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Multi-slice (MS) technology increases the efficacy of CT procedures and offers new promising applications. The expanding use of MSCT, however, may result in an increase in both frequency of procedures and levels of patient exposure. It was, therefore, the aim of this study to gain an overview of MSCT examinations conducted in Germany in 2001. All MSCT facilities were requested to provide information about 14 standard examinations with respect to scan parameters and frequency. Based on this data, dosimetric quantities were estimated using an experimentally validated formalism. Results are compared with those of a previous survey for single-slice (SS) spiral CT scanners. According to the data provided for 39 dual- and 73 quad-slice systems, the average annual number of patients examined at MSCT is markedly higher than that examined at SSCT scanners (5500 vs 3500). The average effective dose to patients was changed from 7.4 mSv at single-slice to 5.5 mSv and 8.1 mSv at dual- and quad-slice scanners, respectively. There is a considerable potential for dose reduction at quad-slice systems by an optimisation of scan protocols and better education of the personnel. To avoid an increase in the collective effective dose from CT procedures, a clear medical justification is required in each case.

HintergrundIn Deutschland resultieren etwa 95 % der zivilisatorischen Strahlenexposition der Bevölkerung aus diagnostischen und interventionellen Röntgenanwendungen, sodass dem Strahlenschutz der Patienten in diesem Anwendungsbereich eine hohe Bedeutung zukommt.Ziel der ArbeitAuswertung und Bewertung aktueller Daten zu Häufigkeit und Dosis von Röntgenanwendungen sowie von zeitlichen Entwicklungen für die Jahre 2007 bis 2014.Material und MethodenDie Häufigkeit von Röntgenanwendungen wurde für den ambulanten Bereich über Gebührenziffern der erbrachten radiologischen Leistungen abgeschätzt, für den stationären Bereich mithilfe von Krankenhausstatistiken. Repräsentative Werte für die effektive Dosis pro Röntgenanwendung wurden für die betrachteten Jahre überwiegend aus Daten der Ärztlichen Stellen ermittelt.ErgebnisseIm Jahr 2014 wurden in Deutschland etwa 140 Mio. Röntgenanwendungen durchgeführt, hiervon etwa 40 % im zahnmedizinischen Bereich. Im Mittel erfolgten 2007–2014 nahezu konstant 1,7 Anwendungen pro Einwohner und Jahr. Neben der zahnmedizinischen Diagnostik wurden am häufigsten konventionelle Untersuchungen des Skeletts und des Thorax durchgeführt. Die CT-Häufigkeit nahm um ca. 40 % zu. Mit etwa 55 % war der Anstieg bei der MRT zwar noch deutlicher, jedoch wurden insgesamt noch immer mehr CT- als MRT-Untersuchungen durchgeführt. Die Dosiswerte pro Untersuchung nahmen trotz der in den letzten Jahren etablierten Methoden zur Dosisreduktion nur leicht ab. In der Konsequenz nahm die mittlere effektive Dosis pro Einwohner im Untersuchungszeitraum von knapp 1,4 auf 1,6 mSv zu – im Wesentlichen aufgrund der zunehmenden CT-Häufigkeit.SchlussfolgerungDie Prinzipien der Rechtfertigung und Optimierung von medizinischen Strahlenanwendungen sind – insbesondere bei CT-Untersuchungen – in jedem Einzelfall konsequent anzuwenden.

The aim of this study was to investigate the potential of dose reduction in multidetector computed tomography (MDCT) by current-modulated automatic exposure control (AEC) and to test the reliability of the dose estimation by the conventional CT dosimetry program CT-EXPO, when an average tube current is used. Phantom measurements were performed at a CT system with 64 detector rows for four representative examination protocols, each without and with current-modulated AEC. Organ and effective doses were measured by thermoluminescence dosimeters (TLD) at an anthropomorphic Alderson phantom and compared with those given by the calculation with CT-EXPO. The application of AEC yielded dose reductions between 27 and 40% (TLD measurements). While good linearity was observed between measured and computed effective dose values both without and with AEC, the organ doses showed large deviations between measurement and calculation. The dose to patients undergoing a MDCT examination can be reduced considerably by applying a current-modulated AEC. Dosimetric algorithms using a constant current–time product provide reliable estimates of the effective dose.

