[en] Due to the current demographic development, the increasing prevalence of dementias represents a serious medical and economical issue. With regard to new and upcoming treatment options, based on this background, the reliable early and differential diagnosis will be of increasing importance, in order not to delay suitable therapies. Functional brain imaging by means of PET and SPECT can substantially contribute to this diagnostic challenge, and PET using [¹⁸F]FDG could be shown to be a highly sensitive method for the early diagnosis of neurodegenerative dementias. The purpose of this article is to give a survey on the current state of nuclear medicine imaging of dementias and to present the typical brain metabolic findings and their differential diagnoses. (orig.)

[en] The increasing life-expectancy of our society results in a continuously growing number of patients suffering from dementing disorders, particularly Alzheimer's disease (AD). Apart from the deleterious consequences for the patients and their relatives, this has also alarming effects on our social systems. These facts have justified increased scientific efforts regarding the identification of basic pathomechanisms of dementia and the development of new treatment options. Increased production of specific proteins and their pathologic aggregation in the brain appears to be a pathomechanism which occurs early in the course of many different neurodegenerative disorders. Among the most well-known of these protein aggregations are the amyloid-plaques, which arise from the aggregation of the β-amyloid protein. Currently, this amyloid-aggregation pathology is regarded as a key pathology, playing a causal role in the development of AD. Consequently, modern therapy approaches are directed towards this target. Limited access to brain tissue has so far restricted the definite diagnosis of AD to post mortem histopathological assessment of brain tissue. For the same reason, a clear association between extent of amyloid deposition pathology and clinical course of AD has not been established so far. However, particularly with regard to new therapeutic options a reliable in vivo diagnosis is required. Modern molecular imaging tracers such as [¹¹C]PIB do now open the possibility to visualize amyloid-depositions in vivo, using Positron Emission Tomography (PET). These techniques allow the characterization of dementing disorders on the basis of the underlying pathology rather than on their symptomatic appearance. This type of ''in vivo histopathology''-approach may offer improved options for early and differential diagnosis, as well as for patient selection for therapy trials and for objective therapy monitoring. (orig.)

[en] For planned and ongoing storage of liquid radioactive waste in a designated plant for a nuclear medicine therapy ward (decontamination system/decay system), detailed knowledge of basic parameters such as the amount of radioactivity and the necessary decay time in the plant is required. The design of the plant at the Department of Nuclear Medicine of the University of Cologne, built in 2001, was based on assumptions about the individual discharge of activity from patients, which we can now retrospectively validate. The decontamination factor of the plant is at present in the order of 10⁻⁹ for ¹³¹I. The annual discharges have been continuously reduced over the period of operation and are now in the region of a few kilobecquerels. This work emphasizes the high efficacy of the decontamination plant to reduce the amount of radioactivity released from the nuclear medicine ward into the environment to almost negligible levels. - Highlights: • Description of a decontamination plant in nuclear medicine. • Annual discharges of radioiodine into the environment have been reduced to a few kBq over the years. • Decontamination factor for radioiodine of ∼10⁻⁹ attainable.

[en] It is well known that a considerable amount of radioiodine is exhaled after radioiodine therapy (RIT) leading to unwanted radiation exposure through inhalation for non-involved persons. This study focuses on the amount of exhalation in the breath-out air of RIT-patients and the dosimetric consequences. Furthermore, the correlation between radioiodine uptake and exhalation was investigated. The radioiodine species were collected in a filter system and quantified over time by measurements with a scintillation counter. The dosimetric implications were then studied for different exposure scenarios. Of the activity administered to the patient, approximately 10⁻³% (50–110 ppm) is exhaled. The radioiodine inhalation taking place following exhalation in the vicinity yields doses of up to 500 μSv (children, staying with the patient immediately after application and for the next 8 h). Three days after administration the doses are significantly reduced. This study lays emphasis on previous assumptions that exhalation depends on thyroid storage. Regardless of the type of thyroid disease, the predominant form exhaled is organic radioiodine. The amount of exhaled radioiodine is small but from the point of view of radiation protection, by no means negligible immediately after administration. Radiation doses received by incorporation of exhaled radioiodine can easily exceed 100 μSv soon after administration of radioiodine. Three days after RIT the radioactivity can still be measured in the exhaled air but even at maximum, the annual doses lie far below 10 μSv and are thus comparatively low. - Highlights: • Measurements were taken of the exhalation of radioiodine after radioiodine therapy. • Effective doses for non-involved persons in the vicinity of patients were estimated. • Considerable doses may arise through inhalation of radioiodine immediately after application. • After an in-patient stay of three days the effective doses become negligible. • Thyroid uptake is not a reliable predictor of the exhalation.

