Abstract
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.
Zusammenfassung
Wir berichten über den Einfluss von zwei verschiedenen Skalenbereichen für Hounsfiled-Werte (HU) auf die Quantifizierung von metallischen Komponenten von aktiven medizinisch implantierbaren Medizinprodukten (AIMD) in der Computertompgraphie (CT). Der konventionelle Hounsfield-Wertebereich (CHU), welcher seine Anwendung in der traditionellen Radiologie findet, ist geeignet für Gewebe jedoch ungeeignet für metallische Materialien. Präzise HU-Werte sind besonders wichtig für eine akurate Dosis-Berechnung in der Strahlentherapie, insbesondere bei Patienten mit medizinischen Implantaten. Einige der heutigen CT-Systeme bieten einen erweiterten HU-Bereich (EHU). In dieser Arbeit werden CT-Aufnahmen von diversen metallischen Platten und einem Kardioverter-Defibrillator (ICD) im Wasserphantom präsentiert. Der Vergleich von HU-Werten bei EHU- und CHU-Bereichen zeigt eine deutlich höhere Genauigkeit im EHU-Bereich. Es werden einige geometrische Diskrepanzen senkrecht zu Schichtaufnahme beobachtet. Festgestellt wird, dass bei EHU-Metall-Artefakt-Reduktionsalgorithmen (MAR) HU-Werte unterschätzt werden, wodurch MAR für RT möglicherweise unangemessen ist.
Funding source: Bundesministerium für Wirtschaft und Energie
Award Identifier / Grant number: ZF4205702AW6
Funding statement: This study is supported by the Federal Ministry for Economic Affairs and Energy on the basis of a decision by the German Bundestag, grant no. ZF4205702AW6.
About the authors
Zehra Ese received in 2013 a B. Sc. degree in Physical Engineering from the Westphalian University of Applied Sciences Gelsenkirchen, Bocholt, Recklinghausen, and in 2015 a M.Sc. degree in Biomedical Engineering from the Ruprecht-Karls Heidelberg University, respectively. She is currently working toward a PhD degree in electrical engineering at the University of Duisburg-Essen in cooperation with the Westphalian University of Applied Sciences Gelsenkirchen, Bocholt, Recklinghausen. Zehra Ese is also involved as a research associate at the MR:comp GmbH. Her general research interest includes biomedical engineering, medical physics, radiation physics and computational modelling. Her recent research investigates the analysis of interactions of ionizing radiation and electronics in medical applications.
Marcel Kressmann received in 2013 a B. Sc. and in 2017 a M.Sc. degree in Medical Engineering from the Westphalian University of Applied Sciences Gelsenkirchen, Bocholt, Recklinghausen, respectively. From 2011 to 2014, he was involved as a student associate and continued as a testing engineer at the MR:comp GmbH until September 2017. Currently, he is a technical support engineer at the stryker GmbH & Co.KG.
Jakob Kreutner studied physics at the University of Würzburg, Germany. After his diploma in 2009 he joined the Research Center for Magnetic Resonance Bavaria e. V. in Würzburg. During that time his work was focused on quantitative characterization of bone microstructure using magnetic resonance imaging. In 2015 he joined the research department at MR:comp GmbH. His research is focusing on MR safety and compatibility for medical devices. Since 2016 he is leading the research department also at MRI-STaR, a newly founded company addressing research related testing of devices.
Gregor Schaefers obtained his Dipl.-Ing. (FH) degree in medical engineering from the University of Applied Sciences Fachhochschule Gelsenkirchen, Germany, in 2001 and received the Erich-Mueller-Award for the best thesis of the year. He is the founder, shareholder, and managing director of MR:comp GmbH (www.mrcomp.com), a specialized test laboratory with a team of over 55 employees working worldwide on MR safety and compatibility testing of medical devices following ISO 17025 accreditation. He is founder, shareholder, and managing director of the MRI-STaR – Magnetic Resonance Institute for Safety, Technology and Research GmbH working in the field of MR safety and compatibility development and optimization of experimental and numerical MR testing methods, RF coil safety, MR sequence programming, MR workflow optimization, international MR Safety Expert (MRSE) and MR Safety Specialist (MRSS) seminars and partner of www.MRI-tec.com ONE-STOP SHOP for MR Safe and MR Conditional devices. Gregor Schaefers is member of DIN - German Institute for Standardization, ISO, and IEC as well as ASTM standardization committees, and he is convener of IEC TC62 working group WG45 for IEC 62570. Furthermore, Gregor Schaefers is author of scientific and technical congress as well as journal publications and book chapters with respect to MR safety and compatibility.
