TY  - JOUR
AB  - BACKGROUND: Paediatric patients with congenital heart disease benefit greatly from X-ray diagnostic and interventional procedures. However, multiple procedures lead to prolonged exposure to ionizing radiation (IR), raising concerns for secondary long-term health issues. PURPOSE: This study aimed to establish local dose reference levels (LDRLs) for a National Reference Center for Congenital Cardiopathies (NRCCC) in Portugal. Additionally, it estimated effective and organ doses in paediatric patients undergoing coronary angiographies (CAs) using measurements and Monte Carlo simulations. METHODS: LDRLs were determined through statistical analysis of patient registry data from 120 patients recorded between 2022 and 2023. For effective dose estimation, personal dose equivalent values Hp(10) were measured with an anthropomorphic phantom (CIRS ATOM 705) and Raysafe dosimeters, used to validate Monte Carlo (MC) simulations, which were then employed with rescaled paediatric voxel phantoms (GsF Baby and Child), to estimate effective doses and dose conversion coefficients (DCCs) for representative patient anatomies across different age and weight groups. RESULTS: LDRLs for coronary angiographies at the NRCCC showed significant dose variability, indicating dose optimization opportunities. Monte Carlo simulations allowed for organ dose and effective dose calculations. Dose Conversion Coefficients were 1.107, 0.882, 0.719, and 0.524 mSv/Gy·cm2 for newborn, 1 year-old, 5 year-old and 10 year-old groups respectively. A strong linear correlation between effective dose and air-kerma area product (KAP) was observed. CONCLUSIONS: The study highlights the strong correlation between effective dose and KAP, offering a practical framework for estimating patient doses and enhancing radiation safety protocols in clinical practice.
AU  - Teles, P.*
AU  - Costa, R.*
AU  - Bettio, T.*
AU  - Pinheiro, T.*
AU  - Loupa, T.*
AU  - Santos, J.*
AU  - Gil, O.M.*
AU  - Ferrari, P.*
AU  - Zankl, M.
C1  - 74922
C2  - 57721
CY  - 125 London Wall, London, England
TI  - Local DRL estimation and effective dose calculation in paediatric interventional cardiology using measurements and Monte Carlo simulations.
JO  - Phys. Med.
VL  - 135
PB  - Elsevier Sci Ltd
PY  - 2025
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - PURPOSE: Microbeam radiation therapy (MRT) has shown superior healthy tissue sparing at equal tumour control probabilities compared to conventional radiation therapy in many preclinical studies. The limitation to preclinical research arises from a lack of suitable radiation sources for clinical application of MRT due to high demands on beam quality. To overcome these limitations, we developed and built the first prototype of a line-focus X-ray tube (LFXT). During commissioning, characterisation of the X-ray focal spot is necessary. For the generation of microbeams, we require a specially designed collimator adapted to the LFXT. METHODS: We present an adapted edge method and a pinhole method for focal spot measurements of the LFXT prototype as well as the design of the microbeam collimator with a slit width of 50μm, spaced by 400μm. Monte Carlo simulations validated the focal spot measurement techniques and the design of the collimator. RESULTS: We showed that the adapted edge method is more complex but superior to the adapted pinhole method in terms of quantitative validity. Simulations for the microbeam collimator showed a sharp microbeam dose profile with a peak-to-valley dose ratio (PVDR) above 23 throughout 50 mm of water. CONCLUSION: During commissioning, the adapted focal spot visualisation methods will be used to determine the focal spot dimensions and to optimise machine parameters. The LFXT prototype will enable preclinical MRT with significantly higher dose rates than any other compact MRT source and will pave the way for the first clinical trials in a hospital setting.
AU  - Petrich, C.
AU  - Winter, J.
AU  - Dimroth, A.*
AU  - Wilkens, J.J.*
AU  - Bartzsch, S.
C1  - 72910
C2  - 56797
CY  - 125 London Wall, London, England
TI  - The compact line-focus X-ray tube for microbeam radiation therapy - Focal spot characterisation and collimator design.
JO  - Phys. Med.
VL  - 129
PB  - Elsevier Sci Ltd
PY  - 2024
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Microbeam radiotherapy (MRT) is a novel concept in radiation oncology with arrays of alternating micrometer-wide high-dose peaks and low-dose valleys. Preclinical experiments have shown a lower normal tissue toxicity for MRT with similar tumor control rates compared to conventional radiotherapy. A promising candidate for the demanded compact radiation source is the line-focus x-ray tube. Here, we present the setup of a prototype for an electron accelerator being able to provide a suitable x-ray beam for the tube. Several beam dynamic calculations and simulations were performed concerning particle tracking, thermal and electrostatic properties of the electron source, resulting in a proper beamline, including the cathode, the pierce electrode (PE) and the focusing magnets. These parts are discussed separately. The simulations showed that a rectangular cathode with a small width of 0.4mm is mandatory. To quickly shut down the electron beam, an additional voltage of -600V must be applied to the PE. Moreover, the electric field inside the vacuum chamber stays below 10MVm-1 to minimize the risk of field emission. The thermal simulation validates a small displacement of 0.1mm of the heated cathode with respect to the PE, which must be considered during manufacturing of the cathode-PE assembly. The simulations lead to an adequate choice of cathode, electrodes and beamline to achieve the required focal spot of 0.05×20mm2 with a beam current of 0.3A and an electron energy of 300keV. With this setup first MRT experiments with high dose rates up to 10Gys-1 can be executed.
AU  - Matejcek, C.*
AU  - Winter, J.
AU  - Aulenbacher, K.*
AU  - Dimroth, A.*
AU  - Natour, G.*
AU  - Bartzsch, S.
