TY - JOUR AB - OBJECTIVES: High prevalence of visceral obesity and its associated complications underscore the importance of accurately quantifying visceral adipose tissue (VAT) depots. While whole-body MRI offers comprehensive insights into adipose tissue distribution, it is resource-intensive. Alternatively, evaluation of defined single slices provides an efficient approach for estimation of total VAT volume. This study investigates the influence of sex-, age-, and BMI on VAT distribution along the craniocaudal axis and total VAT volume obtained from single slice versus volumetric assessment in 3D MRI and aims to identify age-independent locations for accurate estimation of VAT volume from single slice assessment. MATERIALS AND METHODS: This secondary analysis of the prospective population-based German National Cohort (NAKO) included 3D VIBE Dixon MRI from 11,191 participants (screened between May 2014 and December 2016). VAT and spine segmentations were automatically generated using fat-selective images. Standardized craniocaudal VAT profiles were generated. Axial percentage of total VAT was used for identification of reference locations for volume estimation of VAT from a single slice. RESULTS: Data from 11,036 participants (mean age, 52 ± 11 years, 5681 men) were analyzed. Craniocaudal VAT distribution differed qualitatively between men/women and with respect to age/BMI. Age-independent single slice VAT estimates demonstrated strong correlations with reference VAT volumes. Anatomical locations for accurate VAT estimation varied with sex/BMI. CONCLUSIONS: The selection of reference locations should be different depending on BMI groups, with a preference for caudal shifts in location with increasing BMI. For women with obesity (BMI >30 kg/m2), the L1 level emerges as the optimal reference location. AU - Haueise, T. AU - Schick, F. AU - Stefan, N. AU - Grune, E.* AU - von Itter, M.N.* AU - Kauczor, H.U.* AU - Nattenmüller, J.* AU - Norajitra, T.* AU - Nonnenmacher, T.* AU - Rospleszcz, S. AU - Maier-Hein, K.H.* AU - Schlett, C.L.* AU - Weiss, J.B.* AU - Fischer, B.* AU - Jöckel, K.H.* AU - Krist, L.* AU - Niendorf, T.* AU - Peters, A. AU - Sedlmeier, A.M.* AU - Willich, S.N.* AU - Bamberg, F.* AU - Machann, J. C1 - 73733 C2 - 57201 TI - Refining visceral adipose tissue quantification: Influence of sex, age, and BMI on single slice estimation in 3D MRI of the German National Cohort. JO - Z. Med. Phys. PY - 2025 SN - 0939-3889 ER - TY - JOUR AB - This work proposes a method for automatic standardized assessment of bone marrow volume and spatial distribution of the proton density fat fraction (PDFF) in vertebral bodies. Intra- and interindividual variability in size and shape of vertebral bodies is a challenge for comparable interindividual evaluation and monitoring of changes in the composition and distribution of bone marrow due to aging and/or intervention. Based on deep learning image segmentation, bone marrow PDFF of single vertebral bodies is mapped to a cylindrical template and corrected for the inclination with respect to the horizontal plane. The proposed technique was applied and tested in a cohort of 60 healthy (30 males, 30 females) individuals. Obtained bone marrow volumes and mean PDFF values are comparable to former manual and (semi-)automatic approaches. Moreover, the proposed method allows shape-independent characterization of the spatial PDFF distribution inside vertebral bodies. AU - Haueise, T. AU - Stefan, N. AU - Schulz, T.J.* AU - Schick, F. AU - Birkenfeld, A.L. AU - Machann, J. C1 - 67400 C2 - 54169 TI - Automated shape-independent assessment of the spatial distribution of proton density fat fraction in vertebral bone marrow. JO - Z. Med. Phys. PY - 2023 SN - 0939-3889 ER - TY - JOUR AB - In human radiotherapy a safety margin (PTV margin) is essential for successful irradiation and is usually part of clinical treatment planning. In preclinical radiotherapy research with small animals, most uncertainties and inaccuracies are present as well, but according to the literature a margin is used only scarcely. In addition, there is only