Patient safety

Patients who receive radiation therapy are frequently imaged. Despite the relatively large difference between the exposure during therapeutic irradiation and exposure during diagnostic or treatment-planning studies, there are concerns about excessive radiation dose. Reducing dose is desirable in most settings, is possible with DECT technology, and should be feasible with a dual-layer detector CT.34 Contrast medium is underutilized in general radiation oncology departments because of the lack of consistent imaging protocols, concern about reactions, staff monitoring requirements, cost, age of the patients, and lack of temporal coordination with diagnostic studies. Improved visualization of contrast-enhanced structures gained by using dual-layer detector CT systems may facilitate the use of lower doses of contrast agents, increase patient safety, and increase the use of contrast in some departments.35 A 50% reduction in contrast dose on a 50 keV image should maintain comparable or improve the contrast-to-noise ratio, compared with polychromatic CT in more than 80% of CT studies. Radiation therapy might be safer if dual-energy or dual-layer CT technology is used to identify functionally compromised tissues during radiation planning. Bahig H et al. quantified lung function in a planning study to show how the results correlated well with functional single-photon emission CT/CT imaging.36 They proposed treatment plans that include functional lung-sparing irradiation.

Summary

The IQon Spectral CT system was commissioned in 2016 for clinical use in the Department of Radiation Oncology at St. Jude Children’s Research Hospital in Memphis, Tennessee. The installation was one of the first in the United States and unique, with respect to its focused application: radiation treatment planning and the evaluation of children treated with photon and proton therapy. The IQon Spectral CT joins other platforms for dedicated use in radiation oncology, including Philips 1.5T Ingenia MR, 3.0T Ingenia MR, and the Vereos digital PET/CT systems. The Department of Radiation Oncology at St. Jude Children’s Research Hospital is committed to protocol-based clinical research in pediatric oncology, advancing radiation therapy for children, and innovation in radiation treatment planning using photons and protons, adaptive therapy, and novel response evaluation.

Our selection of the IQon Spectral CT was based on the system’s ability to meet the rigorous geometric accuracy and tissue-characterization requirements for radiation-dose calculation. The system was installed in the world’s first and only proton therapy center dedicated solely to the treatment of children with cancer. There is potential for translational research to improve relative proton-stopping power calculations through more accurate estimation of electron density and effective atomic number. Key features of the current system that are relevant to radiation oncology research and practice include increased iodine contrast enhancement, accurate estimation of electron density and effective atomic number, field of view for electron density and effective atomic number data estimation, reduced imaging artifacts, spatially and temporally synchronized acquisition of spectral data, CT simulation software integration with external laser alignment systems, thin-slice imaging without beam hardening artifacts, connectivity with Oncology Information Systems, and the American College of Radiology–American Association of Physicists in Medicine (ACR-AAPM) technical standards for CT simulation. Important features that are relevant to a practice limited to children, adolescents, and young adults with cancer are high-quality virtual monoenergetic and non-contrast images. Future considerations to extend the value of spectral CT in radiation oncology should include 4D-CT for organ motion management, imaging biomarkers for treatment response assessments, connectivity of quantitative imaging data with radiation treatment–planning systems, AAPM Task Group No. 66 couch compliance,37 and potentially a larger bore (>70 cm).

References

1. Mashouf S, Lechtman E, Lai P, Keller BM, Karotki A, Beachey DJ, Pignol JP. Dose heterogeneity correction for low-energy brachytherapy sources using dual-energy CT images. Phys Med Biol. 2014 Sep 21;59(18):5305-16. doi: 10.1088/0031-9155/59/18/5305. PubMed PMID: 25146446.

2. van Elmpt W, Landry G, Das M, Verhaegen F. Dual energy CT in radiotherapy: current applications and future outlook. Radiother Oncol. 2016 Apr;119(1):137-44. doi: 10.1016/j.radonc.2016.02.026.

PubMed PMID: 26975241.

3. Almeida IP, Schyns LEJR, Vaniqui A, van der Heyden B, Dedes G, Resch AF, Kamp F, Zindler JD, Parodi K, Landry G, Verhaegen F. Monte Carlo proton dose calculations using a radiotherapy specific dual-energy CT scanner for tissue segmentation and range assessment. Phys Med Biol. 2018 May 29; 63(11)115008. doi: 10.1088/1361-6560/aabb60. PubMed PMID: 29616662.