C1  - 67274
C2  - 54208
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
TI  - A novel electron source for a compact x-ray tube for microbeam radiotherapy with very high dose rates.
JO  - Phys. Med.
VL  - 106
PB  - Elsevier Sci Ltd
PY  - 2023
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - PURPOSE: Certification of the X-ray shielding garment is based on attenuation testing on flat material samples. We investigated the difference of shielding effectiveness compared to realistic use when the garment is worn on the body of a staff person. METHODS: Attenuation factors of X-ray protective aprons have been evaluated for several clinical scenarios with Monte Carlo (MC) calculations based on the ICRP female reference model and an experimental setup. The MC calculated attenuation factors refer to the effective dose E, whereas the measured attenuation factors refer to the personal dose equivalent Hp(10). The calculated/measured factors were compared to the attenuation factors of the identical materials measured under the conditions of the standard IEC 61331-1 that is currently in use for the type testing of X-ray protective aprons. RESULTS: As a result, for example, at a common tube voltage of 80 kV, the real attenuation factors of a 0.35 mm Pb apron worn by a 3-dimensional body were 38% to 76% higher than when measured under IEC conditions on flat samples. The MC-calculated organ doses show the maximum contribution to E being within the operatoŕs abdomen/pelvis region. CONCLUSIONS: With our findings, personal X-ray protective garments could be improved in effectiveness.
AU  - Eder, H.*
AU  - Schlattl, H.
C1  - 61683
C2  - 50137
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 343-350
TI  - Shielding effectiveness of X-ray protective garment.
JO  - Phys. Med.
VL  - 82
PB  - Elsevier Sci Ltd
PY  - 2021
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Results of a Monte Carlo code intercomparison exercise for simulations of the dose enhancement from a gold nanoparticle (GNP) irradiated by X-rays have been recently reported. To highlight potential differences between codes, the dose enhancement ratios (DERs) were shown for the narrow-beam geometry used in the simulations, which leads to values significantly higher than unity over distances in the order of several tens of micrometers from the GNP surface. As it has come to our attention that the figures in our paper have given rise to misinterpretation as showing 'the' DERs of GNPs under diagnostic X-ray irradiation, this article presents estimates of the DERs that would have been obtained with realistic radiation field extensions and presence of secondary particle equilibrium (SPE). These DER values are much smaller than those for a narrow-beam irradiation shown in our paper, and significant dose enhancement is only found within a few hundred nanometers around the GNP. The approach used to obtain these estimates required the development of a methodology to identify and, where possible, correct results from simulations whose implementation deviated from the initial exercise definition. Based on this methodology, literature on Monte Carlo simulated DERs has been critically assessed.
AU  - Rabus, H.*
AU  - Li, W.B.
AU  - Villagrasa, C.*
AU  - Schuemann, J.*
AU  - Hepperle, P.A.*
AU  - de la Fuente Rosales, L.*
AU  - Beuve, M.*
AU  - di Maria, S.*
AU  - Klapproth, A.
AU  - Li, C.Y.*
AU  - Poignant, F.*
AU  - Rudek, B.*
AU  - Nettelbeck, H.*
C1  - 61682
C2  - 50391
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 241-253
TI  - Intercomparison of Monte Carlo calculated dose enhancement ratios for gold nanoparticles irradiated by X-rays: Assessing the uncertainty and correct methodology for extended beams.
JO  - Phys. Med.
VL  - 84
PB  - Elsevier Sci Ltd
PY  - 2021
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Microbeam radiation therapy (MRT), a so far preclinical method in radiation oncology, modulates treatment doses on a micrometre scale. MRT uses treatment fields with a few ten micrometre wide high dose regions (peaks) separated by a few hundred micrometre wide low dose regions (valleys) and was shown to spare tissue much more effectively than conventional radiation therapy at similar tumour control rates. While preclinical research focused primarily on tumours of the central nervous system, recently also lung tumours have been suggested as a potential target for MRT. This study investigates the effect of the lung microstructure, comprising air cavities of a few hundred mi- crometre diameter, on the microbeam dose distribution in lung. In Monte Carlo simulations different models of heterogeneous lung tissue are compared with pure water and homogeneous air -water mixtures. Experimentally, microbeam dose distributions in porous foam material with cavity sizes similar to the size of lung alveoli were measured with film dosimetry at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France. Simulations and experiments show that the microstructure of the lung has a huge impact on the local doses in the microbeam fields. Locally, material inhomogeneities may change the dose by a factor of 1.7, and also average peak and valley doses substantially differ from those in homogeneous material. Our results imply that accurate dose prediction for MRT in lung requires adequate models of the lung mi- crostructure. Even if only average peak and valley doses are of interest, the assumption of a simple homogeneous air -water mixture is not sufficient. Since anatomic information on a micrometre scale are unavailable for clinical treatment planning, alternative methods and models have to be developed.
AU  - Hombrink, G.
AU  - Wilkens, J.J.*
AU  - Combs, S.E.
AU  - Bartzsch, S.
C1  - 59418
C2  - 48805
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 77-82
TI  - Simulation and measurement of microbeam dose distribution in lung tissue.
JO  - Phys. Med.
