TY - JOUR A1 - Hadert, Nicole A1 - Liu, Qi A1 - Zylka, Waldemar T1 - Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging JF - Current Directions in Biomedical Engineering N2 - Metallic implants in magnetic resonance imaging (MRI) are a potential safety risk since the energy absorption may increase temperature of the surrounding tissue. The temperature rise is highly dependent on implant size. Numerical examinations can be used to calculate the energy absorption in terms of the specific absorption rate (SAR) induced by MRI on orthopaedic implants. This research presents the impact of titanium osteosynthesis spine implants, called spondylodesis, deduced by numerical examinations of energy absorption in simplified spondylodesis models placed in 1.5 T and 3.0 T MRI body coils. The implants are modelled along with a spine model consisting of vertebrae and disci intervertebrales thus extending previous investigations [1, 2]. Increased SARvalues are observed at the ends of long implants, while at the center SAR is significantly lower. Sufficiently short implants show increased SAR along the complete length of the implant. A careful data analysis reveals that the particular anatomy, i.e. vertebrae and disci intervertebrales, has a significant effect on SAR. On top of SAR profile due to the implant length, considerable SAR variations at small scale are observed, e.g. SAR values at vertebra are higher than at disc positions. KW - Kernspintomografie KW - Implantat KW - Spondylodese Y1 - 2016 VL - 2 IS - 1 SP - 653 EP - 658 ER - TY - JOUR A1 - Hadert, Nicole A1 - Liu, Qi A1 - Zylka, Waldemar T1 - Numerical examinations of simplified spondylodesis models concerning energy absorption in magnetic resonance imaging JF - Current Directions in Biomedical Engineering N2 - Metallic implants in magnetic resonance imaging (MRI) are a potential safety risk since the energy absorption may increase temperature of the surrounding tissue. The temperature rise is highly dependent on implant size. Numerical examinations can be used to calculate the energy absorption in terms of the specific absorption rate (SAR) induced by MRI on orthopaedic implants. This research presents the impact of titanium osteosynthesis spine implants, called spondylodesis, deduced by numerical examinations of energy absorption in simplified spondylodesis models placed in 1.5 T and 3.0 T MRI body coils. The implants are modelled along with a spine model consisting of vertebrae and disci intervertebrales thus extending previous investigations [1], [2]. Increased SAR values are observed at the ends of long implants, while at the center SAR is significantly lower. Sufficiently short implants show increased SAR along the complete length of the implant. A careful data analysis reveals that the particular anatomy, i.e. vertebrae and disci intervertebrales, has a significant effect on SAR. On top of SAR profile due to the implant length, considerable SAR variations at small scale are observed, e.g. SAR values at vertebra are higher than at disc positions. Y1 - 2016 U6 - https://doi.org/10.1515/cdbme-2016-0143 SN - 2364-5504 VL - 2 IS - 1 SP - 653 EP - 658 ER - TY - JOUR A1 - Koch, Christian A1 - Schaefers, Gregor A1 - Zylka, Waldemar T1 - A novel phantom design to reduce thermal losses during radio frequency (RF) induced heating testing according to ASTM F2182-09 standard JF - ISRMRM - Proceedings of the International Society for Magnetic Resonance in Medicine Y1 - 2011 UR - https://cds.ismrm.org/protected/11MProceedings/files/3775.pdf SN - 1065-9889 VL - 19 SP - 3775 ER - TY - JOUR A1 - Bertsch, Thomas A1 - Melzer, Andreas A1 - Zylka, Waldemar A1 - Schaefers, Gregor A1 - Busch, Martin T1 - A prototype of an expandable active MRI stent (aMRIs) JF - International Congress Series Y1 - 2001 U6 - https://doi.org/10.1016/S0531-5131(01)00215-1 VL - 1230 SP - 1088 EP - 1093 ER - TY - JOUR A1 - Bartel, Theresa A1 - Mortimer, Jeremy M A1 - Zylka, Waldemar A1 - Paxton, Jennifer A1 - Vorstius, Jan Bernd T1 - Design and Development of a Bioreactor System for Mechanical Stimulation of Musculoskeletal Tissue JF - Current Directions in Biomedical Engineering N2 - We report on the development of a bioreactor system for mechanical stimulation of musculoskeletal tissues. The ultimate object is to improve the quality of medical treatment following injuries of the enthesis tissue. To this end, the tissue formation process through the effect of mechanical stimulation is investigated. A six-well system was designed, 3D printed and tested. An integrated actuator creates strain by applying a force. A contactless position sensor monitors the travels. An electronic circuit controls the bioreactor using a microcontroller. An IoT platform connects the microcontroller to a smartphone, enabling the user to alter variables, trigger actions and monitor the system. The system was stabilised by implementing two PID controllers and safety measures. The results show that the bioreactor design is suited to execute mechanical stimulation and to investigate the tissue formation and regeneration process … Y1 - 2023 U6 - https://doi.org/https://doi.org/10.1515/cdbme-2023-1031 