BACKGROUND:Various imaging modalities, such as multi-detector computed tomography (CT) and cone beam CT are commonly used in infants for the diagnosis of hearing loss and surgical planning of implantation hearing aid devices, with differing results.OBJECTIVE:We compared three different imaging modalities available in our institution, including a high-class CT scanner, a mid-class CT scanner and an angiography system with a cone beam CT option, for image quality and radiation exposure in a phantom study.MATERIALS AND METHODS:While scanning an anthropomorphic phantom imitating a 1-year-old child with vendor-provided routine protocols, organ doses, surface doses and effective doses were determined for these three modalities with thermoluminescent dosimeters. The image quality was evaluated using the signal difference to noise ratio (SDNR) and the spatial resolution of a line-pair insert in the phantom head. The dose efficiency, defined as the ratio of SDNR and effective dose, was also compared.RESULTS:The organ and surface doses were lowest with the high-class CT protocol, but the image quality was the worst. Image quality was best with the cone beam CT protocol, which, however, had the highest radiation exposure in this study, whereas the mid-class CT was in between.CONCLUSION:Based on our results, high-end CT should be used for surgical planning because it has the lowest dose, while the image quality is still sufficient for this purpose. However, if highest image quality is needed and required, e.g., by ENT surgeons, the other modalities should be considered.

In our work, we evaluated the effective dose values for first clinical dark-field chest radiography, both for examinations of the reference person and a certain patient collective consisting of 92 patients. Unfortunately, the histogram in Figure 4 consists of more patients than introduced in the running text, as more of the participants in the ongoing studies were mistakenly included. In the published Figure 4, instead of data points of 92 patients, data points of additional patients are included. This changes the mean value, as indicated by a dashed line, from 38.7 μGy (correct value as given in Figure legend and running text) to 41.1 μGy (as depicted in published Figure 4). The corrected version can be found in the attached Figure 1. Figure legend is not subject to change. Please note that this does not change the message of the paper. All dose values in the running text and figure legends are correct. The reported effective dose value for the reference person is correct. The reported effective dose values for the first 92 patients are correct. Even by including more patients, the recorded mean value is below the reference value, therefore we fulfill the legal requirements regarding the local diagnostic reference level (DRL).

Purpose: X-ray cabinets are replacing Cs-137/Co-60 sources in radiation biology research due to advantages in size, handling, and radiation protection. However, because of their different physical properties, X-ray cabinets are more susceptible to experimental influences than conventional sources. The aim of this study was to examine the variations related to the experimental setups typically used to investigate biological radiation effects with X-ray cabinets. Materials and methods: A combined approach of physical dose measurements by thermoluminescence dosimetry and detection of biological effects by quantification of gamma H2AX and 53BP1 foci was used to analyze field inhomogeneity and evaluate the influence of the components of the experimental setup. Results: Irradiation was performed using an X-ray tube (195 kV, 10 mA, 0.5-mm-thick copper filter, dose rate of 0.59 Gy/min). Thermoluminescence dosimetry revealed inhomogeneity and a dose decrease of up to 42.3% within the beam area (diameter 31.1 cm) compared to the dose at the center. This dose decrease was consistent with the observed decline in the number of radiation-induced foci by up to 55.9 %. Uniform dose distribution was measured after reducing the size of the radiation field (diameter 12.5 cm). However, when using 15-ml test tubes placed at different positions within this field, the dose decreased by up to 17% in comparison to the central position. Analysis of foci number revealed significant differences between the tubes for gamma H2AX (1 h) and 53BP1 (4 h) at different time points after irradiation. Neither removal of some tubes nor of the caps improved the dose decrease significantly. By contrast, when using 1.5-ml tubes, dose differences were less than 4%, and no significant differences in foci number were detected. Conclusion: X-ray cabinets are user-friendly irradiation units for investigating biological radiation effects. However, field inhomogeneities and experimental setup components considerably affect the delivered irradiation doses. For this reason, strict dosimetric monitoring of experimental irradiation setups is mandatory for reliable studies.