4. Hua CH, Shapira N, Merchant TE, Klahr P, Yagil Y. Accuracy of electron density, effective atomic number, and iodine concentration determination with a dual-layer dual-energy computed tomography system. Med Phys. 2018 Apr 6. doi: 10.1002/mp.12903. [Epub ahead of print]

PubMed PMID: 29624708.

5. Vaniqui A, Schyns LEJR, Almeida IP, van der Heyden B, van Hoof SJ, Verhaegen F. The impact of dual energy CT imaging on dose calculations for pre-clinical studies. Radiat Oncol. 2017 Nov 21;12(1):181. doi: 10.1186/s13014-017-0922-9. PubMed PMID: 29157265; PubMed Central PMCID: PMC5696722.

6. Huang JY, Followill DS, Howell RM, Liu X, Mirkovic D, Stingo FC, Kry SF. Approaches to reducing photon dose calculation errors near metal implants. Med Phys. 2016 Sep;43(9):5117. doi: 10.1118/1.4960632. PubMed PMID: 27587042; PubMed Central PMCID: PMC4991994.

7. Schwahofer A, Bär E, Kuchenbecker S, Grossmann JG, Kachelrieß M, Sterzing F. The application of metal artifact reduction (MAR) in CT scans for radiation oncology by monoenergeti extrapolation with a DECT scanner. Z Med Phys. 2015 Dec;25(4):314-325. doi: 10.1016/j.zemedi.2015.05.004. PubMed PMID: 26144602.

8. Hudobivnik N, Schwarz F, Johnson T, Agolli L, Dedes G, Tessonnier T, Verhaegen F, Thieke C, Belka C, Sommer WH, Parodi K, Landry G. Comparison of proton therapy treatment planning for head tumors with a pencil beam algorithm on dual and single energy CT images. Med Phys. 2016 Jan;43(1):495. doi: 10.1118/1.4939106. PubMed PMID: 26745942.

9. Zhang YN, Fowler KJ, Hamilton G, Cui J, Sy EZ, Balanay M, Hooker JC, Szeverenyi N, Sirlin CB. Liver fat imaging - a clinical overview of ultrasound, CT, and MR imaging. Br J Radiol. 2018 May 3:20170959. doi: 10.1259/jr.20170959. [Epub ahead of print] PubMed PMID: 29722568.

10. Shen C, Li B, Chen L, Yang M, Lou Y, Jia X. Material elemental decomposition in dual and multi-energy CT via a sparsity-dictionary approach for proton stopping power ratio calculation. Med Phys. 2018 Apr;45(4):1491-1503. doi: 10.1002/mp.12796. PubMed PMID: 29405340; PubMed Central PMCID: PMC5904041.

11. Xie Y, Ainsley C, Yin L, Zou W, McDonough J, Solberg TD, Lin A, Teo BK. Ex vivo validation of a stoichiometric dual-energy CT proton stopping power ratio calibration. Phys Med Biol. 2018 Mar 7;63(5):055016. doi: 10.1088/1361-6560/aaae91. PubMed PMID: 29513647.

12. Wohlfahrt P, Möhler C, Richter C, Greilich S. Evaluation of stopping-power prediction by dualand single-energy computed tomography in an anthropomorphic ground-truth phantom. Int J Radiat Oncol Biol Phys. 2018 Jan 1; 100(1):244-253. doi: 10.1016/j.ijrobp.2017.09.025. PubMed PMID: 29079119.

13. Bär E, Lalonde A, Zhang R, Jee KW, Yang K, Sharp G, Liu B, Royle G, Bouchard H, Lu HM. Experimental validation of two dual-energy CT methods for proton therapy using heterogeneous tissue samples. Med Phys. 2018 Jan; 45(1):48-59. doi: 10.1002/mp.12666. PubMed PMID: 29134674.

14. Wohlfahrt P, Möhler C, Stützer K, Greilich S, Richter C. Dual-energy CT based proton range prediction in head and pelvic tumor patients. Radiother Oncol. 2017 Dec;125(3):526-533. doi: 10.1016/j.radonc.2017.09.042. PubMed PMID: 29050953.

15. Michalak G, Taasti V, Krauss B, Deisher A, Halaweish A, McCollough C. A comparison of relative proton stopping power measurements across patient size using dual- and single-energy CT. Acta Oncol. 2017 Nov;56(11):1465-1471. doi: 10.1080/0284186X.2017.1372625. PubMed PMID: 28885130.

