Karl Schneider

The construction of computer tomographic phantoms and their application in radiology and radiation protection

SummaryIn order to assess human organ doses for risk estimates under natural and man made radiation exposure conditions, human phantoms have to be used. As an improvement to the mathematical anthropomorphic phantoms, a new family of phantoms is proposed, constructed from computer tomographic (CT) data. A technique is developed which allows any physical phantom to be converted into computer files to be used for several applications. The new human phantoms present advantages towards the location and shape of the organs, in particular the hard bone and bone marrow. The CT phantoms were used to construct three dimensional images of high resolution; some examples are given and their potential is discussed. The use of CT phantoms is also demonstrated to assess accurately the proportion of bone marrow in the skeleton. Finally, the use of CT phantoms for Monte Carlo (MC) calculations of doses resulting from various photon exposures in radiology and radiation protection is discussed.

Screening for vesicoureteral reflux in children using real-time sonography

One hundred and ten children, ages 6 days to 14 years, were investigated for vesicoureteral reflux (VUR) using ultrasound before voiding cystourethrography (VCU). Sonographically a VUR was assumed if a retrovesical dilated ureter and/or an increase of the separation of the central renal echo complex (CRC) could be detected. By means of sonography VUR grades III and IV were seen in 100%, grade II in 84% of all cases. There was a false positive rate of 10%. Sonographic reflux study is a sensitive and specific screening and follow-up procedure for VUR.

Computed tomographies and cancer risk in children: a literature overview of CT practices, risk estimations and an epidemiologic cohort study proposal.

Radiation protection is a topic of great public concern and of many scientific investigations, because ionizing radiation is an established risk factor for leukaemia and many solid tumours. Exposure of the public to ionizing radiation includes exposure to background radiation, as well as medical and occupational exposures. A large fraction of the exposure from diagnostic procedures comes from medical imaging. Computed tomography (CT) is the major single contributor of diagnostic radiation exposure. An increase in the use of CTs has been reported over the last decades in many countries. Children have smaller bodies and lower shielding capacities, factors that affect the individual organ doses due to medical imaging. Several risk models have been applied to estimate the cancer burden caused by ionizing radiation from CT. All models predict higher risks for cancer among children exposed to CT as compared to adults. However, the cancer risk associated with CT has not been assessed directly in epidemiological studies. Here, plans are described to conduct an historical cohort study to investigate the cancer incidence in paediatric patients exposed to CT before the age of 15 in Germany. Patients will be recruited from radiology departments of several hospitals. Their individual exposure will be recorded, and time-dependent cumulative organ doses will be calculated. Follow-up for cancer incidence via the German Childhood Cancer Registry will allow computation of standardized incidence ratios using population-based incidence rates for childhood cancer. Dose–response modelling and analyses for subgroups of children based on the indication for and the result of the CT will be performed.

A Cohort Study of Childhood Cancer Incidence after Postnatal Diagnostic X-Ray Exposure

Abstract Hammer, G. P., Seidenbusch, M. C., Schneider, K., Regulla, D. F., Zeeb, H., Spix, C. and Blettner, M. A Cohort Study of Childhood Cancer Incidence after Postnatal Diagnostic X-Ray Exposure. Radiat. Res. 171, 504–512 (2009). Ionizing radiation is an established cause of cancer, yet little is known about the health effects of doses from diagnostic examinations in children. The risk of childhood cancer was studied in a cohort of 92.957 children who had been examined with diagnostic X rays in a large German hospital during 1976–2003. Radiation doses were reconstructed using the individual dose area product and other exposure parameters, together with conversion coefficients developed specifically for the medical devices and standards used at the radiology department. Newly diagnosed cancers occurring between 1980 and 2006 were determined through record linkage to the German Childhood Cancer Registry. The median radiation dose was 7 μSv. Eight-seven incident cases were found in the cohort: 33 leukemia, 13 lymphoma, 10 central nervous system tumors, and 31 other tumors. The standardized incidence ratio (SIR) for all cancers was 0.99 (95% CI: 0.79–1.22). No trend in the incidence of total cancer, leukemia or solid tumors with increasing radiation dose was observed in the SIR analysis or in the multivariate Poisson regression. Risk did not differ significantly in girls and boys. Overall, while no increase in cancer risk with diagnostic radiation was observed, the results are compatible with a broad range of risk estimates.

Deviated trachea in hypoplasia and aplasia of the right lung: Airway obstruction and its release by aortopexy

Three cases of male infants with hypoplasia and aplasia of the right lung and dextrocardia are reported. The infants developed increasing obstructive respiratory distress in the first 4 months of life. In all three cases, there was an opaque right hemithorax with overinflation of the left lung, a posterior deviation of the trachea with pulsatile stenosis, and a posteriorly located aortic arch. Hypoplasia (two cases) or aplasia (one case) of the right pulmonary artery and an absence or a remnant of the right main bronchus were also observed. Associated malformations were esophageal atresia with an abnormal high pouch of the proximal esophagus in case 1, and hypertelorismus syndrome in case 2. Because of severe respiratory distress in all three patients, an aortopexy was performed at the ages of 5 months (one infant) and 10 months (two infants). The obstructive respiratory signs disappeared postoperatively in the following weeks. It has been observed that tracheal stenosis in aplasia or hypoplasia of the right lung may be caused by the dislocated aortic arch. An aortopexy can release the airway compression in such cases. Because of associated malformations, a careful evaluation of the airway and vessels is recommended.

Paediatric fluoroscopy--a survey of children's hospitals in Europe. I. Staffing, frequency of fluoroscopic procedures and investigation technique.

