Room: Karl Dean Ballroom B1
Purpose: Dual-energy CT (DECT) has the potential of reducing proton range uncertainties. However, very few proton institutes are motivated to adopt DECT in routine practice due to the lack of quantitative demonstration of significant benefit of this technology. We report a case study advocating the utilization of DECT in breast patients with implants.
Methods: One patient with breast implant (Sientra) and another without any implant or contrast were scanned with a single-energy CT (SECT) protocol and a DECT protocol on a Philips Brilliance big bore CT scanner. Proton stopping power ratio (SPR) was reconstructed from the SECT scan on a Stoichiomatric CT calibration based on Schneiderâ€™s method, and from the DECT scan based on Torikoshi algorithm. SPR of the breast implant was compared among the two scans and literature. Water equivalent path length (WEPL) in the patient without any implant and contrast were computed in the anterior-posterior direction for comparison to quantify the variation in the estimate of SPR in normal human tissues in the two CT reconstruction schemes.
Results: The SPR of the breast implant was measured 0.93Â±0.02 in the DECT scan, matching exactly with literature, while the SPR of the breast implant was measured 1.04Â±0.01 in the SECT scan. Lung V20 increased from 20.29% to 35.26% had the DECT not been used. The mean discrepancy in WEPL was 1.21Â±1.12 mm, or 0.93%Â±0.92% relative to the thickness of body in the anterior-posterior direction. 2.2% of WEPL varied more than 3% between SECT and DECT.
Conclusion: Our study showed that image-based DECT approach is able to reconstruct SPR of breast implant much more accurately than SECT. We recommend DECT be standard for breast patients with implant in proton therapy. For patients without implants, DECT showed a modest change from SECT which warrants further investigation.
Not Applicable / None Entered.