VL  - 75
PB  - Elsevier Sci Ltd
PY  - 2020
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Background and purpose: To evaluate the impact of deformation magnitude and image modality on deformable-image-registration (DIR) accuracy using Halcyon megavoltage cone beam CT images (MVCBCT).Materials and methods: Planning CT images of an anthropomorphic Head phantom were aligned rigidly with MVCBCT and re-sampled to achieve the same resolution, denoted as pCT. MVCBCT was warped with twenty simulated pre-known virtual deformation fields (T-i, i = 1-20) with increasing deformation magnitudes, yielding warped CBCT (wCBCT). The pCT and MVCBCT were registered to wCBCT respectively (Multi-modality and Unimodality DIR), generating deformation vector fields V-i and V-i' (i = 1-20). V-i and V-i' were compared with Ti respectively to assess the DIR accuracy geometrically. In addition, V-i, T-i, and V-i' were applied to pCT, generating deformed CT (dCT(i)), ground-truth CT (G(i)) and deformed CT' (dCT(i)') respectively. The Hounsfield Unit (HU) on these virtual CT images were also compared.Results: The mean errors of vector displacement increased with the deformation magnitude. For deformation magnitudes between 2.82 mm and 7.71 mm, the errors of uni-modality DIR were 1.16 mm similar to 1.73 mm smaller than that of multi-modality (p = 0.0001, Wilcoxon signed rank test). DIR could reduce the maximum signed and absolute HU deviations from 70.8 HU to 11.4 HU and 208 HU to 46.2 HU respectively.Conclusions: As deformation magnitude increases, DIR accuracy continues to deteriorate and uni-modality DIR consistently outperformed multi-modality DIR. DIR-based adaptive radiotherapy utilizing the noisy MVCBCT images is only conditionally applicable with caution.
AU  - Huang, Y.*
AU  - Li, C.*
AU  - Wang, H.*
AU  - Hu, Q.*
AU  - Wang, R.*
AU  - Chang, C.*
AU  - Ma, W.*
AU  - Li, W.B.
AU  - Wu, H.*
AU  - Zhang, Y.*
C1  - 58499
C2  - 48164
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 82-87
TI  - A quantitative evaluation of deformable image registration based on MV cone beam CT images: Impact of deformation magnitudes and image modalities.
JO  - Phys. Med.
VL  - 71
PB  - Elsevier Sci Ltd
PY  - 2020
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - PURPOSE: Targeted radiation therapy has seen an increased interest in the past decade. In vitro and in vivo experiments showed enhanced radiation doses due to gold nanoparticles (GNPs) to tumors in mice and demonstrated a high potential for clinical application. However, finding a functionalized molecular formulation for actively targeting GNPs in tumor cells is challenging. Furthermore, the enhanced energy deposition by secondary electrons around GNPs, particularly by short-ranged Auger electrons is difficult to measure. Computational models, such as Monte Carlo (MC) radiation transport codes, have been used to estimate the physical quantities and effects of GNPs. However, as these codes differ from one to another, the reliability of physical and dosimetric quantities needs to be established at cellular and molecular levels, so that the subsequent biological effects can be assessed quantitatively. METHODS: In this work, irradiation of single GNPs of 50 nm and 100 nm diameter by X-ray spectra generated by 50 and 100 peak kilovoltages was simulated for a defined geometry setup, by applying multiple MC codes in the EURADOS framework. RESULTS: The mean dose enhancement ratio of the first 10 nm-thick water shell around a 100 nm GNP ranges from 400 for 100 kVp X-rays to 600 for 50 kVp X-rays with large uncertainty factors up to 2.3. CONCLUSIONS: It is concluded that the absolute dose enhancement effects have large uncertainties and need an inter-code intercomparison for a high quality assurance; relative properties may be a better measure until more experimental data is available to constrain the models.
AU  - Li, W.B.
AU  - Belchior, A.*
AU  - Beuve, M.*
AU  - Chen, Y.Z.*
AU  - di Maria, S.*
AU  - Friedland, W.
AU  - Gervais, B.*
AU  - Heide, B.*
AU  - Hocine, N.*
AU  - Ipatov, A.*
AU  - Klapproth, A.
AU  - Li, C.Y.*
AU  - Li, J.L.*
AU  - Multhoff, G.*
AU  - Poignant, F.*
AU  - Qiu, R.*
AU  - Rabus, H.*
AU  - Rudek, B.*
AU  - Schuemann, J.*
AU  - Stangl, S.*
AU  - Testa, E.*
AU  - Villagrasa, C.*
AU  - Xie, W.Z.*
AU  - Zhang, Y.B.*
C1  - 58462
C2  - 48078
SP  - 147-163
TI  - Intercomparison of dose enhancement ratio and secondary electron spectra for gold nanoparticles irradiated by X-rays calculated using multiple Monte Carlo simulation codes.
JO  - Phys. Med.