VL - 9 IS - 1 SP - 122 EP - 125 ER - TY - JOUR A1 - Garcia, Maíra M. A1 - Oliveira, Tiago R. A1 - Papoti, Daniel A1 - Chaim, Khallil T. A1 - Otaduy, Maria C. G. A1 - Erni, Daniel A1 - Zylka, Waldemar T1 - Experimental and numerical investigations of a small animal coil for ultra-high field magnetic resonance imaging (7T) JF - Current Directions in Biomedical Engineering N2 - The purpose of this work was to develop and investigate a radiofrequency (RF) coil to perform image studies on small animals using the 7T magnetic resonance imaging (MRI) system, installed in the imaging platform in the autopsy room (Portuguese acronym PISA), at the University of Sao Paulo, Brazil, which is the unique 7T MRI scanner installed in South America. Due to a high demand to create new specific coils for this 7T system, it is necessary to carefully assess the distribution of electromagnetic (EM) fields generated by the coils and evaluate the patient/object safety during MRI procedures. To achieve this goal 3D numerical methods were used to design and analyse a 8-rungs transmit/receive linearly driven birdcage coil for small animals. Calculated magnetic field (B 1) distributions generated by the coil were crosschecked with measured results, indicating good confidence in the simulated results. Y1 - 2019 U6 - https://doi.org/10.1515/cdbme-2019-0132 SN - 2364-5504 VL - 5 IS - 1 SP - 525 EP - 528 ER - TY - JOUR A1 - König, Britta A1 - Guberina, Nika A1 - Kühl, Hilmar A1 - Zylka, Waldemar T1 - Design and first results of a phantom study on the suitability of iterative reconstruction for lung-cancer screening with low-dose computer tomography JF - Current Directions in Biomedical Engineering N2 - In this research computer tomography (CT) iterative reconstruction (IR) algorithms are investigated, specifically the impact of their statistical and model-based strength on image quality in low-dose lung screening CT protocols in comparison to filtered back projection (FBP). It has been probed whether statistical, model-based IR in conjunction with low-dose, and ultra-low-dose protocols are suitable for lungcancer screening. To this end, artificial lung nodules shaped as spheres and spicules made from material with calibrated Hounsfield units (HU) were attached on marked positions in the lung structure of an anthropomorphic phantom. Nodule positions were selected by distinguished radiologists. The phantom with nodules was scanned on a CT Scanner using standard high contrast (SHC), low-dose (LD) and ultra low-dose (ULD) protocol. For reconstruction FBP and the IR algorithm ADMIRE at three different … Y1 - 2019 U6 - https://doi.org/10.1515/cdbme-2019-0149 SN - 2364-5504 VL - 5 IS - 1 SP - 593 EP - 596 ER - TY - JOUR A1 - Ese, Zehra A1 - Zylka, Waldemar T1 - Influence of 12-bit and 16-bit CT values of metals on dose calculation in radiotherapy using PRIMO, a Monte Carlo code for clinical linear accelerators JF - Current directions in biomedical engineering N2 - In this paper, the effect of computed tomography (CT) values of metals in 12-bit and 16-bit extended Hounsfield Unit (EHU) scale on dose calculations in radiotherapy treatment planning systems (TPS) were quantified. Dose simulations for metals in water environment were performed with the software PRIMO in 6MV photon mode. The depth dose profiles were analysed and the relative dose differences between the metals determined with 12-bit and 16-bit CT imaging, respectively, were calculated. Maximum dose differences of ΔAl= 3.0%, ΔTi= 4.5%, ΔCr= 6.2% and ΔCu= 11.6% were measured. In order to increase the accuracy of dose calculation on patients with implants, CT imaging in the EHU scale is recommended. Y1 - 2019 U6 - https://doi.org/10.1515/cdbme-2019-0150 SN - 2364-5504 VL - 5 IS - 1 SP - 597 EP - 600 ER - TY - CHAP A1 - König, Britta A1 - Guberina, Nika A1 - Kühl, Hilmar A1 - Zylka, Waldemar T1 - Design and first results of a phantom study on the suitability of iterative reconstruction for lung-cancer screening with low-dose computer tomography T2 - Konferenz: YRA –Young Researchers AcademyMedTech in NRW. 3rd YRA MedTech Symposium, 24.05.2019 in Aachen Y1 - 2019 UR - http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC_high.pdf SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 SP - 29 EP - 30 ER - TY - CHAP A1 - Nguyen, Hoai Thu A1 - König, Britta A1 - Zylka, Waldemar T1 - Establishment of a 4-Alternative-Forced-Choice test to evaluate the radiological performance of iterative reconstruction in computer tomography images T2 - Konferenz: YRA –Young Researchers AcademyMedTech in NRW. 3rd YRA MedTech Symposium, 24.05.2019 in Aachen Y1 - 2019 UR - http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC_high.pdf SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 SP - 31 EP - 32 ER - TY - CHAP A1 - Garcia, Maíra M. A1 - Oliveira, Tiago R. A1 - Papoti, Daniel A1 - Chaim, Khallil T. A1 - Erni, Daniel A1 - Zylka, Waldemar T1 - Numerical evaluation of small animal warming potential when using a birdcage coil for 7T magnetic resonance imaging T2 - Konferenz: YRA –Young Researchers AcademyMedTech in NRW. 