[Voiding cystourethrography : Indications, fluoroscopy technique and radiation protection]. / Miktionszysturethrographie : Indikationen, Durchleuchtungstechnik und Strahlenschutz.

BACKGROUND: Voiding cystourethrography continues to be the gold standard in the diagnostics of a wide range of diseases of the urinary tract in children. MATERIAL AND METHODS: Indications, implementation of voiding cystourethrography in terms of preparation, materials used, dealing with the child and the parents as well as the standardized examination technique are presented. In particular, the technical aspects of fluoroscopy devices and criteria for good image quality are discussed. Case studies are used to illustrate the problems of frequent urological diseases. DISCUSSION: The three standard examinations for the detection of vesicoureteral reflux (VUR), radionuclide cystography, contrast-enhanced voiding urosonography and voiding cystourethrography are compared. Their potential for detecting VUR and additional urological pathologies is discussed in detail. Furthermore, the optimized examination technique of voiding cystourethrography is presented. The applicability of the current dose reference values of the German Federal Office for Radiation Protection (BfS) in the daily routine is discussed and the feasibility of the dose reference values is explained.

[Radiation exposure of the eye lens in orthopedics and trauma surgery : A pilot study]. / Strahlenbelastung der Augenlinse in O&U : Eine Pilotstudie.

BACKGROUND: On 27 June 2017 the Act on new regulation of the law for the protection against the harmful effects of ionizing radiation was passed. One of the main innovations in daily surgical practice in the now legally stipulated provisions is the lowering of the eye lens dose to 20 mSv/year (§§ 78, 212 Radiation Protection Act, StrlSchG). MATERIAL AND METHODS: To estimate the level of exposure of the eye lens to ionizing radiation that is to be expected in the course of surgical interventions, the dose that surgeons receive during surgery was determined. For this, the radiation exposure adjacent to the eye lens was measured using a forehead dosimeter while performing surgical interventions over a period of 8 weeks in 2 different operating rooms. RESULTS: As a result, a mean estimated eye lens radiation dose Hp (3) of 190 µSv could be determined during the 2­month study period. Thus, the estimated cumulative radiation dose in 1 year of approximately 1.2 mSv was significantly below the threshold of 20 mSv/year. CONCLUSION: By complying with the common radiation protection measures in the context of operative interventions in orthopedics and trauma surgery, the legal limit value of 20 mSv/year is generally not expected to be exceeded.

TERTIARY X-RADIATION-A PROBLEM FOR STAFF PROTECTION?

The influence of tertiary x-radiation on the radiological staff is widely unknown. Tertiary radiation is caused as the scattered radiation of the patient impacts the walls, floor, ceiling and surrounding air. The question that arises is does tertiary x-radiation provide a relevant contribution to the staff doses. The impact of tertiary radiation was investigated by means of measurements of the personal dose equivalent Hp(10) on an anthropomorphic Alderson Rando male phantom and also on operators/assistants staying in clinical practice. Further, the protective effect of lead foils, especially under tertiary radiation was also investigated. Correlations could be derived for clinical angiographic/interventional procedures between dose area products (DAPs) and dose length products (DLPs) vs. dorsal doses of staff persons. Generally, the staff doses that are a result of tertiary radiation depend on the x-ray energy and range from 0.15 to 0.55% of the scattered radiation impact caused by irradiation of the patient. Hence, a back panel with 0.125-mm lead equivalent is sufficient to protect the staff from tertiary radiation created within the room environment.

[Aspects of radiation protection during chest X-radiography]. / Strahlenhygienische Aspekte bei der Röntgenuntersuchung des Thorax.

