Do we need improved (dual-energy) CT imaging?

In the era of image-guided high-precision radiotherapy, all clinically used imaging modalities need to benefit the individual patient’s treatment outcome in order to be reimbursed. From a radiation oncologist’s point of view dual-energy CT (DECT) ought to (1) improve target volume delineation, (2) decrease proton range uncertainty and (3) guide patient stratification using advanced image analysis methods, i.e., Radiomics.

(1) With the acquisition of DECT scans more information on the tissue composition and its contrast can be gathered. This may potentially air delineation of the primary tumor and surrounding organs at risk. Possibly, even the inter-observer variability may be reduced. In order to assess whether this is a measurable effect, we are currently conducting a delineation study. However, can this potential benefit also be transferred into clinical routine?

(2) Using DECT, the prediction of electron density (for photon therapy) and stopping-power ratio (for proton therapy) can be improved. Consequently, DECT would increase overall accuracy due to a patient-specific calculation without neglecting the intra- and inter-patient tissue diversity and variability. In particle therapy, CT-related range uncertainties may be reduced and the full potential of the beam modality subsequently exploited. Do we, however, dare to directly apply this in our clinics?

(3) Apart from improved treatment planning and delivery, DECT may also further characterize the primary target volume and possibly metastatically affected lymph nodes to predict outcome and enable patient stratification. This approach has been shown beneficial on non-contrast enhanced CT scans in non-small cell lung and head and neck cancer patients. Thus far, there are no data on the value of DECT. Thus, we need to ask: Are our current imaging protocols good enough to be quantitative? Do we need standardized imaging protocols in our own institution and different institutions? What does it take to make clinical decisions based on Radiomics?