Quantitative imaging performance of MARS spectral photonâcounting CT for radiotherapy
- 24 April 2020
- journal article
- research article
- Published by Wiley in Medical Physics
- Vol. 47 (8), 3423-3434
- https://doi.org/10.1002/mp.14204
Abstract
Purpose To evaluate the quantitative imaging performance of a spectral photonâcounting CT (SPCCT) scanner for radiotherapy applications. An experimental comparison of the quantitative performance of a Siemens dualâenergy CT (DECT) and a MARS SPCCT scanner is performed to estimate physical properties relevant to radiotherapy of human substitute materials and contrast agent solutions. In human substitute materials, the accuracy of quantities relevant to photon therapy, proton therapy and MonteâCarlo simulations, such as the electron density, proton stopping power and elemental composition is evaluated. For contrast agent solutions, the accuracy of the contrast agent concentrations and the virtual nonâcontrast (VNC) electron density is evaluated. Methods Human tissue substitute phantoms (Gammex467and472)as well as diluted solutions of contrast agents (iodine and gadolinium based) are scanned with two commercial systems: a Siemens dualâsource CT (SOMATOM Definition Flash, Siemens Healthineers, Forchheim, Germany) and a MARS spectral photonâcounting microâCT (MARS V5.2, MARS Bioimaging Ltd., Christchurch, New Zealand). Material decomposition is performed in a maximum a posteriori framework with an optimized material basis tailored to characterize either human substitute materials or contrast agents in the context of experimental multiâenergy CT data. Results The rootâmeanâsquare error (RMSE) of the electron density calculated over all Gammex inserts is reduced from 1.09 to 0.89% when going from DECT to SPCCT. For the proton stopping power, the RMSE is reduced from 1.92 to 0.89%. Elemental mass fractions of hydrogen, carbon, nitrogen, oxygen and calcium are more accurately estimated with the MARS scanner. The RMSE ontheiodineâbasedcontrastagentsconcentrationisreducedfrom0.27to0.12mg/mLwithSPCCT, and the VNC electron density from 0.40 to 0.22%. Conclusion In the present phantom study, a MARS photonâcounting scanner provides superior accuracy compared to a Siemens SOMATOM Definition Flash DECT scanner to quantify physical parameters relevant to radiotherapy. This work experimentally demonstrates the benefits of using more energies to characterize human tissue equivalent materials. This highlights the potential of SPCCT for particle therapy, where more accurate tissue characterization is needed, as well as for MonteâCarlo based planning, which requires accurate elemental mass fractions.Keywords
This publication has 36 references indexed in Scilit:
- Experimental validation of two dualâenergy CT methods for proton therapy using heterogeneous tissue samplesMedical Physics, 2017
- Material Separation Using Dual-Energy CT: Current and Emerging ApplicationsRadioGraphics, 2016
- A new method to measure electron density and effective atomic number using dual-energy CT imagesPhysics in Medicine & Biology, 2015
- Initial implementation of the conversion from the energyâsubtracted CT number to electron density in tissue inhomogeneity corrections: An anthropomorphic phantom study of radiotherapy treatment planningMedical Physics, 2015
- Tissue decomposition from dual energy CT data for MC based dose calculation in particle therapyMedical Physics, 2014
- A stoichiometric calibration method for dual energy computed tomographyPhysics in Medicine & Biology, 2014
- A Flexible Method for Multi-Material Decomposition of Dual-Energy CT ImagesIEEE Transactions on Medical Imaging, 2013
- Quantitative imaging of element composition and mass fraction using dualâenergy CT: Threeâmaterial decompositionMedical Physics, 2009
- Generalized image combinations in dual KVP digital radiographyMedical Physics, 1981
- Energy-selective reconstructions in X-ray computerised tomographyPhysics in Medicine & Biology, 1976