BACKGROUND: Radiation safety in conventional X-ray diagnostics is based on the concepts of justification, optimization of an X-ray examination and limitation of the radiation exposure achieved during the examination. Optimization of an X-ray examination has to be considered as a multimodal process in which all technical components of the X-ray equipment have to be adapted to each other and also have to be adapted to the anthropometric characteristics of patients and the clinical indications. OBJECTIVES: In this article the technical components of a conventional pediatric chest X-radiograph are presented, and recommendations for optimizing chest X-rays in children are provided. RESULTS AND DISCUSSION: The following measures are of prime importance: correct x-ray beam limitation, using the posteroanterior projection when possible and not using anti-scatter grids in children under approximately 8 years old. In pediatric radiology chest x-rays that are taken not at the peak of inspiration can also be of some diagnostic significance. Optimization of an X-ray examination inevitably results in the limitation of radiation exposure.

A New Design of a Lead-Acrylic Shield for Staff Dose Reduction in Radial and Femoral Access Coronary Catheterization.

PURPOSE: Today's standard radiation protection during coronary angiography and percutaneous coronary interventions is the combined use of lead acrylic shields and table-mounted lower body protection. Ambient dose measurements, however, have shown that these protection devices need improvement. MATERIALS AND METHODS: Using an anthropomorphic physical phantom, various scenarios were investigated with respect to personnel exposure: a) enlarging the shield b) adding a flexible protective curtain to the bottom side of the shield, and c) application of radioprotective patient drapes. For visualization of the dose reduction effect, Monte Carlo simulations were performed. RESULTS: The flexible curtain in contact with the patient's body reduces the ambient dose rate at the operator's position by up to (87.5% ± 7.1) compared to the situation with the bare shield. The use of both the flexible curtain and the patient drape reduces the ambient dose rate by up to (90.8% ± 7). Similar results were achieved for the assisting personnel when they were positioned next to the operator. In addition, the enlarged shield provides better protection of the head region of tall operators. CONCLUSION: Adding a flexible protective curtain to the bottom side of the shield can protect operators from high doses, especially for body parts which are not protected by lead aprons, e.g. head, and eye lenses. This may be important with respect to lower dose limits for eye lenses in future. The protective effect in real-life working conditions is still being evaluated in an ongoing clinical study. KEY POINTS: Lead acrylic shields need improvement for a better protection of head and eye lenses. An additional flexible lead curtain at the bottom of the shield can considerably reduce the operator dose. Using the additional lead curtain, lighter protection clothing can be worn. Special eye protection may be no longer needed in most applications.

Risk of cancer incidence before the age of 15 years after exposure to ionising radiation from computed tomography: results from a German cohort study.

The aim of this cohort study was to assess the risk of developing cancer, specifically leukaemia, tumours of the central nervous system and lymphoma, before the age of 15 years in children previously exposed to computed tomography (CT) in Germany. Data for children with at least one CT between 1980 and 2010 were abstracted from 20 hospitals. Cancer cases occurring between 1980 and 2010 were identified by stochastic linkage with the German Childhood Cancer Registry (GCCR). For all cases and a sample of non-cases, radiology reports were reviewed to assess the underlying medical conditions at time of the CT. Cases were only included if diagnosis occurred at least 2 years after the first CT and no signs of cancer were recorded in the radiology reports. Standardised incidence ratios (SIR) using incidence rates from the general population were estimated. The cohort included information on 71,073 CT examinations in 44,584 children contributing 161,407 person-years at risk with 46 cases initially identified through linkage with the GCCR. Seven cases had to be excluded due to signs possibly suggestive of cancer at the time of first CT. Overall, more cancer cases were observed (O) than expected (E), but this was mainly driven by unexpected and possibly biased results for lymphomas. For leukaemia, the SIR (SIR = O/E) was 1.72 (95 % CI 0.89-3.01, O = 12), and for CNS tumours, the SIR was 1.35 (95 % CI 0.54-2.78, O = 7). Despite careful examination of the medical information, confounding by indication or reverse causation cannot be ruled out completely and may explain parts of the excess. Furthermore, the CT exposure may have been underestimated as only data from the participating clinics were available. This should be taken into account when interpreting risk estimates.