[en] The increasing life expectancy in our society results in a continuously growing number of patients suffering from neurodegenerative disorders, particularly Alzheimer's disease (AD). Apart from the deleterious consequences for patients and their relatives, this issue has also alarming effects on our social systems. These facts have justified increased scientific efforts regarding the identification of basic pathomechanisms of dementia and the development of new treatment options. Increased production of specific proteins and their pathologic aggregation in the brain appears to be a pathomechanism which occurs early in the course of many different neurodegenerative diseases. Among the most well-known of these protein aggregations are amyloid plaques, which arise from the aggregation of the β-amyloid protein. Currently, this amyloid-aggregation pathology is regarded as a key pathology, playing a causal role in the development of AD. Consequently, modern therapy approaches are directed towards this target. Limited access to brain tissue has so far restricted the definite diagnosis of AD to postmortem histopathological assessment of brain tissue. For the same reason, a clear association between extent of amyloid deposition pathology and clinical course of AD has not been established so far. However, particularly with regard to new therapeutic options, a reliable in vivo diagnosis is required. Modern molecular imaging tracers such as [¹¹C]Pittsburgh Compound B (PIB) do now open the possibility to visualize amyloid depositions in vivo, using positron emission tomography. This type of ''in vivo histopathology'' approach allows the characterization of neurodegenerative disorders on the basis of the underlying pathology rather than on their symptomatic appearance. In this manuscript, we will discuss the options of amyloid-plaque imaging regarding early and differential diagnosis of different forms of dementia as well as for patient selection for therapy trials and for objective therapy monitoring. (author)

[en] In this work, the radiation exposure in nuclear medicine is evaluated by measuring dose rates in the proximity of patients and those in close contact to sources like capsules and syringes. A huge number of different survey meters (SMs) are offered commercially. This topic has recently gained interest since dosemeters and active personal dosemeters (APD) for the new dose quantities (ambient and directional dose equivalent) have become available. One main concern is the practical use of SMs and APD in daily clinical routines. Therefore, the radiation field of four common radiopharmaceuticals containing ¹⁸F, ⁹⁰Y, ^99mTc and ¹³¹I in radioactive sources or after application to the patient was determined. Measurements were carried out with different SMs and for several distances. Dose rates decline significantly with the distance to the patient, and with some restrictions, APD can be used as SMs. (authors)

[en] Hybrid PET/MRI systematically offers a complementary combination of two modalities that has often proven itself superior to the single modality approach in the diagnostic work-up of many neurological and psychiatric diseases. Emerging PET tracers, technical advances in multiparametric MRI and obvious workflow advantages may lead to a significant improvement in the diagnosis of dementia disorders, neurooncological diseases, epilepsy and neurovascular diseases using PET/MRI. Moreover, simultaneous PET/MRI is well suited to complex studies of brain function in which fast fluctuations of brain signals (e.g. related to task processing or in response to pharmacological interventions) need to be monitored on multiple levels. Initial simultaneous studies have already demonstrated that these complementary measures of brain function can provide new insights into the functional and structural organization of the brain. (orig.)

[en] Aim: To assess the regional cerebral activation during navigation in a virtual reality (VR) environment in healthy volunteers and patients with mild cognitive impairment (MCI) to identify possible differences in cerebral processing of a complex cognitive task. Materials and Methods: A computer-based VR-system has been developed that allows movements in a virtual labyrinth using a special space-mouse and 3-dimensional perception by shutter-glasses. In 11 healthy, right-handed volunteers (3 female, age 66+/-9 years) and 9 patients with MCI (3 female, 69+/-10 years, diagnosis according to criteria of the Mayo-Clinic) twelve H215O PET-scans were performed (each 370 MBq i.v.-bolus). During the scan subjects had to navigate actively from startpoint to a predefined destination point. Three difficulty levels were presented, 4 times each, in randomized order. Test performance (speed, mistakes) was co-registered. PET data were analyzed using statistical parametric mapping (SPM99, Wellcome Inst., London, UK) including correlation analysis with the acquired test performance results. A significance threshold of p<0,001 uncorrected was applied. Results: In both groups a similar network of extended cerebral activation was identified during active navigation, including maxima in the cerebellum, premotor cortex (Brodmann area [BA] 6), parietal cortex (BA 7, 40) and posterior cingulate cortex (BA 31). However, in MCI-patients a significantly stronger activation of anterior cingulate cortex (BA 24), prefrontal cortex (BA 8) and parietal cortex (BA 40) was observed, as compared to healthy volunteers. Conclusion: The applied combination of PET and VR-technology allows to examine the processing of complex cognitive tasks in the brain. During active navigation significant differences have been observed between the activated cerebral networks in MCI-patients and healthy volunteers. In MCI-patients stronger activation has been identified in cerebral regions associated with attention and spatial orientation. This may represent increased cognitive work in these patients, who have a higher risk to develop Alzheimer's disease and may already suffer from neuro degenerative processes

