Accumulation of BRI2-BRICHOS ectodomain correlates with a decreased clearance of Aß by insulin degrading enzyme (IDE) in Alzheimer's disease.

The precursor protein BRI2 that in its mutated form is associated with British and Danish dementia, can regulate critical processes involved in AD pathogenesis including not only the metabolism of amyloid precursor protein (APP) and formation of Aß, but also the levels of secreted insulin degrading enzyme (IDE), an enzyme involved in Aß clearance. We recently observed increased levels of a 45kDa BRI2 form as well as BRI2 ectodomain deposits in Aß plaques in human AD hippocampus, which may affect BRI2 functional activity. Since BRI2 regulated the levels of secreted IDE and subsequent degradation of Aß in human cell culture models, we explored if BRI2 changes could affect the Aß degradation capacity of IDE in human hippocampus (n=28). We observed that IDE is the main enzyme involved in Aß degradation, and both IDE levels as well as Aß degradation tend to be decreased in AD. Interestingly, the levels of the 45kDa BRI2 form and BRI2 deposits in hippocampal tissue were inversely correlated with IDE protein levels (r=-0.52, p=0.005; r=-0.4, p=0.045) and IDE activity (r=-0.5935, p=0.0004; r=-0.4, p=0.03). Taken together, the current results suggest a relationship between BRI2 protein changes, IDE activity and Aß levels in human hippocampus. Thus, the formation and accumulation high of molecular weight BRI2 forms observed in AD may impair IDE functioning and consequently lead to impaired Aß clearance and to the accumulation of Aß.

[Multislice spiral CT (MSCT) in pediatric radiology: dose reduction for chest and abdomen examinations]. / Mehrschicht-Spiral-CT (MSCT) in der Kinderradiologie: Dosisreduktion bei der Untersuchung von Thorax und Abdomen.

The advent of multislice spiral CT (MSCT) technique has led to new aspects of dose reduction, especially for the dedicated use of MSCT in children. Optimizing pediatric MSCT protocols according to the clinical problem allows reduction of radiation exposure to a minimum without loss of diagnostic quality. The different parameters that influence the degree of dose reduction, like tube current-time product (mAs), tube voltage (kV), collimation and pitch, are discussed in context with previously published data and our own experience in nearly 200 pediatric CT examinations. In our department, the effective mAs is calculated for a pediatric chest MSCT by multiplication of the body weight in kilogram with a factor of 1 to 1.5 and for a pediatric abdominal MSCT by multiplication with a factor of 2 to 2.5. To calculate the equivalent effective dose for a contrast media-enhanced 80 kV protocol, the effective mAs of the 120 kV protocol can be multiplied by 2.7. A factor less than 2.7 means further dose reduction. Compared to the radiation exposure with a standard adult protocol, the effective dose in a pediatric thoracic MSCT could be reduced by up to 92 % in neonates, 89 % in toddlers and 80 % in school children. In abdominal MSCT, the effective dose could be reduced by up to 90 % in neonates, 89 % in toddlers and 83 % in school children. Using an adequate MSCT technique in children by adjusting the CT scanning parameters to the clinical question and body weight of the examined child enables a significant reduction of radiation exposure in comparison to standard MSCT protocols.

Individually weight-adapted examination protocol in retrospectively ECG-gated MSCT of the heart.

The standard protocol in multislice spiral CT (MSCT) angiography for coronary arteries with fixed tube current-time settings leads to an overexposure and thus to an unnecessary high radiation dose in patients with lower weight when compared to heavier patients. The purpose of this study was to estimate the effect of reducing the radiation dose by adapting the tube current-time settings individually. Fifty patients underwent retrospectively ECG-gated MSCT of the heart. In 25 patients (group A1) a standard protocol with constant tube current-time settings was used (4 x 1-mm collimation, 120 kV, 400 mAs(eff)). Subsequently, artificial image noise was added to the data of these patients simulating a directive for weight-adapted tube current-time settings (group A2). In the other 25 patients (group B) an alternative protocol with individually weight-adapted tube current-time settings was applied. The data of all groups were evaluated by a regression analysis. The image quality was assessed objectively by measuring the CT attenuation in standardised regions of interest and subjectively by three radiologists using a five-point scoring system in a consensus reading. Applying the weight-adapted tube current-time settings the effective radiation dose was reduced by 17.9% for men and 26.3% for women. The standard protocol leads to an overexposure in light patients as seen in the plot of noise vs weight (slope 0.16+/-0.07 HU/kg). By applying the weight-adapted tube current-time settings a weight-independent, constant image noise is achieved (slope 0.04+/-0.1 HU/kg). Diagnostic image quality was preserved in all patients. Individually weight-adapted tube current-time settings allow for a substantial dose reduction when performing retrospectively ECG-gated MSCT angiography for coronary arteries without impairment of diagnostic image quality.

