Terahertz line detection by a microlens array coupled photoconductive antenna array.

We present THz ultrashort pulse detection by a photoconductive antenna array consisting of 16 photoconductive antennas. The efficient excitation of the photoconductive antennas has been realized by a microlens array which generates 16 single spots from the exciting fs-laser beam. This combination of optoelectronics and microoptics improves the detection efficiency by an order of magnitude in comparison to an excitation by a line focus.

Multichannel balanced electro-optic detection for Terahertz imaging.

We present THz imaging with 1D electro-optic sampling of ultrashort THz pulses by multichannel balanced detection. Using a lock-in technique, it combines the advantage of a high signal to noise ratio along with the fast acquisition time of multichannel detection. The object is probed by a line focus and the resolution can be adjusted. The performance of the system is demonstrated exemplarily by imaging two objects.

[Presbyopia treatment using a femtosecond laser]. / Presbyopietherapie mit Femtosekundenlaser.

Presbyopia is by far the most common refractive error worldwide, with no permanent therapeutic option available. All efforts to restore accommodation by the use of surgery have not led to a generally accepted therapy. However, there is evidence from an animal model that the use of a femtosecond (fs) laser might influence the modulus of elasticity in the lens. Fs-laser impulses can create intralenticular disruption in animal eyes as well as human cadaver lenses and improve elasticity. The concept of treating presbyopia with fs-laser requires a new, complex theory combining the optical and the mechanical aspects of accommodation in the eye. Diagnostic tools for measuring optical change in power and geometrical modification as the eye views from far to near are needed to obtain objective clinical data. A non-invasive treatment of presbyopia to restore accommodation might be possible in the future.

Reduced phosphodiesters and high-energy phosphates in the frontal lobe of schizophrenic patients: a (31)P chemical shift spectroscopic-imaging study.

BACKGROUND: (31)Phosphorous magnetic resonance spectroscopy has been widely used to evaluate schizophrenic patients in comparison to control subjects, because it allows the investigation of both phospholipid and energy metabolism in vivo; however, the results achieved so far are inconsistent. Chemical shift imaging (CSI) has the advantage that instead of only one or a few preselected voxels the tissue of a whole brain slice can be examined. The aim of the present investigation was to determine whether the results of previous studies of our group, showing that phosphodiesters (PDE) are decreased in the frontal lobe of schizophrenic patients as compared to control subjects, might be confirmed in an independent unmedicated patient sample using the CSI technique. METHODS: A carefully selected new cohort including 11 neuroleptic-free schizophrenic patients and 11 age- and gender-matched healthy control subjects was recruited. CSI was applied and an innovative analysis method for CSI data based on a general linear model was used. RESULTS: PDE, phosphocreatine, and adenosine triphosphate (ATP) were found to be significantly decreased in the frontal lobe of patients with schizophrenia. CONCLUSIONS: Because PDE was decreased in schizophrenic patients, the membrane phospholipid hypothesis of schizophrenia could not be corroborated. Further results indicate decreased ATP production in the frontal lobe of patients with schizophrenia.

Increase of phosphodiesters during neuroleptic treatment of schizophrenics: a longitudinal 31P-magnetic resonance spectroscopic study.

BACKGROUND: Increased levels of phosphodiesters (PDE%) and reduced relative concentrations of phosphomonoesters (PME%) have been reported in unmedicated schizophrenics, whereas findings in brain of medicated patients were not consistent. METHODS: We determined in vivo the metabolism of phospholipids and high-energy phosphates in the left and right frontal lobes of 8 patients with schizophrenia using 31P-magnetic resonance spectroscopy (31P-MRS). Serial investigations were performed first after a neuroleptic-free period (mean 7.5 +/- 1.9 days) and second, after neuroleptic treatment (mean 20.6 +/- 11.1 days). RESULTS: PDE% increased significantly in the left frontal lobe (32.0 +/- 5.9% versus 36.9 +/- 5.6%, p = .009) after medication. All other parameters showed no significant differences. CONCLUSIONS: Our study suggests that neuroleptics do not decrease phospholipase A2 activity in schizophrenia. Individual neuroleptics may have different effects on phospholipase A2 activity as indicated by animal studies. An influence of neuroleptics on high-energy phosphates cannot be confirmed by our data.

Cerebral phosphate metabolism in first-degree relatives of patients with schizophrenia.