VL  - 69
PY  - 2020
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - In our paper [1] we presented the dose enhancement ratios (DERs) and the electron spectra for a single gold nanoparticle (GNP) irradiated by a narrow X-ray beam calculated with multiple Monte Carlo simulation codes. During further analysis of the data for an internal EURADOS report, we identified the following inconsistencies in the simulations, which affect the results presented in the above-mentioned article [1]: 1. PENELOPE#1 and PENELOPE#2: The X-ray spectra in the input files were given as cumulative probabilities. The start points of the X-ray photons were sampled from a square rather than a circular area as PENELOPE main programs do not provide the option of a circular source. The first error was corrected in new simulations of PENELOPE#1 using PENELOPE-2018. The variant source geometry was taken into account for the electron spectra by using a fluence correction factor of 4/π (area of the square divided by the area of circle). The impact of the source geometry on the DER is assumed to be small enough to be disregarded for the purpose of this corrigendum. PENELOPE#2 has not performed new simulations and, therefore, data of PENELOPE#2 are not presented in this corrigendum.2. G4/DNA#1: The electron spectra for a GNP of diameter 50 nm irradiated by 50 kVp X-rays, a GNP of diameter 100 nm irradiated by 50 kVp X-rays and a GNP of diameter 100 nm irradiated by 100 kVp X-rays were not divided by the energy bin width of 5 eV. This error has been corrected in this corrigendum.3. G4/DNA#2: There was an error in the readout file. The electron spectrum for a GNP of 50 nm diameter irradiated by 50 kVp X-rays was newly simulated and the corrected spectrum is shown in this corrigendum. No new simulations for a GNP of diameter 100 nm irradiated by 50 kVp X-rays have been performed, therefore no data for this spectrum are included in this corrigendum.4. G4/DNA#3: The electron spectra were not divided by the energy bin width of 5 eV. This error has been corrected in this corrigendum.5. TOPAS-nBio: The X-rays were sampled from a larger circular source area with a total radius of the radius of the GNP plus 10 nm. Factors of 1.36 and 1.19 (calculated by [Formula presented]) have been used for correction of the electron spectra of a GNP with diameter of 50 nm and 100 nm, respectively. In this corrigendum, as for PENELOPE#1, the impact of the variant source geometry on the DER is assumed to be small enough to be disregarded.6. MCNP6: The electron spectra were recorded only for electrons ejected from the GNP in the angular bin 0–15 degree (approximately normal direction with respect to the surface of the GNP). The electron spectra were not divided by the energy bin width of 50 eV. In this corrigendum, the electron spectra were multiplied by a factor of 11 (estimated by the participant of MCNP6 from the ratio of the total number of ejected electrons and those ejected in the close-to-normal bin) and divided by the energy bin width of 50 eV in order to reconstruct the total electron spectrum emitted from a GNP.7. MDM: The electron spectra were normalized to a photon fluence of 1 photon per cm2 instead of one photon per circular source area. In this corrigendum, the electron spectra for a GNP of diameter 50 nm and a GNP of diameter 100 nm were multiplied by the respective ratio of the two photon fluences of 7.09x107 and 2.11x107, respectively.For the aforementioned reasons, Figs. 4-8 and Table 2 presented in our paper [1] were replotted and tabulated in the following. In addition to the above corrected Figs. 4-8 and Table 2, the text regarding to the UF in Sections of “Abstract”, “Results”, “Discussions” and “Conclusion” were correspondingly corrected in the following. Abstract “Results: The mean dose enhancement ratio of the first 10 nm-thick water shell around a 100 nm GNP ranges from 400 for 100 kVp X-rays to 600 for 50 kVp X-rays with large uncertainty factors up to 1.6.” 3 Results 3.1.2 Uncertainty factor of DER in nanometer ranges “∙∙∙. It can be seen in Fig. 5(a)-(d) that the UFs of DERs for the results are 1.3–1.6, 1.3–1.5, 1.3–1.5 and 1.2–1.5, respectively, with the maximum UF values occurring at the water shells located at 280 nm, 440 nm, 470 nm and 540 nm, respectively. The UFs at the first 10 nm-thick shells for the four radiation scenarios are relatively small and close to 1.3.” 3.1.3 DER in micrometer ranges This sentence “It is noted that, for 100 kVp X-rays, the DER calculated by PENELOPE at 2 µm to 8 µm from the surface of the GNP drops down more steeply than the other results, in contrast to the irradiation scenarios by 50 kVp X-rays.” should be removed. 3.2.2 Uncertainty factor of electron energy spectra “∙∙∙. Overall, the highest UF, from maximum 8.6 to minimum 1.3 was found for a GNP of diameter 100 nm irradiated by 50 kVp X-rays, and the lowest UF, from maximum 5.6 to minimum 1.1, for a GNP of diameter 100 nm irradiated by 100 kVp X-rays. If the high UF values at the low energy range, say from 50 eV to 200 eV were neglected due to the very high uncertainty of the cross sections of lower electron energies, then the UF of the energy spectra ranges from 2.5 for the scenario of a GNP of diameter 100 nm irradiated by 50 kVp X-rays to 2.2 for the scenario of a GNP of diameter 100 nm irradiated by 50 kVp X-rays. ∙∙∙. As an example, ∙∙∙. The UF at 100 eV for the four radiation scenarios is very large, expanding from 2.8 to 4.8. The UFs at 1,000 eV and 10,000 eV for these four scenarios is smaller than that at 100 eV, ranging from 1.4 to 1.7 and from 1.3 to 2.9, respectively.” 4 Discussion 4.1 Uncertainty of DER and energy spectra of secondary electrons ”∙∙∙. A quantitative uncertainty analysis revealed a larger uncertainty factor ranging from 1.3 up to 4.8 (see Table 2). A very large uncertainty was found at energy 100 eV for the scenario of a GNP of diameter 50 nm irradiated by 50 kVp X-ray spectra. ∙∙∙.” “Despite the large variation of electron energy spectra shown in the lower to middle energy ranges in Fig. 7, the DER showed comparably smaller uncertainty factors, from 1.2 up to 1.6 in the whole range from 10 nm to 1000 nm for 10 nm-thick water shells. If the maximum UFs of DERs for each radiation scenario were excluded, the overall UF is smaller than a factor of 1.4. ∙∙∙.” The authors would like to apologize for any inconvenience caused. 5 Conclusion “∙∙∙. Despite the larger uncertainty with a maximum UF up to 4.8 for the electron energy spectra, the uncertainty of DER in the 10 nm-thick water shells showed a maximum UF up to 1.6. ∙∙∙.”
AU  - Li, W.B.
AU  - Beuve, M.*
AU  - di Maria, S.*
AU  - Friedland, W.
