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Biomedical subjects

R Hinz

Publications and source records attributed to R Hinz.

At least 19 recordsLinked to original sources
PubMed2006

Amyloid, hypometabolism, and cognition in Alzheimer disease: an [11C]PIB and [18F]FDG PET study.

OBJECTIVE: To investigate the association between brain amyloid load in Alzheimer disease (AD) measured by [11C]PIB-PET, regional cerebral glucose metabolism (rCMRGlc) measured by [18F]FDG-PET, and cognition. METHODS: Nineteen subjects with AD and 14 controls had [11C]PIB-PET and underwent a battery of psychometric tests. Twelve of those subjects with AD and eight controls had [18F]FDG-PET. Parametric images of [11C]PIB binding and rCMRGlc were interrogated with a region-of-interest atlas and statistical parametric mapping. [11C]PIB binding and rCMRGlc were correlated with scores on psychometric tests. RESULTS: AD subjects showed twofold increases in mean [11C]PIB binding in cingulate, frontal, temporal, parietal, and occipital cortical areas. Higher cortical amyloid load correlated with lower scores on facial and word recognition tests. Two patients fulfilling the clinical criteria for AD had normal [11C]PIB at baseline. Over 20 months this remained normal in one but increased in the cingulate of the other. Mean levels of temporal and parietal rCMRGlc were reduced by 20% in AD and these correlated with mini mental scores, immediate recall, and recognition memory test for words. Higher [11C]PIB uptake correlated with lower rCMRGlc in temporal and parietal cortices. CONCLUSION: [11C]PIB-PET detected an increased amyloid plaque load in 89% of patients with clinically probable Alzheimer disease (AD). The high frontal amyloid load detected by [11C]PIB-PET in AD in the face of spared glucose metabolism is of interest and suggests that amyloid plaque formation may not be directly responsible for neuronal dysfunction in this disorder.

Aged↗
PubMed2006

Multi-resolution Bayesian regression in PET dynamic studies using wavelets.

In the kinetic analysis of dynamic PET data, one usually posits that the variation of the data through one dimension, time, can be described by a mathematical model encapsulating the relevant physiological features of the radioactive tracer. In this work, we posit that the remaining dimension, space, can also be modeled as a physiological feature, and we introduce this concept into a new computational procedure for the production of parametric maps. An organ and, in the instance considered here, the brain presents similarities in the physiological properties of its elements across scales: computationally, this similarity can be implemented in two stages. Firstly, a multi-scale decomposition of the dynamic frames is created through the wavelet transform. Secondly, kinetic analysis is performed in wavelet space and the kinetic parameters estimated at low resolution are used as priors to inform estimates at higher resolutions. Kinetic analysis in the above scheme is achieved by extension of the Patlak analysis through Bayesian linear regression that retains the simplicity and speed of the original procedure. Application to artificial and real data (FDG and FDOPA) demonstrates the ability of the procedure to reduce remarkably the variance of parametric maps (up to 4-fold reduction) without introducing sizeable bias. Significance of the methodology and extension of the procedure to other data (fMRI) and models are discussed.

Bayes Theorem↗
PubMed2003

In vivo measurement of the serotonin transporter with (S)-([18F]fluoromethyl)-(+)-McN5652.

The radiolabeled serotonin transporter (SERT) ligand [(11)C](+)-McN5652 has recently been used in clinical positron emission tomography (PET) studies for SERT imaging. However, this radioligand offers disadvantages in routine clinical settings because of its short radioisotope half-life (eg PET facilities within hospitals without a cyclotron need to acquire such radioligands from distant cyclotron units for clinical use). S-([(18)F]fluoromethyl)-(+)-McN5652 ([(18)F](+)-FMe-McN5652) is an analogue which has been synthesized newly, and has a significantly longer radioisotope half-life. In the porcine brain, it demonstrates the same characteristic distribution pattern of serotonin-uptake sites like the (11)C-labeled congener with the highest binding in the midbrain and thalamus and the lowest in the cerebellum and occipital cortex. It shows a 30% higher blood-brain transfer and a slower peripheral metabolism than [(11)C](+)-McN5652. Rather uniform brain binding was observed after injection of the pharmacologically inactive radiolabeled enantiomer, or after pretreatment with the highly selective SERT inhibitor citalopram. The norepinephrine uptake inhibitor maprotiline did not show any inhibitory effect. Using a one-tissue compartment model (K(1), k"(2)) or a two-tissue compartment model (K(1) to k(4)) with or without constraints for calculation, the regional binding parameters of [(11)C](+)-McN5652 and [(18)F](+)-FMe-McN5652 are highly correlated among each other and with the SERT density, as determined by in vitro binding of [(3)H]citalopram. Using constraints to correct for the free fraction and nonspecific binding of the radiotracers, a considerable increase of the midbrain-occipital cortex ratios with higher values for [(18)F](+)-FMe-McN5652 compared to [(11)C](+)McN5652 was revealed. It is concluded that [(18)F](+)-FMe-McN5652 has better features than [(11)C](+)McN5652 for SERT imaging with PET.

Animals↗
PubMed1999

The application of PET to quality assurance of heavy-ion tumor therapy.