[A differentiated approach to the diagnosis of pulmonary embolism and deep venous thrombosis using multi-slice CT]. / Abklärung von Lungenembolie und venöser Thromboembolie mittels Mehrschicht-Spiral CT.

PURPOSE: To establish a differentiated protocol for multi-slice CT (MSCT) examinations in cases of clinically suspected pulmonary embolism (PE) using pulmonary CT-angiography (CTA) and indirect CT-phlebography (CTP). MATERIALS AND METHODS: 161 patients with suspected PE were examined using an MSCT (SOMATOM Volume Zoom; Siemens, Forchheim, Germany). After intravenous administration of 120 ml of contrast material, a thin collimation chest-CT scan was performed (120 kV, 100 mAs, collimation: 4 x 1 mm). If PE was present, or previous examinations and clinical signs suggested deep venous thrombosis (DVT), a CTP was subsequently completed. CTPs were performed using a 4 x 5 mm protocol (120 kV, 170 mAs). Venous phase scanning, starting from the pelvic crest, was completed in the popliteal fossa three minutes after contrast material injection. In 73 extremities, CTP were compared to the results of ultrasound, phlebography and autopsy. Scan ranges were documented in all patients. Cumulative doses were calculated for male and female subgroups. RESULTS: 62 patients in our series suffered from PE and in 47 of these patients deep venous thrombosis was seen additionally. Of the 99 patients without PE, 47 also received indirect CTP. CTP confirmed the suspicion and extent of DVT in 8 patients. Only in 2 of 39 patients (5.1 %) was previously unknown DVT found, despite the exclusion of PE. Regarding DVT, sensitivity was 94.3 % and specificity was 92.1 % for indirect CTP. Cumulative chest CT doses averaged 3.3 mSv for males and 4.2 mSv for females, the calculated CTP dosage was 9.3 mSv (according to ICRP 60). CONCLUSIONS: The examination protocol presented is suitable for clinical usage in patients with suspected PE. If PE is confirmed, indirect CTP is justified, so that detailed information of the venous system can be obtained. However, the relatively high radiation dosage of an additional CTP requires a strict indication regiment in patients with a negative CTA.

Individually adapted examination protocols for reduction of radiation exposure in chest CT.

RATIONALE AND OBJECTIVES: To develop a simple directive for the reduction of radiation exposure without loss of diagnostic information in routine chest CT examinations. METHODS: Two hundred fifty adult patients (164 male, 86 female) were entered into a prospective trial. All examinations were performed with a multislice CT technique (Somatom Volume Zoom, Siemens). Four groups of 50 patients each were scanned with patient-related specific parameters: individual mA-s values were derived from the estimated body weight: kilograms + 10, +/- 0, - 10, and - 20 mAs. The results were compared with those of 50 patients who were examined by a standard chest protocol by using the parameters 120 mAs and 140 kV. All other parameters including the tube voltage were kept constant. Subjective image quality was rated on a three-point scale: 1 = excellent, 2 = fair, 3 = nondiagnostic. In addition, objective criteria based on signal-to-noise measurements were assessed by using a region-of-interest methodology. RESULTS: Image quality was sufficient in all cases. Mean subjective gradings of image quality, based on soft-tissue window settings, were 1.1 for the 120-mAs protocol, 1.1 for the (body weight [kg] + 10) mAs protocol, 1.1 for the (body weight [kg] +/- 0) mAs protocol, 1.3 for the (body weight [kg] - 10) mAs protocol, and 1.2 for the (body weight [kg] - 20) mAs protocol. Objective criteria based on noise measurements showed mean +/- standard deviation values of 5.7 +/- 0.8 Hounsfield units (HU) for the 120-mAs protocol. For the reduced-dose protocols, values were calculated as 7.6 +/- 1.2 HU (group + 10), 7.9 +/- 1.3 HU (group +/- 0), 8.7 +/- 1.2 HU (group - 10), and finally 9.1 +/- 1.3 HU (group - 20). The best correlation for an entire subgroup was achieved with the - 10 protocol (body weight [kg] - 10) mAs, with nearly constant noise related to body weight in all patients. CONCLUSIONS: By deriving mAs values from body weight estimation, an individually adapted protocol for chest CT can be recommended and easily employed in a clinical setting. With an adaptation of the tube current-time product based on the estimated body weight of the patient - 10 (body weight [kg] - 10 mAs), a well-balanced examination without significant loss of information, even in soft-tissue window settings, can be performed with this particular scanner. For this adapted mAs protocol, a mean reduction of radiation exposure of 45% was achievable, compared with the standard protocol. A maximum decrease per case down to 31 mAs was obtained, without relevant loss of image quality. Therefore, for other types of CT scanners, analogous protocols may be adapted.

