Title: Feasibility of cone beam CT image-guided adaptive radiotherapy to treat esophageal carcinoma
Abstract: Objective To investigate the feasibility of reducing the exposure dose on normal tissue by creating a specific planning target volume(PTV) using cone beam computed tomography(CBCT) imaging during the first week of radiotherapy in patients with esophageal carcinoma.Methods Ten patients with esophageal carcinoma treated by radical radiotherapy were investigated.CBCT im ages were acquired on days 1~5 of the first week of radiotherapy and once a week later.The images were imported into the planning system and matched with the planning CT for the same treatment position.The same tumor and esophagus as in the initial plan(plan A) for the length of the clinic target volume(CTV) were contoured on each CBCT image.Then CTV was contoured again on each CBCT image according to the plan prior to radiotherapy.The PTV was defined as CTV(tumor,nodes)plus setup error,which was acquired during the first weeks of treatment.A composite volume(PTV1)was created by combining the five CBCT volumes in the first week.PTV2 was generated in the same way using the five CBCT volumes of weeks 2~6.An adaptive plan(plan B)was formulated based on the PTV1 target in order to maintain the same radiation planning parameters and target prescription dose as in plan A,while limiting the exposure dose to organs at risk.Coverage of the 95% prescription isodose was evaluated on PTV1 and PTV2 with the same radiation planning.Dose-volume histograms(DVHs)for lung,heart and spinal cord of the two plans were compared.Results For the adaptive plan,the coverage of the 95% prescription isodose for PTV1 was 95.5±3.4%(P=0.001),while for PTV2 it was 99.1±1.7%(P=0.001).Several parameters with plan B were significantly smaller than with plan A(P0.05):lung V 20(25.1% vs 26.9%)and mean dose(14.1Gy vs 15.1Gy),heart mean dose(26.9Gy vs 20.7Gy)and spinal cord maximum dose(41.5Gy vs 42.9Gy).Conclusions A reduced planning volume can be constructed based on CBCT images acquired during the first week of radiotherapy.The modified plan can be implemented in the follow-up treatment,considerably reducing the dosage on organs around the target area and potentially increasing the dosage on the target.
Publication Year: 2012
Publication Date: 2012-01-01
Language: en
Type: article
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