Dose calculations in aircrafts after Fukushima nuclear power plant accident - Preliminary study for aviation operations.

There is little information to decision support in air traffic management in case of nuclear releases into the atmosphere. In this paper, the dose estimation due to both, external exposure (i.e. cloud immersion, deposition inside and outside the aircraft), and due to internal exposure (i.e, inhalation of radionuclides inside the aircraft) to passengers and crew is calculated for a worst-case emergency scenario. The doses are calculated for different radionuclides and activities. Calculations are mainly considered according to International Commission on Radiological Protection (ICRP) recommendations and Monte Carlo simulations. In addition, a discussion on potential detectors installed inside the aircraft for monitoring the aerosol concentration and the ambient dose equivalent rate, H*(10), for during-flight monitoring and early warning is provided together with the evaluation of a response of a generic detector. The results show that the probability that a catastrophic nuclear accident would produce significant radiological doses to the passengers and crew of an aircraft is very low. In the worst-case scenarios studied, the maximum estimated effective dose was about 1 mSv during take-off or landing operations, which is the recommended yearly threshold for the public. However, in order to follow the ALARA (As Low As Reasonably Achievable) criteria and to avoid aircraft contamination, the installation of radiological detectors is considered. This would, on one hand help the pilot or corresponding decision maker to decide about the potential change of the route and, on the other, allow for gathering of 4D data for future studies.

Evaluation of an OSCE assessment tool for abdominal ultrasound courses.

PURPOSE: The purpose of this study was the conception and evaluation of a standardized and reliable assessment tool in the OSCE format to measure the performance and practical skills of abdominal ultrasound users in PGME. MATERIALS AND METHODS: The design, logistics, pacing and the choice of tested competencies of a rotating OSCE parcours, as well as the options for quality control using detailed checklists versus global rating scales and different approaches to the training of the involved raters are described. Over the last 15 years the parcours has undergone incremental improvement and has been used in final examinations of abdominal ultrasound courses with approximately 5000 medical students and 2000 residents and fellows. For evaluation, all item difficulties and discrimination coefficients of the individual stations and the reliability (Cronbach's alpha) were calculated for the last 626 assessments. RESULTS: All 14 hands-on stations showed discrimination coefficients from 0.31 to 0.65 (mean 0.48; SD 0.09). The 13 diagram stations showed mean values of 0.50 (SD 0.16). Data analysis revealed mean homogeneous item difficulties of 0.78 (SD 0.02) and 0.62 (SD 0.04), respectively. Cronbach's alpha was 0.69 with five stations and reached values above 0.8 when more than 8 stations are combined in one parcours. CONCLUSION: The homogeneous distribution of item difficulties provides an opportunity for designing different OSCE versions with different levels of reliability. Several options to adjust the cut-off values, the choice of the examined contents and factors that influence the examinees' acceptance of this assessment tool for PGME or CME ultrasound courses are discussed. Overall, the values of reliability and accuracy of this assessment tool are high enough to be used also for high-stakes examinations in the field of abdominal ultrasound.

[Structure, methodology and ethics of German commissions on living organ donation]. / Struktur, Arbeitsweise und Ethik von Lebendspendekommissionen. Ergebnisse einer bundesweiten Befragung.

Living organ donation is a medically established and morally acceptable method of transplantation. According to German Transplantation Law, an expert review by a local "Commission on Living Donation" (Lebendspendekommission, LSK) is required before transplantation. The legal task of this review is to ensure a voluntary decision by the donor and to rule out illegal trading of organs. Results from a national survey among all LSKs show that the process of review and assessment varies considerably among German LSKs. Most of them carry out a compulsory hearing of every potential donor, but this is omitted by some LSKs in a number of cases. Only 60% of all LSKs feel confident to determine donors' free will and protect their self-determination. Only 33% claim to be able to recognise illegal trading of organs. The LSKs even disagree on the exact borderline between legal incentives and illegal commerce. An expansion of living donation by financial incentives, pool-donation or crossover donation is supported only by a minority of German LSKs. The article argues in favour of establishing national standards for the process of LSK-reviews in order to foster procedural ethics and trustworthiness in the field of living organ donation.

[Mechanical stimulation of venous blood flow in below-the-knee plaster cast]. / Mechanische Förderung des venösen Rückflusses im Unterschenkelgipsverband.

