Abstract
The purpose of this study was to evaluate the feasibility of assessing bladder and rectal point doses, using orthogonal radiographs without treatment planning, for vaginal cylinder applicator (VC), high‐dose‐rate (HDR) vaginal cuff brachytherapy (BT) after hysterectomy. Thirty‐three VC HDR BT treatment plans from 31 postoperative endometrial cancer patients were retrospectively analyzed. Single‐channel VC with four differing diameters — 2.0 cm, 2.3 cm, 2.6 cm, and 3.0 cm — were analyzed. Dose‐distance modeling was performed to estimate bladder and rectal point doses by measuring distances on each orthogonal radiograph without treatment planning. The estimated doses were then compared with doses calculated on treatment planning system (TPS). Their percent (%) dose differences were recorded. Analysis was performed for each VC size, ICRU bladder and rectal points, and the closest rectal point. The estimated doses obtained from dose‐distance modeling displayed on average less than 2.5% difference when compared with TPS doses at ICRU bladder and rectal points for each VC size. Dose percent differences between estimated values and TPS values were on average 1.9% and 2.5% for ICRU bladder and rectal point, respectively, regardless of VC sizes. Dose‐distance modeling for closest rectal point presented on average 5.4% dose difference when compared with TPS values of all VC sizes. It was feasible to estimate rectal and bladder point doses by measuring distances on orthogonal radiographs without treatment planning. Percent dose differences were 2.5% less for both ICRU bladder and rectal points, regardless of VC sizes. The use of closest rectal point is not recommended for estimating rectal dose.PACS number: 87.53.‐j, 87.53.Jw, 87.55.‐x, 87.55.D‐, 87.55dk
Highlights
241 Zhang et al.: Dose estimations for vaginal cylinder brachytherapy standard treatment planning in vaginal cylinder applicator (VC) HDR BT is based on two-dimensional (2D) orthogonal radiographs
We evaluate the feasibility of assessing bladder and rectal point doses using only orthogonal radiographs without treatment planning for hysterectomy patients receiving adjuvant VC HDR BT for endometrial cancer
The estimated doses obtained from the dose-distance modeling displayed on average less than 2.5% difference when compared with treatment planning system (TPS) doses at ICRU bladder and rectal points for each VC size
Summary
241 Zhang et al.: Dose estimations for vaginal cylinder brachytherapy standard treatment planning in VC HDR BT is based on two-dimensional (2D) orthogonal radiographs. VC HDR BT treatment is typically planned for the first implant, and delivered after 2D imaging validations on treatment day. The VC HDR BT prescription dose is conventionally specified to 0 mm or 5 mm depth from the surface of the VC.[9] The 2D-based planning isodose lines are generated using two lateral reference lines at either 0 mm or 5 mm depth, and are not specific to the patient’s anatomy but depend on the VC size. Dwell times for each VC size can, be generated by scaling them so as to account for activity differences. Precalculated dwell times for each VC size are described as an alternative to VC HDR BT treatment planning. Radiographs are not a prerequisite for dosimetric purposes, but for the validation of VC implants, per ABS guideline.[9]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
