11.5 mmho/cm-2 to about 7 mmho/cm-2. When under a stimulus of 30 nA the sodium conductance decreases to an average value of 37 mmho/cm-2 only a distorted spike can be elicited, while the spike activity was completely suppressed at upstroke-gNa equals 27.5 mmho/cm-2 was essentially the same under both conditions. The results have been interpreted in terms of the model for impulse generation formulated by Michaelis and Chaplain (1973). According to the model both sodium and potassium inactivation reduce the pulse amplitude. However, while Na-inactivation reduces the frequency of impulse discharge, the K-inactivation actually leads to an increase in spike frequency. As the frequency of the short train of pulses recorded under high-intensity current stimulation remained essentially unaltered, it is suggested that the coupling between Na- and K-inactivation actually leads to an increase in spike frequency. As the frequency of the short train of pulses recorded under high-intensity current stimulation remained essentially unaltered, it is suggested that the coupling between Na- and K-inactivation ensures a constancy of the information-carrying parameter, i.e. the average impulse density.