ZusammenfassungHintergrundBildgebende radiologische Verfahren wie die Computertomographie (CT) bieten sich für die Früherkennung verschiedener Krankheiten an. Da den möglichen Vorteilen einer Früherkennungsuntersuchung immer auch unerwünschte Wirkungen gegenüberstehen, insbesondere bei Anwendung ionisierender Strahlung, muss eine sorgfältige Nutzen-Risiko-Abwägung erfolgen.Material und MethodenSowohl die International Basic Safety Standards als auch die Europäische Richtlinie 2013/59/Euratom haben Rahmenbedingungen für den Einsatz radiologischer Verfahren in der Früherkennung formuliert. Diese wurden in Deutschland mit dem neuen Strahlenschutzgesetz umgesetzt. Danach legt das Bundesministerium für Umwelt, Naturschutz und nukleare Sicherheit (BMU) unter Berücksichtigung einer wissenschaftlichen Bewertung des Bundesamts für Strahlenschutz (BfS) in einer Verordnung fest, welche Früherkennungsmaßnahme unter welchen Voraussetzungen zur Ermittlung einer Krankheit für eine besonders betroffene Personengruppe zulässig ist.ErgebnisseMit Ausnahme des Mammographie-Screening-Programms ist in Deutschland bislang noch kein radiologisches Untersuchungsverfahren für die Früherkennung von Krankheiten zugelassen. Dennoch werden in Deutschland derartige Untersuchungen widerrechtlich anboten. Für die Lungenkrebsfrüherkennung mittels Niedrigdosis-CT erfolgt derzeit eine wissenschaftliche Bewertung durch das BfS.DiskussionFrüherkennungsuntersuchungen mittels radiologischer Bildgebung können nur zugelassen werden, wenn durch Studien höchsten Evidenzgrades ein Überwiegen des Nutzens gegenüber dem Risiko nachgewiesen wurde. Um dies auch in der allgemeinen Gesundheitsversorgung sicherzustellen, sind strenge Anforderungen an den gesamten Früherkennungsprozess, einschließlich der Qualitätssicherung, zu stellen.

For quantification of hepatic [(18)F]FDG uptake, the dual blood supply to the liver must be considered. In contrast to the arterial input, however, the portal venous blood supply to the liver cannot be monitored directly by PET because of the inaccessibility of the portal vein on PET scans. In this study, we investigated whether the dual hepatic input can be predicted from the measurable arterial input. Moreover, we assessed the effect of different input models on the rate constants of the standard 3-compartment model describing regional uptake of FDG. Dynamic FDG PET scanning was performed on 5 foxhounds. Activity concentrations in blood from the aorta and the portal vein were measured simultaneously using external circuits. After image reconstruction, time--activity courses were determined from the aorta and the liver. The venous input was approximated by convolving the arterial input with a notional system function describing the dispersion of the arterial input on its way through the gastrointestinal tract. On the basis of these data, 5 different hepatic input models, which pertain to a single-input as well as a dual-input scenario, were statistically compared with regard to the adequacy of the model fits to liver data and to differences in the estimated rate constants. Portal venous input to the liver could be approximated by convolving the arterial input function with a system function. From this function, a mean transit time of 25 s was computed for FDG to pass through the gastrointestinal tract. According to the statistical analysis, dual-input models were superior to their single-input counterparts. However, differences in the rate constants estimated for the 5 input models were in the same order as interindividual variations within the different model groups. For the dephosphorylation rate constant, a consistent value of 0.05 +/- 0.01 min(-1) was found. Dual-input models proved to be superior to single-input models with respect to the adequacy of FDG model fits to normal liver data. However, the hepatic blood supply may be approximated by the arterial input function as well, especially for the evaluation of liver lesions mainly fed by the hepatic artery.

It was the aim of this methodology-oriented clinical pilot study to compare the potential of dynamic MRI and 2-[18F]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) for the detection and characterization of breast cancer. Fourteen women with suspicious breast lesions were examined. The MRI data were acquired with a turbo fast low-angle shot sequence and analyzed using a pharmacokinetic model. Emission data were detected in the sensitive 3D modus, iteratively reconstructed, and superimposed onto corresponding transmission images. In the 14 patients, 13 breast masses with a suspicious contrast enhancement and FDG uptake were detected. For these lesions, no statistically significant correlation between evaluated MR and PET parameters was found. Of the 9 histologically confirmed carcinomas, 8 were correctly characterized with MRI and PET. Two inflammatory lesions were concordantly classified as cancer. Moreover, dynamic MRI yielded another false-positive finding. In 6 patients, PET detected occult lymph node and/or distant metastases. Although both functional imaging techniques provide independent tissue information, the results concerning the diagnosis of primary breast lesions were almost identical. An advantage of PET, however, is its ability to localize lymph node involvement and distant metastases as an integral part of the examination.

ProblemstellungIn den letzten Jahren wurden neue Studien zu biologischen Wirkungen starker statischer Magnetfelder und zu thermischen Effekten hochfrequenter elektromagnetischer Feldern, wie sie bei der Magnetresonanztomographie (MRT) verwendet werden, publiziert. Viele dieser Studien sind noch nicht in aktuelle Sicherheitsempfehlungen eingeflossen.MethodeWissenschaftliche Publikationen ab dem Jahr 2010 zur biologischen Wirkung statischer und elektromagnetischer Felder der MRT wurden recherchiert und bewertet.ErgebnisseNeue Studien bestätigen ältere Arbeiten, die bereits Wirkungen statischer Magnetfelder auf Sinnesorgane und das zentrale Nervensystem, begleitet von Sinneswahrnehmungen, beschrieben haben. Ein neues Ergebnis ist die direkte Wirkung von Lorentz-Kräften auf Ionenströme in den semizirkulären Kanälen des Gleichgewichtsorgans. Aktuelle Untersuchungen zu thermischen Wirkungen hochfrequenter Felder fokussierten auf die Entwicklung anatomisch realistischer Körpermodelle und eine genauere Simulation von Expositionsszenarien.Empfehlung für die PraxisStarke statische Magnetfelder können unangenehme Wahrnehmungen, insbesondere Schwindel, hervorrufen. Darüber hinaus können sie die Leistungsfähigkeit des medizinischen Personals beeinflussen und dadurch potenziell die Patientensicherheit gefährden. Vorsorglich sollte sich das medizinische Personal im Feldgradienten langsam bewegen. Hochfrequente elektromagnetische Felder führen bei Patienten zur Erwärmung von Geweben und Organen. Dies ist insbesondere bei Patienten mit eingeschränkter Thermoregulation sowie bei Schwangeren und Neugeborenen zu berücksichtigen; die Exposition ist in diesen Fällen möglichst gering zu halten.