Systematic survey of the dose enhancement in tissue-equivalent materials facing medium- and high-Z backscatterers exposed to X-rays with energies from 5 to 250 keV.

The present study has been inspired by the results of earlier dose measurements in tissue-equivalent materials adjacent to thin foils of aluminum, copper, tin, gold, and lead. Large dose enhancements have been observed in low-Z materials near the interface when this ensemble was irradiated with X-rays of qualities known from diagnostic radiology. The excess doses have been attributed to photo-, Compton, and Auger electrons released from the metal surfaces. Correspondingly, high enhancements of biological effects have been observed in single cell layers arranged close to gold surfaces. The objective of the present work is to systematically survey, by calculation, the values of the dose enhancement in low-Z media facing backscattering materials with a variety of atomic numbers and over a large range of photon energies. Further parameters to be varied are the distance of the point of interest from the interface and the kind of the low-Z material. The voluminous calculations have been performed using the PHOTCOEF algorithm, a proven set of interpolation functions fitted to long-established Monte Carlo results, for primary photon energies between 5 and 250 keV and for atomic numbers varying over the periodic system up to Z = 100. The calculated results correlate well with our previous experimental results. It is shown that the values of the dose enhancement (a) vary strongly in dependence upon Z and photon energy; (b) have maxima in the energy region from 40 to 60 keV, determined by the K and L edges of the backscattering materials; and (c) are valued up to about 130 for "International Commission on Radiological Protection (ICRP) soft tissue" (soft tissue composition recommended by the ICRP) as the adjacent low-Z material. Maximum dose enhancement associated with the L edge occurs for materials with atomic numbers between 50 and 60, e.g., barium (Z = 56) and iodine (Z = 53). Such materials typically serve as contrast media in medical X-ray diagnostics. The gradual reduction in the dose enhancement with increasing distance from the material interface, owed to the limited ranges of the emitted secondary electrons, has been documented in detail. The discussion is devoted to practical radiological aspects of the dose enhancement phenomenon. Cytogenetic effects in cell layers closely proximate to surfaces of medium-Z materials might vary over two orders of magnitude, because the dose enhancement is accompanied by the earlier observed about twofold increase in the low-dose RBEM at a tissue-to-gold interface.

[Cancer incidence rate after diagnostic X-ray exposure in 1976 - 2003 among patients of a university children's hospital]. / Inzidenz von Kinderkrebs nach Röntgendiagnostik im Patientenkollektiv der Jahre 1976 - 2003 einer Universitäts-Kinderklinik.

PURPOSE: Although the carcinogenic effect of ionizing radiation is well known, knowledge gaps persist on the health effects of low-dose radiation, especially in children. The cancer incidence rate in a cohort of 92,957 children diagnosed using X-rays in the years 1976 - 2003 in the radiology department of a large university clinic was studied. MATERIALS AND METHODS: Individual radiation doses per examination were reconstructed using an algorithm taking into account the dose area product and other exposure parameters together with conversion factors computed specifically for the equipment and protocols used in the radiology department. Incident cancer cases in the period 1980 - 2006 were identified via record linkage to the German Childhood Cancer Registry using pseudonymized data. RESULTS: A total of 87 cancers occurred in the cohort between 1980 and 2006: 33 leukemia, 13 lymphoma, 10 brain tumors, and 31 other tumors. The standardized incidence ratio (SIR) for all cancers was 0.99 (95 % CI: 0.79 1.22). A dose-response relationship was not observed for all cancers, leukemia and lymphoma or solid tumors. The cancer risks for boys and girls did not differ. CONCLUSION: No increase in the cancer incidence risk in relation to very low doses of diagnostic ionizing radiation was observed in this study. However, the results are compatible with a broad range of risk estimates.

