Radiation therapy to women with large pendulous breasts presents dosimetric challenges when the whole breast (WB) and supraclavicular and axillary (SCF + AX) nodes need to be encompassed. The aim of this case study was to demonstrate the feasibility of planning and treating a pendulous breasted patient in the prone position. Computerised tomography (CT) images were acquired of the patient in both the prone and supine positions. A Perspex plate was added to the CDR Systems Inc. (Calgary, Canada) prone breastboard to minimize SCF + AX contour variations. Dosimetry was performed on both CT scans and the resultant treatment plans were evaluated for conformity, homogeneity, dose to the lung and maximum doses to the spinal cord (SC) and irradiated volume. The daily set-up in the prone position was monitored for stability and reproducibility. The patient completed her treatment course in the prone position. Minimal daily interventions were required to ensure the position was reproduced. Grade 3 skin toxicity was recorded in the SCF + AX region where the Perspex plate was added to the prone positioning device. There was minimal difference in dosimetry between prone and supine plans in the SCF + AX region. The prone WB plan showed improved homogeneity (prone 0.15; supine 0.22) and conformity (prone 0.90; supine 0.77). A simple addition to the breastboard has enabled a pendulous breasted woman with SC + AX involvement to be treated in the prone position. Set-up of this technique is achievable on a daily basis with minimal impact on workflow. It is a feasible alternative to supine treatment for this patient group.
IntroductionTime‐consuming manual methods have been required to register cone‐beam computed tomography (CBCT) images with plans in the Pinnacle3 treatment planning system in order to replicate delivered treatments for adaptive radiotherapy. These methods rely on fiducial marker (FM) placement during CBCT acquisition or the image mid‐point to localise the image isocentre. A quality assurance study was conducted to validate an automated CBCT‐plan registration method utilising the Digital Imaging and Communications in Medicine (DICOM) Structure Set (RS) and Spatial Registration (RE) files created during online image‐guided radiotherapy (IGRT).Methods CBCTs of a phantom were acquired with FMs and predetermined setup errors using various online IGRT workflows. The CBCTs, DICOM RS and RE files were imported into Pinnacle3 plans of the phantom and the resulting automated CBCT‐plan registrations were compared to existing manual methods. A clinical protocol for the automated method was subsequently developed and tested retrospectively using CBCTs and plans for six bladder patients.ResultsThe automated CBCT‐plan registration method was successfully applied to thirty‐four phantom CBCT images acquired with an online 0 mm action level workflow. Ten CBCTs acquired with other IGRT workflows required manual workarounds. This was addressed during the development and testing of the clinical protocol using twenty‐eight patient CBCTs. The automated CBCT‐plan registrations were instantaneous, replicating delivered treatments in Pinnacle3 with errors of ±0.5 mm. These errors were comparable to mid‐point‐dependant manual registrations but superior to FM‐dependant manual registrations.ConclusionThe automated CBCT‐plan registration method quickly and reliably replicates delivered treatments in Pinnacle3 for adaptive radiotherapy.
potentially suboptimal. All plans were replanned automatically using the model to determine possible improvements. For each OAR, the manual and model plan DVHs were compared against the estimated DVH range. The predicted, manual, and model plan mean doses were compared. Results: For each test case, DVH predictions were generated by the KBP model in <1 minute, and model plans were generated on average in 5 minutes (meanZ306 seconds) compared to 15 minutes for manual plans (meanZ885 seconds). All plans met minimum clinical objectives for target coverage and OAR sparing. Using the model to evaluate manual plan DVHs, 8 of 12 plans were identified as having !1 OAR >1 SD above the estimated DVH. In 6 out of 8 of those cases, the corresponding model plan was able to improve quality and bring every DVH within or below its estimated range. Using the model plans instead of the manual plans resulted in an average decrease in mean OAR dose of 1.2 Gy (meanZ5.1 Gy vs 6.3 Gy; P<0.001), and the mean improvement was particularly pronounced in the small bowel (1.9 Gy), colon (1.8 Gy), esophagus (1.6 Gy), and heart (1.6 Gy). Conclusion: The use of a custom liver SBRT KBP model was tested as a QA tool to identify suboptimal manual planning. Eight out of 12 plans that met initial dosimetric criteria were identified to be capable of improved OAR sparing, and the model was able to generate improved plans automatically in 6 of those 8 cases. These findings demonstrate that a KBP model could be used in QA to verify whether plans achieve adequate OAR sparing.
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