Physical methods became recently more important as an alternative to anticoagulation for prophylaxis of thromboembolism and were studied for their efficacy. The AV-impulse-system proved efficient in reducing thromboembolic complications in patients undergoing hip surgery by increasing the return of venous blood in the deep veins of the leg. In a preclinical trial we studied the influence of the AV-impulse-system and of active forefoot movement on venous blood return in 12 lower extremities of 6 healthy individuals immobilized in below the knee plaster casts. Our results show a significant increase in venous blood flow caused by the AV-impulse-system (p < 0.05) and by active forefoot movements (p < 0.05). Prevention of thromboembolic complications in trauma and orthopaedic patients immobilized in plaster cast seems possible by using the AV-impulse-system which significantly increases the venous blood flow independent from patient compliance.

Dosimetry of rotational partial-skin electron irradiation.

BACKGROUND AND PURPOSE: Often, the most appropriate treatment for superficially and extensively spreading tumors of the skin is to use electron irradiation at enlarged distances. Rotational skin electron irradiation is a proven method for the treatment of the entire skin surface. We here report modifications of this technique in the set-up of partial-skin electron irradiation and the results of dosimetric examinations with regard to optimal shielding, dose profiles and depth dose curves under various irradiation conditions. MATERIALS AND METHODS: Irradiation was performed using electron beams with nominal energies of 6 MeV from a linear accelerator. The phantom was located on a rotating platform at a source-surface distance SSD=300 cm. A horizontal slit aperture (height: 32 cm) within a 2 cm thick polymethylmethacrylate (PMMA) shielding plate near the phantom was used to define the size of the irradiated region. Influences on dose distributions due to scattering processes on the PMMA edges were investigated using a flat ionization chamber and films. Absolute dose measurements and film calibration were made with the flat chamber. The quality of bremsstrahlung radiation behind the shielding was determined with a thimble ionization chamber in the phantom. RESULTS AND CONCLUSIONS: The results of rotational partial-skin electron irradiation reveal some of the investigated shielding geometries to be optimal. Depth dose distributions and dose rates correspond to the results obtained in total skin electron rotational irradiation. It is possible to apply the dose superficially in the first millimeters of the skin; the dose maximum is located at a depth of 0-2 mm, the 80% isodose at 9 mm. The amount of bremsstrahlung contamination is 2.5%. The local amount of absorbed dose per monitor unit depends strongly on patient/phantom cross-section geometry. At our institute, rotational partial-skin electron irradiation was implemented into clinical routine in 1997.

A simple and reliable method to simulate multileaf-plans.

To combine conformity of the irradiation with time effectiveness during treatment, the use of multileaf collimators has become more and more common. However, the simulation of the leaf positions is rather difficult compared with metal blocks. We developed a new method, utilizing an acrylic template in which the contour produced by the leaves is machined in the form of a 1 mm groove by a computerized numerically controlled milling machine. This template is then inserted into a mount attached to the simulator. The main advantages are the errorfree, direct communication from the therapy planning system to the milling machine via a network, the possibility to transfer the contour to the skin, and the documentation on the simulation film. The use of templates is reliable and, e.g. the costs of the materials are lower than for block simulation.

Paranasal sinuses and nasopharynx CT and MRI.

Neoplastic disease of the nose, paranasal sinuses, the nasopharynx and the parapharyngeal space requires thorough assessment of location and extent in order to plan appropriate treatment. CT allows the deep soft tissue planes to be evaluated and provides a complement to the physical examination. It is especially helpful in regions involving thin bony structures (paranasal sinuses, orbita); here CT performs better than MRI. MRI possesses many advantages over other imaging modalities caused by its excellent tissue contrast. In evaluating regions involving predominantly soft tissue structures (ec nasopharynx and parapharyngeal space) MRI is superior to CT. The possibility to obtain strictly consecutive volume data sets with spiral CT or 3D MRI offer excellent perspectives to visualize the data via 2D or 3D postprocessing. Because head and neck tumors reside in a complex area, having a 3D model of the anatomical features may assist in the delineation of pathology. Data sets may be transferred directly into computer systems and thus be used in computer assisted surgery.

Comparison of calibration procedures for 192Ir high-dose-rate brachytherapy sources.

