RESUMO
PURPOSE: The study evaluates the efficacy of cone-beam computed tomography (CBCT)-based synthetic CTs (sCT) as a potential alternative to verification CT (vCT) for enhanced treatment monitoring and early adaptation in proton therapy. METHODS: Seven common treatment sites were studied. Two sets of sCT per case were generated: direct-deformed (DD) sCT and image-correction (IC) sCT. The image qualities and dosimetric impact of the sCT were compared to the same-day vCT. RESULTS: The sCT agreed with vCT in regions of homogeneous tissues such as the brain and breast; however, notable discrepancies were observed in the thorax and abdomen. The sCT outliers existed for DD sCT when there was an anatomy change and for IC sCT in low-density regions. The target coverage exhibited less than a 5% variance in most DD and IC sCT cases when compared to vCT. The Dmax of serial organ-at-risk (OAR) in sCT plans shows greater deviation from vCT than small-volume dose metrics (D0.1cc). The parallel OAR volumetric and mean doses remained consistent, with average deviations below 1.5%. CONCLUSION: The use of sCT enables precise treatment and prompt early adaptation for proton therapy. The quality assurance of sCT is mandatory in the early stage of clinical implementation.
RESUMO
Craniospinal irradiation (CSI) is associated with infertility risk for adolescent/young adult women. We explore two methods of reducing ovarian exposure: oophoropexy (surgical removal of the ovaries from the path of the X-ray beam) and proton therapy (to allow the beam to stop without exposing the ovaries/uterus). In the case discussed, oophoropexy followed by X-ray CSI reduced ovarian dose to that at which 50% of oocytes are expected to survive, and the patient appears to have viable oocytes; this technique did not reduce uterine dose. Proton therapy would have eliminated the ovarian and uterine dose and the need for oophoropexy.