little experience about the appropriate size of the margin, which should carefully be investigated and considered, since sparing of organs at risk or normal tissue is affected. Here we estimate the needed margin for preclinical irradiation by adapting a well-known human margin recipe from van Herck et al. to the dimensions and requirements of the specimen on a small animal radiation research platform (SARRP). We adjusted the factors of the described formula to the specific challenges in an orthotopic pancreatic tumor mouse model to establish an appropriate margin concept. The SARRP was used with its image-guidance irradiation possibility for arc irradiation with a field size of 10 × 10 mm2 for 5 fractions. Our goal was to irradiate the clinical target volume (CTV) of at least 90% of our mice with at least 95% of the prescribed dose. By carefully analyzing all relevant factors we gain a CTV to planning target volume (PTV) margin of 1.5 mm for our preclinical setup. The stated safety margin is strongly dependent on the exact setting of the experiment and has to be adjusted for other experimental settings. The few stated values in literature correspond well to our result. Even if using margins in the preclinical setting might be an additional challenge, we think it is crucial to use them to produce reliable results and improve the efficacy of radiotherapy. AU - Kampfer, S.* AU - Dobiasch, S. AU - Combs, S.E. AU - Wilkens, J.J. C1 - 67900 C2 - 54378 CY - Radarweg 29, 1043 Nx Amsterdam, Netherlands SP - 533-541 TI - Development of a PTV margin for preclinical irradiation of orthotopic pancreatic tumors derived from a well-known recipe for humans. JO - Z. Med. Phys. VL - 34 IS - 4 PB - Elsevier PY - 2023 SN - 0939-3889 ER - TY - JOUR AB - Absorbed dose heterogeneity in kidney tissues is an important issue in radiopharmaceutical therapy. The effect of absorbed dose heterogeneity in nephrotoxicity is, however, not fully understood yet, which hampers the implementation of treatment optimization by obscuring the interpretation of clinical response data and the selection of optimal treatment options. Although some dosimetry methods have been developed for kidney dosimetry to the level of microscopic renal substructures, the clinical assessment of the microscopic distribution of radiopharmaceuticals in kidney tissues currently remains a challenge. This restricts the anatomical resolution of clinical dosimetry, which hinders a thorough clinical investigation of the impact of absorbed dose heterogeneity. The potential of absorbed dose-response modelling to support individual treatment optimization in radiopharmaceutical therapy is recognized and gaining attraction. However, biophysical modelling is currently underexplored for the kidney, where particular modelling challenges arise from the convolution of a complex functional organization of renal tissues with the function-mediated dose distribution of radiopharmaceuticals. This article reviews and discusses the heterogeneity of absorbed dose distribution in kidney tissues and the absorbed dose-response modelling of nephrotoxicity in radiopharmaceutical therapy. The review focuses mainly on the peptide receptor radionuclide therapy with beta-particle emitting somatostatin analogues, for which the scientific literature reflects over two decades of clinical experience. Additionally, detailed research perspectives are proposed to address various identified challenges to progress in this field. AU - Saldarriaga Vargas, C.* AU - Andersson, M.* AU - Bouvier-Capely, C.* AU - Li, W.B. AU - Madas, B.* AU - Covens, P.* AU - Struelens, L.* AU - Strigari, L.