AU  - Heide, B.*
AU  - Klapproth, A.
AU  - Li, C.Y.*
AU  - Poignant, F.*
AU  - Rabus, H.*
AU  - Rudek, B.*
AU  - Schuemann, J.*
AU  - Villagrasa, C.*
C1  - 60578
C2  - 49411
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 383-388
TI  - Corrigendum to “Intercomparison of dose enhancement ratio and secondary electron spectra for gold nanoparticles irradiated by X-rays calculated using multiple Monte Carlo simulation codes” [Phys. Med. 69 (2020) 147–163] (Physica Medica (2020) 69 (147–163), (S1120179719305320), (10.1016/j.ejmp.2019.12.011)).
JO  - Phys. Med.
VL  - 80
PB  - Elsevier Sci Ltd
PY  - 2020
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Purpose: To review scoring assessments in re-irradiation of high-grade glioma (HGG) patients and how to use scoring for patient stratification. The next aim was to investigate the different approaches employed by the scoring systems and the way they can be applied to build homogeneous patient groups for a reliable prognosis.Methods: We searched the Medline/Pubmed and Web of science databases for relevant articles regarding scores for re-irradiation of recurrent HGG. All references were divided into the following groups: novel score establishment (n = 5), score validation (n = 6), not relevant to this evaluation (n = 26).Results: We identified five scoring systems. Two are modifications of an already existing score. Calculations differ immensely from easy point addition to a more complex formula with including three up to 10 individual parameters. Six validation articles were found for three of the scores; one was validated four times. Two scores were never validated.Conclusion: For recurrent HGG, the clinical situation remains demanding. Due to the heterogeneity of data at reirradiation, patient stratification is important. Several scoring systems have been developed to predict prognosis. As a digital biomarker, scores are of high value regarding quick patient assessment and therapy decision making. For the next generation of digital biomarkers, easy calculation, and inclusion of easily available parameters are crucial.
AU  - Kessel, K.A.
AU  - Combs, S.E.
C1  - 57124
C2  - 47550
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 20-26
TI  - Digital biomarkers: Importance of patient stratification for re-irradiation of glioma patients - Review of latest developments regarding scoring assessment.
JO  - Phys. Med.
VL  - 67
PB  - Elsevier Sci Ltd
PY  - 2019
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Purpose: Microbeam radiation therapy is a developing technique that promises superior tumour control and better normal tissue tolerance using spatially fractionated X-ray beams only tens of micrometres wide.Radiochromic film dosimetry at micrometric scale was performed using a microdensitometer, but this instrument presents limitations in accuracy and precision, therefore the use of a microscope is suggested as alternative. The detailed procedures developed to use the two devices are reported allowing a comparison.Methods: Films were irradiated with single microbeams and with arrays of 50 mu m wide microbeams spaced by a 400 mu m pitch, using a polychromatic beam with mean energy of 100 keV. The film dose measurements were performed using two independent instruments: a microdensitometer (MDM) and an optical microscope (OM).Results: The mean values of the absolute dose measured with the two instruments differ by less than 5% but the OM provides reproducibility with a standard deviation of 1.2% compared to up to 7% for the MDM. The resolution of the OM was determined to be similar to 1 to 2 mu m in both planar directions able to resolve pencil beams irradiation, while the MDM reaches at the best 20 mu m resolution along scanning direction. The uncertainties related to the data acquisition are 2.5-3% for the OM and 9-15% for the MDM.Conclusion: The comparison between the two devices validates that the OM provides equivalent results to the MDM with better precision, reproducibility and resolution. In addition, the possibility to study dose distributions in two-dimensions over wider areas definitely sanctions the OM as substitute of the MDM.
AU  - Pellicioli, P.*
AU  - Bartzsch, S.
AU  - Donzelli, M.*
AU  - Krisch, M.*
AU  - Bräuer-Krisch, E.*
C1  - 56813
C2  - 47399
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 106-113
TI  - High resolution radiochromic film dosimetry: Comparison of a microdensitometer and an optical microscope.
JO  - Phys. Med.
VL  - 65
PB  - Elsevier Sci Ltd
PY  - 2019
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - One measurement and an algebraic formula are used to calculate the incident air kerma (Ka,i) at the skin after any CT examination, including cone-beam CT (CBCT) and multi-slice CT (MSCT). Empty scans were performed with X-ray CBCT systems (dental, C-arm and linac guidance scanners) as well as two MSCT scanners. The accumulated Ka,i at the flat panel (in CBCT) or the maximum incident air kerma at the isocentre (in MSCT) were measured using a solid-state probe. The average Ka,i(skin), at the skin of a hypothetical patient, was calculated using the proposed formula. Additional measurements of dose at the isocentre (DFOV) and kerma-area product (KAP), as well as Ka,i(skin) from thermoluminiscence dosimeters (TLDs) and size-specific dose estimates are presented for comparison. The Ka,i(skin) for the standard head size in the dental scanner, the C-arm (high dose head protocol) and the linac (head protocol) were respectively 3.33 ± 0.19 mGy, 15.15 ± 0.76 mGy and 3.23 ± 0.16 mGy. For the first MSCT, the calculated Ka,i(skin) was 13.1 ± 0.7 mGy and the TLDs provided a Ka,i(skin) between 10.3 ± 1.1 mGy and 13.8 ± 1.4 mGy. Estimation of patient air kerma in tomography with an uncertainty below 7% is thus feasible using an empty scan and conventional measurement tools. The provided equations and website can be applied to a standard size for the sake of quality control or to several sizes for the definition of diagnostic reference levels (DRLs). The obtained incident air kerma can be directly compared to the Ka,i from other X-ray modalities as recommended by ICRU and IAEA.