[en] Procedures to determine the release of hazardous gaseous substances including radioactive iodine are covered by different norms such as the European standard EN 14175 and the German national standard DIN 25466. The detection of sulphur hexafluoride (SF₆) is required to comply with the prescribed methodology. The detection limit of this test is 4.5·10⁻⁷ mol/m³ in exhaust air. This detection limit would represent a very high activity in the region of 0.27 TBq/m³ leading to an unacceptable risk. We therefore developed a test using a filter system, consisting of a combination of filters capable of separating various chemical forms of airborne radioiodine. Air samples were collected directly in front of the fume hood and in the laboratory beside two different fume hoods of a similar construction with a final activated carbon filter for retention of radioiodine. Particular attention was therefore paid to air samples taken after passage over the filters. Significant differences in the degree of retention of iodine were found between the two fume hoods investigated. In one test a malfunction of the fume hood was demonstrated. In this case 0.148 × 10⁻³% of the total released activity per m³ air was found 1 cm in front of the hood sash. A remarkably high fraction of the activity released in the fume hood (1.3 × 10⁻³%/m³ air) was measured after the activated carbon filter. In the ambient air, values of up to 8.6 × 10⁻⁶% pro m³ laboratory air sampled were measured, despite a 6–8-fold air exchange. The selected procedure is a factor of 10¹¹ (Schomäcker et al., 2001) more sensitive than the standard recommended methods (EN 14175). The standard test prescribed by the DIN/EN failed to reveal any inadequacy in the protective function of the radionuclide hood with respect to radioiodine retention. - Highlights: • The retention efficiency of fume hoods in which radioactivity is handled was tested. • The test prescribed by international standards uses chemical substances which are proven to be inadequate. • We propose an alternative method of testing fume hoods in laboratories where radionuclides are handled.

[en] The protective effect of stable iodide against radiation on thyroid cells was investigated. One physiological effect of stable iodine is well-rooted: stable iodine leads to a reduced thyroid uptake of radioactive iodine. This work wants to focus on an intrinsic effect of stable iodine by which DNA-damage in cells is prevented. To investigate this intrinsic effect thyroid cells (FRTL-5) were externally irradiated by use of a linear accelerator (LINAC) applying energy doses of 0.01 Gy–400 Gy and by incubation with various activity concentrations of ¹³¹I (0.1–50 MBq/ml for 24 h). We added stable iodine (NaI) to the cells prior to external irradiation and investigated the effect of the concentration of stable iodine (1, 5, 15 μg/ml). In order to clarify whether thyroid cells have a distinctive and iodine-dependent reaction to ionizing radiation, keratinocytes (HaCaT) without NIS were exposed in the same way. As indicators for the cellular reaction, the extent of DNA fragmentation was determined (Roche, Mannheim, Germany). Both cell types showed distinct ability for apoptosis as proven with camptothecin. The addition of “cold” iodine from 1 to 15 μg/ml without irradiation (“negative control”) did not change the response in both cell types. Plausibly, the radio-sensitivity of both cell types did increase markedly with increasing radiation dose but the radiation effect is diminished if iodine is added to the thyroid cells beforehand. The DNA-damage in thyroid cells after addition of cold iodine is reduced by a factor of 2–3. The skin cells did not show an significant change of radio-sensitivity depending on the presence of cold iodine. Elementary iodine possibly acts as a radical scavenger and thus markedly reduces the secondary radiation damage caused by the formation of cytotoxic radicals. This intrinsic radioprotective effect of iodine is seen only in cells with NIS. - Highlights: • The influence of the cellular iodine concentration on the DNA-fragmentation after irradiation was studied. • Irradiations using linear accelerators and ¹³¹I and Na¹³¹I revealed a radioprotective effect of cold iodine. • The reduced DNA-damage was observed for thyroid cells and was not found for equally irradiated skin cells.