PURPOSE:The purpose of this study was to evaluate the dose characteristic for patient examinations at the first clinical X-ray dark-field chest radiography system and to determine whether the effective patient dose is within a clinically acceptable dose range.METHODS:A clinical setup for grating-based dark-field chest radiography was constructed and commissioned, operating at a tube voltage of 70 kVp. Thermoluminescent dosimeter (TLD) measurements were conducted using an anthropomorphic phantom modeling the reference person to obtain a conversion coefficient relating dose area product (DAP) to effective patient dose at the dark-field system. For 92 patients, the DAP values for posterior-anterior measurements were collected at the dark-field system. Using the previously determined conversion coefficient, the effective dose was calculated.RESULTS:A reference person, modeled by an anthropomorphic phantom, receives an effective dose of 35 µSv. For the examined patients, a mean effective dose of 39 µSv was found.CONCLUSIONS:The effective dose at the clinical dark-field radiography system, generating both attenuation and dark-field images, is within the range of reported standard dose values for chest radiography.

Die 3D-Bildgebung mittels Flachdetektoren gewinnt durch den Einsatz in der Angiografie und im OP zunehmend an Bedeutung. Einfache Änderungen der Programmkonfigurationen können erhebliche Unterschiede der Strahlenexposition hervorrufen, was gerade in der pädiatrischen Bildgebung besondere Beachtung finden sollte. Ein häufig variierter Parameter für diese 3D-Aufnahmen ist das Field of View (FOV). In der vorliegenden Arbeit wurde dessen Einfluss auf die Bildqualität und die Strahlenexposition untersucht.

Various strategies have been developed to reduce radiation exposure of patients in CT examinations. The aim of this study was to evaluate the efficacy of high pitch in representative CT protocols examining lung embolism. We performed thermoluminescence measurements with an anthropomorphic phantom exposing it to CT algorithms for lung embolism in a 128-multislice, dual-source CT scanner: a standard CT protocol (sCT) and a CT protocol with a high pitch (+ F). Radiation doses for both CT algorithms were compared and the dose reduction potential of high pitch for individual organs was evaluated. As expected, the  +F mode reduced the effective dose and organ doses in the primary beam of radiation (namely, lung, bone marrow, heart, breast, skin and skeleton) compared with sCT by up to 52% for an equivalent image quality. On the contrary, for organs at the margin of the primary beam (thymus, thyroid, liver, pancreas, kidneys, colon and small intestine), the  +F mode reduced effective radiation doses by only 0-30%, compared with sCT. The dose reduction potential of the  +F mode greatly depends on the position of the organ in the scan field. While for organs in the primary beam  + F leads to a considerable dose reduction, it is less effective for tissues at the margin of the scanned area.

The purpose of this experimental phantom study was to compare radiation doses imparted to patients undergoing classical two-plane digital subtraction angiography (2-plane DSA) and 3D rotational angiography in interventional neuroradiology.

Purpose: To provide an experimental basis for spectral optimization of iodine-enhanced CT by a quantitative analysis of image quality and radiation dose characteristics consistently measured for a large variety of scan settings at an anthropomorphic phantom.Methods: CT imaging and thermoluminescent dosimetry were performed at an anthropomorphic whole-body phantom with iodine inserts for different tube voltages (U, 70-140 kV) and current-time products (Q, 60-300 mAs). For all U-Q combinations, the iodine contrast (C), the noise level (N) and, from these, the contrast-to-noise ratio (CNR) of reconstructed CT images were determined and parameterized as a function of U, Q or the measured absorbed dose (D). Finally, two characteristic curves were derived that give the relative increase of CNR at constant D and the relative decrease of D at constant CNR when lowering U.Results: Lowering U affects the measured CNR only slightly but markedly reduces D. For example, reducing U from 120 kV to 70 kV increases the CNR at constant D by a factor of nearly 1.8 or, alternatively, reduces D at constant CNR by a factor of nearly 5.Conclusion: Spectral optimization by lowering U is an effective approach to attain the necessary CNR for a specific diagnostic task at hand while at the same time reducing radiation exposure as far as practically achievable. The characteristic curves derived in this study from extensive measurements at a reference 'person' can support CT users in an easy-to-use manner to select an appropriate voltage for various clinical scenarios. (C) 2016 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Analyse der Gründe von Dosisalarmen im ersten Jahr der Anwendung des Dosis Monitoring Programms eXposure (Bayer HealthCare, Germany). Korrelation dieser Alarme mit Phantommessungen zur Evaluation der tatsächlichen Dosis am Beispiel der Augenlinse und am Beispiel von Lungenarterienembolien.