[Radiation exposure of children in pediatric radiology part 8: radiation doses during thoracoabdominal babygram and abdominal X-ray examination of the newborn and young infants]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie Teil 8: Strahlendosen beim thorakoabdominalen Babygramm und bei der Abdomenaufnahme Neugeborener und Säuglinge.

PURPOSE: Reconstruction of radiation doses for the thoracoabdominal babygram and the abdomen X-ray from radiographic settings and exposure data acquired at Dr. von Hauner's Kinderspital (children's hospital of the University of Munich, DvHK) between 1976 and 2007; comparison of these dose values with values reported in the literature; recommendation of a reference dose value for the thoracoabdominal babygram. MATERIALS AND METHODS: The data from all X-ray examinations performed since 1976 at DvHK were stored electronically in a database. After 30 years of data collection, the database now includes 305 107 radiological examinations (radiographs and fluoroscopies), especially 1493 thoracoabdominal babygrams and 3632 abdomen X-rays of newborns and young infants. With the computer program PADOS, a specific dose reconstruction algorithm was developed. RESULTS: The entrance dose values of thoracoabdominal babygrams and abdomen X-rays in DvHK could be reduced in the last 30 years by a factor of 5 to 8. They are far below the entrance dose values reported by other radiology departments in Europe. Nevertheless, a slight increase in the entrance doses that correlates with the introduction of a digital storage phosphor system could be observed in the last years. CONCLUSION: Because nearly all radiosensitive body organs in early life are involved during a thoracoabdominal babygram and because of the high radiation sensitivity of newborns, thoracoabdominal babygrams should be performed in neonatology with caution. A dose value of 1.0 cGy cm(2) could serve as the actual reference dose value for the thoracoabdominal babygram of the newborn.

[Radiation exposure of children in pediatric radiology. Part 7: conversion factors for reconstruction of organ dose during thoracoabdominal babygrams]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie. Teil 7: Konversionsfaktoren zur Rekonstruktion von Organdosen beim thorakoabdominalen Babygramm.

PURPOSE: Calculation of conversion coefficients for the reconstruction of organ doses from entrance doses for thoracoabdominal babygrams of premature neonates with a gestational age of 23 and 27 weeks and of mature neonates. MATERIALS AND METHODS: Using the commercially available personal computer program PCXMC developed by the Finnish Centre for Radiation and Nuclear Safety (Säteilyturvakeskus STUK), conversion coefficients for conventional thoracoabdominal babygrams were calculated with Monte Carlo simulations in mathematical hermaphrodite phantom models describing patients of different ages. RESULTS: Conversion coefficients for the reconstruction of organ doses in approximately 40 organs and tissues of the human body from measured entrance doses during thoracoabdominal babygrams were calculated for the standard sagittal beam projections and the standard focus film distance of 100 cm. CONCLUSION: The conversion coefficients presented in this paper may be used for organ dose assessments from entrance doses measured during thoracoabdominal babygrams especially in patients in special care baby units.

[Radiation exposure of children in pediatric radiology. Part 6: conversion factors for reconstruction of organ dose in abdominal radiography]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie. Teil 6: Konversionsfaktoren zur Rekonstruktion von Organdosen bei Abdomenaufnahmen.

PURPOSE: Calculation of conversion coefficients for the reconstruction of organ doses from entrance doses for abdomen radiographs of 0, 1, 5, 10, 15, and 30-year-old patients in conventional pediatric radiology for the radiographic settings recommended by the German and European guidelines for quality management in diagnostic radiology. MATERIALS UND METHOD: Using the commercially available personal computer program PCXMC developed by the Finnish Center for Radiation and Nuclear Safety (Säteilyturvakeskus STUK), conversion coefficients for conventional abdomen radiographs were calculated performing Monte Carlo simulations in mathematical hermaphrodite phantom models describing patients of different ages. The possible clinical variation of beam collimation was taken into consideration by defining optimal and suboptimal radiation fields on the phantoms' surfaces. RESULTS: Conversion coefficients for the reconstruction of organ doses in about 40 organs and tissues of the human body from measured entrance doses during abdomen radiographs for 0, 1, 5, 10, 15, and 30-year-old pediatric patients were calculated for the standard sagittal and lateral beam projections and the standard focus film distances of 100 cm and 115 cm. CONCLUSION: The conversion coefficients presented in this paper may be used for organ dose assessments from entrance doses measured during abdomen radiographs of patients of all age groups and all beam collimations within the optimal and suboptimal standard beam collimations.