3rd YRA MedTech Symposium, 24.05.2019 in Aachen Y1 - 2019 UR - http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC_high.pdf SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 SP - 33 EP - 34 ER - TY - CHAP A1 - Ese, Zehra A1 - Erni, Daniel A1 - Zylka, Waldemar T1 - The influence of CT tube current and voltage on extended Hounsfield unit values T2 - Konferenz: YRA –Young Researchers AcademyMedTech in NRW. 3rd YRA MedTech Symposium, 24.05.2019 in Aachen Y1 - 2019 UR - http://yra-medtech.de/daten_medtech/dokumente2019/YRA_2019_PROC_high.pdf SN - 978-3-940402-22-6 U6 - https://doi.org/10.17185/duepublico/48750 SP - 27 EP - 28 ER - TY - CHAP A1 - Hadert, Nicole A1 - Zylka, Waldemar ED - Erni, Daniel T1 - Numerical examinations of energy absorption in simplified spondylodesis models T2 - 1st YRA MedTech Symposium 2016. April 8th / 2016 / University of Duisburg-Essen N2 - A simplified model for spondylodesis, ie fixation of vertebrae by osteosynthesis, is developed for virtual magnetic resonance imaging (MRI) examinations to numerically calculate energy absorption. This paper presents results of calculated energy absorption in body tissue surrounding titanium rod implants. In general each wire or rod behaves like an antenna in electromagnetic fields. The specific absorption rate (SAR) profile describes dependence of implant size. SAR hotspots appear near the rod edges. Depending of the size of implant fixation SAR is 62%(small fixation) up to 90.95%(large fixation) higher than without implants. In addition, local SAR profile displays local dependency on tissue: SAR is lower between the vertebrae. Y1 - 2016 SN - 978-3-940402-10-3 U6 - https://doi.org/10.17185/duepublico/40821 SP - 14 EP - 15 ER - TY - CHAP A1 - Lübeck, Robin A1 - Demirel, Cengiz A1 - Riesenbeck, Dorothea A1 - Reimann, Petra A1 - Zylka, Waldemar T1 - Intensitäts-Modulierte-Strahlentherapie (IMRT) und 3D-Planung im Vergleich bei Prostatakrebs-Patienten mit beidseitiger Hüftgelenksprothese T2 - Konferenz: 17. Jahrestagung der Deutschen Gesellschaft für Radioonkologie, 2.-5. Juni 2011 in Wiesbaden Y1 - 2011 ER - TY - CHAP A1 - Schmitjans, Michael A1 - Vorstius, Jan Bernd A1 - Zylka, Waldemar ED - Erni, Daniel ED - Fischerauer, Alice ED - Himmel, Jörg ED - Seeger, Thomas ED - Thelen, Klaus T1 - Upgrade of Bioreactor System Providing Physiological Stimuli to Engineered Musculoskeletal Tissues T2 - 2nd YRA MedTech Symposium 2017. June 8th - 9th / 2017 / Hochschule Ruhr-West N2 - A novel central control interface (CCI) is developed to improve the modular bioreactor system with regard to extendability and modifiability in Tissue Engineering (TE) applications. This paper presents the results developed in the project with open-source hardware and the graphical programming system LabVIEW. A new platform independent User Interface was further developed to contribute to the new flexibility of the device. Y1 - 2017 SN - 978-3-940402-10-3 U6 - https://doi.org/10.17185/duepublico/43984 SP - 45 EP - 46 ER - TY - JOUR A1 - König, Britta A1 - Kühl, Hilmar A1 - Zylka, Waldemar T1 - Computed tomography lung-cancer screening: does iterative reconstruction matter? JF - Shanghai Chest N2 - Background: By reviewing image quality and diagnostic perception, the suitability of a statistical model-based iterative reconstruction algorithm in conjunction with low-dose computed tomography for lung cancer screening is investigated. Methods: Artificial lung nodules shaped as spheres and spiculated spheres made from material with calibrated Hounsfield units were attached on marked positions in the lung structure of anthropomorphic phantoms. The phantoms were scanned using standard high contrast, and two low-dose computed tomography protocols: low-dose and ultra-low-dose. For the reconstruction, the filtered back projection and the iterative reconstruction algorithm ADMIRE at different strength levels (S1–S5) and the kernels Bl57, Br32, Br69 were used. Expert radiologists assessed image quality by performing 4-field-ranking tests and reading all image series to examine the aptitude for the detectability of lung nodules. Signal-to-noise ratio was investigated as objective image quality parameter. Results: In ranking tests for lung foci detection expert radiologists prefer medium to high iterative reconstruction strength levels. For the standard clinical kernel Bl57 and varying phantom diameter, a noticeable preference for S4 was detected. Experienced radiologists graded filtered back projection reconstructed images with the highest perceptibility. Less experienced readers assessed filtered back projection and iterative reconstruction equally with the highest grades for the Bl57 kernel. Independently of the dose protocol, the signal-to-noise ratio increases with the iterative reconstruction strength level, specifically for Br69 and Bl57. Conclusions: Subjective image perception does not significantly correlate with the experience of the radiologist, which presumably mirrors reader’s training and accustomed reading adjustments. Regarding signal-to-noise ratio, iterative reconstruction outperforms filtered back projection for spheres and spiculated spheres. Iterative reconstruction matters. It promises to be an alternative to filtered back projection allowing for lung-cancer screening at markedly decreased radiation exposure but comparable or even improved image quality. Y1 - 2021 U6 - https://doi.org/10.21037/shc-21-9 SN - 2521-3768 VL - 5 IS - October SP - Artikelnr. 