Radiographic control of fixture-abutment connection in Brånemark implant technique

Abstract— In the treatment with osseointegrated implants ad modum Brånemark a radiographic control of the fixture-abutment connection is recommended. The purpose of the present study was to analyze the possibilities of detecting incomplete connection by radiography using the recommended technique. In an experimental model the influence of film density, orientation of the fixture hexagon, angulation between film plane and fixture axis, leakage width, and partial connection were analyzed. Slits of 0.05 mm were detectable under optimum projection conditions. On the other hand, slits of 0.1 mm were obscured even at deviations of 5°. A number of factors, e.g. low density level and "unfavorable" orientation of the hexagon in relation to the X-ray beam, reduce the possibilities of detecting slits. It is concluded that in clinical cases a demonstration of incomplete fixture-abutment connection by the use of the recommended radiographic technique radiography to some extent is fortuitous, and that radiographic control has certain limitations.     

Elevated [18F]FDOPA utilization in the periaqueductal gray and medial nucleus accumbens of patients with early Parkinson's disease

PET studies with the DOPA decarboxylase substrate 6-[¹⁸F]fluoro-l-DOPA (FDOPA) reveal the storage of [¹⁸F]-fluorodopamine within synaptic vesicles, mainly of dopamine fibres. As such, FDOPA PET is a sensitive indicator of the integrity of the nigrostriatal dopamine innervation. Nonetheless, there have been several reports of focal elevations of FDOPA utilization in brain of patients with Parkinson's disease (PD), all based on reference tissue methods. To investigate this phenomenon further, we used voxel-wise steady-state kinetic analysis to search for regions of elevated FDOPA utilization (K; ml g^? 1 min^? 1) and steady-state trapping (V_d; ml g^? 1) in a group of well-characterized patients with early, asymmetric PD, who were contrasted with an age-matched control group. Subtraction of the population mean parametric maps revealed foci of increased FDOPA utilization K (+ 25%) in the bilateral medial nucleus accumbens, whereas the expected declines in the trapping of FDOPA were seen in the caudate and putamen. This observation suggests hyperfunction of catecholamine fibres innervating specifically the limbic striatum, which could guide the design of future prospective FDOPA-PET studies of the impulse control disorders occurring in some PD patients under treatment with dopamine agonists. A focus of increased FDOPA influx and also V_d was detected in the periaqueductal grey, consistent with some earlier reports based on reference tissue analysis. Increased FDOPA trapping in the periaqueductal grey of PD patients seems consistent with recent reports of increased activity of serotonin neurons in a rat model of parkinsonism.     

Therapeutic plasma concentrations of antidepressants and antipsychotics: lessons from PET imaging

Therapeutic Drug Monitoring (TDM) of psychotropic drugs is strongly depending on the validity of recommended therapeutic plasma concentration reference ranges. Rational pharmacotherapy is based on the assumption that plasma concentrations are directly related to target occupancy by the respective drug. Here we show that positron emission tomography (PET) of molecular drug targets in the brain (neuroreceptors and transporters) allows for establishment of these relationships, thereby providing guidance for TDM services. Associations between brain target occupancy, plasma concentrations, and clinical effects and adverse reactions will be discussed for the most commonly used antidepressant and antipsychotic drugs.     

Welche Eigenschaften machen ein Neuroleptikum “atypisch”?

Zusammenfassung Die Gruppe der “atypischen” Neuroleptika ist keine einheitliche Substanzklasse, sondern sowohl nach pharmakologischen als auch nach klinischen Kriterien sehr heterogen. Die überg?nge von dem prototypischen “atypischen” Neuroleptikum Clozapin zu den “konventionellen” Neuroleptika erscheinen flie?end. Anhand der pr?klinischen Besonderheiten dieser Substanzen und ihrer Charakteristika in SPECT- und PET-Studien werden die wesentlichen Konzepte diskutiert, die man heute für die “Atypie” eines Neuroleptikums verantwortlich macht. Dazu z?hlen insbesondere der kombinierte Antagonismus von D₂-artigen Dopamin- und 5-HT₂-Serotoninrezeptoren und die pr?ferentielle Beeinflussung mesolimbischer dopaminerger Neurone. Daneben sind für einzelne Substanzen m?glicherweise Affinit?ten für spezifische Neurotransmitterrezeptoren bzw. die Interaktion mit anderen nicht-dopaminergen Systemen bedeutsam. Auch die Bedeutung einer relativ niedrigen Affinit?t zu D₂-artigen Dopaminrezeptoren und die Bindung an Dopamin-Autorezeptoren werden diskutiert. Die Vielfalt der m?glichen Mechanismen verdeutlicht, dass es wahrscheinlich keine einheitliche, pharmakologisch begründbare Konzeption von “atypischem” Neuroleptikum gibt. Verschiedene biologische Mechanismen charakterisieren eine heterogene Substanzgruppe, die sich auch in ihren klinischen Eigenschaften teilweise erheblich unterscheiden.      

Parametric mapping of binding in human brain of D2 receptor ligands of different affinities.

