Dual Energy CT: Treatment Planning for Proton and Ion Radiation Therapy Beyond Standard Tissue Composition

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Purpose/Objective(s)

Dual energy computed tomography (DECT) scanners are increasingly available in the clinic today. Most commonly, they are used for fast image acquisition or advanced techniques such as virtual native scans and bone removal. But they also provide new ways for a better tissue characterization. The latter is especially needed in proton and ion radiation therapy where uncertainties in the CT calibration jeopardize the potential of high accuracy treatment delivery. When tissues deviate significantly

Materials/Methods

DECT scans with two different photon spectra were used to compute the electron density and effective atomic number of tissue surrogates and materials with elevated atomic number. Furthermore, preclinical reconstruction algorithms with extended CT range and raw data based beam hardening correction were used for imaging artifact correction and an improved geometrical characterization. We scanned a series of tissue equivalent materials, polymers and metal samples in a second generation DECT

Results

We extracted the electron densities and effective atomic numbers of the measured materials. Using this additional information, a better material differentiation was feasible. Furthermore, we were able to correlate the effective atomic number to the mean ionization energy which is crucial for the ion range estimation of materials with higher atomic number. This allowed us to improve the WEPL predictions not only for tissue equivalent, but also for non tissue-equivalent materials such PMMA (from

Conclusions

DECT imaging offers additional tissue information that can enhance ion range calculations in materials with non standard elemental composition. It can provide better geometrical information on metal implants with less noise and artifacts.

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Author Disclosure: C. Tremmel: None. N. Huenemohr: None. B. Krauss: A. Employee; Siemens AG. H. Schlemmer: None. O. Jaekel: None. S. Greilich: None.

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