35 ER - TY - JOUR A1 - Gorges, Verena A1 - Zylka, Waldemar T1 - Reducing dose of Cone-Beam CT used for patient positioning in radiooncology JF - Current Directions in Biomedical Engineering N2 - Cone-Beam computed tomography (CBCT) has become the most important component of modern radiotherapy for positioning tumor patients directly before treatment. In this work we investigate alternations to standard acquisition protocol, called preset, for patients with a tumor in the thoracic region. The effects of the changed acquisition parameters on the image quality are evaluated using the Catphan Phantom and the image analysis software Smári. The weighted CT dose index (CTDIW) is determined in each case and the effects of the different acquisition protocols on the patient dose are classified accordingly. Additionally, the clinical suitability of alternative presets is tested by investigating correctness of image registration using the CIRS thorax phantom. The results show that a significant dose reduction can be achieved. It can be reduced by 51% for a full rotation by adjusting the gantry speed. Y1 - 2021 U6 - https://doi.org/10.1515/cdbme-2021-2058 SN - 2364-5504 VL - 7 IS - 2 SP - 227 EP - 230 ER - TY - CHAP A1 - Qamhiyeh, Sima A1 - Khouya, A. A1 - Zylka, Waldemar A1 - Stuschke, M. A1 - Pöttgen, C. T1 - Vergleich der interfraktionellen Variation der Zwerchfell-Position im atemgetriggerten CBCT mit dem Planungs-4D-CT als Basis für das Atemcoaching und für die Dosisakkumulation T2 - Strahlentherapie und Onkologie. Journal of radiation oncology, biology, physics Y1 - 2021 U6 - https://doi.org/10.1007/s00066-021-01791-4 SN - 0179-7158 VL - 197 IS - Supplement 1 SP - S39 EP - S40 ER - TY - CHAP A1 - König, Britta A1 - Gernhardt, C. A1 - Guberina, Nika A1 - Kühl, Hilmar A1 - Forsting, Michael A1 - Zylka, Waldemar T1 - Suitability of iterative reconstruction for lung-cancer screening with low-dose computer tomography: First results of a phantom study. T2 - European Congress of Radiology 2020 Y1 - 2020 U6 - https://doi.org/10.26044/ecr2020/C-02150 SP - C-02150 ER - TY - JOUR A1 - Bos, Denise A1 - König, Britta A1 - Blex, Sebastian A1 - Zensen, Sebastian A1 - Opitz, Marcel A1 - Maier, Sandra A1 - Forsting, Michael A1 - Zylka, Waldemar A1 - Kühl, Hilmar A1 - Wetter, Axel A1 - Guberina, Nika T1 - Experimental examination of radiation doses from cardiac and liver CT perfusion in a phantom study as a function of organ, age and sex JF - Journal of Radiological Protection N2 - Cardiac and liver computed tomography (CT) perfusion has not been routinely implemented in the clinic and requires high radiation doses. The purpose of this study is to examine the radiation exposure and technical settings for cardiac and liver CT perfusion scans at different CT scanners. Two cardiac and three liver CT perfusion protocols were examined with the N1 LUNGMAN phantom at three multi-slice CT scanners: a single-source (I) and second- (II) and third-generation (III) dual-source CT scanners. Radiation doses were reported for the CT dose index (CTDIvol) and dose–length product (DLP) and a standardised DLP (DLP10cm) for cardiac and liver perfusion. The effective dose (ED10cm) for a standardised scan length of 10 cm was estimated using conversion factors based on the International Commission on Radiological Protection (ICRP) 110 phantoms and tissue-weighting factors from ICRP 103. The proposed total lifetime attributable risk of developing cancer was determined as a function of organ, age and sex for adults. Radiation exposure for CTDIvol, DLP/DLP10 cm and ED10 cm during CT perfusion was distributed as follows: for cardiac perfusion (II) 144 mGy, 1036 mGy·cm/1440 mGy·cm and 39 mSv, and (III) 28 mGy, 295 mGy·cm/279 mGy·cm and 8 mSv; for liver perfusion (I) 225 mGy, 3360 mGy·cm/2249 mGy·cm and 54 mSv, (II) 94 mGy, 1451 mGy·cm/937 mGy·cm and 22 mSv, and (III) 74 mGy, 1096 mGy·cm/739 mGy·cm and 18 mSv. The third-generation dual-source CT scanner applied the lowest doses. Proposed total lifetime attributable risk increased with decreasing age. Even though CT perfusion is a high-dose examination, we observed that new-generation CT scanners could achieve lower doses. There is a strong impact of organ, age and sex on lifetime attributable risk. Further investigations of the feasibility of these perfusion scans are required for clinical implementation. Y1 - 2021 U6 - https://doi.org/10.1088/1361-6498/abf71f SN - 0952-4746 VL - 41 IS - 3 SP - 512 ER - TY - JOUR A1 - Bos, Denise A1 - König, Britta A1 - Blex, Sebastian A1 - Zensen, Sebastian A1 - Opitz, Marcel A1 - Maier, Sandra A1 - Forsting, Michael A1 - Zylka, Waldemar A1 - Kühl, Hilmar A1 - Wetter, Axel A1 - Guberina, Nika T1 - Experimental Examination of Radiation Doses Of Dual-and Single-Energy Computed Tomography