Dual-Energy CT Applications in Radiation Therapy THE UNIVERSITY OF WISCONSIN–MADISON - Jessica Miller 1
Dual-Energy CT Applications in Radiation Therapy
THE UNIVERSITY OF WISCONSIN–MADISON
- Jessica Miller
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• Funding provided by Siemens Medical
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Disclosures
• General principles of dual‐energy CT
• Technical approaches to dual‐energy CT
• Potential applications and challenges of dual‐energy CT in radiation oncology
Learning objectives
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What is dual‐energy CT?
80 kVp – Low Energy Image 140 kVp – High Energy Image
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• Above k‐edge energy, a linear attenuation can be approximated by the sum of PE and CS (basis pairs)
• + • Where ∝ and ∝
• Alternatively, the linear attenuation coefficient for an arbitrary material can be represented as a weighted sum of two independent material’s attenuation coefficients
• +
Basis pair decomposition
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Basis pair decomposition
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Szczykutowicz, T. in press. “Dual‐Energy and Spectral Imaging.” Comprehensive Biomedical Physics
Basis pair decomposition
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Szczykutowicz, T. in press. “Dual‐Energy and Spectral Imaging.” Comprehensive Biomedical Physics
Dual source DECT technology
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• Two x‐ray tubes separated by 90 degrees
• Dual‐Energy CT FOV of 33 cm
• Filters can be optimized for spectral separation
Image courtesy of SIEMENS
• Sequential CT scans: • 140 kV • 80 kV
• Creates a low‐ and high‐energy spectra, sequentially
Image courtesy of SIEMENS
Sequential scans
140 kV
80 kV
return to starting position
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Fast kVp switching
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• 0.5 ms switching between 80 and 140 kVp to acquire interleaved projection data
• Requires fast generator response and detector response
Image courtesy of GE Healthcare
Dual‐layer detector
11Cynthia H. McCollough; Shuai Leng; Lifeng Yu; Joel G. Fletcher; Radiology 2015, 276, 637‐653.
• ”Sandwich” scintillation detectors:
• Low energy data collected from the top/proximal layer• High energy data acquired from the bottom/distal layer
• A removable split‐filter composed of gold (Au) and tin (Sn) which filters a 120 kV x‐ray beam
• Creates a low‐ and high‐energy spectra simultaneously
Images courtesy of SIEMENS
Single‐source DECT TwinBeam system
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Potential radiation therapy applications for DECT
Mixed – 120 kVp equivalent
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Potential radiation therapy applications for DECT
True Contrast Image Virtual Non‐contrast
Iodine Map Rho/Z Map
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40 keV 55 keV
77 keV 190 keV
Potential radiation therapy applications for DECT
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Virtual monoenergetic reconstructions (VMI)
Roele, E.D., Timmer, V.C.M.L., Vaassen, L.A.A. et al. Curr Radiol Rep (2017) 5: 19.
Metal Artifact Reduction at Higher VMI Energies
Shima Aran, Laleh Daftari Besheli, Musturay Karcaaltincaba, Rajiv Gupta, Efren J. Flores and Hani H. AbujudehAmerican Journal of Roentgenology 2014 202:4, W314‐W324
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Improved dose calculation
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Radiation therapy applications:
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Wouter van Elmpt et al. Radiotherapy and Oncology 2016, 3119, 137‐144.
Improved dose calculations
• Brachytherapy
• Protons
• External Beam – Photon Therapy
N. Hudobivnik et al. Med. Phys. 2016, 43, 495.
Dose calculations – virtual non‐contrast (VNC) images
True Contrast Image Virtual Non‐contrast
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HU difference map (Mixed – VNC)
Dose calculations – virtual non‐contrast (VNC) images
Images courtesy of Dr. Huang‐Vredevoogd, University of Wisconsin
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• Ideal plan – VNC plan• Ideal plan – No override plan
Dose calculations – virtual non‐contrast (VNC) images
Images courtesy of Dr. Huang‐Vredevoogd, University of Wisconsin
Tumor identification, characterization and delineation
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Radiation therapy applications:
Cyst or Carcinoma?