(11)C-Raclopride has been widely used for PET studies of dopamine D(2/3) receptors in human brain. The long half-life of (18)F may impart advantages to the novel moderate-affinity benzamide (18)F-desmethoxyfallypride and its high-affinity congener (18)F-fallypride for competition studies and for detection of extrastriatal binding. However, the in vivo kinetics of these compounds and the quantification approaches for parametric mapping of their specific bindings have not been systematically compared. METHODS: Dynamic emission recordings of the 3 tracers were obtained in groups of healthy subjects. A conventional model, graphical analysis using metabolite-corrected arterial inputs, and models with reference tissue inputs were used to calculate voxelwise parametric maps of the equilibrium distribution volume (V(d)) and the binding potential (BP) of the 3 radioligands in brain. To test for bias, voxelwise kinetic results were compared with those obtained by volume-of-interest (VOI) analysis. RESULTS: The V(d) and BP estimates obtained by VOI analysis did not differ from the mean of voxelwise estimates in the same striatal volumes. In striatum, the mean (18)F-desmethoxyfallypride BP ranged from 1.9 to 2.5, whereas the mean (11)C-raclopride BP ranged from 3 to 4, depending on the method used for calculation. In contrast, the mean BP of (18)F-fallypride ranged from 16 to 27 in striatum and could also be readily quantified in the thalamus. CONCLUSION: Reference tissue methods for the voxelwise calculation of binding parameters are suitable for parametric mapping of the 3 dopamine D(2/3) receptor ligands.     

GAD-7量表精确诊断广泛性焦虑障碍

问题：广泛性焦虑障碍（GAD）-7量表的诊断精确性如何？ 方法 设计：采用盲法比较GAD-7量表与DSM—Ⅳ中的GAD标准。[第一段]     

Subchronic haloperidol downregulates dopamine synthesis capacity in the brain of schizophrenic patients in vivo.

The antipsychotic effect of neuroleptics cannot be attributed entirely to acute blockade of postsynaptic D(2)-like dopamine (DA) receptors, but may arise in conjunction with the delayed depolarization block of the presynaptic neurons and reduced DA synthesis capacity. Whereas the phenomenon of depolarization block is well established in animals, it is unknown if a similar phenomenon occurs in humans treated with neuroleptics. We hypothesized that haloperidol treatment should result in decreased DA synthesis capacity. We used 6-[(18)F]fluoro-L-dopa (FDOPA) and positron emission tomography (PET) in conjunction with compartmental modeling to measure the relative activity of DOPA decarboxylase (DDC) (k(D)(3), min(-1)) in the brain of nine unmedicated patients with schizophrenia, first in the untreated condition and again after treatment with haloperidol. Patients were administered psychometric rating scales at baseline and after treatment. Consistent with our hypothesis, there was a 25% decrease in the magnitude of k(D)(3) in both caudate and putamen following 5 weeks of haloperidol therapy. In addition, the magnitudes of k(D)(3) in cerebral cortex and thalamus were also decreased. Psychopathology as measured with standard rating scales improved significantly in all patients. The decrease of k(D)(3) in the thalamus was highly significantly correlated with the improvement of negative symptoms. Subchronic treatment with haloperidol decreased the activity of DDC in the brain of patients with schizophrenia. This observation is consistent with the hypothesis that the antipsychotic effect of chronic neuroleptic treatment is associated with a decrease in DA synthesis, reflecting a depolarization block of presynaptic DA neurons. We link an alteration in cerebral catecholamine metabolism in human brain with the therapeutic action of neuroleptic medication.     

Performance for obtaining maximal gain from a program for digital subtraction radiography

Abstract – The aim of this study was to evaluate the effect on subtraction image quality of number of a) gray shades sampled during camera recording, and b) reference points positioned in the two images to be subtracted. Intraoral radiographs were obtained in each of 12 patients, one at 0° and one at 15° horizontal angulation in a standardized recording procedure. The radiographs were videorecorded twice sampling 1) 160–180 and 2) 200–220 shades of gray. The 0° radiographic image was digitally copied. Subtractions were performed between the identical (0°/0°) and the non-identical (0°/15°) radiographs from both gray shade samples after positioning 5, 10, 15, and 20 reference points, respectively, in each of the images to be subtracted. The standard deviation in the subtraction image histogram was used as the test parameter for image quality. No differences existed between image quality obtained from the radiographs sampled using 160–180 and 200–220 shades of gray (P>0.05). The standard deviation fell continuously, the more reference points were positioned in the images. For the 0°/0° images the difference was statistically significant between the 5 and 10 point images ( F= 0.045) while for the 0°/15° images differences existed between 5 and 10 point images (P = 0.077) and the 10 and 15 point images ( P= 0.048). The precision of reference point positioning as evaluated in the two identical images was satisfactory, the divergence being on average 1.4 pixels. The conclusion from cost/benefit analysis was that, when working with subtraction radiography, time should not be spent adjusting camera diaphragm to utilize the full range of gray shades but rather on a precise positioning of 10–15 reference points in the images to be subtracted.     

The contribution of general practice based research to the development of national policy: case studies from Ireland and Australia

Background

This paper aims to describe the influence of general practice based research on the development of two specific policy initiatives, namely the Heartwatch Programme in Ireland and the Better Outcomes in Mental Health Care (BOiMHC) program in Australia. A case study approach was used to explore the extent to which relevant general practice based research shaped these initiatives.

Results

In both case studies, a range of factors beyond general practice based research shaped the initiative in question, including political will, the involvement of stakeholders (including key opinion leaders), and the historical context. Nonetheless, the research played an important role, and was not merely put to 'symbolic use' to support a position that had already been reached independently. Rather, both case studies provide examples of 'instrumental use': in the case of Heartwatch, the research was considered early in the piece; in the case of the BOiMHC program, it had a specific impact on the detail of the components of the initiative.

Conclusion

General practice based research can influence policy-making and planning processes by strengthening the foundation of evidence upon which they draw. This influence will not occur in a vacuum, however, and general practice researchers can maximise the likelihood of their work being 'picked up' in policy if they consider the principles underpinning knowledge transfer.