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.

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.

Considerations on recombination losses in ionization chambers using pulsed electron beams with beam scanning.

Based on Boag's theory, referring to saturation effects in ionization chambers with pulsed electron beams, we developed a simple method of determining recombination losses. The correction factors for chamber readings result from slope and intercept of a regression line M1/3 = f(M/V) obtained with at least two different chamber voltages, V, and chamber readings, M. The deviation of these correction factors, compared with those of Boag's precise theory, does not exceed +/- 0.5%.

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.

Assessment of left ventricular wall thickness in healed myocardial infarction by magnetic resonance imaging.

The ability of magnetic resonance imaging (MRI) to detect and localize healed myocardial infarction (MI) was assessed. Seventeen consecutive patients with healed MI assessed by biplane contrast ventriculography underwent MRI using oblique imaging planes. Seven normal subjects underwent MRI as controls. In each patient, ventriculography identified regional wall motion abnormalities. MRI, performed with a 0.15-Tesla resistive magnet and oblique imaging planes relating to the left ventricle, detected zones of regional wall thinning conforming to the wall motion abnormalities localized by ventriculography in 16 patients. In these patients, adjacent areas of intact myocardium were identified in areas shown by ventriculography to be normal. The left ventricular wall thickness at the site of MI was significantly less than adjacent noninfarcted myocardium (p less than 0.001) and normal hearts (p less than 10(-6)). The ratio of the thickness of the infarct to adjacent normal wall averaged 0.40 (range 0.22 to 0.62). MRI could differentiate healed MI from adjacent noninfarcted myocardium and normal hearts.

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.

Clinical investigations on blood perfusion in human malignancies of the pelvis and abdomen: significance for tumor therapy.

Blood flow of deep pelvic and abdominal tumors was investigated with the thermal clearance method, dynamic CT and dynamic MRI. There are good correlations between the measurement values obtained by these methods. A low flow was observed in rectal cancer and soft tissue sarcoma in contrast to pancreatic cancer and hypernephroma. The temperature increase induced by regional hyperthermia was dependent on the individual tumor blood flow. Dynamic CT can be used pretherapeutically and predict the quality of a heat treatment, which is important with regard to concepts consisting in radiotherapy or chemotherapy plus hyperthermia.

Musculoskeletal disorders as determinants of disability in Finns aged 30 years or more.

The relationship between disability and various musculoskeletal disorders was investigated in 7217 men and women representative of the Finnish population aged 30 years or more. They participated in the Mini-Finland Health Survey and were first screened by interview and questionnaire about limitations in daily activities. The outcome variables were reduced working capacity, an occasional need for assistance in daily activities, and a regular need for assistance in daily activities. In a two-phase medical examination, all cases fulfilling predetermined diagnostic criteria of musculoskeletal, cardiovascular, respiratory and mental disorders and diabetes were recorded independently. In multivariate logistic regression analyses, inflammatory arthritis was the strongest determinant of all forms of disability. Osteoarthritis, especially in the hip, was a strong determinant of both occasional and regular need for assistance, and chronic low back pain was a strong determinant of reduced working capacity and occasional need for assistance among those aged 30-64 years. Other musculoskeletal disorders also determined the prevalence disability, but these relationships were reduced by taking comorbidity into account. A low level of education and a low (less than 20 kg/m2) or very high (at least 35 kg/m2) body mass index represented independent determinants of all forms of disability, and a history of physically strenuous work an independent determinant of reduced working capacity, when disabling illness was adjusted for. The proportion of all forms of disability attributable to musculoskeletal disorders, in models including, age, sex, other disabling illness and significant non-medical determinants of disability, was close to 20%. The disorders with the highest community impact were chronic low back pain among those aged 30-64, osteoarthritis of the hips and knees and inflammatory arthritis.

Lumbar disc syndrome in Finland.