in Chest And Upper Abdomen in a Phantom Study JF - Radiation Protection Dosimetry N2 - The aim of this phantom study is to examine radiation doses of dual- and single-energy computed tomography (DECT and SECT) in the chest and upper abdomen for three different multi-slice CT scanners. A total of 34 CT protocols were examined with the phantom N1 LUNGMAN. Four different CT examination types of different anatomic regions were performed both in single- and dual-energy technique: chest, aorta, pulmonary arteries for suspected pulmonary embolism and liver. Radiation doses were examined for the CT dose index CTDIvol and dose-length product (DLP). Radiation doses of DECT were significantly higher than doses for SECT. In terms of CTDIvol, radiation doses were 1.1–3.2 times higher, and in terms of DLP, these were 1.1–3.8 times higher for DECT compared with SECT. The third-generation dual-source CT applied the lowest dose in 7 of 15 different examination types of different anatomic regions. Y1 - 2021 U6 - https://doi.org/10.1093/rpd/ncab052 SN - 0144-8420 VL - 193 IS - 3-4 SP - 237 EP - 246 ER - TY - JOUR A1 - König, Britta A1 - Guberina, Nika A1 - Kühl, Hilmar A1 - Zylka, Waldemar T1 - Eignet sich die statistische modellbasierte iterative Rekonstruktion mit low-dose Protokollen der Computertomografie für Lungenkrebs-Screening? Erste Ergebnisse einer Phantomstudie. JF - RöFo. Fortschritte auf dem Gebiet der Röntgenstrahlen und der bildgebenden Verfahren Y1 - 2020 U6 - https://doi.org/10.1055/s-0040-1703452 SN - 1438-9010 VL - 192 IS - S01 SP - 110 ER - TY - JOUR A1 - König, Britta A1 - Guberina, Nika A1 - Kühl, Hilmar A1 - Zylka, Waldemar T1 - Validation of iterative CT reconstruction by inter and intra observer performance assessment of artificial lung foci JF - Current Directions in Biomedical Engineering Y1 - 2020 U6 - https://doi.org/10.1515/cdbme-2020-3137 SN - 2364-5504 VL - 6 IS - 3 ER - TY - CHAP A1 - Ese, Zehra A1 - Qamhiyeh, Sima A1 - Kreutner, Jakob A1 - Schaefers, Gregor A1 - Erni, Daniel A1 - Zylka, Waldemar ED - Lhotska, Lenka ED - Sukupova, Lucie ED - Lacković, Igor ED - Ibbott, Geoffrey S. T1 - CT Extended Hounsfield Unit Range in Radiotherapy Treatment Planning for Patients with Implantable Medical Devices T2 - World Congress on Medical Physics and Biomedical Engineering 2018. June 3-8, 2018, Prague, Czech Republic (Vol.3) N2 - Radiotherapy (RT) treatment planning is based on computed tomography (CT) images and traditionally uses the conventional Hounsfield unit (CHU) range. This HU range is suited for human tissue but inappropriate for metallic materials. To guarantee safety of patient carrying implants precise HU quantification is beneficial for accurate dose calculations in planning software. Some modern CT systems offer an extended HU range (EHU). This study focuses the suitability of these two HU ranges for the quantification of metallic components of active implantable medical devices (AIMD). CT acquisitions of various metallic and non-metallic materials aligned in a water phantom were investigated. From our acquisitions we calculated that materials with mass-density ρ > 3.0 g/cm3 cannot be represented in the CHU range. For these materials the EHU range could be used for accurate HU quantification. Since the EHU range does not effect the HU values for materials ρ < 3.0 g/cm3, it can be used as a standard for RT treatment planning for patient with and without implants. Y1 - 2018 SN - 978-981-10-9022-6 U6 - https://doi.org/10.1007/978-981-10-9023-3_111 SP - 599 EP - 603 PB - Springer CY - Singapore ER - TY - JOUR A1 - Ese, Zehra A1 - Kressmann, Marcel A1 - Kreutner, Jakob A1 - Schaefers, Gregor A1 - Erni, Daniel A1 - Zylka, Waldemar T1 - Influence of conventional and extended CT scale range on quantification of Hounsfield units of medical implants and metallic objects JF - Technisches Messen (tm). Plattform für Methoden, Systeme und Anwendungen der Messtechnik N2 - We report on the suitability of two different ranges of Hounsfield units (HU) in computed tomography (CT) for the quantification of metallic components of active implantable medical devices (AIMD). The conventional Hounsfield units (CHU) range, which is traditionally used in radiology, is well suited for tissue but suspected inappropriate for metallic materials. Precise HU values are notably beneficial in radiotherapy (RT) for accurate dose calculations, thus for the safety of patient carrying implants. Some of today’s CT machines offers an extended Hounsfield units (EHU) range. This study presents CT acquisitions of a water phantom containing various metallic discs and an implantable-cardioverter defibrillator (IPG). We show that the comparison of HU values at EHU and CHU ranges clearly reveals the superiority and accuracy of EHU. Some geometrical discrepancies perpendicular to slices are observed. At EHU metal artifact reduction algorithms (MAR) underestimates HU values rendering MAR potentially inappropriate for RT. Y1 - 2018 U6 - https://doi.org/10.1515/teme-2017-0122 SN - 0171-8096 VL - 85 IS - 5 SP - 343 EP - 350 ER - TY - JOUR A1 - Roque, Thaís A1 - Zylka, Waldemar T1 - Modelling the Growth and Treatment of Tumours JF - GIT laboratory journal Europe N2 - Cancer is a leading cause of morbidity and mortality worldwide, with approximately 14 million new cases and 8.2 million cancer related deaths in 2012 [1]. Moreover, the global cancer burden is expected to exceed 20 million new cancer cases by 2025. Understanding the spatial and temporal behaviour of cancer is a crucial precondition to achieve a successful treatment. Because no two cancer cases are the same, every patient should receive a treatment plan designed specifically for her case, in order to improve the patient’s survival chances. Y1 - 2016 SN - 1611-6038 VL - 3-4 SP - 34 EP - 36 ER - TY - CHAP A1 - Ese, Zehra A1 - Tuma, Lara A1 - Qamhiyeh, Sima A1 - Kreutner, Jakob A1 - Schaefers, Gregor A1 - Erni, Daniel A1 - Zylka, Waldemar T1 - Extended CT Hounsfield values scale as a method to improve radiotherapy for patients with active and metallic implants T2 - Biomedical engineering = Biomedizinische Technik. Joint journal of the German Society for Biomedical Engineering in VDE and the Austrian and Swiss Societies for Biomedical Engineering Y1 - 2018 U6 - https://doi.org/10.1515/bmt-2018-6051 SN - 0013-5585 VL - 63 IS - S1 SP - 303 ER - TY - CHAP A1 - Wassenberg, Jörg A1 - Zylka, Waldemar ED - Erni, Daniel T1 - Modeling of avascular tumor growth by reaction-diffusion equations and cellular automata T2 - 1st YRA MedTech Symposium 2016. April 8th / 2016 / University of Duisburg-Essen Y1 - 2016 SN - 978-3-940402-10-3 U6 - https://doi.org/10.17185/duepublico/40821 SP - 56 ER - TY - CHAP A1 - Euting, Stephan A1 - Araújo-Moreira, Fernando M. A1 - Zylka, Waldemar ED - Buzug, Thorsten M. ED - Borgert, Jörn T1 - Magnetic Particle Imaging Using Ferromagnetic Magnetization T2 - Magnetic Particle Imaging. A Novel SPIO Nanoparticle Imaging Technique N2 - Nanofluids, defined as fluids containing suspended solid nanoparticles, are potential systems for utilization in biomedical applications. Magnetic Particle Imaging (MPI) uses superparamagnetic nanofluids, e.g. a colloidal suspension of iron oxide particles. In this work a new biocompatible nanofluid based on pure and stable ferromagnetic carbon is investigated. Although this material has a relatively small value of coercive magnetic field, it does exhibit a true ferromagnetic behavior up to 300 K. We present results obtained from numerical investigations performed to calculate the impact of a ferromagnetic magnetization to the MPI signal chain. Moreover, by modeling ferromagnetic magnetization we prove here the general suitability of ferromagnetic materials for MPI. Due to the low saturation magnetization, however, MPI for ferromagnetic carbon will be possible only in the near future when realistic concentrations of the nanofluid ferromagnetic carbon will be experimentally obtainable. Y1 - 2012 SN - 978-3-642-24132-1 U6 - https://doi.org/10.1007/978-3-642-24133-8_3 SP - 15 EP - 20 PB - Springer CY - Berlin ER - TY - JOUR A1 - Zylka, Waldemar A1 - Wassenberg, Jörg T1 - Investigation of avascular tumor–immune system interactions using a CA–PDE model JF - Current directions in biomedical engineering N2 - We report on investigations that illustrate the interaction between the specific immune system and a young avascular tumor growing due to a diffusive nutrient supply. We formulate a hybrid cellular automata-partial differential equation (CA-PDE) model which includes cell cycle dynamics and allows for tracking the spatial and temporal evolution of this elaborate biological system. We present results of two dimensional numerical simulations that, specifically in this work, include special cases of the spherical and papillary tumor growth, the infiltration of immune system cells into the tumor and the escape of tumor cells from the regime of the immune cells. Y1 - 2018 U6 - https://doi.org/10.1515/cdbme-2018-0148 SN - 2364-5504 VL - 4 IS - 1 SP - 615 EP - 619 ER - TY - JOUR A1 - Galonske, Kirsten A1 - Thiele, Martin A1 - Ernst, Iris A1 - Lehrke, Ralph A1 - Zylka, Waldemar T1 - Comparison of treatment plans calculated by Ray Tracing and Monte Carlo algorithms for head and thorax radiotherapy with Cyberknife JF - Current directions in biomedical engineering N2 - This study investigates differences between treatment plans generated by Ray Tracing (RT) and Monte Carlo (MC) calculation algorithms in homogeneous and heterogeneous body regions. Particularly, we focus on the head and on the thorax, respectively, for robotic stereotactic radiotherapy and radiosurgery with Cyberknife. Radiation plans for tumors located in the head and in the thorax region have been calculated and compared to each other in 47 cases and several tumor types. Y1 - 2017 U6 - https://doi.org/10.1515/cdbme-2017-0136 SN - 2364-5504 VL - 3 IS - 2 SP - 647 EP - 650 ER - TY - JOUR A1 - Roque, Thaís A1 - Kalkan, Zehra A1 - Zylka, Waldemar T1 - Biological effectiveness in hypofractionation: Modeling tumor survival probability for large doses with a stochastic cell-cycle model JF - Biomedical engineering = Biomedizinische Technik. Joint journal of the German Society for Biomedical