Errors of computer-assisted migration analysis in conventional radiographs of femoral hip implants--an experimental study.

Several methods have been described in the literature in order to analyze migration of femoral hip implants in conventional radiographs. However, no measurements were done regarding the potential errors inherent in such unstandardized radiographs of daily routine. In order to quantify this lack of reproducibility, we carried out experimental examinations with radiographs of a hip revision prosthesis, where different variables of technical X-ray conditions and femoral positions were changed. All radiographs were analyzed with a computer-assisted processing system by different procedures. At first, the radiographs were calibrated geometrically. Then, particular reference distances between defined points of the implant and cortical bone structures were analyzed quantitatively. The error of the axial migration analysis was up to 11.11 mm concerning different femoral positions, up to 8.29 mm in the case of different source-to-film distances and up to 2.21 mm due to different lateral localizations of the central X-ray focus. Significant errors for the migration analysis in the transverse and rotational planes were only found under conditions of varying the femoral position, and not under different technical X-ray conditions. From these experimental results, we derived the following criteria to minimize failure in a quantitative radiographic migration analysis: (1) the patient's leg has to be placed into an antirotation device to ensure identical object position; (2) the same source-to-film distance has to be used; (3) the central X-ray focus has to be localized on the center of the film-cassette; (4) film-screen systems should be of the same type and size; (5) the object has to be placed in the same position as in previous radiographs. As a conclusion, only if these standardization criteria are respected in the daily routine of conventional radiographs will an effective and meaningful use of migration analysis systems be possible to prove or to exclude mechanical failure of femoral hip implants in prospective longitudinal follow-up series.

[New TIPS placement in pregnancy in recurrent esophageal varices hemorrhage--assessment of fetal radiation exposure]. / TIPS-Neuanlage in der Schwangerschaft bei rezidivierender Osophagusvarizenblutung--Abschätzung der fetalen Strahlenexposition.

Recurrent variceal bleeding due to liver cirrhosis led to treatment with a transjugular intrahepatic portosystemic shunt (TIPS) in a pregnant woman at 20 weeks' gestation. Fetal radiation exposure was estimated to be less than 10 mSv. The use of a graduated catheter allowed measurement of field size and reliable determination of the patient's entrance dose. Radiation exposure of an approximated fetal dosage of 5.2 mSv did not justify abortion for medical reasons. Therefore, TIPS procedure is not generally contraindicated during pregnancy itself. TIPS placement may be a therapeutic option related to the severity of the underlying maternal disease, after radiation exposure of the fetus has been estimated.

Interventional magnetic resonance. Initial clinical experience with a 1.5-tesla magnetic resonance system combined with c-arm fluoroscopy.

