High
density materials are assigned with an apparent density of 3.2 g/cm3 in 12-bit CT images due to saturation. This is often ignored in planning for
spine tumors with titanium (density 4.40 g/cm3) spinal hardware.
However, new cobalt-chrome hardware has a density of 8.11 g/cm3,
which would increase dosimetric uncertainty if the true density is not utilized
in planning. This effect was evaluated in this study. Calculation accuracy was
examined using MapCHECK2 with a single 20×10 cm2 field with a titanium and a cobalt-chrome rod in a solid water phantom for 6X, 6FFF and 15X, at 2 cm
and 6 cm beneath the rods. Measurement was
compared to the calculation with density override (DO) with the true density and to the calculation with
no-density override (NDO). Additionally, the dosimetric effect in clinical
treatment plans was investigated for six IMRT and VMAT paraspinal cases. Plan
quality was compared with the original NDO calculation and the DO
recalculation. Compared to measurements, the treatment
planning system (TPS) overestimated the dose locally by up to 13.2% for cobalt-chrome
and 4.8% for titanium with NDO calculations. DO calculations improved the
differences to 8.4% and 4.0%, respectively. Scatter from the rod increased the
lateral dose and diminished as depth increased but was not properly accounted for by the TPS even with the
correct density assigned. For the clinical plans, PTV coverage was lowered by
an average of ~1.0% (range: 0.5% - 2.0%) and ~0.3% (range: 0.2% - 0.7%) in DO
recalculations for cobalt-chrome and titanium, respectively. In conclusion, neglecting the true density of cobalt-chrome hardware during planning
may result in an unexpected decrease in target coverage.
References
[1]
Anick Nater, A.S. and Fehlings, M. (2018) Chapter 16. Management—Spinal Metastases. In: Schiff, D. and van den Bent, M.J., Eds., Handbook of Clinical Neurology, Vol. 149, Elsevier, Amsterdam, 239-255. https://doi.org/10.1016/B978-0-12-811161-1.00016-5
[2]
Park, S.-J., Lee, C.-S., Chang, B.-S., Kim, Y.-H., Kim, H., Kim, S.-I. and Chang, S.-Y. (2019) Rod Fracture and Related Factors after Total en Bloc Spondylectomy. The Spine Journal, 19, 1613-1619. https://doi.org/10.1016/j.spinee.2019.04.018
[3]
Shah, K.N., Walker, G., Koruprolu, S.C. and Daniels, A.H. (2018) Biomechanical Comparison between Titanium and Cobalt Chromium Rods Used in a Pedicle Subtraction Osteotomy Model. Orthopedic Reviews, 10, 7541-7541. https://doi.org/10.4081/or.2018.7541
[4]
Yamanaka, K., Mori, M., Yamazaki, K., Kumagai, R., Doita, M. and Chiba, A. (2015) Analysis of the Fracture Mechanism of Ti-6Al-4V Alloy Rods That Failed Clinically after Spinal Instrumentation Surgery. Spine, 40, E767-E773. https://doi.org/10.1097/BRS.0000000000000881
[5]
Li, C.S., Vannabouathong, C., Sprague, S. and Bhandari, M. (2015) The Use of Carbon-Fiber-Reinforced (CFR) PEEK Material in Orthopedic Implants: A Systematic Review. Clinical Medicine Insights. Arthritis and Musculoskeletal Disorders, 23, 33-45. https://doi.org/10.4137/CMAMD.S20354
[6]
Müller, B., Ryang, Y.M., Oechsner, M., Düsberg, M., Meyer, B., Combs, S.E. and Wilkens, J.J. (2020) The Dosimetric Impact of Stabilizing Spinal Implants in Radiotherapy Treatment Planning with Protons and Photons: Standard Titanium Alloy vs. Radiolucent Carbon Fiber-Reinforced PEEK Systems. Journal of Applied Clinical Medical Physics, 21, 6-14. https://doi.org/10.1002/acm2.12905
[7]
Shi, C., Lin, H., Huang, S., Xiong, W., Hu, L., Choi, I., Press, R., Hasan, S., Simone, C. and Chhabra, A. (2022) Comprehensive Evaluation of Carbon-Fiber-Reinforced Polyetheretherketone (CFR-PEEK) Spinal Hardware for Proton and Photon Planning. Technology in Cancer Research and Treatment, 21, 1-11. https://doi.org/10.1177/15330338221091700
[8]
Liebross, R.H., Starkschall, G., Wong, P.F., Horton, J., Gokaslan, Z.L. and Komaki, R. (2002) The Effect of Titanium Stabilization Rods on Spinal Cord Radiation Dose. Medical Dosimetry, 27, 21-24. https://doi.org/10.1016/S0958-3947(02)00083-3
[9]
Mesbahi, A. and Nejad, F.S. (2007) Monte Carlo Study on the Impact of Spinal Fixation Rods on Dose Distribution in Photon Beams. Reports of Practical Oncology and Radiotherapy, 12, 261-266. https://doi.org/10.1016/S1507-1367(10)60064-8
[10]
Son, S.H., Kang, Y.N. and Ryu, M.R. (2012) The Effect of Metallic Implants on Radiation Therapy in Spinal Tumor Patients with Metallic Spinal Implants. Medical Dosimetry, 37, 98-107. https://doi.org/10.1016/j.meddos.2011.01.007
[11]