Daniel Erni is a full professor for General and Theoretical Electrical Engineering at the University of Duisburg-Essen, Germany. After an apprenticeship as an electrician and mechanic he received his two degrees in electrical engineering from HSR Rapperswil and ETH Zürich in 1986 and 1990, respectively, and a PhD degree in laser physics from ETH Zurich in 1996. He has co-authored and authored over 400 scientific publications. His current research interests include optical interconnects, nanophotonics, plasmonics, optical and electromagnetic metamaterials, RF, mm-wave and THz engineering, biomedical engineering, marine electromagnetics, computational electromagnetics, multiscale and multiphysics modeling, numerical structural optimization, and science and technology studies (STS).
Waldemar Zylka is a full professor of Physics and Medical Engineering at the Westphalian University, Campus Gelsenkirchen, Germany. He received the degree Diplom-Physiker and in 1993 the Doctor degree in theoretical Physics, both from the Albert-Ludwigs-University Freiburg i. Br., Germany. He has co-/authored numerous scientific publications and patents. He is serving as member of program committees and as reviewer for international meetings and journals. His current research focuses are system biology, multi-scale modelling, and computational electromagnetics particularly for medical imaging modalities.
Acknowledgment
We would like to thank L. Lüdemann, University Hospital Essen, Germany, for supporting this study.
References
1. Robert Koch Institute. Beitraege zur gesundheutsberichterstattung des bundes. krebs in deutschland, 2016. URL http://www.rki.de/Krebs/DE/Content/Publikationen. last visited on 2017-09-26.Search in Google Scholar
2. Krebsgesellschaft. Strahlentherapie, 2017. URL https://www.krebsgesellschaft.de/onko-internetportal/basis-informationen-krebs/therapieformen/strahlentherapie-bei-krebs.html. last visited on 2017-09-26.Search in Google Scholar
3. B. Gauter-Fleckenstein, C.W. Israel, M. Dorenkamp, J. Dunst, M. Roser, R. Schimpf, V. Steil, J. Schäfer, U. Höller, and F. Wenz. Degro/dgk guideline for radiotherapy in patients with cardiac implantable electronic devices. Strahlentherapie Onkologie, 191: 393–404, March 2015.10.1007/s00066-015-0817-3Search in Google Scholar PubMed
4. T. Zaremba. Radiotherapy in Patients with Pacemakers and Implantable Cardioverter-Defibrillators. PhD thesis, Aalborg University, 2015.10.1093/europace/euv135Search in Google Scholar PubMed
5. J.I. Prisciandaro, A. Makkar, C.J. Fox, J.A. Hayman, F. Horwood, L. Pelosi, and J.M. Moran. Dosimetric review of cardiac implantable electronic device patients receiving radiotherapy. Journal of Applied Clinical Medical Physics, 16: 1–8, October 2014.10.1120/jacmp.v16i1.5189Search in Google Scholar PubMed PubMed Central
6. C.W. Hurkmans, E. Scheepers, B.G.F. Springorum, and H. Uiterwaal. Influence of radiotherapy on the latest generation of implantable cardioverter-defibrillator. Int. J. Radiation Oncology Biol. Phys., 63 (1): 282–289, April 2005.10.1016/j.ijrobp.2005.04.047Search in Google Scholar PubMed
7. C.W. Hurkmans, E. Scheepers, B.G.F. Springorum, and H. Uiterwaal. Influence of radiotherapy on the latest generation of pacemakers. Radiotherapy and Oncology, 76 (1): 93–98, April 2005.10.1016/j.radonc.2005.06.011Search in Google Scholar PubMed
8. J.R. Marbach, M.R. Sontag, J. Van Dyk, and A.B. Wolbarst. Management of radiation oncology patients with implanted cardiac pacemakers: Report of aapm task group no. 34. Medical Physics, 21 (1): 85–90, January 1994.10.1118/1.597259Search in Google Scholar PubMed