RATIONALE AND OBJECTIVES: The authors evaluate the feasibility of performing magnetic resonance (MR) procedures on a 1.5-tesla (T) system combined with conventional c-arm fluoroscopy. METHODS: A 1.5-T MR imaging system was combined with a conventional c-arm fluoroscopy unit in one room. The two systems were connected via a floating table top. Twenty-six interventional procedures (biopsies, MR-portography, percutaneous alcohol injection, laser ablation, fluid aspiration, and breast marking) were performed in 22 patients under MR, fluoroscopic control, or both. For MR guidance, fast gradient echo sequences were used, initiated from a panel at the front of the magnet. Images were displayed on an liquid crystal display screen positioned on the magnet. RESULTS: All MR-guided procedures were performed successfully without complications. The addition of c-arm fluoroscopy was useful for bone interventions and MR-portography. All diagnostic biopsies yielded sufficient amounts of tissue for histologic diagnosis. In breast lesions, the target identified on dynamic MR imaging was marked correctly in each case. In interstitial laser thermotherapy the laser effect could be visualized, and in percutaneous ethanol injection the distribution of the alcohol could be seen. Both imaging systems worked without image distortions and high-quality MR images were obtained. CONCLUSIONS: The combination of a 1.5-T MR imager with a c-arm fluoroscopy system seems to be a promising technical solution for performing interventional MR procedures.

Quality control of bioprosthetic heart valves by means of holographic interferometry.

BACKGROUND AND AIMS OF THE STUDY: Limited durability of porcine bioprostheses is mainly caused by the progressive development of calcification. We tested the hypothesis that hidden tissue anomalies or unfavorable stress concentrations of commercially available bioprostheses may lead to later calcification and dysfunction. Application of holographic interferometry for non-destructive testing of biological heart valves enables a full-field analysis of heart valves and reveals deformation irregularities of valve tissue. MATERIAL AND METHODS: We developed an accelerated calcification protocol for bioprosthetic heart valves including an accelerated pulsatile valve tester for simultaneous testing of 10 heart valves under identical conditions and a rapid synthetic calcification fluid containing a final Ca x P of 130 (mg/dl)2 in barbital buffer solution. Ten porcine bioprostheses (St. Jude Medical, Bioimplant) were assessed by holographic interferometry and subjected to the pulsatile accelerated calcification process. Distribution and amount of calcification was evaluated by microradiography after 12 x 10(6) and 19 x 10(6) cycles, respectively. Areas of irregular fringe patterns detected by holography as well as areas of calcification were calculated and compared using a personal computer. RESULTS: All tested bioprostheses had localized or extended areas with holographic irregularities and the accelerated valve testing protocol resulted in even macroscopically visible calcifications at various sites. Comparative analysis of the obtained microradiographs revealed that 74.2% +/- 6.0% of calcified leaflet areas lay within the previously detected holographic anomalies. CONCLUSIONS: Our first results show a strong correlation between holographic anomalies and calcification of porcine bioprostheses. We conclude that suitable methods for evaluation and quality control of bioprosthetic heart valves are available and seem to be predictive with regard to valve calcification.

[The potentials of digital image-intensifier radiography exemplified by digital spot imaging (DSI)]. / Möglichkeiten der digitalen Bildverstärkerradiographie am Beispiel des Digital Spot Imaging (DSI).

PURPOSE: We performed a comparative study of digitally and conventionally acquired images in gastrointestinal examinations. MATERIAL AND METHODS: Radiation dose and spatial resolution were determined in a water phantom. In 676 examinations with either conventional or digital imaging (system: Diagnost 76, DSI) the number of images and the duration of the fluoroscopy time were compared. 101 examinations with digital as well as conventional documentation were evaluated by using 5 criteria describing the diagnostic performance. RESULTS: The entrance dose of the DSI is 12% to 36% of the film/screen system and the spatial resolution of the DSI may be better than that of a film/screen system with a speed of 200. The fluoroscopy time shows no significant difference between DSI and the film/screen technique. In 2 of 4 examination modes significantly more images were produced by the DSI. With exception of the criterion of edge sharpness, DSI yields a significantly inferior assessment compared with the film/screen technique. CONCLUSION: The DSI system was well integrated in the daily routine of gastrointestinal examinations. Low dose imaging, direct availability of images and dynamic studies with a frame rate up to 8 images per second are the advantages of the DSI. The lower spatial resolution in some cases is a diagnostic disadvantage that can reduce the diagnostic information.

[A new concept for rational emergency diagnosis of polytrauma patients]. / Neues Konzept zur rationellen Notfalldiagnostik polytraumatisierter Patienten.