[Radiation exposure of children in pediatric radiology. Part 5: organ doses in chest radiography]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie. Teil 5: Organdosen bei der Röntgenuntersuchung des Thorax.

PURPOSE: Reconstruction of organ doses of selected organs and tissues from radiographic settings and exposure data collected during chest X-ray examinations of children of various age groups performed in Dr. von Hauner's Kinderspital (children's hospital of the University of Munich, DvHK) between 1976 and 2007. MATERIALS AND METHOD: The dosimetric data of all X-ray examinations performed since 1976 at DvHK were stored electronically in a database. After 30 years of data collection, the database now includes 305 107 radiological examinations (radiographs and fluoroscopies), especially 119 150 chest radiographs of all age groups. Reconstruction of organ doses in 40 organs and tissues in X-ray examinations of the chest was performed based on the conversion factor concept. RESULTS: The radiation exposure of organs in projection radiography is determined by the exact site of the organs relative to the edges of the X-ray field and the beam direction of X-rays. Optimal collimation in chest radiography can reduce the exposure of organs located at the periphery of the X-ray field, e. g. thyroid gland, stomach and partially the liver, by a factor of 2 to 3, while organs located in the center of the X-ray-field, e. g. thymus, breasts, lungs, esophagus and red bone marrow, are not affected by exact collimation. CONCLUSIONS: The high frequency of the roentgen examination of the chest in early age groups increases the collective radiation burden to radiosensitive organs. Therefore, radiation protection of the patient during chest radiographies remains of great importance.

[Radiation exposure of children in pediatric radiology. Part 4: Entrance doses achieved during the X-ray examination of the chest]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie. Teil 4: Einfalldosen bei der Röntgenuntersuchung des Thorax.

PURPOSE: Reconstruction of the entrance dose from radiographic settings and exposure data acquired during chest X-ray examinations of children of various age groups performed at Dr. von Hauner's Kinderspital (children's hospital of the university of Munich, DvHK), between 1976 and 2007. Comparison of these entrance doses with dose values published by other radiological departments. MATERIALS AND METHODS: All relevant data of all X-ray examinations performed since 1976 at DvHK, in particular the individual radiographic settings and dose measurements (dose area product), were stored electronically in a database. After 30 years of data gathering, the database now covers 305,107 radiological examinations (radiographs and fluoroscopies), especially 119 150 chest radiographs of all age groups. With the computer program PADOS developed by the authors, a specific algorithm was created to calculate radiation doses from the database using the individual dose area product values and other known exposure parameters. RESULTS: The entrance dose values of the chest X-rays at DvHK were able to be reduced in the last 30 years by a factor of 2 to 3 depending on the patients' age group and the beam projection. In our sample, the measured dose values for chest X-rays were far below the reference dose levels set by the Bundesamt für Strahlenschutz (BfS) in 2003 and far below the entrance dose values reported by other radiological departments in Europe as well. Nevertheless, in the last years an increase in the entrance doses has been observed that easily corresponds to the introduction of a digital storage phosphor system in the department. CONCLUSION: Chest radiography is a frequently performed X-ray examination at a very low dose level. However, because of its frequency, it makes a notable contribution to the collective radiation risk of the population. Therefore, for the reduction of the collective radiation exposure, the optimization of the dose level required by chest X-rays continues to be of great importance. A reduction can be achieved with a consistent and simultaneous optimization of beam quality, exposure field and image processing system. Because of the statistically relevant number of analyzed cases, the entrance dose values presented in this paper can provide a basis for the definition of new reference dose levels.