Background: Behavioural parent training is effective in improving child disruptive behavioural problems in preschool children by increasing parenting competence. The indicated Prevention Programme for Externalizing Problem behaviour (PEP) is a group training programme for parents and kindergarten teachers of children aged 3–6 years with externalizing behavioural problems. Aims: To evaluate the effects of PEP on child problem behaviour, parenting practices, parent-child interactions, and parental quality of life. Method: Parents and kindergarten teachers of 155 children were randomly assigned to an intervention group (n = 91) and a nontreated control group (n = 64). They rated children's problem behaviour before and after PEP training; parents also reported on their parenting practices and quality of life. Standardized play situations were video-taped and rated for parent-child interactions, e.g. parental warmth. Results: In the intention to treat analysis, mothers of the intervention group described less disruptive child behaviour and better parenting strategies, and showed more parental warmth during a standardized parent-child interaction. Dosage analyses confirmed these results for parents who attended at least five training sessions. Children were also rated to show less behaviour problems by their kindergarten teachers. Conclusions: Training effects were especially positive for parents who attended at least half of the training sessions. Abbreviations: CBCL: Child Behaviour Checklist; CII: Coder Impressions Inventory; DASS: Depression anxiety Stress Scale; HSQ: Home-situation Questionnaire; LSS: Life Satisfaction Scale; OBDT: observed behaviour during the test; PCL: Problem Checklist; PEP: prevention programme for externalizing problem behaviour; PPC: Parent Problem Checklist; PPS: Parent Practices Scale; PS: Parenting Scale; PSBC: Problem Setting and Behaviour checklist; QJPS: Questionnaire on Judging Parental Strains; SEFS: Self-Efficacy Scale; SSC: Social Support Scale; TRF: Caregiver-Teacher Report Form

Dose assessment in computed tomography (CT) is challenging due to the vast variety of CT scanners and imaging protocols in use. In the present study, the accurateness of a theoretical formalism implemented in the PC program CT-EXPO for dose calculation was evaluated by means of phantom measurements. Phantom measurements were performed with four 1-slice, four 4-slice and two 16-slice spiral CT scanners. Firstly, scanner-specific nCTDIw values were measured and compared with the corresponding standard values used for dose calculation. Secondly, effective doses were determined for three CT scans (head, chest and pelvis) performed at each of the ten installations from readings of thermoluminescent dosimeters distributed inside an anthropomorphic Alderson phantom and compared with the corresponding dose values computed with CT-EXPO. Differences between standard and individually measured nCTDIw values were less than 16%. Statistical analysis yielded a highly significant correlation (P < 0.001) between calculated and measured effective doses. The systematic and random uncertainty of the dose values calculated using standard nCTDIw values was about -9 and +/- 11%, respectively. The phantom measurements and model calculations were carried out for a variety of CT scanners and representative scan protocols validate the reliability of the dosimetric formalism considered-at least for patients with a standard body size and a tube voltage of 120 kV selected for the majority of CT scans performed in our study.

Advanced bronchial carcinomas by means of perfusion and peak enhancement using dynamic contrast-enhanced multislice CT are characterized. Twenty-four patients with advanced bronchial carcinoma were examined. During breathhold, after injection of a contrast-medium (CM), 25 scans were performed (1 scan/s) at a fixed table position. Density-time curves were evaluated from regions of interest of the whole tumor and high- and low-enhancing tumor areas. Perfusion and peak enhancement were calculated using the maximum-slope method of Miles and compared with size, localization (central or peripheral) and histology. Perfusion of large tumors (> 50 cm3) averaged over both the whole tumor (P = 0.001) and the highest enhancing area (P = 0.003) was significantly lower than that of smaller ones. Independent of size, central carcinomas had a significantly (P = 0.04) lower perfusion (mean 27.9 ml/min/100 g) than peripheral ones (mean 66.5 ml/min/100 g). In contrast, peak enhancement of central and peripheral carcinomas was not significantly different. Between non-small-cell lung cancers and small-cell lung cancers, no significant differences were observed in both parameters. In seven tumors, density increase after CM administration started earlier than in the aorta, indicating considerable blood supply from pulmonary vessels. Tumor perfusion was dependent on tumor size and localization, but not on histology. Furthermore, perfusion CT disclosed blood supply from both pulmonary and/or bronchial vessels in some tumors.