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Comparison of Radiotherapy Target Delineation Between MR and Sequential Dual-Energy CT with and Without Contrast

L Chen*, J Liu , T Lin , X Chen , R Price , C Ma , Fox Chase Cancer Center, Philadelphia, PA


(Sunday, 7/14/2019) 4:00 PM - 5:00 PM

Room: 225BCD

Purpose: This study investigates the potential clinical application of sequential dual-energy CT in radiotherapy treatment planning for intracranial target delineation.

Methods: Thirty-four patients were included in this study. Each patient was scanned on a GE 1.5T MR scanner (T1-weighted with contrast) and on a Siemens SOMATOM Definition AS (Open 20RT) scanner with and without contrast. Twenty-eight patients were CT scanned without contrast and 6 patients were scanned with contrast (5 minutes after an intravenous injection of 100 ml 37% organically bound iodine ISOVUE-370). The CT scanner allows sequential acquisition of two image datasets at 80 kVp and 140 kVp with the same acquisition time and radiation dose as a conventional single energy scan. Images were reconstructed for nominal monoenergies between 40 keV and 190 keV, and a mixed energy of 120 kVp, which is equivalent to that currently used in routine clinical practice. The reconstructed images together with MR images were transferred to the CyberKnife Multiplan system for imaging fusion and comparison for target delineation.

Results: Meaningful clinical differences were found on CT images with contrast at different nominal energies reconstructed from dual-energy CT images. Comparing the contrast-enhanced brain metastases at different energies, the 40 keV image delineated the tumor much clearer than images for other energies. The brain tumor volume at 40 keV was identical to that on T1-wighted MR images with contrast. In contrast, CT images without contrast could not show brain metastases clearly even at 40 keV as compared to T1-wighted MR images with contrast.

Conclusion: Our results demonstrated that dual-energy CT with contrast is advantageous for intracranial target delineation. The brain metastasis volume at 40 keV appeared to be comparable to that with T1 weighted MR imaging with contrast. Therefore, dual-energy CT with contract may be used along for intracranial target delineation for radiotherapy treatment planning.


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