At the new heavy ion tumor therapy facility of the Gesellschaft für Schwerionenforschung at Darmstadt positron emission tomography (PET) has been implemented for in-beam and in-situ therapy control, i.e. during the tumor irradiation. The components necessary for this dedicated PET-imaging and their integration into the framework of therapy planning and quality assurance of heavy ion cancer treatments are presented. Results of the first application of this PET-method to patient treatments are reported.

Germany↗
PubMed1999

Response of pig lung to irradiation with accelerated 12C-ions.

The response of pig lungs to irradiation with 12C-ions was assessed in two experiments to validate the procedures for heavy ion therapy planning at the Gesellschaft für Schwerionenforschung (GSI) and to explore their range of applicability. In both experiments, the target volume (spread-out Bragg peak, SOBP) was planned to be a 4 cm long cylinder with a diameter of 4 cm. Doses in the SOBP were prescribed to be equivalent to 5x4 Gy, 5x5.5 Gy and 5x7 Gy of x-rays in the first experiment, and to 5 fractions of 7 Gy and 9 Gy in the second experiment. The lung response in the first experiment was less than expected on the basis of earlier experiments with photons. Pneumonitis reaction and chronic fibrotic changes were observed outside the prescribed high-dose region. In the second experiment, the effects were more pronounced than had been expected on the basis of the first experiment. Changes were most intense in the high-dose region, but were also seen throughout the lung along the beam channel. Moreover, significant skin reactions were observed at the beam entrance site in all animals and - less pronounced - at the beam exit site in 3 of the 6 animals. In conclusion, the complex irradiation geometry of the pig lung, the changes of body weight between the two experiments, and insufficient accounting for a change in the relative biological effectiveness (RBE) computation led to substantial deviations of the observed reactions from expectations, the reasons for which could be identified in a subsequent analysis. The less pronounced lung reaction in the first experiment was due to an overestimation of RBE in a preliminary version of the algorithm for its determination. The extension of the fibrotic reaction resulted from the smear-out of the high-dose region due to density variations in tissue structures, respiratory movement, and limited positioning accuracy. The skin reactions at the entrance port reflect the different treatment geometry in the two experiments. The one unexplained observation is the mild skin reaction that was observed in the second experiment at the beam exit site.

Animals↗
PubMed1991

[Elasto-orthodontic system--a development of the positioner].

A clear classification of the various types of elasto-appliances is necessary in order to understand the indications of such appliances. The elasto-finisher, for example, is used over brackets left in situ after the completion of multibracket therapy whilst the elasto-aligner is placed over specially placed buttons. The elasto-orthodontic system and the indications for the four different types of appliances are presented together with typical case examples. The basic principle of the positioner construction to determine the treatment objectives, namely the set-up, is also essential for the construction of elasto-appliances. The differences between the conventional positioner and elasto-appliances are describe in detail.

Humans↗
PubMed1990

The relationship between pKa and skin irritation for a series of basic penetrants in man.

For a series of bases, which penetrate through human skin in vitro at similar rates (0.056-0.49 microM/cm2/hr), penetrant pKa is shown to correlate with erythema, edema, and color meter readings. As estimates of irritation, erythema, edema, and redness measurements are highly linearly correlated. For the selected series, irritation becomes significant for bases with a pKa greater than 8. The irritation potential of acids with pKa less than or equal to 4 has been previously reported; pKa appears highly predictive of acute skin irritation for acids and bases in man.

Adult↗
PubMed1990

[Extrafocal radiation of medical x-ray tubes with a rotating anode].

A method for measuring the fraction of extrafocal radiation in the x-ray output of x-ray tubes was developed and tested under clinical conditions. A fraction of 10% was found, that increases with tube voltage and field size, while tube current and focal spot size have no influence. As a measure for the influence of off-focus radiation on image quality the contrast transfer function was used. Off-focus radiation causes detectable geometric unsharpness. If screen-film-systems are used, the unsharpness is negligible compared with the screen unsharpness. Ways for reducing off-focus radiation from medical x-ray tubes are discussed.

Humans↗
PubMed1988

First experiences with resin-bonded bridges and splints--a cross-sectional retrospective study, Part II.

This second report establishes that the success of treatment with resin-bonded bridges was dependent upon many factors. Factors controlled by the clinician, such as case selection and treatment planning greatly influence the clinical success. It was possible to show that framework preparation and the amount of available enamel were significant factors, whereas isolation technique, type of retention mechanism and type of adhesive used were of less importance. Longitudinal studies are needed to confirm these observations. Seventeen clinicians placed 496 resin-bonded bridges and splints with different retention mechanisms and bonding agents. These reconstructions were examined in regard to the failure rate and in regard to reattachment problems. Ninety-seven per cent of the bridges and 90% of the splints were still in place after 1 year. For bridges and splints a 90% success rate was ascertained after 2 years.

Adhesives↗
PubMed1987

Experiences with resin-bonded bridges and splints--a retrospective study.

In a joint evaluation of 496 resin-bonded bridges and splints anchored by various retention principles and composites, the initial experiences of seventeen clinicians were compiled. The main indications for treatment were congenital anodontia and loss of teeth due to caries and trauma. After 3 months, 95% of the bridges were still in place without need of reattachment procedure. After 6 months the figure was 91%, after 1 year 81.5% and after 1 1/2 years 73%. Seventy-five per cent of the loosened bridges were attached successfully a second time. The success rate for splints was significantly lower.

Adolescent↗