Background. Fluoroscopy is an important, sometimes vital radiological procedure in paediatric patients with high variability in frequency and technique. Objective. To obtain data on paediatric fluoroscopy practice in Europe using a simple questionnaire mailed to 191 childrens hospitals. Results. Eighty-eight radiology departments in 21 European countries participated in the survey. There was great variation in the size of paediatric hospitals in Europe and, consequently, the numbers of staff members (radiographers and radiologists). The total number of fluoroscopy procedures varied widely; the mean value was 1,073 examinations per year. The most frequent fluoroscopic examination was the micturating cystourethrogram, comprising 40 % of total fluoroscopies. For all types of investigations there were enormous differences in the number of spot film images routinely obtained. Only a few departments have prepared protocols for junior doctors or radiographers. Conclusions. Although the number of fluoroscopic investigations per radiologist does not reflect real workload (the difficulty of the investigation was not requested), it can be stated that a considerable percentage of childrens hospitals are understaffed. These results also clearly demonstrate that fluoroscopy guidelines for the most common investigations in paediatric patients are needed to improve the quality of examinations and limit radiation exposure to the patients.

Childhood cancer risk from conventional radiographic examinations for selected referral criteria: results from a large cohort study.

OBJECTIVEnLittle is known about the long-term effects of exposure to diagnostic ionizing radiation in childhood. Current estimates are made with models derived mainly from studies of atomic bomb survivors, a population that differs from todays patients in many respects.nnnMATERIALS AND METHODSnWe analyzed the cancer incidence among children who underwent diagnostic x-ray exposures between 1976 and 2003 in a large German university hospital. We reconstructed individual radiation doses for each examination and sorted results by groups of referral criteria for all cancers combined, solid tumors, and leukemia and lymphoma combined.nnnRESULTSnA total of 68 incidence cancer cases between 1980 and 2006 were identified in a 78,527-patient cohort in the German childhood cancer registry: 28 leukemia, nine lymphoma, six tumors of the CNS, and 25 other tumors. The standardized incidence ratio for all cancers was 0.97 (95% CI, 0.75-1.23). Dose-response relations were analyzed by multivariable Poisson regression. Although the cancer incidence risk differed by initial referral criterion for radiographic examination, a positive dose-response relation was observed in five patients with endocrine or metabolic disease.nnnCONCLUSIONnOverall, we observed no increase in cancer risk among children and youths with very low radiation doses from diagnostic radiation, which is compatible with model calculations. The growing use of CT warrants further studies to assess associated cancer risk. Our work is an early contribution of epidemiologic data for quantifying these risks among young patients.

Prospective randomised multicentre trial with the birth trainer EPI‐NO® for the prevention of perineal trauma

Background: In several non‐randomised trials training with EPI‐NO® increased the rate of intact perineum and decreased episiotomy rates, shortened the second stage of labour and lowered use of pain killers.

Coupling remote sensing observation models and a growth model for improved retrieval of (geo)biophysical information from optical remote sensing data

In the ESA study GeoBIRD (Geo- and Biophysical Information from Remote Sensing Data) the process-based vegetation growth model PROMET-V was coupled to the GeoSAIL canopy reflectance model for the retrieval of spatially distributed biophysical parameters from surface reflectance images derived from Landsat TM data. The raster based PROMET-V model calculates plant growth, water and nitrogen fluxes using meteorological data, a land use map, and a soil map. In this study the total leaf area index (LAI), the fraction brown leaf area and surface soil moisture, as modelled in PROMET-V, were used in conjunction with GeoSAIL, to model the surface reflectance spectra. Besides modelling the canopy reflectance GeoSAIL, also accounts for the soil reflectance using the dry soil spectrum and surface moisture as inputs. By minimising the difference between observed reflectance spectra derived from LANDSAT images and the modelled surface reflectance spectra, the total LAI, fraction of brown leaves and surface soil moisture were estimated. This optimisation process is constrained by physically and plant physiologically meaningful boundaries in order to obtain valid results and accelerate the process. By re-initialising the PROMET-V model, the retrieved and simulated LAI were matched. This leads to improved model results regarding biomass and yield.

Pulmonary sling: Morphological findings. Pre- and postoperative course

Pulmonary sling (PS) is a congenital condition in which the left pulmonary artery (LPA) arises from the right pulmonary artery (RPA), forming a sling around the trachea causing tracheal compression. The incidence is not so rare as initially thought. Symptoms of severe airway obstruction often begin in the newborn or young infant. Echo-colour-Doppler may reveal the PS but emphysema can mask the typical findings. Deviation of fluid-filled lungs may be detected prenatally. Chest radiographs show unusual air distribution, deviation of heart and mediastinum and altered tracheobronchial angles. Bronchography and bronchoscopy demonstrate the high incidence of associated tracheal anomalies such as cartilagenous rings and long tracheal stenosis. Anterior oesophageal indentation is not always seen in the oesophogram. Magnetic resonance imaging (MRI) and computed tomography (CT) reveal the PS, but cautious interpretation is necessary because of different levels of the anomalous LPA. PS and associated cardiovascular malformations can be clearly detected by angiography. Associated extrathoracic anomalies are common. Early diagnosis and therapy of PS is mandatory and consists of reimplantation of the LPA into the pulmonary trunk and division of the ligamentum arteriosum. The postoperative course may be cumbersome necessitating bronchological interventions. Tracheal resection may be necessary but restenosis is frequent. A one-stage repair has been proposed in such cases and was successfully done in a few reported cases. Relief of respiratory obstruction is often complete when there are no associated tracheobronchial anomalies. Late postoperative course is favourable but respiratory obstructive attacks may occur with decreasing incidence over time and tracheal growth.