[Radiation exposure of children in pediatric radiology--part 2: the PAEDOS algorithm for computer-assisted dose reconstruction in pediatric radiology and results for X-ray examinations of the skull]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie--Teil 2: der PADOS-Algorithmus zur rechnergestützten Dosisrekonstruktion in der Kinderradiologie am Beispiel der Röntgenuntersuchung des Schädels.

PURPOSE: Development of an algorithm for computer-assisted dose reconstruction using exposure data from a very large electronic database of a university children's hospital. Radiation dose values and new conversion factors for pediatric radiology were calculated and selected results for skull X-rays of 5-year-old patients will be presented. MATERIALS AND METHODS: Since 1976 all relevant data from daily routine X-ray examinations performed in Dr. von Hauner's Kinderspital (children's hospital of the university of Munich, DvHK) have been stored electronically in a database. This database now encompasses basic personal patient data, type of radiological procedure, individual radiographic/fluoroscopic settings, dose measurements (dose area product), individual referral criteria and radiological diagnosis. After 30 years of data gathering, the database now includes 305 434 radiological examinations (radiographs and fluoroscopies) of all age groups, from newborns to adolescents. With a computer program, called PADOS, a specific algorithm was created to calculate radiation doses using the individual dose area product values and other known exposure parameters extracted from the databases. The dose reconstruction procedure is based on the conversion factor concept. By means of the PCXMC program developed by the Finnish Center for Radiation and Nuclear Safety (STUK, Helsinki), Monte Carlo simulations were performed to calculate new conversion factors for pediatric radiology based on the radiographic technique used in the DvHK. RESULTS: The entrance dose values of skull X-rays showed a very good correlation with the changes of examination technique in the last 30 years. In our sample, the measured dose values for skull X-rays were far below the reference dose levels set by the Bundesamt für Strahlenschutz (BfS) in 2003. Conversion factors for 28 different radiographic procedures, 6 age groups, 40 reference organs, 3 beam projections, 12 voltage settings and 3 total filtration levels were calculated. The influence of collimation on the organ doses of radiosensitive organs, e. g. thyroid, bone marrow, in all age groups, especially in the very young, was able to be demonstrated. CONCLUSION: The PADOS algorithm seems to be suitable for the handling of very large and heterogeneous radiological databases and allows the reconstruction of various dose entities.

[Radiation exposure of children in pediatric radiology]. / Zur strahlenexposition von kindern in der pädiatrischen radiologie.

PURPOSE: Analysis of all relevant data of X-ray examinations performed in a university children's hospital and stored electronically in a database since 1976. MATERIALS AND METHOD: After 30 years of data gathering, the database now covers 276 739 radiological examinations (radiographs & fluoroscopies) of all age groups from newborns to adolescents. This database now encompasses basic personal patient data, type of the radiological procedure, individual radiographic/fluoroscopic settings, dose measurements (dose area product), individual referral criteria and radiological diagnosis. The preparation and analysis of this database was made with a set of self-written algorithms (PC program: PADOS [Programm zur PAdiatrischen DOSimetrie = Program for PEdiatric DOSimetry]). RESULTS: The frequency of childhood X-rays and fluoroscopic examinations per patient has substantially changed over the last 30 years. We could show that the indication for X-ray diagnostics for newborns and infants was higher than for the other childhood age groups. In addition, the number of patients who had a high number of X-ray examinations clearly declined in the last years and the time for standard fluoroscopic examinations was considerably reduced. CONCLUSIONS: A comprehensive database as described is a prerequisite for quality assurance in X-ray diagnostics as well as for the calculation of cumulative radiation dose and follow-up epidemiological studies.