16. Zhu J, Penfold SN. Review of 3D image data calibration for heterogeneity correction in proton therapy treatment planning. Australas Phys Eng Sci Med. 2016 Jun;39(2):379-390. doi: 10.1007/s13246-016-0447-9. PubMed PMID: 27115163.

17. Yamada S, Ueguchi T, Ogata T, Mizuno H, Ogihara R, Koizumi M, Shimazu T, Murase K, Ogawa K. Radiotherapy treatment planning with contrast-enhanced computed tomography: feasibility of dual-energy virtual unenhanced imaging for improved dose calculations. Radiat Oncol. 2014 Jul 29;9:168. doi: 10.1186/1748-717X-9-168. PubMed PMID: 25070169; PubMed Central PMCID: PMC4118618.

18. Hua CH, Shapira N, Merchant TE, Klahr P, Yagil Y. Accuracy of electron density, effective atomic number, and iodine concentration determination with a dual-layer dual-energy computed tomography system. Med Phys. 2018 Jun;45(6):2486-2497. doi: 10.1002/mp.12903. Epub 2018 Apr 23. PubMed PMID:29624708.

19. Hünemohr N, Paganetti H, Greilich S, Jäkel O, Seco J. Tissue decomposition from dual energy CT data for MC based dose calculation in particle therapy. Med Phys. 2014 Jun;41(6):061714. doi: 10.1118/1.4875976. PubMed PMID: 24877809; PubMed Central PMCID: PMC4032427.

20. Berndt B, Landry G, Schwarz F, Tessonnier T, Kamp F, Dedes G, Thieke C, Würl M, Kurz C, Ganswindt U, Verhaegen F, Debus J, Belka C, Sommer W, Reiser M, Bauer J, Parodi K. Application of single- and dual-energy CT brain tissue segmentation to PET monitoring of proton therapy. Phys Med Biol. 2017 Mar 21;62(6):2427-2448. doi: 10.1088/1361-6560/aa5f9f. PubMed PMID: 28182581.

21. Lapointe A, Lalonde A, Bahig H, Carrier JF, Bedwani S, Bouchard H. Robust quantitative contrast-enhanced dual-energy CT for radiotherapy applications. Med Phys. 2018 Apr 26. doi: 10.1002/mp.12934. [Epub ahead of print] PubMed PMID: 29697145.

22. Zhao W, Vernekohl D, Han F, Han B, Peng H, Yang Y, Xing L, Min JK. A unified material decomposition framework for quantitative dual- and triple-energy CT imaging. Med Phys. 2018 Apr 21. doi: 10.1002/mp.12933. [Epub ahead of print] PubMed PMID: 29679500.

23. Men K, Dai J, Chen X, Li M, Zhang K, Huang P. Dual-energy imaging method to improve the image quality and the accuracy of dose calculation for cone-beam computed tomography. Phys Med. 2017 Apr;36:110-118. doi: 10.1016/j.ejmp.2017.03.023. PubMed PMID: 28410679.

24. Gainey M, Carles M, Mix M, Meyer PT, Bock M, Grosu AL, Baltas D. Biological imaging for individualized therapy in radiation oncology: part I physical and technical aspects. Future Oncol. 2018 Apr;14(8):737-749. doi: 10.2217/fon-2017-0464. PubMed PMID: 29521520.

25. Kovacs DG, Rechner LA, Appelt AL, Berthelsen AK, Costa JC, Friborg J, Persson GF, Bangsgaard JP, Specht L, Aznar MC. Metal artefact reduction for accurate tumour delineation in radiotherapy. Radiother Oncol. 2018 Mar; 126(3):479-486. doi: 10.1016/j.radonc.2017.09.029.. PubMed PMID: 29050958; PubMed Central PMCID: PMC5864514.

26. Wang T, Ishihara T, Kono A, Yoshida N, Akasaka H, Mukumoto N, Yada R, Ejima Y, Yoshida K, Miyawaki D, Kakutani K, Nishida K, Negi N, Minami T, Aoyama Y, Takahashi S, Sasaki R. Application of dual-energy CT to suppression of metal artefact caused by pedicle screw fixation in radiotherapy: a feasibility study using original phantom. Phys Med Biol. 2017 Jul 17;62(15):6226-6245. doi: 10.1088/1361-6560/aa7d7f. PubMed PMID: 28675378.

27. Poort LJ, Stadler AAR, Ludlage JHB, Hoebers FJP, Kessler PAWH, Postma AA. Detection of bone marrow edema pattern with dual-energy computed tomography of the pig mandible treated with radiotherapy and surgery compared with magnetic resonance imaging. J Comput Assist Tomogr.