OBJECTIVES:Radiation exposure of patients during endovascular aneurysm repair (EVAR) procedures ranks in the upper sector of medical exposure. Thus, estimation of radiation doses achieved during EVAR is of great importance.MATERIAL AND METHODS:Organ doses (OD) and effective doses (ED) administered to 17 patients receiving EVAR were determined (1) from the exposure parameters by performing Monte Carlo simulations in mathematical phantoms and (2) by measurements with thermoluminescent dosimeters in a physical anthropomorphic phantom.RESULTS:The mean fluoroscopy time was 26 min, the mean dose area product was 24995 cGy cm2. The mean ED was 34.8 mSv, ODs up to 626 mSv were found. Whereas digital subtraction angiographies (DSA) and fluoroscopies each contributed about 50% to the cumulative ED, the ED rates of DSAs were found to be ten times higher than those of fluoroscopies. Doubling of the field size caused an ED rate enhancement up to a factor of 3.CONCLUSION:EVAR procedures cause high radiation exposure levels that exceed the values published thus far. As a consequence, (1) DSAs should be only performed when necessary and with a low image rate, (2) fluoroscopies should be kept as short as possible, and (3) field sizes should be minimized.KEY POINTS:• During endovascular aneurysm repair (EVAR) considerable patient doses are achieved. • For each EVAR procedure organ (OD) and effective (ED) doses were determined. • The mean ED was 34.8 mSv, the highest OD was 626 mSv. • Number of DSAs, fluoroscopy durations and field sizes should be minimized.

•We summarize the most recent recommendations of the ICRP on radiation effects.•We present dose distributions for three representative DCE-CT protocols.•We estimate stochastic radiation risks of patients using most recent risk models.•We discuss aspects to be considered in the process of justification and optimization.

Summary Aim: Reinvestigation of the radiation exposure of patients undergoing whole-body [18F]FDG-PET/CT examinations pursuant to the revised recommendations of the ICRP. Methods: Conversion coefficients for equivalent organ doses were determined for realistic anthropomorphic phantoms of reference persons. Based on these data, conversion coefficients for the effective dose were calculated using the revised tissue-weighting factors that account for the different radiation susceptibilities of organs and tissues, and the redefinition of the group ‘remainder tissues’. Results: Despite the markedly changed values of the equivalent organ doses estimated for FDG and of the tissue-weighting factors, the conversion coefficient for the effective dose resulting from FDG administration decreases only slightly by 10 %. For whole-body CT scans it remains even unchanged. Conclusion: The updated dose coefficients provide a valuable tool to easily assess the generic radiation risk of patients undergoing whole- body PET/CT (or PET/MRI) examinations and can be used, amongst others, for protocol optimization.

Aim: Reinvestigation of the radiation exposure of patients undergoing whole-body [18F]FDG-PET/CT examinations pursuant to the revised recommendations of the ICRP. Methods: Conversion coefficients for equivalent organ doses were determined for realistic anthropomorphic phantoms of reference persons. Based on these data, conversion coefficients for the effective dose were calculated using the revised tissue-weighting factors that account for the different radiation susceptibilities of organs and tissues, and the redefinition of the group ‘remainder tissues’. Results: Despite the markedly changed values of the equivalent organ doses estimated for FDG and of the tissue-weighting factors, the conversion coefficient for the effective dose resulting from FDG administration decreases only slightly by 10 %. For whole-body CT scans it remains even unchanged. Conclusion: The updated dose coefficients provide a valuable tool to easily assess the generic radiation risk of patients undergoing whole-body PET/CT (or PET/MRI) examinations and can be used, amongst others, for protocol optimization.