The prevalence of lumbar disc syndrome (herniated disc or typical sciatica) and its consequences in terms of disability, handicap, and need for medical care were studied as part of the Mini-Finland Health Survey. A sample of 8000 persons representative of the Finnish population aged 30 or over was asked to come for examination, and 7217 (90%) participated. A diagnosis of lumbar disc syndrome based on medical history, symptoms, and standardised physical examination was made for 5.1% of the men and for 3.7% of the women. Half of these patients were assessed to be in need of medical care, over 80% of which was considered to be adequately met. One third of all patients with lumbar disc syndrome had been previously hospitalised for that syndrome, and one fifth of the patients had undergone lumbar surgery. At least slight disability was found in almost 60% of the patients, though severe functional limitations were rare. About 6% of the population's work disability was estimated to be attributable to lumbar disc syndrome.

A new approach to overcome the inconveniences in electron dosimetry associated with the beam scanning technique in linacs.

The therapeutic advantages of scanned electron beams from medical linear accelerators are accompanied by difficulties in electron dosimetry. Owing to short-time dose inhomogeneities in the treatment field, implicit in the system, time-consuming point-by-point measurements of dose distributions are normally required. However, by triggering the measuring time synchronously with the slow scan frequency, the time necessary to record reliable dose distributions can be shortened considerably. The instrumentation for the computer-controlled dosimetry system developed for this task is described. The results of our measurements show that reproducibility in dose within +/- 1% is achievable in less than 6.3 s per point for scanned electron beams.

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.

Evaluation of tumor blood perfusion by dynamic MRI and CT in patients undergoing thermoradiotherapy.

In 18 patients who were treated with combined regional hyperthermia and radiation for recurrent pelvic tumors, blood flow related data were obtained using dynamic computed tomography and dynamic magnetic resonance imaging. The enhancement of contrast material (delta HU) and Gadolinium DTPA (delta SI) over baseline in the early phase (15-30 s) after bolus injection is dependent upon perfusion. With both methods significant differences in global perfusion have been observed between tumor center and tumor periphery. With regard to the mean perfusion values we are able to separate high, medium and low perfused pelvic tumors. Flow rates expressed as delta HU for dynamic CT and delta SI for dynamic MRI show a significant inverse correlation with the achieved steady state temperatures above baseline. Values of enhancement of contrast material higher than 15-35 delta HU or 300-700 delta SI indicate flow rates which were limiting in achieving steady state temperatures higher than 3 degrees C above baseline (core temperature).

Pulsatile flow index for qualitative measurements of blood flow with duplex ultrasound. An experimental study.

We determined the accuracy of Doppler blood flow measurements in an experimental investigation using a tissue-simulating phantom, pulsatile flow pumps and heparinized blood. A new index for qualitative assessment of blood flow, the pulsed flow index (PFI) is described. The PFI takes advantage of the area under the flow velocity curve between the true zero line and the diastolic baseline. Under conditions of continuous flow, the PFI ranged from 0.82 to 0.94 (mean value 0.90). The PFI was found to be relatively independent of the transducer/vessel angle (+/- 8%) and the inter/intra-operator variation was small (+/- 7.5%, or +/- 7%, respectively).

[Flow time analysis in sonographic flow measurements: an in vitro measurement for testing their accuracy]. / Die Laufzeitanalyse in der sonographischen Flussmessung: In-vitro-Messung zur Uberprüfung der Wertigkeit.

Flow-time analysis is a new technique for colour coded sonographic flow measurements. The measurements depend on a pattern of ultrasound pulses and have some significant advantages compared with Doppler procedures. The accuracy of the method and possible sources of error have been studied under experimental conditions. Measurements on continuous blood flow showed a correlation of r > 0.99 for duplex sonography and of r > 0.93 for flow-time analysis. For this method, the colour coding parameters must be optimal in order to achieve high accuracy. Under these conditions quantitative measurement of pulsatile flow also becomes possible during colour mode.

[Computed tomographic assessment of orbital fractures in traumatic damage of the optic nerve]. / Computertomographische Beurteilung von Orbitafrakturen bei traumatischer Schädigung des Nervus opticus.