OBJECTIVE: Most phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) studies have described measures of lower membrane anabolism or greater catabolism in the frontal lobes of patients with schizophrenia. The purpose of the present study was to evaluate whether these findings can also be detected in young subjects at genetic risk for schizophrenia. METHOD: Fourteen children and siblings of patients with schizophrenia (mean age=16.7 years) and 14 comparison subjects (mean age=16.9 years) were included in a (31)P-MRS study of the frontal lobe. RESULTS: The high-risk subjects had significantly lower mean ratios of phosphomonoesters to phosphodiesters (0.25 versus 0.31) and higher mean phosphodiester values (37.59% versus 34.87%) than comparison subjects. CONCLUSIONS: These findings suggest greater phospholipid breakdown even in young first-degree relatives of patients with schizophrenia. This suggestion is discussed with respect to the membrane phospholipid hypothesis of schizophrenia.

[Quantitative measurement of induced skin reddening using optical reflection spectroscopy--methodology and clinical application]. / Quantitative Messung induzierter Hautrötungen durch optische Reflexionsspektroskopie--Methodik und klinische Anwendung.

Optical reflection spectroscopy is a simple and quick method for the quantification of colour intensity, and is thus suitable for the determination of changes in skin reddening (erythema) due to local vasodilatation. To quantify the time course of this erythema, the oxyhaemoglobin absorption double peak with maxima at 542 and 577 nm is an appropriate parameter. A compact handheld optical spectrometer makes the technique applicable to clinical use, an example being the niacin patch test described herein. This noninvasive test provides information about the cell membrane metabolism via the skin flush induced by niacin (vitamin B3) and mediated by prostaglandin. The aim of this study was to adapt optical reflection spectroscopy to the requirements of the clinical niacin patch test. To that end, we investigated 60 healthy volunteers. Analysis of the spectroscopic data with regard to physiological covariables of niacin sensitivity revealed faster and more intense erythema in females--a gender effect that to our knowledge has not previously been reported. In the light of these results, the findings of other researchers based on semi-quantitative test methods should be reassessed, with consideration given to the gender effect.

[Diseases of phospholipid metabolism as possible pathogenetic factors in schizophrenia. Current findings and critical evaluation]. / Störungen im Phospholipidmetabolismus als mögliche pathogenetische Faktoren der Schizophrenie. Zusammenfassung aktueller Befunde und kritische Würdigung.

During the last few years analyses of the lipidmetabolism have been performed on schizophrenic patients. Anabolic and katabolic metabolite-concentrations from blood and cell samples have been measured. By means of new investigation techniques, such as 31P-magnetic-resonance-spectroscopy, it is nowadays even possible to determine membrane metabolites non-invasively in vivo. Arachidonic acid deficits in peripheral cell membranes, turnover of phosphodiesters in the brain, increased phospholipase A2 (PLA2)-activity in serum and blood cells, disturbed niacin-response and abnormalities of the PLA2-gene are summarised as phospholipid-membrane-hypothesis of schizophrenia. Although there is some evidence for correlations between those findings and psychotic symptoms, the connection to the pathogenesis of schizophrenia still has speculative character. Furthermore it has to be confirmed that peripheral biochemical findings acquired in schizophrenics are transferable to the metabolism of the central nervous system. Actual results of enzyme and metabolite measurements reported in literature and current findings of our own 31P-MR-spectroscopic studies are surveyed and summarised. To point out possible connections between the phospholipid-metabolism of the central nervous system and of peripheral blood-cells, systemic approaches are considered.

Detecting structural changes in whole brain based on nonlinear deformations-application to schizophrenia research.

This paper describes a new method for detecting structural brain differences based on the analysis of deformation fields. Deformations are obtained by an intensity-based nonlinear registration routine that transforms one brain onto another one. We present a general multivariate statistical approach to analyze deformation fields in different subjects. This method was applied to the brains of 85 schizophrenic patients and 75 healthy volunteers to examine whether low frequency deformations are sufficiently sensitive to detect regional deviations in the brains of both groups. We observed significant changes caused by volume reduction in brains of schizophrenics bilaterally in the thalamus and in the superior temporal gyrus. On the left side, the superior frontal gyrus and precentral gyrus are found to be changed, while on the right side, the middle frontal gyrus was altered. In addition, there were significant changes in the occipital lobe (left lingual gyrus) and in the left cerebellum. Volume enlargement in brains of schizophrenics was observed in the right putamen and in the adjacent white matter of the thalamic region. Our data suggest a disturbance in the nodes of a prefrontal-thalamic-cerebellar circuitry. This provides further support for the model of "cognitive dysmetria," which postulates a disruption in these nodes. We have demonstrated the application of deformation-based morphometry by detecting structural changes in the whole brain. This technique is fully automatic, thus allowing for the inclusion of large samples, with no user bias or a priori-defined regions of interest.