Objectives: Recent technical developments have facilitated the application of cone-beam computed tomography (CBCT) for interventional and intraoperative imaging. The aim of this study was to compare the radiation doses and image quality in CBCT with those of conventional multislice spiral computed tomography (MSCT) for abdominal and genitourinary imaging.Methods: Different CBCT and MSCT protocols for imaging soft tissues and hard-contrast objects at different dose levels were investigated in this study. Local skin and organ doses were measured with thermoluminescent dosimeters placed in an anthropomorphic phantom. Moreover, the contrast-to-noise ratio, the noise-power spectrum, and the high-contrast resolution derived from the modulation transfer function were determined in a phantom with the same absorption properties as those of anthropomorphic phantom.Results: The effective dose of the examined abdominal/genitourinary CBCT protocols ranged between 0.35 mSv and 18.1 mSv. As compared with MSCT, the local skin dose of CBCT examinations could locally reach much higher doses up to 190 mGy. The effective dose necessary to realize the same contrast-to-noise ratio with CBCT and MSCT depended on the MSCT convolution kernel: the MSCT dose was smaller than the corresponding CBCT dose for a soft kernel but higher than that for a hard kernel. The noise-power spectrum of the CBCT images at tube voltages of 85/90 kV(p) is at least half of that of images measured at 103/115 kV(p) at any arbitrarily chosen spatial frequency. Although the pixel size and slice thickness of CBCT were half of those of the MSCT images, high-contrast resolution was inferior to the MSCT images reconstructed with a hard convolution kernel.Conclusions: As compared with MSCT using a medium-hard convolution kernel, CBCT produces images at medium noise levels and, simultaneously, medium spatial resolution at approximately the same dose. It is well suited for visualizing hard-contrast objects in the abdomen with relatively low image noise and patient dose. For the detection of low-contrast objects at standard tube voltages of approximately 120 kV(p), however, MSCT should be preferred.

Objectives: To present a detailed analysis of the cumulative radiation exposure and cancer risk of patients with ischemic heart diseases (IHD) from diagnostic and therapeutic imaging.Methods: For 1219 IHD patients, personal and examination data were retrieved from the information systems of a university hospital. For each patient, cumulative organ doses and the corresponding effective dose ((E) over bar) resulting from all imaging procedures performed within 3 months before and 12 months after the date of the diagnosis were calculated. The cumulative lifetime attributable risk ((LAR) over bar) of the patients to be diseased by radiation-related cancer was estimated using sex-, age-, and organ-specific risk models.Results: Among the 3870 procedures performed in the IHD patients, the most frequent were radiographic examinations (52.4%) followed by coronary catheter angiographies and percutaneous cardiac interventions (41.3%), CT scans (3.9%), and perfusion SPECT (2.3%). 87% of patient exposure resulted from heart catheter procedures. E and (LAR) over bar were significantly higher in males than females (average, 13.3 vs. 10.3 mSv and 0.09 vs. 0.07%, respectively). Contrary to the effective dose, the cancer risk decreased markedly for both sexes with increasing age.Conclusions: Although IHD patients were partially exposed to considerable amounts of radiation, estimated (LAR) over bars were small as compared to their baseline risk to develop cancer in the remaining life. (C) 2013 Elsevier Ireland Ltd. All rights reserved.

Objective This study aimed to show the simulation of the radiation exposure of the brain during perfusion measurements multi-detector-CT. Material and Methods The effective dose and different organ doses were measured with thermoluminescent dosimeters in an Alderson-Rando phantom and compared with the data of a simulation program (CT-Expo V1.6) for varying scan protocols with different tube voltages (in kilovolts) and constant parameters for tube current (270 mAs), scan length (28.8 mm), scan time (40 seconds), slice thickness (24 × 1.2 mm), and number of scans (40) for multi-detector-CT perfusion measurements of the brain. Results The thermoluminescent dosimeter measurements yielded effective doses of 3.8 mSv (80 kV), 8.6 mSv (100 kV), 14.1 mSv (120 kV), and 22.2 mSv (140 kV). These values were in line with the data from the simulation program CT-Expo V1.6. The organ doses varied between 97 and 556 mGy (brain), 10.7 and 80.9 mGy (eye lens), 9.6 and 46 mGy (bone marrow), 1.2 and 6.7 mGy (thyroid gland), and 4.1 to 22.3 mGy (skin). The maximum local skin dose ranged from 355 mGy (80 kV) to 1855 mGy (140 kV) in the directly exposed part of the skin. Conclusions The radiation exposure during perfusion measurements of the brain is strongly dependent on the tube voltage and can vary widely even if the other exposure parameters remain constant. Maximum organ doses up to 556 mGy (brain) can be measured. Even if we never reached local organ doses that can cause a direct radiation injury, the review of the tube voltages implemented by the vendor is mandatory beside the limitation of the scanned area by clinical examination and the reduction of the number of scans. Simulation programs are a valuable tool for dose measurements.