PURPOSE: To compare the efficacy of different calibration procedures for 192Ir high-dose-rate (HDR) brachytherapy sources and to determine their suitability in clinical practice. In addition the manufacturer's calibration is compared with our experimental measurements so that the accuracy of the source strength on the manufacturer certificate which is supplied with each new 192Ir source can be accessed. METHODS AND MATERIALS: We compared three types of calibration system: well-type chambers (HDR-1000 and SDS), cylindrical phantom, and plate phantom. The total number of measurements we obtained was 365. The number of sources used for the calibration procedure comparison was 20 and the number used for comparison with the manufacturer's calibration was 46. This study was made during the period 1989-1997. Also, Physikalisch-Technische Bundesanstalt (PTB) calibrated one of our sources using their PTB protocol so that the results could be compared with our own. RESULTS: The sensitivity of each system on scattering from the room walls was studied. It was found that different minimum lateral distances from the walls were required for the different systems tested: 15 cm and 25 cm for the well-type chambers, 75 cm for the cylindrical phantom, and 13 cm for the plate phantom. The minimum thickness required to reach phantom scattering saturation for the plate phantom setup is 24 cm. The influence of the applicator material used in the calibration setup was found to be 1.7% for the stainless steel dosimetry applicator compared to the plastic 5F applicator. The accuracy of source positioning within the applicator can lead to dosimetric errors of +/-1.2% for the radial distance of 8.0 cm used with both solid phantoms. The change in the response for both well-type chambers was only 0.1% for changes in the source position within +/-7.5 mm around the response peak. Good agreement was found between all dosimetry systems included in our study. Taking the HDR-1000 well-type chamber results as a reference, we observed percentage root mean square (RMS) values of 0.11% for the SDS well-type chamber, 0.44% for the cylindrical, and 0.60% for the plate phantom setup. A comparison of our results using the cylindrical phantom with those of the manufacturer showed a percentage RMS value of 3.3% with a percentage fractional error range of -13.0% to +6.0%. The comparison of our calibration results with those of PTB gave deviations less than 0.4% for all systems. CONCLUSIONS: Our results have shown that with careful use of all calibration system protocols an accurate determination of source strength can be obtained. However, the manufacturer's calibration is not accurate enough on its own, and it should be mandatory for clinics to always measure the source strength of newly delivered 192Ir brachytherapy sources. The influence of the applicator material, metal or plastic, should always be taken into account.

[A multileaf collimator: additional quality assurance in a GE linear accelerator]. / Multileafkollimator: erweiterte Qualitätssicherung an einem GE-Linearbeschleuniger.

BACKGROUND: In comparison to a conventional collimator, a multileaf collimator demands a great deal of quality assurance procedures due to its large number of leaves. A concept for daily quality assurance is presented, mainly concerning the positioning accuracy of the leaves. MATERIAL AND METHODS: Two leaf configurations including maximal opening as well as overtravel of single leaves, at a maximal opening of the jaws, are transmitted online in daily exchange from our record- and verify system to the linac. Aiming at a special test phantom a visual control of the positioning accuracy is performed. The leaf positioning is documented by an electronic portal imaging system and is compared with a reference shot by superposition of a grid. RESULTS: This method of quality assurance offers a fast and effective possibility to guarantee the proper function of the whole system by simulating the routine treatment situation. CONCLUSIONS: Compared to a conventional collimator only a slightly greater workload is needed for quality assurance of a multileaf collimator.

Changes of sonographic, magnetic resonance tomographic, electromyographic, and histopathologic findings within a 2-month period of examinations after experimental muscle denervation.

This study compares sonographical, histopathological, magnetic resonance imaging (MRI), and electromyographical (EMG) findings following acute muscle denervation. We performed an experimental denervation of the supraspinatus and infraspinatus muscles on 35 New Zealand white rabbits by segment resection of the suprascapular nerve. The sonographical appearance of the supraspinatus muscle was followed and documented at short time intervals within a 2-month follow-up period. The sonographical, histopathological, and MRI changes due to denervation suggest a regular pattern. Apart from the reduction of the muscle diameter, there were considerable sonographical signs of denervation with an increase of echointensity and inhomogenicity of echotexture that appeared on day 14 after injury, and progressed continuously with time. MRI revealed a remarkable increase in signal intensity 3 weeks after denervation and reproducible T2 times. Pathological spontaneous activity on EMG could also be detected from day 14 after injury. Conventional histopathological staining methods (H&E, NADH, ATPase, basic and acid phosphatase) confirmed denervation and absence of reinnervation. The first nonspecific histopathological changes were seen 11 days after denervation in the form of moderately atrophic fibers. Typical histopathological signs of denervation appeared 3 weeks after nerve dissection. In summary, EMG, ultrasound, MRI, and histopathology each showed first abnormalities after about 2 weeks. In addition to EMG, sonography and MRI can document the course of muscle atrophy and mesenchymal abnormalities in neurogenic muscle lesions.