References

2017 Jul/Aug;41(4):553-558. doi: 10.1097/RCT.0000000000000559. PubMed PMID: 28722700.

28. Ren Y, Jiao Y, Ge W, Zhang L, Hua Y, Li C, Zhai W, Tang X, He W, Fang M, Zheng X. Dual-energy computed tomography-based iodine quantitation for response evaluation of lung cancers to chemoradiotherapy/radiotherapy: a comparison with fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography-based positron emission tomography/computed tomography response evaluation criterion in solid tumors. J Comput Assist Tomogr. 2018 Apr 2. doi: 10.1097/ RCT.0000000000000734. [Epub ahead of print] PubMed PMID: 29613988.

29. Jiang C, Yang P, Lei J, Li J, Yan K, Li F, Yan R, Xia L. The application of iodine quantitative information obtained by dual-source dual-energy computed tomography on chemoradiotherapy effect monitoring for cervical cancer: a preliminary study. J Comput Assist Tomogr. 2017 Sep/Oct;41(5):737-745. doi: 10.1097/RCT.0000000000000603. PubMed PMID: 28448413.

30. Ashton JR, Castle KD, Qi Y, Kirsch DG, West JL, Badea CT. Dual-energy CT imaging of tumor liposome delivery after gold nanoparticle-augmented radiation therapy. Theranostics. 2018 Feb 12;8(7):1782-1797. doi: 10.7150/thno.22621. eCollection 2018. PubMed PMID: 29556356; PubMed Central PMCID: PMC5858500.

31. Landry G, Gaudreault M, van Elmpt W, Wildberger JE, Verhaegen F. Improved dose calculation accuracy for low energy brachytherapy by optimizing dual energy CT imaging protocols for noise reduction using sinogram affirmed iterative reconstruction. Z Med Phys. 2016 Mar;26(1):75-87.

doi: 10.1016/j.zemedi.2015.09.001. PubMed PMID: 26422576.

32. Aoki M, Takai Y, Narita Y, Hirose K, Sato M, Akimoto H, Kawaguchi H, Hatayama Y, Miura H, Ono S. Correlation between tumor size and blood volume in lung tumors: a prospective study on dual-energy gemstone spectral CT imaging. J Radiat Res. 2014 Sep;55(5):917-923.

doi: 10.1093/jrr/rru026. PubMed PMID: 24829253; PubMed Central PMCID: PMC4202284.

33. Al-Najami I, Drue HC, Steele R, Baatrup G. Dual energy CT - a possible new method to assess regression of rectal cancers after neoadjuvant treatment. J Surg Oncol. 2017 Dec;116(8):984-988.

doi: 10.1002/jso.24761. PubMed PMID: 28703886.

34. Dzierma Y, Minko P, Ziegenhain F, Bell K, Buecker A, Rübe C, Jagoda P. Abdominal imaging dose in radiology and radiotherapy - phantom point dose measurements, effective dose and secondary cancer risk. Phys Med. 2017 Nov;43:49-56. doi: 10.1016/j.ejmp.2017.10.019. PubMed PMID: 29195562.

35. Tsang DS, Merchant TE, Merchant SE, Smith H, Yagil Y, Hua CH. Quantifying potential reduction in contrast dose with monoenergetic images synthesized from dual-layer detector spectral CT. Br J Radiol. 2017 Oct;90(1078):20170290. doi: 10.1259/bjr.20170290. PubMed PMID: 28749176; PubMed Central PMCID: PMC5853359.

36. Bahig H, Campeau MP, Lapointe A, Bedwani S, Roberge D, de Guise J, Blais D, Vu T, Lambert L, Chartrand-Lefebvre C, Lord M, Filion E. Phase 1-2 study of dual-energy computed tomography for assessment of pulmonary function in radiation therapy planning. Int J Radiat Oncol Biol Phys. 2017 Oct 1;99(2):334-343. doi: 10.1016/j.ijrobp.2017.05.051. PubMed PMID: 28871983.

37. Mutic S, Palta JR, Butker EK, Das IJ, Huq MS, Loo LN, Salter BJ, McCollough CH, Van Dyk J; AAPM Radiation Therapy Committee Task Group No. 66. Quality assurance for computed-tomography simulators and the computed-tomography-simulation process: report of the AAPM Radiation Therapy Committee Task Group No. 66. Med Phys. 2003 Oct;30(10):2762-3792. PubMed PMID: 14596315.