To optimize the emergency care of patients with multiple injuries, a special emergency room with integrated radiological equipment has been developed. It consists of a linear array of a computed tomography system, a mobile C-arm with an integrated scattered radiation grid for conventional films and a C-arm fluorographic system. The intent is to avoid delay caused by transport and repositioning of the patient. It enables all necessary diagnostic procedures to be performed within a minimal amount of time. If there are no emergency patients, the room can be divided by a sliding door and the equipment can be used separately.

Gadolinium-enhanced T1-weighted versus T2-weighted imaging of scrotal disorders: is there an indication for MR imaging?

To evaluate the use of gadopentetate dimeglumine in magnetic resonance (MR) imaging of scrotal disorders, the clinical, ultrasound, and MR imaging data of 29 patients (age range, 19-75 years) with various intra- and extratesticular disorders were retrospectively analyzed. T1- and T2-weighted spin-echo images (T1-T2 group) were compared with T1-weighted spin-echo images before and after intravenous administration of gadopentetate dimeglumine (T1-Gd group). A receiver operating characteristic (ROC) analysis of the findings was undertaken. Better contrast between tumor and parenchyma and a clearer demonstration of the tunica albuginea were noted in the T1-T2 group (although not of diagnostic relevance). ROC analysis revealed no differences between the two imaging groups in the diagnosis of tumor, trauma, hydrocele, or hemorrhage; however, epididymitis was diagnosed more easily with contrast enhancement (0.8834 vs 0.7759, P = .04) and the diagnosis of orchitis was expressed more strongly (0.8221 vs 0.7184, P = .17). Four of the five observers were more confident in making the diagnosis with contrast enhancement. With MR imaging, the diagnosis was correctly suggested in three patients in whom clinical and ultrasound data were inconclusive. Gadolinium-enhanced MR imaging gives additional information in scrotal disorders and facilitates diagnosis. It may be helpful when findings at physical examination and ultrasound differ and when plain T1- and T2-weighted images are equivocal.

[Effect of ambient lighting on the diagnostic efficiency of display screen workplaces]. / Einfluss der Raumbeleuchtung auf die diagnostische Leistung an Bildschirmarbeitsplätzen.

The aim of our study was to determine the influence of ambient lighting conditions on the diagnostic performance when using digital reporting work-stations. We acquired 15 normal and 30 fractured porcine femurs using a storage phosphor system. All images were demonstrated on a high-quality image display under optimised (128 lx) and non-optimised (450 lx) ambient lighting conditions and on a conventional viewing-box under non-optimised conditions (450 lx). Results were analysed using ROC-statistics. The area under the ROC-curve was 0.895 for optimised conditions and 0.684 for non-optimised conditions using digital displays and 0.849 for the conventional viewing-box. The difference in diagnostic performance between optimised and non-optimised conditions using a digital display was highly significant (p < 0.001). Our results emphasise the importance of adequate surrounding lighting conditions for radiologic diagnostic performance, particularly for the use of digital reporting consoles.

[Computer-assisted speech recognition and display of x-ray findings]. / Computergestützte Spracherkennung und Ausdruck von Röntgenbefunden.

A voice recognition system, called Tangora, has been designed for the German language; its prototype has been tested to assess its clinical usefulness for radiological reporting. Its technical vocabulary consists of 20,000 words. The system recognises words spoken provided short pauses are inserted. The Tangora system was compared with conventional methods of dictation, using 68 radiological reports. The work necessary for each system was analysed. The average time taken by the Tangora system per report was 671 seconds compared with 182 seconds for conventional dictation but improvements in the speed of the new system for radiological reporting is to be expected.

Comparative evaluation of digital radiography versus conventional radiography of fractured skulls.

OBJECTIVES: The authors assessed the relative efficacy of conventional and digital storage-phosphor radiographs for the detection of skull fractures. METHODS: Fifty conventional film-screen radiographs (FSR) and 50 digital storage-phosphor radiographs (DR) with 66 fractures were compared. Five radiologists evaluated image quality and fracture detectability. The results were analyzed by receiver operating characteristic (ROC) curve analysis. RESULTS: With a standard exposure, the ability to evaluate skull fractures was equally good with either technique (ROC area for DR, 0.8954; for FSR, 0.8870). Digital radiography was superior in evaluating nasal bone. For petrosal bone, the DR image simulates an underexposure. This disadvantage compared with FSR can be compensated by image postprocessing. CONCLUSION: In evaluation of skull fractures, radiologists performance with DR is equivalent to FSR.