Imaging of the normal and pathological orbit.

Computerized techniques (CT and MRI) allow precise delineation of orbital anatomy and abnormalities. Orbital tumors are nicely depicted by these methods; various examples are illustrated in this article, with discussion of the respective impact of CT and MRI. Orbital inflammation and foreign bodies usually represent radiologic emergencies, prompting use of CT (frequently) or MRI (occasionally). Digital subtraction angiography (DSA) is indicated for diagnosis of vascular changes (mainly carotid-cavernous fistula, aneurysms, angiomas, Rendu-Osler disease). Angiography is usually done to ascertain the possibility of an interventional procedure. Orbital vascular interventions include re-canalization of occluded vessels, and embolization of pathologic (tumorous or post-traumatic) vessels.

[Rational imaging strategies in laryngeal diseases]. / Rationelle bildgebende Strategien bei Kehlkopferkrankungen.

Clinical information is indispensable for swift and cost-effective clarification of diseases of the larynx. While quality clarification of neurological changes in the area of the posterior cranial fossa and in the course of the vagus nerve as a cause of glottis malfunction is possible with MRI, localized disease of the larynx can more effectively be assessed with low-artifact CT. In the particularly difficult assessment of the post-operative larynx, a recurrence can be diagnosed only after a baseline study has been carried out after the end of therapy. With knowledge of the pretherapeutic findings, the findings immediately post-therapy, and the operation technique used, the optimal CT examination, which can be carried out quickly, will be able to provide more information about recurrence.

ACL reconstruction by patellar tendon. A comparison of length by magnetic resonance imaging.

In 50 knees the length of the anterior cruciate ligament (ACL), the patellar tendon, and the distance between the tibial tuberosity and the femoral origin of the ACL were evaluated by means of three-dimensional magnetic resonance imaging (MRI), which permits subsequent reconstruction of any sectional view. The measurements showed that the patellar tendon was always markedly longer than the ACL (mean 14.4 mm), but always shorter than the distance between the tibial tuberosity and the femoral insertion of the ACL (mean 19.2 mm). The mean lengths of the ACL and the patellar tendon were 38.2 mm and 52.6 mm, respectively. The mean distance between the femoral ACL origin and the tibial insertion of the patellar tendon was 71.8 mm. These results demonstrate that a distally based patellar tendon autograft alone (with the patellar bone block but without extension into the periosteum of the patella or the quadriceps tendon) cannot be placed anatomically correctly to the isometric femoral insertion of the ACL. When the patellar tendon is used for ACL reconstruction, it must be implanted as a free autograft. Nevertheless, considerable variations of length must be taken into account.

Sonography and MRI of experimental muscle injuries.

After sonographical examination with a 7.5-MHz linear array scanner, we created an experimental muscle injury of known site and location on 28 New Zealand white rabbits by stabbing them with a scalpel in the supraspinatus muscle. The changes in the healing process were followed and documented by sonography and magnetic resonance imaging (MRI) before and 2, 5, 11, 14, 36 and 64 days after injury. The changes in sonography and MRI followed a regular course. Ultrasound revealed an echo-poor area after injury with ever increasing echogenicity from the 14th day. Strong reflexes were found after 2 months. MRI showed few changes, only a slight increase of signal intensity, but a characteristic curve of calculated T2-times (a program of the MRI software). The interpretation of the sonographical picture in histopathological terms remained limited. The development of a hematoma and of fibrous scars can be followed up by sonography, but it is not possible to determine the point of time after injury very accurately. Nevertheless, sonography is a method of great value in the diagnosis of muscle injuries and, given certain limits, in the follow-up of the healing process, too. The significance of MRI can be increased by calculations with the implemented software, as in our study calculated T2-times produced a characteristic curve reflecting the shift of fluids after muscle injury.