* C1 - 67624 C2 - 53931 CY - Radarweg 29, 1043 Nx Amsterdam, Netherlands SP - 491-509 TI - Heterogeneity of absorbed dose distribution in kidney tissues and dose-response modelling of nephrotoxicity in radiopharmaceutical therapy with beta-particle emitters: A review. JO - Z. Med. Phys. VL - 34 IS - 4 PB - Elsevier PY - 2023 SN - 0939-3889 ER - TY - JOUR AB - PURPOSE: Ventilation-induced tumour motion remains a challenge for the accuracy of proton therapy treatments in lung patients. We investigated the feasibility of using a 4D virtual CT (4D-vCT) approach based on deformable image registration (DIR) and motion-aware 4D CBCT reconstruction (MA-ROOSTER) to enable accurate daily proton dose calculation using a gantry-mounted CBCT scanner tailored to proton therapy. METHODS: Ventilation correlated data of 10 breathing phases were acquired from a porcine ex-vivo functional lung phantom using CT and CBCT. 4D-vCTs were generated by (1) DIR of the mid-position 4D-CT to the mid-position 4D-CBCT (reconstructed with the MA-ROOSTER) using a diffeomorphic Morphons algorithm and (2) subsequent propagation of the obtained mid-position vCT to the individual 4D-CBCT phases. Proton therapy treatment planning was performed to evaluate dose calculation accuracy of the 4D-vCTs. A robust treatment plan delivering a nominal dose of 60Gy was generated on the average intensity image of the 4D-CT for an approximated internal target volume (ITV). Dose distributions were then recalculated on individual phases of the 4D-CT and the 4D-vCT based on the optimized plan. Dose accumulation was performed for 4D-vCT and 4D-CT using DIR of each phase to the mid position, which was chosen as reference. Dose based on the 4D-vCT was then evaluated against the dose calculated on 4D-CT both, phase-by-phase as well as accumulated, by comparing dose volume histogram (DVH) values (Dmean, D2%, D98%, D95%) for the ITV, and by a 3D-gamma index analysis (global, 3%/3mm, 5Gy, 20Gy and 30Gy dose thresholds). RESULTS: Good agreement was found between the 4D-CT and 4D-vCT-based ITV-DVH curves. The relative differences ((CT-vCT)/CT) between accumulated values of ITV Dmean, D2%, D95% and D98% for the 4D-CT and 4D-vCT-based dose distributions were -0.2%, 0.0%, -0.1% and -0.1%, respectively. Phase specific values varied between -0.5% and 0.2%, -0.2% and 0.5%, -3.5% and 1.5%, and -5.7% and 2.3%. The relative difference of accumulated Dmean over the lungs was 2.3% and Dmean for the phases varied between -5.4% and 5.8%. The gamma pass-rates with 5Gy, 20Gy and 30Gy thresholds for the accumulated doses were 96.7%, 99.6% and 99.9%, respectively. Phase-by-phase comparison yielded pass-rates between 86% and 97%, 88% and 98%, and 94% and 100%. CONCLUSIONS: Feasibility of the suggested 4D-vCT workflow using proton therapy specific imaging equipment was shown. Results indicate the potential of the method to be applied for daily 4D proton dose estimation. AU - Bondesson, D. AU - Meijers, A.* AU - Janssens, G.* AU - Rit, S.* AU - Rabe, M.* AU - Kamp, F.* AU - Niepel, K.* AU - Otter, L.A.D.* AU - Both, S.* AU - Brousmiche, S.* AU - Dinkel, J. AU - Belka, C.* AU - Parodi, K.* AU - Knopf, A.* AU - Kurz, C.* AU - Landry, G.* C1 - 61239 C2 - 49762 SP - 74-84 TI - Anthropomorphic lung phantom based validation of in-room proton therapy 4D-CBCT image correction for dose calculation. JO - Z. Med. Phys. VL - 32 IS - 1 PY - 2022 SN - 0939-3889 ER - TY - JOUR AB - In the field of preclinical radiotherapy, many new developments were driven by technical innovations. To make research of different groups comparable in that context and reliable, high quality has to be maintained. Therefore, standardized protocols and programs should be used. Here we present a guideline for a comprehensive and efficient quality assurance program for an image-guided small animal irradiation system, which is meant to test all the involved subsystems (imaging, treatment planning, and the irradiation system in terms of geometric accuracy and dosimetric aspects) as well as the complete procedure (end-to-end test) in a time efficient way. The suggestions are developed on a Small Animal Radiation Research Platform (SARRP) from Xstrahl (Xstrahl Ltd., Camberley, UK) and are presented together with proposed frequencies (from monthly to yearly) and experiences on the duration of each test. All output and energy related measurements showed stable results within small variation. Also, the motorized parts (couch, gantry) and other geometrical alignments were very stable. For the checks of the imaging system, the results are highly dependent on the chosen protocol and differ according to the settings. We received nevertheless stable and comparably good results for our mainly used protocol. All investigated aspects of treatment planning were exactly fulfilled and also the end-to-end test showed satisfying values. The mean overall time we needed for our checks to have a well monitored machine is less than two hours per month. AU - Kampfer, S.