Engineering in VDE and the Austrian and Swiss Societies for Biomedical Engineering Y1 - 2012 U6 - https://doi.org/https://doi.org/10.1515/bmt-2012-4111 VL - 57 IS - SI-1-Track-O SP - 202 EP - 205 ER - TY - CHAP A1 - Galonske, Kirsten A1 - Thiele, Martin A1 - Zylka, Waldemar ED - Erni, Daniel ED - Fischerauer, Alice ED - Himmel, Jörg ED - Seeger, Thomas ED - Thelen, Klaus T1 - Monte Carlo and Ray Tracing Algorithm for treatment planning in clinical applications with Cyberknife T2 - 2nd YRA MedTech Symposium 2017. June 8th - 9th / 2017 / Hochschule Ruhr-West Y1 - 2017 SN - 978-3-940402-10-3 U6 - https://doi.org/10.17185/duepublico/43984 SP - 16 EP - 17 ER - TY - CHAP A1 - Ese, Zehra A1 - Qamhiyeh, Sima A1 - Kreutner, Jakob A1 - Schaefers, Gregor A1 - Erni, Daniel A1 - Zylka, Waldemar T1 - Erweiterte CT Hounsfield Werte Skala als eine Methode zu Verbesserung der Strahlentherapie für Patienten mit aktiven und metallischen Implantaten T2 - Konferenz: 49. Jahrestagung der DGMP und 21. Jahrestagung der Deutschen Sektion der ISMRM, 19.-22. September 2018 in Nürnberg Y1 - 2018 ER - TY - JOUR A1 - Otto, Heinz A1 - Zylka, Waldemar A1 - Kloska, Jenny T1 - MTRA-Mangel entgegenwirken – Erste Absolventen des Studienganges „Medizinische Radiologietechnologie“ in Deutschland JF - Der Radiologe. Zeitschrift für diagnostische und interventionelle Radiologie, Radioonkologie, Nuklearmedizin Y1 - 2017 U6 - https://doi.org/10.1007/s00117-017-0293-0 SN - 0033-832X VL - 57 IS - 8 SP - 684 EP - 685 ER - TY - JOUR A1 - Roque, Thaís A1 - Garcia Otaduy, Maria Concepcion A1 - Zylka, Waldemar T1 - Integration of Patient Specific MRI Imaging Data Into a Stochastic Low-Grade Glioma Model JF - Biomedical Engineering. Biomedizinische Technik Y1 - 2013 U6 - https://doi.org/10.1515/bmt-2013-4342 SN - 0013-5585 VL - 58 IS - SI-1-Track-N ER - TY - JOUR A1 - Kalkan, Zehra A1 - Zylka, Waldemar T1 - Protraction Effects in a Stochastic Cell-Cycle Tumor Model Exposed to Fractionated Radiotherapy JF - Biomedical Engineering. Biomedizinische Technik Y1 - 2013 U6 - https://doi.org/10.1515/bmt-2013-4340 SN - 0013-5585 VL - 58 IS - SI-1-Track-N ER - TY - JOUR A1 - Breeuwer, Marcel M. A1 - Holden, Mark A1 - Zylka, Waldemar T1 - Detection and correction of geometric distortion in 3D MR images JF - Proceedings Volume 4322, Medical Imaging 2001: Image Processing N2 - Three-dimensional magnetic resonance medical images may contain scanner- and patient-induced geometric distortion. For qualitative diagnosis, geometric errors of a few millimeters are often tolerated. However, quantitative applications such as image-guided neurosurgery and radiotherapy can require an accuracy of a millimeter or better. We have developed a method to accurately measure scanner-induced geometric distortion and to correct the MR images for this type of distortion. The method involves a number of steps. First, a specially designed phantom is scanned that contains a large number of reference structures on positions with a manufacturing error of less than 0.05 mm. Next, the positions of the reference structures are automatically detected in the scanned images and a higher-order polynomial distortion-correction transformation is estimated. Then the patient is scanned and the transformation is applied to correct the patient images for the detected distortion. The distortion-correction method is explained in detail in this paper. The accuracy of the method has been measured with synthetically generated phantom scans that contain an exactly-known amount and type of distortion. The reproducibility of the method has been measured by applying it to a series of consecutive phantom scans. Validation results are briefly described in this paper, a more-detailed description is given in another submission to SPIE Medical Imaging 2001. Y1 - 2001 U6 - https://doi.org/10.1117/12.430986 ER - TY - JOUR A1 - Zylka, Waldemar A1 - Sabczynski, Jörg T1 - Effect of Localization Devices and Registration Methods on the Accuracy of Stereotactic Frame Systems Predicted by the Gaussian Approach JF - Computer Aided Surgery N2 - A qualitative work‐flow analysis of a neurosurgical procedure indicates that the resolution of the image used to plan the intervention is the major source of inaccuracy. Quantitative experimental measurements confirm this observation. They fail, however, to explain the relationship between the accuracy of the frame components involved in a stereotactic procedure and the overall application accuracy. This investigation shows that the novel Gaussian approach is a flexible framework for the calculation of the application accuracy of frame systems. Therefore, the Gaussian approach provides a detailed understanding of the interplay between the various factors affecting accuracy. The basic ideas and limitations of the Gaussian approach are briefly explained. The effect of fiducial marker distribution and registration is investigated and shown to introduce a spatial dependence to the accuracy. The results of the Gaussian approach are compared with experimental data for three stereotactic frame devices: Leksell G, Cosman–Roberts–Wells, and