Ten patients with orbital fractures and optic nerve trauma are reported. Fractures of the optic canal could be demonstrated by computed tomography in six cases and fractures of the orbital apex in another three cases. Surgical decompression of the optic canal was performed in seven cases. Computed tomography enhanced decision for surgery in cases of intraorbital haematoma with exophthalmus and narrowing of the canal by bony fragments, especially in those patients presenting with incomplete or progressive visual disturbance.

[High-resolution 3-D imaging in MR tomographic knee joint diagnosis. Correlation with arthroscopy]. / Hochauflösende 3-D-Bildgebung in der kernspintomographischen Kniegelenksdiagnostik: Korrelation zur Arthroskopie.

84 knee joints were examined by a 3-dimensional MR method and the results correlated with subsequent arthroscopy. The findings showed good demonstration of the normal anatomical structures and excellent reliability for the diagnosis of meniscus tears (sensitivity 91%, specificity 95%), cruciate ligament lesions (sensitivity 90%, specificity 99%) and serious cartilage damage (sensitivity 100%, specificity 100%). Demonstration of mild cartilage damage (sensitivity 60%, specificity 99%) was better than with a spin echo technique but is not yet optimal. It is concluded that, by using a 3-dimensional technique, time-consuming spin echo sequences can be abandoned. Significant advantages of the 3-D method are the speed of the examination, narrow section thickness, marked flexibility in contrast rendering and the ability for multiplanar reconstruction.

[The pulsatile flow index (PFI) in the diagnosis of dysfunctional kidney transplants]. / Der Pulsationsflussindex (PFI) in der Diagnostik dysfunktioneller Nierentransplantate.

In 61 patients (167 examinations) the pulsatile flow index (PFI) was used to diagnose the cause of renal transplant dysfunction. The results were correlated with histology and clinical course and outcome, angiography or quantitative radionuclide renography. Renal transplant rejection was diagnosed by PFI with a sensitivity of 85%. The specificity was 81% and the diagnostic accuracy 83%. The positive predictive value was found to be 76%, whereas the negative predictive value was 89%. In presence of acute tubular necrosis (ATN) the PFI was normal in 89% of examinations and therefore distinguishable from acute rejection.

[The value of dynamic MRT in the perfusion evaluation of pelvic tumors under hyperthermia]. / Uber die Wertigkeit der dynamischen MRT in der Perfusionsbeurteilung von Beckentumoren unter Hyperthermie.

For the purpose of assessing perfusion of deep seated pelvic tumours 22 dynamic MR studies were carried out and correlated with relevant CT studies as well as with the intratumoural distribution of temperature under hyperthermia in different areas. Using changes of signal intensity, dynamic MR could thus distinguish between well and poorly perfused tumours, besides supplying reliable information on inhomogeneities in tumour perfusion. Altogether, a correlation of 0.92 (p < 0.001) was found between MR and CT and 0.72 (p < 0.001) between MR and the steady state determination of intratumoural temperature. Thus, dynamic MR provides prognostic information concerning therapeutic temperatures (> = 42 degrees C) in tumours and therefore their response to hyperthermia.

Changes of soft-tissue water examined with magnetic resonance and electrical impedance tomography: an in vivo experiment.

The purpose of this study was the examination of short-term changes in soft-tissue water under in vivo conditions. In 12 healthy volunteers the water distribution of a selected slice of the lower limb was examined after change of position and rapid infusion of 0.9% saline solution. Two methods were used for data acquisition: magnetic resonance imaging (MRI) (Repetition Time (TR) = 1600 msec, Inversion Time (TI) = 300 msec, Echo Time (TE) = 22 msec) and electrical impedance tomography (EIT). In orthostatic equilibrium all 12 volunteers demonstrated changes of MR signal intensity and resistivity in the range of 12% and 7%, respectively. After infusion, mean changes of signal intensity and resistivity were 7% and 4%, respectively. The overall correlation of MRI and EIT was -0.96 (p < 0.001). Results indicate that inversion recovery sequences are a sensitive method of detecting in vivo changes of water distribution in selected areas of the body.