* AU - Duda, M.A.* AU - Dobiasch, S. AU - Combs, S.E. AU - Wilkens, J.J.* C1 - 64733 C2 - 52426 SP - 261-272 TI - A comprehensive and efficient quality assurance program for an image-guided small animal irradiation system. JO - Z. Med. Phys. VL - 32 IS - 3 PY - 2022 SN - 0939-3889 ER - TY - JOUR AB - Purpose: To simulate secondary neutron radiation fields that had been measured at different relative positions during phantom irradiation inside a scanning proton therapy gantry treatment room. Further, to identify origin, energy distribution, and angular emission of the secondary neutrons as a function of proton beam energy. Methods: The FLUKA Monte Carlo code was used to model the relevant parts of the treatment room in a scanned pencil beam proton therapy gantry including shielding walls, floor, major metallic gantry-components, patient table, and a homogeneous PMMA target. The proton beams were modeled based on experimental beam ranges in water and spot shapes in air. Neutron energy spectra were simulated at 0°, 45°, 90° and 135° relative to the beam axis at 2 m distance from isocenter for monoenergetic 11 × 11 cm2 fields from 200 MeV, 140 MeV, 75 MeV initial proton beams, as well as for 118 MeV protons with a 5 cm thick PMMA range shifter. The total neutron spectra were scored for these four positions and proton energies. FLUKA neutron spectra simulations were crosschecked with Geant4 simulations using initial proton beam properties from FLUKA-generated phase spaces. Additionally, the room-components generating secondary neutrons in the room and their contributions to the total spectrum were identified and quantified. Results: FLUKA and Geant4 simulated neutron spectra showed good general agreement with published measurements in the whole simulated neutron energy range of 10−10 to 103 MeV. As in previous studies, high-energy (E ≥ 19.6 MeV) neutrons from the phantom are most prevalent along 0°, while thermalized (1 meV ≤ E < 0.4 eV) and fast (100 keV ≤ E < 19.4 MeV) neutrons dominate the spectra in the lateral and backscatter direction. The iron of the large bending magnet and its counterweight mounted on the gantry were identified as the most determinant sources of secondary fast-neutrons, which have been lacking in simplified room simulations. Conclusions: The results helped disentangle the origin of secondary neutrons and their dominant contributions and were strengthened by the fact that a cross comparison was made using two independent Monte Carlo codes. The complexity of such room model can in future be limited using the result. They may further be generalized in that they can be used for an assessment of neutron fields, possibly even at facilities where detailed neutron measurements and simulations cannot be performed. They may also help to design future proton therapy facilities and to reduce unwanted radiation doses from secondary neutrons to patients. AU - Englbrecht, F.S.* AU - Trinkl, S. AU - Mares, V. AU - Rühm, W. AU - Wielunski, M. AU - Wilkens, J.J.* AU - Hillbrand, M.* AU - Parodi, K.* C1 - 61401 C2 - 50210 CY - Radarweg 29, 1043 Nx Amsterdam, Netherlands SP - 215-228 TI - A comprehensive Monte Carlo study of out-of-field secondary neutron spectra in a scanned-beam proton therapy gantry room. JO - Z. Med. Phys. VL - 31 IS - 2 PB - Elsevier PY - 2021 SN - 0939-3889 ER - TY - JOUR AB - The aim of this study was to investigate a single crystal diamond detector, the microDiamond detector from PTW (PTW-Freiburg, Freiburg, Germany), concerning the particular requirements in the set-up and energy range used in small animal radiotherapy (RT) research (around 220 kV). We tested it to find out the minimal required pre-irradiation dose, the dose linearity, dose