Digital radiography versus conventional radiography for the detection of a skull fracture under varying exposure parameters.

RATIONALE AND OBJECTIVES: The effect of varying exposure parameters on the detectability of a fracture with digital and conventional radiography were examined. METHODS: A macerated fractured skull was imaged by film-screen radiography (FSR) and digital storage phosphor radiography (DR) with various exposure values. Five radiologists traced the course of a fracture line. The length of the fracture was reported and the results were analyzed by Student's t test for paired samples. RESULTS: At 35% of the conventional radiation dose, the standard DR screen displayed an average of 48% of the fracture length. The difference from the conventional image (45%) was not significant in this case. An increase of the dose to ten times the conventional dose (250 mAs) yielded no significant improvement in the detectability of the length of the fracture (51%). CONCLUSIONS: This experiment shows that with use of the DR with the standard screen, a dose reduction of approximately 35% appears to be possible without any resulting loss of image quality compared to FSR. Use of the high resolution screens should be avoided, since they require a higher incident image dose than standard screens without offering any diagnostic advantages. The image dose of digital radiographs can be roughly estimated based on the digital device sensitivity value. As a rule, the sensitivity value should range between 100 and 200.

Efficiency of a lead-containing tie for radiation protection of the thyroid gland.

During fluoroscopy the examiner is usually protected by a radiation-reducing body shield, leaving the thyroid unprotected. The fact that the thyroid is located in a region of the neck usually covered by the shirt collar led to the idea of designing a tie with lead core, providing easy and "decorative" reduction of the radiation dose. Sonographic examinations were carried out in 20 volunteers (10 men, 10 women) to determine the size of the gland and its coverage by such a tie. The reduction of the surface and organ dose was assessed using film dosimetry with scattered radiation, the body of the examiner being simulated by an Alderson phantom. On average 88% of the thyroid gland surface area was covered. Surface dose was reduced to 1%, and organ dose to 10% of the value without the protection tie.

[Fracture diagnosis with digital luminescence radiography]. / Frakturdiagnostik mit der digitalen Lumineszenzradiographie.

Conventional screen-film radiographs were compared with storage phosphorus images concerning diagnostic performance in traumatologic radiography. We used an image pool of 106 radiographs including 50 conventionally and 56 digitally recorded images. The images were reviewed by four experienced radiologists. Detectability of fractures was coded in a five-point scale of confidence and analysed by ROC statistics. Furthermore the image quality and the optical density was compared. Digital images are superior under difficult exposure conditions and offer advantages by additional image processing and documentation. For some indications (follow-up, functional examination), reduced x-ray exposure is tolerable. The detectability of subtle lesions, which is essential for the primary diagnosis of fractures was significantly better by conventional radiography.

[The renaissance of simultaneous tomography with the fluorescent-film storage system]. / Renaissance der Simultantomographie mit dem Speicherleuchtstoffoliensystem.

The handling, technical and exposure details of digital simultaneous tomography are explained, while particular emphasis is placed on image quality. Selected case reports demonstrate the application of this technique by using the digital storage fluorescent system (Fa. Siemens, Erlangen). Simultaneous tomography with storage fluorescent screens is particularly suitable to demonstrate or exclude osseous findings at the skull, the column and large joints.

[Digital radiography: a new approach in roentgen diagnosis]. / Digitale Radiographie: ein neuer Ansatz in der Röntgendiagnostik.

Digital electronics now play a role in every branch of diagnostic imaging. One of the most recent methods, digital radiography (DR) makes it possible to store and view radiographs in the form of a matrix of discrete values. The present review describes the components needed for DR imaging and archiving as well as the advantages and disadvantages of the system. The use of storage phosphor is hereby of special interest. By enableing the viewer to process the images, it is hoped that DR will open up new possibilities for projection radiography and strengthen its position as a routine method in comparison to other digital imaging systems, e.g. CT. It remains to be seen whether or not DR, as an isolated system, will be widely used. But in any case it represents the missing link in the chain of digital imaging methods and opens new ways of imaging archiving and administration.