AU  - de las Heras Gala, H.
AU  - Schöfer, F.*
AU  - Schöfer, H.*
AU  - Sánchez Casanueva, R.M.*
AU  - Zervides, C.*
AU  - Mair, K.*
AU  - Al-Zoubi, Q.*
AU  - Renger, B.*
AU  - de Las Heras Gala, T.*
AU  - Schlattl, H.
C1  - 53360
C2  - 44577
CY  - Oxford
SP  - 92-102
TI  - A patient-centric approach to quality control and dosimetry in CT including CBCT.
JO  - Phys. Med.
VL  - 47
PB  - Elsevier Sci Ltd
PY  - 2018
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Purpose: Lead free protective clothing can create a higher part of secondary radiation (SR) than products that are based on lead. Hence, the attenuation properties may be downgraded. The international measuring standard IEC 61331-1:2014 declares the "inverse broad beam geometry" (IBG) as standard method, which has recently been modified to IBG* by the Physikalisch Technische Bundesanstalt (PTB). Because of the unspecific partial irradiation of the ionization chamber problems in the evaluation of lead equivalence values (LEVs) can occur. An alternative method proposed in this paper overcomes these problems.& para;& para;Materials and methods: The alternative setup "modified broad beam geometry" (BBG*) was tested and compared to the IBG* method by performing Monte Carlo simulations and radiation measurements including several lead-composite and lead-free protective materials.& para;& para;Results: Simulations show a reduced collection efficiency of SR under IBG* whereas BBG* features a high degree of SR collection. Material samples with a high amount of SR can feature up to 8% higher LEVs compared to IBG*. For most of the currently salable materials the differences of BBG* vs IBG* amount to < 3% (0.25 mm LEV) and < 1% (0.50 mm LEV). In special cases the currently practiced method can lead to heavier protective clothings.& para;& para;Conclusions: The proposed BBG* setup meets the specifications of the IEC standard with respect to energy response and SR collection. The method should be implemented in the IEC standard.
AU  - Eder, H.*
AU  - Schlattl, H.
C1  - 52817
C2  - 44180
CY  - Oxford
SP  - 6-11
TI  - IEC 61331-1: A new setup for testing lead free X-ray protective clothing.
JO  - Phys. Med.
VL  - 45
PB  - Elsevier Sci Ltd
PY  - 2018
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Flatworms of the species Schmidtea mediterranea are immortal-adult animals contain a large pool of pluripotent stem cells that continuously differentiate into all adult cell types. Therefore, single-cell transcriptome profiling of adult animals should reveal mature and progenitor cells. By combining perturbation experiments, gene expression analysis, a computational method that predicts future cell states from transcriptional changes, and a lineage reconstruction method, we placed all major cell types onto a single lineage tree that connects all cells to a single stem cell compartment. We characterized gene expression changes during differentiation and discovered cell types important for regeneration. Our results demonstrate the importance of single-cell transcriptome analysis for mapping and reconstructing fundamental processes of developmental and regenerative biology at high resolution.
AU  - Gennaro, G.*
AU  - Avramova-Cholakova, S.*
AU  - Azzalini, A.*
AU  - Luisa Chapel, M.*
AU  - Chevalier, M.*
AU  - Ciraj, O.*
AU  - de las Heras Gala, H.
AU  - Gershan, V.*
AU  - Hemdal, B.*
AU  - Keavey, E.*
AU  - Lanconelli, N.*
AU  - Menhart, S.*
AU  - João Fartaria, M.*
AU  - Pascoal, A.*
AU  - Pedersen, K.*
AU  - Rivetti, S.*
AU  - Rossetti, V.*
AU  - Semturs, F.*
AU  - Sharp, P.*
AU  - Torresin, A.*
C1  - 53488
C2  - 44888
CY  - 1200 New York Ave, Nw, Washington, Dc 20005 Usa
SP  - 55-64
TI  - Quality controls in digital mammography protocol of the EFOMP mammo working group.
JO  - Phys. Med.
VL  - 48
PB  - Amer Assoc Advancement Science
PY  - 2018
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Purpose: The objective of this study was to evaluate the image degrading factors in quantitative Lu-177 SPECT imaging when using both main gamma photopeak energies.Methods: Phantom measurements with two different vials containing various calibrated activities in air or water were performed to derive a mean calibration factor (CF) for large and small volumes of interest (VOIs). In addition, Monte Carlo simulations were utilized to investigate the effect of scatter energy window width, scatter correction method, such as effective scatter source estimation (ESSE) and triple energy window (TEW), and attenuation map on the quantification of Lu-177. Results: The measured mean CF using large and small VOIs in water was 4.50 +/- 0.80 and 4.80 +/- 0.72 cps MBq(-1) , respectively. Simulations showed a reference CF of 3.3 cps MBq(-1) for the water-filled phantom considering all photons excluding scattered events. By using the attenuation map generated for 190 keV photons, the calculated CFs for 113 keV and 208 keV are 10% lower than by using the weighted mean energy of 175 keV for Lu-177. The calculated CF using the TEW correction was 17% higher than using the ESSE method for a water-filled phantom. However, our findings showed that an appropriate scatter window combination can reduce this difference between TEW and ESSE methods.Conclusions: The present work implies that choosing a suitable width of scatter energy windows can reduce uncertainties in radioactivity quantification. It is suggested to generate the attenuation map at 113 keV and 208 keV, separately. Furthermore, using small VOIs is suggested in CF calculation.
AU  - Karimi Ghodoosi, E.