rate dependency and the angular response as well as usability in the small animal radiation research platform, SARRP (Xstrahl Ltd., Camberley, UK).For a stable signal in the range of energies used in the study, we found a required pre-irradiation dose of 10 Gy. The dose linearity and dose rate dependence measurements showed a very good performance of the microDiamond detector. Regarding the effect of angular dependency, the variation of the response signal is less than 0.5% within the first 15 degrees of the polar angle. In the azimuthal angle, however, there are differences in detector response up to 20%, depending on the range of energies used in the study. In addition, we compared the detector to a radiosensitive film for a profile measurement of a 5 x 5 mm(2) irradiation field. Both methods showed a good accordance with the field size, however, the film has a steeper dose gradient in the penumbra region but also a higher noise than the microDiamond detector.We demonstrated that the microDiamond detector is a useful measurement tool for small animal RT research due to its small size. Nevertheless, it seems to be very important to verify the response of the detector in the given set-up and energy range. AU - Kampfer, S.* AU - Cho, N.H.* AU - Combs, S.E. AU - Wilkens, J.J. C1 - 53596 C2 - 44921 CY - Po Box 211, 1000 Ae Amsterdam, Netherlands SP - 303-309 TI - Dosimetric characterization of a single crystal diamond detector in X-ray beams for preclinical research. JO - Z. Med. Phys. VL - 28 IS - 4 PB - Elsevier Science Bv PY - 2018 SN - 0939-3889 ER - TY - JOUR AB - Estimations of organ doses DT received during computed tomographic examinations are usually performed by applying conversion factors to basic dose indicators like the computed tomography dose index (CTDI) or the dose-length-product (DLP). In addition to the existing conversion factors for beam apertures of 5 mm or 10 mm, we present new DLP-DT conversion factors adapted to high-resolution CT (HRCT) examinations of infants and young children with beam apertures of the order of 1 mm and under consideration of bow tie filtration. Calculations are performed on mathematical MIRD phantoms for an age range from 0, 1, 5, 10, 15 up to (for comparison) 30 years by adapting PCXMC, a Monte Carlo algorithm originally developed by STUK (Helsinki, Finland) for dose reconstructions in projection radiography. For this purpose, each single slice CT examination is approximated by a series of corresponding virtual planar radiographies comprising all focus positions. The transformation of CT exposure parameters into exposure parameters of the series of corresponding planar radiographies is performed by a specially developed algorithm called XCT. The DLP values are evaluated using the EGSRay code. The new method is verified at a beam aperture of 10 mm by comparison with formerly published conversion factors. We show that the higher spatial resolution leads to an enhanced DLP-DT conversion factor if a small organ (e. g. thyroid gland, mammae, uterus, ovaries, testes) is exactly met by the chosen CT slice, while the conversion factor is drastically reduced if the chosen CT slice is positioned above or below the organ. This effect is utilized for dose-saving examinations with only a few single slices instead a full scan, which technique is applied in about 10% of all paediatric chest CT examinations. AU - Seidenbusch, M.C.* AU - Harder, D.* AU - Regulla, D.F. AU - Schneider, K.* C1 - 30869 C2 - 33987 CY - Jena SP - 123-137 TI - Conversion factors for determining organ doses received by paediatric patients in high-resolution single slice computed tomography with narrow collimation. JO - Z. Med. Phys. VL - 24 IS - 2 PB - Elsevier Gmbh, Urban & Fischer Verlag PY - 2014 SN - 0939-3889 ER - TY - JOUR AB - Ziel Ein experimenteller Vergleich des Kontrast-zu-Rausch-Verhältnisses von Transmission und Dunkelfeld-Signalen in Gitterbasiertem Röntgen bei ex-vivo-Mäuse-Lungengewebe. Material und Methoden Lungen dreier gesunder Mäuse wurden ex-vivo in einer Laser-getriebenen kompakten Synchrotron-Röntgenquelle untersucht. Das