9. C.W. Hurkmans, J.L. Knegjens, B.S. Oei, Ad.J.J Maas, G.J. Uiterwaal, A.J. Van der Borden, M.J. Ploegmakers, and L. Van Erven. Management of radiation oncology patents with a pacemaker or icd: a new comprehensive practical guideline in the netherlands. dutch society of radiotherapy and oncology (nvro). Radiation Oncology, 7 (198): 1–10, November 2012.10.1186/1748-717X-7-198Search in Google Scholar PubMed PubMed Central
10. A. Bourgouin, N. Varfalvy, and L. Archambault. Estimating and reducing dose received by cardiac devices for patients undergoing radiotherapy. Journal of Applied Clinical Medical Physics, 16 (6): 411–420, August 2015.10.1120/jacmp.v16i6.5317Search in Google Scholar PubMed PubMed Central
11. J.Y. Huang, D.S. Followill, X.A. Wang, and S.f. Kry. Accuracy and sources of error out-of-field dose calculations by commercial treatment planning system for intensity-modulated radiation therapy treatments. Journal of Applied Clinical Medical Physics, 14 (2): 4139, 2015.10.1120/jacmp.v14i2.4139Search in Google Scholar PubMed PubMed Central
12. R.M. Howell, S.B. Scarboto, S.F. Kry, and D.Z. Yaldo. Accuracy of out-of-field dose calculations by a commercial treatment planning system. Physics in Medicine and Biology, 55 (23): 6999–7008, 2010.10.1088/0031-9155/55/23/S03Search in Google Scholar PubMed PubMed Central
13. T. Kairn, S.B. Crowe, J. Kenny, J. Mitchell, D. Burke, M. Schlect, and J.V. Trapp. Dosimetric effects of a high-density spinal implant. Journal of Physics: Conference Series, 7th International Conference on 3D Radiation Dosimetry, 444: 1–4, January 2008.10.1088/1742-6596/444/1/012108Search in Google Scholar
14. J.P. Mullins, M.P. Grams, M.G. Herman, D.H. Brinkmann, and J.A. Antolak. Treatment planning for metals using an extended ct number scale. Journal of Applied Clinical Medical Physics, 17 (6): 179–188, August 2016.10.1120/jacmp.v17i6.6153Search in Google Scholar PubMed PubMed Central
15. M.S. Gossman, A.R. Graves-Calhoun, and J.D. Wilkinson. Establishing radiation therapy treatment planning effects involving implantable pacemakers and implantable cardioverter-defibrillator. Journal of Applied Clinical Medical Physics, 11 (1): 33–45, August 2009.10.1120/jacmp.v11i1.3115Search in Google Scholar PubMed PubMed Central
16. C. Coolens and P.J. Childs. Calibration of ct Hounsfield units for radiotherapy treatment planning of patients with metallic hip prostheses: the use of the extended ct-scale. Physics in Medicine and Biology, 48: 1591–1603, May 2003.10.1088/0031-9155/48/11/308Search in Google Scholar PubMed
17. G. Hilgers, T. Nuver, and A. Minken. The ct number accuracy of a novel commercial metal artifact reduction algorithm for large orthopedic implants. Journal of Applied Clinical Medical Physics, 15 (1): 274–278, September 2014.10.1120/jacmp.v15i1.4597Search in Google Scholar PubMed PubMed Central
18. K.M. Andersson, A. Ahnesjö, and C.V. Dahlgren. Evaluation of a metal artifact reduction algorithm in ct studies used for proton radiotherapy treatment planning. Journal of Applied Clinical Medical Physics, 15 (5): 112–119, May 2014.10.1120/jacmp.v15i5.4857Search in Google Scholar PubMed PubMed Central
19. J. Schindelin, I. Arganda-Carreras, and E. Frise. Fiji: an open-source platform for biological-image analysis. Nature methods, 9 (7): 676–682, 2012.10.1038/nmeth.2019Search in Google Scholar PubMed PubMed Central
20. M.S. Gossman. Clinical Concerns and Strategies in Radiation Oncology, Aspects of Pacemakers-Functions and Interactions in Cardiac and Non-cardiac Indications. InTech, 2016.Search in Google Scholar
© 2018 Walter de Gruyter GmbH, Berlin/Boston
