Dual-energy CT for photon therapy – benefits and limitations


Dual-energy CT for photon therapy – benefits and limitations

Möhler, C.; Wohlfahrt, P.; Richter, C.; Greilich, S.

In current treatment planning for both photon and particle therapy, a heuristic Hounsfield look-up table (HLUT) is used for the conversion of CT numbers to electron density or particle stopping-power ratios, respectively. However, this conversion is ambiguous and cannot account for patient-specific tissue variability or non-tissue materials (e.g., implants, contrast agent). This can lead to substantial difference in dose distributions. In contrast, dual-energy computed tomography (DECT) allows for direct patient- and tissue- specific determination of radiological quantities. Therefore, DECT is currently being investigated by many groups as an alternative imaging modality.
While the benefit of DECT is rather pertinent in particle therapy, where an accurate range prediction is crucial, we suggest that it might also improve conventional photon treatment planning, especially in the presence of non-tissue materials such as implants. In this context, DECT-based material characterization can help to identify implants of unkown composition. Moreover, their electron density can automatically be correctly assigned, as the DECT algorithm does not require tissue equivalency. This might provide more accurate dose distributions in cases, where the beam traverses a non-tissue material that would deviate considerably from the HLUT.
Furthermore, the acquisition of a DECT scan of patients with administered contrast agent enables the calculation of an image, where the influence of the contrast agent can effectively be removed. This would render the additional native CT scan obsolete, reducing overall CT dose to the patient. Finally, DECT also allows for a certain tuning of contrast by an overlay of the two images, which might be exploited for diagnostic or delineation purposes.

  • Lecture (Conference)
    Jahrestagung der BIOMEDIZINISCHEN TECHNIK und Dreiländertagung der MEDIZINISCHEN PHYSIK, 10.-13.09.2017, Dresden, Germany

Permalink: https://www.hzdr.de/publications/Publ-25548
Publ.-Id: 25548