Brown–Roberts–Wells. Although the Gaussian approach is an approximation, it reproduces the accuracy measured in the experiment within the statistical error of that experiment. Comp Aid Surg 4:77–86 (1999). © 1999 Wiley‐Liss, Inc. Y1 - 1999 U6 - https://doi.org/10.3109/10929089909148162 SN - 1092-9088 VL - 4 IS - 2 SP - 77 EP - 86 ER - TY - JOUR A1 - Garcia, Maira M. A1 - Chaim, Khallil T. A1 - Otaduy, Maria C. G. A1 - Rennings, Andreas A1 - Erni, Daniel A1 - Vatanchi, Maryam A1 - Zylka, Waldemar T1 - Investigating the influence of dielectric pads in 7T magnetic resonance imaging – simulated and experimental assessment JF - Current Directions in Biomedical Engineering Y1 - 2020 U6 - https://doi.org/10.1515/cdbme-2020-3007 SN - 2364-5504 VL - 6 IS - 3 ER - TY - CHAP A1 - Smajic-Peimann, Sylvia A1 - Euting, Stephan A1 - Kotrache, Sami A1 - Zylka, Waldemar T1 - Simulation of SAR and temperature distributions for human organs with two different Birdcage designs at 42,6MHz and 127,8MHz T2 - Konferenz: Jahrestagung der DGBMT und 3-Länder-Tagung D-A-CH, 05.-08. Oktober 2010 in Rostock Y1 - 2010 ER - TY - JOUR A1 - Schaefers, Gregor A1 - Zylka, Waldemar A1 - Busch, Martin A1 - Melzer, Andreas T1 - Wireless application of an intravascular resonator within the Vena Cava for MRI JF - International Congress Series Y1 - 2001 U6 - https://doi.org/10.1016/S0531-5131(01)00227-8 VL - 1230 IS - June SP - 1094 EP - 1099 ER - TY - CHAP A1 - Koch, Christian A1 - Schaefers, Gregor A1 - Zylka, Waldemar T1 - Heating of Fractured Stent in MRI at 64 & 128 MHZ: A Numerical Study T2 - Konferenz: ISMRM Workshop on MR Safety: RF Heating of the Human in MRI, 15.-17. Oktober 2010 in Stillwater, Minnesota (USA) Y1 - 2010 ER - TY - JOUR A1 - Ese, Zehra A1 - Zylka, Waldemar T1 - Extension of the Stoichiometric Calibration of CT Hounsfield values to Metallic Materials JF - Current Directions in Biomedical Engineering Y1 - 2020 U6 - https://doi.org/10.1515/cdbme-2020-3135 SN - 2364-5504 VL - 6 IS - 3 ER - TY - CHAP A1 - Zylka, Waldemar T1 - Auf dem Weg zur Beherrschung der Gefahren - Simulation der Wechselwirkungen des HF-Feldes mit Implantaten T2 - Konferenz: 14. Fortbildungsseminar der Arbeitsgemeinschaft Physik und Technik der Deutschen Röntgengesellschaft, 18.-19. Juni 2010 in Münster Y1 - 2010 ER - TY - JOUR A1 - Zylka, Waldemar A1 - Sabczynski, Jörg A1 - Schmitz, Georg T1 - A Gaussian approach for the calculation of the accuracy of stereotactic frame systems JF - Medical Physics N2 - Stereotactic frame systems are widely used in neurosurgery. The accuracy of frame devices is considered as a gold standard to which the accuracy of new frameless stereotactic navigation systems is compared. The purpose of this study is to develop a general approach for the prediction of the application accuracy of stereotactic systems. The approach will be applied to the frame‐based biopsy performed with three frame devices: Leksell G, Cosman–Roberts–Wells (CRW), and Brown–Roberts–Wells (BRW). A work‐flow analysis will be carried out demonstrating that the accuracy relevant for a clinical application comprises several error sources including imaging, target and entry point selection, image to frame coordinates registration, and the setting of mechanical parameters of the frame. These error sources will be postulated to obey a Gaussian distribution probability density. The linear, i.e., Gaussian, error propagation, will be used to link all error contributions thus to calculate the cumulative accuracy of the frame used in the application. Although the Gaussian approach is an approximation, it allows for an analytical treatment of the accuracy. Both the accuracy at the target point and the accuracy of the probe needle guidance along the planned trajectory have been investigated. Of great significance is the relationship found between accuracy, pixel dimension, and image slice thickness, the latter being the dominant factor for slices of more than 1.5 mm thickness, yielding inaccuracies larger than 1.5 mm. For target points the predictions for the application accuracy have been compared to the results of measurements, showing good agreement with the experimental data. Y1 - 1999 U6 - https://doi.org/10.1118/1.598529 VL - 26 IS - 3 SP - 381 EP - 391 ER - TY - CHAP A1 - Ese, Zehra A1 - Kressmann, Marcel A1 - Kreutner, Jakob A1 - Douiri, Amin A1 - Scholz, Stefan A1 - Görtz, Wolfgang A1 - Schaefers, Gregor A1 - Erni, Daniel A1 - Zylka, Waldemar ED - Erni, Daniel ED - Fischerauer, Alice ED - Himmel, Jörg ED - Seeger, Thomas ED - Thelen, Klaus T1 - A comparison of CT Hounsfield units of medical implants and their metallic and electrical components determined by a conventional and an extended CT-scale T2 - 2nd YRA MedTech Symposium 2017. June 8th - 9th / 2017 / Hochschule Ruhr-West Y1 - 2017 SN - 978-3-940402-10-3 U6 - https://doi.org/10.17185/duepublico/43984 SP - 12 EP - 13 ER - TY - CHAP A1 - Rudigkeit, Nina A1 - Gouvêa Santos, Bruno A1 - Roque, Thaís A1 - Zylka, Waldemar T1 - Modeling Tumor Growth and Treatment using Imaging Data T2 - Konferenz: 45. Jahrestagung der DGBMT, 27.-30. September 2011 in Freiburg Y1 - 2011 ER -