Wang, X., Yang, J.N., Li, X., Tailor, R., Vassilliev, O., Brown, P., Rhines, L. and Chang, E. (2013) Effect of Spine Hardware on Small Spinal Stereotactic Radiosurgery Dosimetry. Physics in Medicine and Biology, 58, 6733-6747. https://doi.org/10.1088/0031-9155/58/19/6733
[12]
Li, J., Yan, L., Wang, J., Cai, L. and Hu, D. (2015) Influence of Internal Fixation Systems on Radiation Therapy for Spinal Tumor. Journal of Applied Clinical Medical Physics, 16, 279-289. https://doi.org/10.1120/jacmp.v16i4.5450
[13]
Yazici, G., Sari, S.Y., Yedekci, F.Y., Yucekul, A., Birgi, S.D., Demirkiran, G., Gultekin, M., Hurmuz, P., Yazici, M., Ozyigit, G. and Cengiz, M. (2016) The Dosimetric Impact of Implants on the Spinal Cord Dose during Stereotactic Body Radiotherapy. Radiation Oncology, 11, Article No. 71. https://doi.org/10.1186/s13014-016-0649-z
[14]
Cheng, Z.J., Bromley, R.M., Oborn, B., Carolan, M. and Booth, J.T. (2016) On the Accuracy of Dose Prediction near Metal Fixation Devices for Spine SBRT. Journal of Applied Clinical Medical Physics, 17, 475-485. https://doi.org/10.1120/jacmp.v17i3.5536
[15]
Ulmer, W. and Harder, D. (1995) A Triple Gaussian Pencil Beam Model for Photon Beam Treatment Planning. Zeitschrift für Medizinische Physik, 5, 25-30. https://doi.org/10.1016/S0939-3889(15)70758-0
[16]
Ulmer, W. and Harder, D. (1996) Applications of a Triple Gaussian Pencil Beam Model for Photon Beam Treatment Planning. Zeitschrift für Medizinische Physik, 6, 68-74. https://doi.org/10.1016/S0939-3889(15)70784-1
[17]
Sievinen, J., Ulmer, W. and Kaissl, W. (2005) AAA Photon Dose Calculation in Eclipse. Varian Documentation RAD #7170B.
[18]
Glide-Hurst, C., Chen, D., Zhong, H. and Chetty, I.J. (2013) Changes Realized from Extended Bit-Depth and Metal Artifact Reduction in CT. Medical Physics, 40, Article ID: 061711. https://doi.org/10.1118/1.4805102
[19]
Mullins, J.P., Grams, M.P., Herman, M.G., Brinkmann, D.H. and Antolak, J.A. (2016) Treatment Planning for Metals Using an Extended CT Number Scale. Journal of Applied Clinical Medical Physics, 17, 179-188. https://doi.org/10.1120/jacmp.v17i6.6153
[20]
Guggenberger, R., Winklhofer, S., Osterhoff, G., Wanner, G.A., Fortunati, M. andreisek, G., Alkadhi, H. and Stolzmann, P. (2021) Metallic Artefact Reduction with Monoenergetic Dual-Energy CT: Systematic ex Vivo Evaluation of Posterior Spinal Fusion Implants from Various Vendors and Different Spine Levels. European Radiology, 22, 2357-2364. https://doi.org/10.1007/s00330-012-2501-7
[21]
Pessis, E., Sverzut, J.M., Campagna, R., Guerini, H., Feydy, A. and Drapé, J.L. (2015) Reduction of Metal Artifact with Dual-Energy CT: Virtual Monospectral Imaging with Fast Kilovoltage Switching and Metal Artifact Reduction Software. Seminars in Musculoskeletal Radiology, 19, 446-455. https://doi.org/10.1055/s-0035-1569256
[22]
Pettersson, E., Bäck, A. and Thilander-Klang, A. (2021) Comparison of Metal Artefacts for Different Dual Energy CT Techniques. Radiation Protection Dosimetry, 195, 232-245. https://doi.org/10.1093/rpd/ncab105
[23]
Wieslander, E. and Knöös, T. (2003) Dose Perturbation in the Presence of Metallic Implants: Treatment Planning System versus Monte Carlo Simulations. Physics in Medicine and Biology, 48, 3295-3305. https://doi.org/10.1088/0031-9155/48/20/003
[24]
Spadea, M.F., Verburg, J.M., Baroni, G. and Seco, J. (2014) The Impact of Low-Z and High-Z Metal Implants in IMRT: A Monte Carlo Study of Dose Inaccuracies in Commercial Dose Algorithms. Medical Physics, 41, Article ID: 011702. https://doi.org/10.1118/1.4829505
[25]
Lloyd, S.A.M. and Ansbacher, W. (2013) Evaluation of an Analytic Linear Boltzmann Transport Equation Solver for High-Density in Homogeneities. Medical Physics, 40, Article ID: 011707. https://doi.org/10.1118/1.4769419
[26]
Keall, P.J., Siebers, J.V., Jeraj, R. and Mohan, R. (2003) Radiotherapy Dose Calculations in the Presence of Hip Prostheses. Medical Dosimetry, 28, 107-112. https://doi.org/10.1016/S0958-3947(02)00245-5
[27]
Reft, C., Alecu, R., Das, I.J., Gerbi, B.J., Keall, P., Lief, E., Mijnheer, B.J., Papanikolaou, N., Sibata, C. and Van Dyk, J. (2003) Dosimetric Considerations for Patients with HIP Prostheses Undergoing Pelvic Irradiation. Report of the AAPM Radiation Therapy Committee Task Group 63. Medical Physics, 30, 1162-1182. https://doi.org/10.1118/1.1565113
[28]
Prabhakar, R., Kumar, M., Cheruliyil, S., Jayakumar, S., Balasubramanian, S. and Cramb, J. (2013) Volumetric Modulated Arc Therapy for Prostate Cancer Patients with Hip Prosthesis. Reports of Practical Oncology and Radiotherapy, 18, 209-213. https://doi.org/10.1016/j.rpor.2013.03.006.