Ziele: Aufgrund technischer Weiterentwicklungen stellt die Cone-Beam-CT (CBCT) eine Alternative zur konventionellen Mehrschichtspiral-CT (MSCT) dar – insbesondere für bildgestützte Interventionen und operative Eingriffe. Ziel dieser Studie war ein Vergleich zwischen beiden Gerätetypen bezüglich Bildqualität und Strahlendosis im Abdominalbereich. Methode: Zu diesem Zweck wurden mehrere CT-Scans mit unterschiedlichen Akquisitionsprotokollen und Rekonstruktionsfilter an einem CBCT (Dyna-CT, Siemens) und einem MSCT (Emotion 16, Siemens) akquiriert. Die Scanlänge war an beiden Systemen identisch. Die lokale Dosisverteilung wurde mit Thermolumineszens-Dosimetern auf der Oberfläche und im Inneren eines Alderson-Rando-Phantoms gemessen. Die Bildqualität wurde anhand physikalischer Parameter wie dem Kontrast-zu-Rausch-Verhältnis (CNR) oder der Modulationsübertragungsfunktion am AAPM-CT-Phantom bestimmt. Um identische Absorptionsverhältnisse an beiden Phantomen zu gewährleisten, wurden zwei Plexiglas-Halbschalen auf gegenüberliegenden Seiten des AAPM-CT-Phantoms angebracht. Ergebnis: Obwohl für ein Standardprotokoll bei beiden Gerätetypen im Mittel die gleiche lokale Hautdosis gemessen wurde, traten beim CBCT im Gegensatz zum MSCT lokale Dosismaxima auf. Die effektive Dosis, die appliziert werden musste, um bei beiden Gerätetypen die gleiche Bildqualität zu erzielen, hängt vom verwendeten Rekonstruktionsfilter ab. Bei Verwendung eines weichen oder mittleren Rekonstruktionsfilters war die Dosis für ein vergleichbares CNR beim MSCT gegenüber dem CBCT nur etwa halb so hoch, für einen harten Rekonstruktionsfilter dagegen ungefähr doppelt so hoch. Schlussfolgerung: Unter strahlenhygienischen Gesichtspunkten bieten CBCT-Geräte vielversprechende Anwendungsmöglichkeiten, um Hartkontraste wie feine Knochenpartikel oder Harnsteine intraoperativ visualisieren zu können. Demgegenüber ist die MSCT im Bereich der Weichteildarstellung weiterhin zu bevorzugen.

Ziele: Geschlechts-, alters- und organspezifische Ermittlung und Bewertung der kumulativen Strahlenexposition sowie des daraus resultierenden Strahlenrisikos von Patienten mit ischämischen Herzerkrankungen (IHK) durch diagnostische und interventionelle Strahlenanwendungen. Methode: Für 1219 IHK-Patienten wurden sowohl personen- als auch untersuchungsbezogene Daten aus dem KIS/RIS eines großen Universitätsklinikums extrahiert. Für jeden Patienten wurden die kumulativen Organdosen sowie die korrespondierende effektive Dosis für alle Bildgebungsprozeduren berechnet, die 3 Monate vor und 12 Monate nach Festlegung der Entlassungsdiagnose durchgeführt wurden. Basierend auf den ermittelten Organdosiswerten wurde schließlich unter Verwendung geschlechts-, alters- und organspezifischer Strahlenrisikomodelle (BEIR VII) das zusätzliche Lebenszeitrisiko abgeschätzt, im weiteren Verlauf des Lebens an einem strahleninduzierten Tumor zu erkranken. Ergebnis: Im Mittel wurden in den 15 Monaten 3,2 Prozeduren pro Patient durchgeführt. Am häufigsten waren Röntgenaufnahmen (52,4%) gefolgt von Herzkatheteruntersuchungen und Koronarinterventionen (41,3%), CT-Scans (3,9%) und Myokard-SPECT-Untersuchungen (2,3%). 87% der effektiven Dosis resultierte aus den Herzkatheteruntersuchungen und Koronarinterventionen. Das Maximum der effektiven Dosis und des zusätzlichen Lebenszeitrisikos lag bei 95 mSv bzw. 0,9%. Beide Größen waren bei Männern im Vergleich zu Frauen signifikant höher (im Mittel 13,3 vs. 10,3 mSv bzw. 0,09 vs. 0,07%). Im Gegensatz zur effektiven Dosis nahm das zusätzliche Krebsrisiko für beide Geschlechter signifikant mit zunehmendem Alter ab. Schlussfolgerung: Obwohl die betrachteten IHK-Patienten zum Teil einer relativ hohen Strahlenexposition ausgesetzt waren, ist das resultierende strahleninduzierte Krebsrisiko aufgrund ihres höheren Alters sowohl im Vergleich zum Spontanrisiko an Krebs zu erkranken als auch zum Nutzen aus den durchgeführten diagnostischen und therapeutischen Maßnahmen als gering zu bewerten.