Hintergrundrauschen der Transmissions- und Dunkelfeld-Bilder wurde aus der Standardabweichung des Signals in einer homogenen Region außerhalb der Probe bestimmt. Der Bildkontrast wurde aus dem Signalumfang in rechteckigen ROIs in peripheren und zentralen Lungengebieten berechnet. Der relative contrast gain (RCG) des Dunkelfeldes im Vergleich zum Transmissionsbild wurde als CNRDF / CNRT berechnet. Ergebnisse Über alle Bilder und Lungen hinweg gab es einen Trend zu einem größeren Kontrast-zu-Rausch-Verhältnis im Dunkelfeld- (CNRDF) als im Transmissionsbild (CNRT) (Median 61 vs. 38, p = 0.10), aber der Unterschied war nur für periphere ROIs signifikant (61 vs. 32, p = 0.03). Der Median des RCG über alle ROIs war >1 (1.84). Die RCG Werte waren für zentrale ROIs signifikant kleiner als für periphere ROIs (1.34 vs. 2.43, p = 0.03). Schlussfolgerung Das Kontrast-zu-Rausch-Verhältnis der Dunkelfeld-Bilder ist im Vergleich zu dem bei Transmissionsbildern insbesondere in peripheren Lungenregionen noch vorteilhafter als in zentralen Regionen. Für eine bestimmte Probe kann eine Berechnung des RCG einen Vergleich erlauben, welche Modalität das bessere Kontrast-zu-Rausch-Verhältnis in einer wohl definierten ROI liefert. AU - Schwab, F.* AU - Schleede, S.* AU - Hahn, D.* AU - Bech, M.* AU - Herzen, J.* AU - Auweter, S.* AU - Bamberg, F.* AU - Achterhold, K.* AU - Yildirim, A.Ö. AU - Bohla, A. AU - Eickelberg, O. AU - Loewen, R.* AU - Gifford, M.* AU - Ruth, R.* AU - Reiser, M.F.* AU - Nikolaou, K.* AU - Pfeiffer, F.* AU - Meinel, F.G.* C1 - 11892 C2 - 30841 SP - 236-242 TI - Vergleich des Kontrast-zu-Rausch-Verhältnisses von Transmissions- und Dunkelfeld-Signal in der gitterbasierten Röntgenbildgebung für gesunde Mäuselungen. JO - Z. Med. Phys. VL - 23 IS - 3 PB - Elsevier PY - 2013 SN - 0939-3889 ER - TY - JOUR AB - The robust algorithm OPED for the reconstruction of images from Radon data has been recently developed. This reconstructs an image from parallel data within a special scanning geometry that does not need rebinning but only a simple re-ordering, so that the acquired fan data can be used directly for the reconstruction. However, if the number of rays per fan view is increased, there appear empty cells in the sinogram. These cells need to be filled by interpolation before the reconstruction can be carried out. The present paper analyzes linear interpolation, cubic splines and parametric (or “damped”) splines for the interpolation task. The reconstruction accuracy in the resulting images was measured by the Normalized Mean Square Error (NMSE), the Hilbert Angle, and the Mean Relative Error. The spatial resolution was measured by the Modulation Transfer Function (MTF). Cubic splines were confirmed to be the most recommendable method. The reconstructed images resulting from cubic spline interpolation show a significantly lower NMSE than the ones from linear interpolation and have the largest MTF for all frequencies. Parametric splines proved to be advantageous only for small sinograms (below 50 fan views). AU - de las Heras, H. AU - Tischenko, O. AU - Xu, Y.* AU - Hoeschen, C. C1 - 3305 C2 - 25240 SP - 7-16 TI - Comparison of interpolation functions to improve a rebinning-free CT-reconstruction algorithm. JO - Z. Med. Phys. VL - 18 IS - 1 PB - Elsevier PY - 2008 SN - 0939-3889 ER - TY - JOUR AU - Regulla, D.F. AU - Griebel, J.* AU - Noßke, D.* AU - Bauer, B.* AU - Brix, G.* C1 - 9824 C2 - 21012 SP - 127-135 TI - Erfassung und Bewertung der Patientenexposition in der diagnostischen Radiologie und Nuklearmedizin. JO - Z. Med. Phys. VL - 13 PY - 2003 SN - 0939-3889 ER - TY - JOUR AU - Zankl, M. C1 - 21710 C2 - 19903 SP - 141-150 TI - Die Berechnung von Konversionsfaktoren für den Strahlenschutz bei äußerer Strahlenexposition. JO - Z. Med. Phys. VL - 11 PY - 2001 SN - 0939-3889 ER - TY - JOUR AU - Regulla, D.F. AU - Hieber, L. AU - Seidenbusch, M.C. C1 - 21235 C2 - 19338 SP - 52-62 TI - Erhöhung von Dosis und biologischen Wirkungen durch rückgestreute Elektronen aus röntgenbestrahlten Materialien höherer Ordnungszahl. JO - Z. Med. Phys. VL - 10 PY - 2000 SN - 0939-3889 ER -