Renal call carcinomaHyperattenuating cyst
Mukta D. Agrawal; Daniella F. Pinho; Naveen M. Kulkarni; Peter F. Hahn; Alexander R. Guimaraes; Dushyant V. Sahani; RadioGraphics 2014, 34, 589‐612. 24
Calcium or hemorrhage?
Ranliang Hu; Laleh DaftariBesheli; Joseph Young; Markus Wu; Stuart Pomerantz; Michael H. Lev; Rajiv Gupta; Radiology 2016, 280, 177‐183. 25
Material decomposition – iodine map
Roele, E.D., Timmer, V.C.M.L., Vaassen, L.A.A. et al. Curr Radiol Rep (2017) 5: 19.
Material decomposition – iodine map
Mukta D. Agrawal; Daniella F. Pinho; Naveen M. Kulkarni; Peter F. Hahn; Alexander R. Guimaraes; Dushyant V. Sahani; RadioGraphics 2014, 34, 589‐612.27
Tumor delineation
Mukta D. Agrawal; Daniella F. Pinho; Naveen M. Kulkarni; Peter F. Hahn; Alexander R. Guimaraes; Dushyant V. Sahani; RadioGraphics 2014, 34, 589‐612.
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Tumor delineation for pancreatic cancer
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Tumor delineation for pancreatic cancer
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Tumor delineation
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Treatment response assessment
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Radiation therapy applications:
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Treatment response with DECT
Xu Dai et al. European Journal of Radiology (2013) 82: 327‐334
Apfaltrer et al. Invest Radiol. (2012) 42:(1): 65‐70
Normal tissue segmentation
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Radiation therapy applications:
Normal tissue delineation
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Postma et al. Dual‐Energy CT: What the Neuroradiologist Should Know. Current Radiology Reports. 2015;3(5):16.
Supratentorialwhite matter/basal ganglia
Posterior fossa
50 keV to 70 keV
Higher energies
Functional normal tissue segmentation and toxicity
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Radiation therapy applications:
Material decomposition – xenon map & iodine map
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Zhang, L.J., Zhou, C.S., Schoepf, U.J. et al. EurRadiol (2013) 23: 2666
Ventilation
Perfusion
Xenon inhalation
Iodine injection
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Houda Bahig et al., International Journal of Rad. Onc., Biology, Physics. V99,Issue 1, Paes 334‐343 (Oct 2017).
Dose calculation accounting for functional lung
Bone Marrow
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Fornaro et al. Dual‐ and multi‐energy CT: approach to functional imaging. Insights into Imaging. 2011;2(2):149‐159.
Taiki Magome et al., Int J Radiation OncolBiol Phys, Vol. 96, No. 3, pp. 679‐687, 2016
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Sarah McGuire et al., Radiotherapy and Oncology, Vol. 99, No. 1, pp. 49‐54, 2011
Bone Marrow
Conclusions
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• Improving dose calculation
• Tumor identification and delineation
• Treatment response
• Normal tissue segmentation
• Functional normal tissue toxicities
Challenges in commissioning and quality assurance of DECT systems for radiation therapy applications
Thank you
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A. Visualization of bone marrow edema via virtual calcium removal
B. Enhancement of CNR between tumor and healthy tissue via iodine uptake
C. Visualization of tissue metabolic activity via glucose uptake
D. Improvement of dose calculation accuracy with effective atomic number information
Which of the following is NOT a current application of Dual‐energy CT?
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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.
McCollough CH, Leng S, Yu L, Fletcher JG. Dual‐ and multi‐energy CT: principles, technical approaches, and clinical applications. Radiology 2015; 276: 637–53.
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Houda Bahig et al., International Journal of Rad. Onc., Biology, Physics. V99,Issue 1, Paes 334‐343 (Oct 2017).