[Radiation exposure of children in pediatric radiology. Part 3: Conversion coefficients for reconstruction of organ doses achieved during chest X-ray examinations]. / Zur Strahlenexposition von Kindern in der pädiatrischen Radiologie. Teil 3: Konversionsfaktoren zur Rekonstruktion von Organdosen bei Thoraxaufnahmen.

PURPOSE: Calculation of conversion coefficients for the reconstruction of organ doses from entrance doses for chest radiographs of 0, 1, 5, 10, 15, and 30-year-old patients in conventional pediatric radiology for the radiographic settings recommended by the German and European guidelines for quality management in diagnostic radiology. MATERIALS AND METHODS: The conversion coefficients for pediatric chest radiographs were calculated using the commercially available personal computer program PCXMC developed by the Finnish Centre for Radiation and Nuclear Safety (Säteilyturvakeskus STUK). PCXMC is a Monte Carlo program for computing organ and effective doses in about 40 organs of mathematical hermaphrodite phantom models describing patients of different ages. The possible clinical variation of beam collimation was taken into consideration by defining optimal and suboptimal radiation fields on the phantoms' surfaces. RESULTS: Conversion coefficients for the reconstruction of organ doses from measured entrance doses during chest radiographs for 0, 1, 5, 10, 15, and 30-year-old pediatric patients were presented. Conversion coefficients were calculated for the standard sagittal and lateral beam projections and the standard focus film distances of 100 cm, 115 cm, and 150 cm using the standard radiation qualities according to the recommendations of the German and European guidelines for quality management in diagnostic radiology. These conversion coefficients allow the reconstruction of the absorbed dose in about 40 organs and tissues of the human body for optimal and suboptimal radiation field collimations. CONCLUSION: The conversion coefficients presented in this paper may be used for organ dose assessments from entrance doses measured during chest radiographs of patients of all age groups with all beam collimations within optimal and suboptimal standard beam collimations. While the influence of the beam collimation on organ doses of organs localized near the center of the beam is expectedly low, the radiation exposure of organs and tissues near the boundaries of the radiation field can be considerably reduced by an optimal beam collimation. The conversion coefficients calculated for the STUK phantoms are in good conformity with values published for the GSF phantoms "Adam", "Golem" and "Visible Human".

Physical and biological interface dose effects in tissue due to X-ray-induced release of secondary radiation from metallic gold surfaces.

Dose enhancement up to more than a factor of 100 was found in an environment of tissue-equivalent polymethylmethacrylate (PMMA) close to the surface of a thin metallic gold foil. The enhancement factors were determined for heavily filtered X rays (40 to 120 kV tube potential) under backscatter conditions, using thin-film radiation detectors with sub-micrometer resolution. The secondary electrons were found to range up to some 10 microm in tissue-equivalent material. Correspondingly, enhanced biological effects could be shown in vitro, using monolayers of C3H 10T1/2 mouse embryo fibroblasts exposed in intimate contact with the gold surface. The decay of the survival curves of cells irradiated on gold was significantly steeper than for those obtained from irradiation between PMMA disks with the same dose, also giving biological evidence for significantly enhanced doses at the gold interface. The shape of the inactivation curves resembled those for high-LET radiation, lacking a pronounced shoulder at the lower doses. Quantitatively, doses of e.g. 50 mGy (80 kV X rays) in homogeneous PMMA caused about 35% cell killing and 200 mGy about 80% when the cells were irradiated at the gold surface. From a comparison of these inactivation numbers with those found for irradiation between PMMA disks, biological dose enhancement factors for the cell system considered ranged up to about a factor of 50. In addition to cell inactivation, the in vitro irradiations of C3H 10T1/2 cells adjacent to the gold surface resulted in increased rates of oncogenic transformation. A dose of 100 mGy 80 kV X rays (measured in homogeneous PMMA) caused a frequency at an inserted gold surface comparable to that obtained with a dose of about 4.5 Gy of 60Co gamma rays in homogeneous PMMA.