OBJECTIVES:To establish the essential basis for balancing the dose versus noise trade-off in dynamic contrast-enhanced (DCE) CT by means of a phantom study.MATERIALS AND METHODS:Measurements were performed at a 64-section dual-source system, using the default protocols for DCE imaging (40 scans) of the trunk (current-time product per scan, 100 mAs; voltage, 120 kVp; pixel size, 0.9 × 0.9 × 8 mm3; CTDIvol per examination, 264 mGy) and head (270 mAs, 80 kVp, 0.45 × 0.45 × 8 mm3, 429 mGy). For 3 representative sections of an anthropomorphic phantom (head, upper abdomen, pelvis) transaxial dose distributions were measured by thermoluminescent dosimeters. The image noise was determined for 5 values of the current-time product (but otherwise identical parameter settings) and 4 pixel resolutions at a water-filled trunk and head phantom.RESULTS:Highest exposures occurred at the periphery of the trunk and head with maximum skin entrance doses of about 300 mGy. Effective doses related to the 3 exposure scenarios were between 4 and 20 mSv, but were not at all predictive of local exposure levels. The image noise was inversely proportional to the square root of the current-time product and, with restrictions, to the pixel size. Noise levels determined for the standard settings were 13.8 HU (trunk) and 4.4 HU (head) and thus comparable with the contrast enhancement typically detected in tumors and ischemic brain tissues, respectively.CONCLUSIONS:The opposing requirements of risk and noise limitation in DCE-CT cannot be balanced without substantially reducing the spatial resolution. But even so, local radiation exposures are rather high for a diagnostic procedure. Indications to perform a DCE examination should thus be strictly limited to patients who really benefit from it.

OBJECTIVE. The purpose of this study was to assess the radiation doses of different coronary CTA (CTA) protocols: second-generation dual-source 128-MDCT, first-generation dual-source 64-MDCT, and single-source 64-MDCT.MATERIALS AND METHODS. Thermoluminescent dosimetry was used to determine scanner-specific dose coefficients for standard coronary CTA of an anthropomorphic phantom. These coefficients were used to estimate the effective doses (EDs) of retrospectively gated, prospectively triggered, and prospectively triggered high pitch coronary CTA performed at 100 and 120 kV. The coronary CTA protocols used in imaging of 43 patients undergoing dual-source 128-MDCT were analyzed for ED, image quality, and signal-to-noise ratio.RESULTS. Regardless of coronary CTA protocol and CT system, imaging at 100 kV lowered the ED 40-50%. In retrospectively gated 120-kV coronary CTA, the ED ranged from 5.7 to 10.7 mSv and was approximately 50% lower with single-source 64-MDCT than with either DSCT protocol. In prospectively triggered 120-kV coronary CTA, the ED ranged from 3.8 to 4.0 mSv. The lowest ED of all protocols (1.3 mSv) was observed in prospectively triggered high-pitch 100-kV coronary CTA performed with dual-source 128-MDCT. Patient measurements showed similar dose reductions for prospective triggering and low voltage settings without an influence on signal-to-noise ratio or image quality.CONCLUSION. A combination of prospective triggering with low voltage settings is an effective measure for reducing the ED of coronary CTA to values of 2-4 mSv independent of scanner system. Further dose reduction to nearly 1 mSv can be achieved with high-pitch prospectively triggered coronary CTA.