[A quality assurance program of simulators in radiation therapy. 2. Extent and results of long-term quality assurance test on a therapy simulator]. / Ein Qualitätssicherungsprogramm für Simulatoren in der Strahlentherapie. Teil 2: Umfang und Ergebnisse langjähriger Konstanzprüfungen an einem Therapiesimulator.

BACKGROUND: Since 1990 we follow a quality assurance program with periodical tests of functional performance values of a 16-year-old simulator. MATERIAL AND METHOD: For this purpose we adopted and modified German standards for quality assurance on linear accelerators and international standards elaborated for simulators (International Electrotechnical Commission). The tests are subdivided into daily visual checks (light field indication, optical distance indicator, isocentre-indicating devices, indication of gantry and collimator angles) and monthly and annually tests of relevant simulator parameters. Some important examples demonstrate the small variation of parameters over 6 years: position of the light field centre when rotating the collimator, diameter of the isocentre circle when rotating the gantry, accuracy of the isocentre indication device, and coincidence of light field and simulated radiation field. RESULTS: As an important result we can state, that by these rigid periodic tests it was possible to detect and compensate deteriorations of simulators quality rapidly. CONCLUSIONS: Technical improvements and specific calling-in of maintenance personnel whenever felt appropriate provided performance characteristics of our old simulator which are required by international recommendations as a basis for modern radiotherapy.

[Promoting venous return in plaster cast by AV impulse system. A preclinical study]. / Förderung des venösen Rückstroms im Liegegipsverband durch das AV-Impulssystem. Eine präklinische Untersuchung.

A new pneumatic compression pump--the AV-impulse system--causes increased return of venous blood from the lower limbs to the heart and increases total blood flow in the lower limbs by emptying the plantar venous plexus. Up to date there exist no experiences with using this system in plaster cast. We studied the maximum venous blood flow, the venous blood flow per minute and the venous diameters above the popliteal and femoral vein by duplexsonography in 12 lower limbs of 6 healthy persons before and after applying below-the-knee plaster casts. After applying the plaster cast we observed a slight increase in venous diameter (p = 0.02). By using the AV-impulse-system we observed a significant increase in maximum venous blood flow and venous blood flow per minute (p < 0.05). We demonstrated a significant increase of venous blood return in the deep veins of the lower limbs after applying a lower limb plaster cast by using the AV-impulse-system. These results indicate the possible benefit of using the AV-impulse-system as a physical method of thromboprophylaxis in orthopaedic and trauma patients with plaster cast immobilisation of the leg.

[CT-guided punctures in the area of the spine. The "fluorotechnique" as localization method]. / CT-gesteuerte Punktionen im Wirbelsäulenbereich. Die "Fluorotechnik" als Lokalisationsmethode.

The increased anatomical resolution of the Computed Tomography allows the localized excision of tissue malformation even less than 5 mm in diameter. Within difficult areas of the body, e.g. the spine, it is possible to reach intra- as well as extraosseous lesions with high accuracy. Results and technique of puncture are reported in 31 patients with unclear diagnosis or therapy (Neurolysis). In 24 cases diagnosis was established or therapy was successful, in 2 cases the result was false negative. In 5 cases the tissue was non diagnostic. According to the low number of complications (n = 1) a repeated study would have been possible.

[Magnetic resonance tomography and histopathologic findings after muscle denervation. A comparative animal experiment study during a two month follow-up]. / Kernspintomographische und histopathologische Befunde nach Muskeldenervierungen. Eine vergleichende tierexperimentelle Studie während einer zweimonatigen Verlaufsuntersuchung.

Recently, MRI was described as a method in the diagnosis of changes of muscle after acute neurogenic muscle atrophy. This study was performed to compare MRI results with myopathological findings, to document the appearance of the MRI changes and to check the sensitivity of this method. We performed a segment resection of the suprascapular nerve resulting in a denervation of the supraspinatus and infraspinatus muscles on 18 Newzeeland white rabbits. MRI changes were followed and documented for two months in short periods of time. The results were compared with histological findings. In myopathology and MRI we found systematical changes: Apart from the reduction of the muscle diameter visual assessment revealed increased signal intensities on the 21st and 35th examination day after denervation. On the 2nd, 5th, 11th and 64th examination day signal intensities were normal. The changes were represented by calculated T2 times, too.