AU  - D'Alessandria, C.*
AU  - Li, Y.*
AU  - Bartel, A.*
AU  - Köhner, M.*
AU  - Höllriegl, V.
AU  - Navab, N.*
AU  - Eiber, M.*
AU  - Li, W.
AU  - Frey, E.*
AU  - Ziegler, S.*
C1  - 54866
C2  - 45840
CY  - The Boulevard, Langford Lane, Kidlington, Oxford Ox5 1gb, Oxon, England
SP  - 74-80
TI  - The effect of attenuation map, scatter energy window width, and volume of interest on the calibration factor calculation in quantitative Lu-177 SPECT imaging: Simulation and phantom study.
JO  - Phys. Med.
VL  - 56
PB  - Elsevier Sci Ltd
PY  - 2018
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Flatworms of the species Schmidtea mediterranea are immortal-adult animals contain a large pool of pluripotent stem cells that continuously differentiate into all adult cell types. Therefore, single-cell transcriptome profiling of adult animals should reveal mature and progenitor cells. By combining perturbation experiments, gene expression analysis, a computational method that predicts future cell states from transcriptional changes, and a lineage reconstruction method, we placed all major cell types onto a single lineage tree that connects all cells to a single stem cell compartment. We characterized gene expression changes during differentiation and discovered cell types important for regeneration. Our results demonstrate the importance of single-cell transcriptome analysis for mapping and reconstructing fundamental processes of developmental and regenerative biology at high resolution.
AU  - Peeken, J.C.*
AU  - Bernhofer, M.*
AU  - Wiestler, B.*
AU  - Goldberg, T.*
AU  - Cremers, D.*
AU  - Rost, B.*
AU  - Wilkens, J.J.*
AU  - Combs, S.E.
AU  - Nüsslin, F.*
C1  - 53489
C2  - 44882
CY  - 1200 New York Ave, Nw, Washington, Dc 20005 Usa
SP  - 27-36
TI  - Radiomics in radiooncology - Challenging the medical physicist.
JO  - Phys. Med.
VL  - 48
PB  - Amer Assoc Advancement Science
PY  - 2018
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - The aim of the guideline presented in this article is to unify the test parameters for image quality evaluation and radiation output in all types of cone-beam computed tomography (CBCT) systems. The applications of CBCT spread over dental and interventional radiology, guided surgery and radiotherapy. The chosen tests provide the means to objectively evaluate the performance and monitor the constancy of the imaging chain. Experience from all involved associations has been collected to achieve a consensus that is rigorous and helpful for the practice. The guideline recommends to assess image quality in terms of uniformity, geometrical precision, voxel density values (or Hounsfield units where available), noise, low contrast resolution and spatial resolution measurements. These tests usually require the use of a phantom and evaluation software. Radiation output can be determined with a kerma-area product meter attached to the tube case. Alternatively, a solid state dosimeter attached to the flat panel and a simple geometric relationship can be used to calculate the dose to the isocentre. Summary tables including action levels and recommended frequencies for each test, as well as relevant references, are provided. If the radiation output or image quality deviates from expected values, or exceeds documented action levels for a given system, a more in depth system analysis (using conventional tests) and corrective maintenance work may be required.
AU  - de las Heras Gala, H.
AU  - Torresin, A.*
AU  - Dasu, A.*
AU  - Rampado, O.*
AU  - Delis, H.*
AU  - Hernández Girón, I.*
AU  - Theodorakou, C.*
AU  - Andersson, J.*
AU  - Holroyd, J.*
AU  - Nilsson, M.*
AU  - Edyvean, S.*
AU  - Gershan, V.*
AU  - Hadid-Beurrier, L.*
AU  - Hoog, C.*
AU  - Delpon, G.*
AU  - Sancho Kolster, I.*
AU  - Peterlin, P.*
AU  - Garayoa Roca, J.*
AU  - Caprile, P.*
AU  - Zervides, C.*
C1  - 51297
C2  - 43128
CY  - Oxford
SP  - 67-72
TI  - Quality control in cone-beam computed tomography (CBCT) EFOMP-ESTRO-IAEA protocol (summary report).
JO  - Phys. Med.
VL  - 39
PB  - Elsevier Sci Ltd
PY  - 2017
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - The feasibility of reducing the differences between patient-specific internal doses and doses estimated using reference phantoms was evaluated. Relatively simple adjustments to a polygon-surface ICRP adult male reference phantom were applied to fit selected individual dimensions using the software Rhinoceros®4.0. We tested this approach on two patient-specific phantoms: the biggest and the smallest phantoms from the Helmholtz Zentrum München library. These phantoms have unrelated anatomy and large differences in body-mass-index. Three models approximating each patient's anatomy were considered: the voxel and the polygon-surface ICRP adult male reference phantoms and the adjusted polygon-surface reference phantom. The Specific Absorbed Fractions (SAFs) for internal photon and electron sources were calculated with the Monte Carlo code EGSnrc. Employing the time-integrated activity coefficients of a radiopharmaceutical (S)-4-(3-(18)F-fluoropropyl)-l-glutamic acid and the calculated SAFs, organ absorbed-dose coefficients were computed following the formalism promulgated by the Committee on Medical Internal Radiation Dose. We compared the absorbed-dose coefficients between each patient-specific phantom and other models considered with emphasis on the cross-fire component. The corresponding differences for most organs were notably lower for the adjusted reference models compared to the case when reference models were employed. Overall, the proposed approach provided reliable dose estimates for both tested patient-specific models despite the pronounced differences in their anatomy. To capture the full range of inter-individual anatomic variability more patient-specific phantoms are required. The results of this test study suggest a feasibility of estimating patient-specific doses within a relative uncertainty of 25% or less using adjusted reference models, when only simple phantom scaling is applied.