Hypofrontality in neuroleptic-naive schizophrenic patients during the Wisconsin Card Sorting Test--a fMRI study.

Functional neuroimaging findings of "hypofrontality" in schizophrenic patients - as tested with the Wisconsin Card Sorting Test (WCST) - are still controversial, mainly due to methodological aspects and the heterogeneity of the patient samples. To measure WCST specific and reproducible reduced cerebral activations in schizophrenic patients, we revised the study design and patient recruitment, respectively. For this purpose, we used an adequate active control task instead of an undefined rest condition to determine exclusively WCST specific cerebral activations. In addition, we focused on the investigation of modified activations between a selected group of neuroleptic-naive schizophrenic patients and carefully matched healthy controls by means of functional magnetic resonance imaging. The results indicate that neuroleptic-naive schizophrenic patients show reduced activations in the right frontal and left temporal lobe, as well as in the left cerebellum. By utilizing an active control task all unwanted activations are suppressed. Furthermore the influence of different task performances is reduced. The findings are in line with previous PET and SPECT studies and confirm the "hypofrontality" hypothesis. The findings suggest that "hypofrontality" is not caused by neuroleptic medication.

[Phosphorus 31 magnetic resonance spectroscopy in schizophrenia research. Pathophysiology of cerebral metabolism of high-energy phosphate and membrane phospholipids]. / 31Phosphor-Magnetresonanzspektroskopie in der Schizophrenieforschung. Zur Pathophysiologie des zerebralen Stoffwechsels energiereicher Phosphate und Membranphospholipide.

31Phosphorus nuclear magnetic resonance spectroscopy (31P-MRS) has gained much interest in schizophrenia research in the last years, since it allows noninvasive measurement of high energy phosphates and phospholipids of the human brain in vivo. Thus, several studies have reported cerebral metabolic differences between patients and healthy controls as well as on lateralization effects and influences of epidemiological and psychopathological factors. This review gives a survey of the potential of 31P-MRS in schizophrenia research and summarizes and comments on the results of preceding studies. The discussion covers the reduction of phospholipids in patients in the context of the membrane phospholipid hypotheses, the question of an energetic hypometabolism in schizophrenics, and the influence of neuroleptic medication.

Frontal lobe in vivo (31)P-MRS reveals gender differences in healthy controls, not in schizophrenics.

Phosphorus-31 magnetic resonance spectroscopy ((31)P-MRS) has gained much interest in schizophrenia research in recent years since it allows the non-invasive measurement of high-energy phosphates and phospholipids in vivo. However, until now only differences in metabolite concentrations between certain brain areas of schizophrenic patients and healthy controls have been examined. We investigated the influence of gender on the concentrations of different phosphorus compounds. For this purpose, well-defined volumes in the frontal lobe of 32 healthy controls and 51 schizophrenic in-patients were examined with an image selected in vivo spectroscopy (ISIS) sequence on a whole-body scanner at 1.5 T. Healthy females exhibited increased values of inorganic phosphate (P(i)) and decreased values of phosphocreatine (PCr) in comparison to their male counterparts. In schizophrenic patients such gender differences were not present. Thus, the results can be interpreted in the sense that frontal energy demanding processes are enhanced in female compared to male healthy volunteers; schizophrenia seems to reduce these gender differences.

31P magnetic resonance spectroscopy in the frontal lobe of major depressed patients.

Most research with 31P-magnetic resonance spectroscopy (31P-MRS) in affective disorders has been done in the field of bipolar disturbances. Reduced frontal and temporal lobe phosphomonoester (PME) concentrations were measured in the euthymic state, whereas increased values were found in the depressed state. In bipolar-II patients reduced phosphocreatine (PCr) concentrations were reported in the euthymic, depressed, and manic state. The aim of the present study was to explore whether PME and PCr were also altered in the frontal lobe of major depressed, unipolar patients. Therefore, we used 31P-MRS to investigate the relative phospholipid and high-energy phosphate concentrations in the frontal lobe of 14 unipolar patients, mostly medicated, and 8 age-matched controls. We found increased PME and decreased ATP values. Other 31P-MRS parameters were not different in both groups. Phosphomonoester percentages correlated negatively with the degree of depression. Thus, the main alterations found in bipolar depressed patients could also be demonstrated in unipolar depressed patients. The results are discussed with regard to disturbed phospholipid and intracellular high-energy phosphate metabolism in depressed patients.