AU  - Zvereva, A.
AU  - Schlattl, H.
AU  - Zankl, M.
AU  - Becker, J.
AU  - Petoussi-Henß, N.
AU  - Yeom, Y.S.*
AU  - Kim, C.H.*
AU  - Hoeschen, C.*
AU  - Parodi, K.*
C1  - 51364
C2  - 43095
CY  - Oxford
SP  - 100-112
TI  - Feasibility of reducing differences in estimated doses in nuclear medicine between a patient-specific and a reference phantom.
JO  - Phys. Med.
VL  - 39
PB  - Elsevier Sci Ltd
PY  - 2017
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - PURPOSE: To demonstrate the feasibility of gold-specific spectral CT imaging for the detection of liver lesions in humans at low concentrations of gold as targeted contrast agent. METHODS: A Monte Carlo simulation study of spectral CT imaging with a photon-counting and energy-resolving detector (with 6 energy bins) was performed in a realistic phantom of the human abdomen. The detector energy thresholds were optimized for the detection of gold. The simulation results were reconstructed with the K-edge imaging algorithm; the reconstructed gold-specific images were filtered and evaluated with respect to signal-to-noise ratio and contrast-to-noise ratio (CNR). RESULTS: The simulations demonstrate the feasibility of spectral CT with CNRs of the specific gold signal between 2.7 and 4.8 after bilateral filtering. Using the optimized bin thresholds increases the CNRs of the lesions by up to 23% compared to bin thresholds described in former studies. CONCLUSIONS: Gold is a promising new CT contrast agent for spectral CT in humans; minimum tissue mass fractions of 0.2 wt% of gold are required for sufficient image contrast.
AU  - Müllner, M.
AU  - Schlattl, H.
AU  - Hoeschen, C.
AU  - Dietrich, O.*
C1  - 46278
C2  - 37467
SP  - 875-881
TI  - Feasibility of spectral CT imaging for the detection of liver lesions with gold-based contrast agents - a simulation study.
JO  - Phys. Med.
VL  - 31
IS  - 8
PY  - 2015
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - PURPOSE: The purpose of this study was to assess whether grating-based X-ray imaging may have a role in imaging of pulmonary nodules on radiographs. MATERIALS AND METHODS: A mouse lung containing multiple lung tumors was imaged using a small-animal scanner with a conventional X-ray source and a grating interferometer for phase-contrast imaging. We qualitatively compared the signal characteristics of lung nodules on transmission, dark-field and phase-contrast images. Furthermore, we quantitatively compared signal characteristics of lung tumors and the adjacent lung tissue and calculated the corresponding contrast-to-noise ratios. RESULTS: Of the 5 tumors visualized on the transmission image, 3/5 tumors were clearly visualized and 1 tumor was faintly visualized in the dark-field image as areas of decreased small angle scattering. In the phase-contrast images, 3/5 tumors were clearly visualized, while the remaining 2 tumors were faintly visualized by the phase-shift occurring at their edges. No additional tumors were visualized in either the dark-field or phase-contrast images. Compared to the adjacent lung tissue, lung tumors were characterized by a significant decrease in transmission signal (median 0.86 vs. 0.91, p = 0.04) and increase in dark-field signal (median 0.71 vs. 0.65, p = 0.04). Median contrast-to-noise ratios for the visualization of lung nodules were 4.4 for transmission images and 1.7 for dark-field images (p = 0.04). CONCLUSION: Lung nodules can be visualized on all three radiograph modalities derived from grating-based X-ray imaging. However, our initial data suggest that grating-based multimodal X-ray imaging does not increase the sensitivity of chest radiographs for the detection of lung nodules.
AU  - Meinel, F.G.*
AU  - Schwab, F.*
AU  - Yaroshenko, A.*
AU  - Velroyen, A.*
AU  - Bech, M.*
AU  - Hellbach, K.*
AU  - Fuchs, J.*
AU  - Stiewe, T.*
AU  - Yildirim, A.Ö.
AU  - Bamberg, F.*
AU  - Reiser, M.F.*
AU  - Pfeiffer, F.*
AU  - Nikolaou, K.*
C1  - 28636
C2  - 33508
CY  - Oxford
SP  - 352-357
TI  - Lung tumors on multimodal radiographs derived from grating-based X-ray imaging - a feasibility study.
JO  - Phys. Med.
VL  - 30
IS  - 3
PB  - Elsevier Science
PY  - 2014
SN  - 1120-1797
ER  - 

TY  - JOUR
AB  - Exposures to the extremities have increased due to new therapeutic protocols involving beta sources. In this study, thermoluminescent dosimeters based on α-Al2O3:C were used to map the dose distribution to the extremities of physicians and paramedical personnel handling beta emitters. The results showed a strong inhomogeneous dose distribution between different phalanxes, fingers and hands of all the investigated subjects, without an indication of systematic trends in the dose patterns. Consequently, conventional dosimetric practices, based on the use of wrist or ring dosimeters, may be not suitable for providing reliable assessments of the inhomogeneous doses received at the fingertip.
AU  - Mancosu, P.*
AU  - Cantone, M.C.*
AU  - Veronese, I.*
AU  - Giussani, A.
C1  - 1976
C2  - 27026
SP  - 44-48
TI  - Spatial distribution of beta extremity doses in nuclear medicine: A feasibility study with thin α-AI₂O₃:C TLDs.
JO  - Phys. Med.
VL  - 26
IS  - 1
PB  - Elsevier
PY  - 2010
SN  - 1120-1797
ER  -