8 research outputs found

    Class solutions for SABR-VMAT for high-risk prostate cancer with and without elective nodal irradiation

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    BACKGROUND: The purpose of this study is to find the optimal planning settings for prostate SABR-VMAT for high-risk prostate cancer patients irradiated to prostate only (PO) or prostate and pelvic lymph nodes (PPLN). METHODS: For 10 patients, plans using 6MV flattened, flattening-filter-free (FFF) 6MV (6 F) and FFF 10MV (10 F) photon beams with full and partial arc arrangements were generated and compared. The prescribed dose was 40Gy to the prostate with 25Gy to the PLN in 5 fractions. Plans were then evaluated for PTV coverage, dose fall-off, and OAR doses. The number of monitor units and the treatment delivery times were also compared. Statistical differences were evaluated using a paired sample Wilcoxon signed rank test with a significance level of 0.05%. RESULTS: A total of 150 plans were generated for this study. Acceptable PO plans were obtained using single arcs, while two arcs were necessary for PPLN. All plans were highly conformal (CI ≥1.3 and CN ≥0.90) with no significant differences in the PTV dose coverage. 6MV plans required significantly longer treatment time and had higher dose spillage compared to FFF plans. Superior plans were obtained using 10 F 300° partial arcs for PO with the lowest rectal dose, dose spillage and the shortest treatment times. For PPLN, 6 F and 10 F plans were equivalent. CONCLUSIONS: SABR-VMAT with FFF photon beams offers a clear benefit with respect to shorter treatment delivery times and reduced dose spillage. Class solutions using a single 10 F 300° arc for PO and two 10 F or 6 F partial 300° arcs for PPLN are proposed. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s13014-016-0730-7) contains supplementary material, which is available to authorized users

    Accuracy in automatic image registration between MV cone beam computed tomography and planning kV computed tomography in image guided radiotherapy

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    AimTo verify the accuracy of automatic image registration (IR) between the planning kilo voltage computed tomography (kV CT) and megavoltage cone beam computed tomography (MV CBCT) datasets using phantom and patient images.BackgroundThe automatic IR between MV CBCT and planning kV CT is a fast solution for performing online image guided radiotherapy (IGRT). The IR accuracy has to be verified periodically as it directly affects patient setup accuracy.Materials and methodsThe automatic IR accuracy was evaluated using image quality phantom acquired with different kV CT slice thickness, different MV CBCT acquisition MUs and reconstruction slice size and thickness. The IR accuracy was also evaluated on patient images on different anatomical sites such as brain, head & neck, thorax and pelvis. The uncertainty in the automatic registration was assessed by introducing known offset to kV CT dataset and compared with the registration results.ResultsThe result with the phantom images was within 2[[ce:hsp sp="0.25"/]]mm in all three translational directions. The accuracy in automatic IR using patient images was within 2[[ce:hsp sp="0.25"/]]mm in most of the cases. 3[[ce:hsp sp="0.25"/]]mm planning kV CT slice thickness was sufficient to perform automatic IR successfully within 2[[ce:hsp sp="0.25"/]]mm accuracy. The MV CBCT reconstruction parameters such as slice thickness and slice size had no effect on the registration accuracy.ConclusionThis study shows that the automatic IR is accurate within 2[[ce:hsp sp="0.25"/]]mm and provides confidence in performing them between planning kV CT and MV CBCT image datasets for online image guided radiotherapy

    Assessment and evaluation of MV image guidance system performance in radiotherapy

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    Background and aimThe clinical use of imaging system in image guided radiotherapy (IGRT) necessitates performing periodic quality assurance of the system to be confident in applying corrections for patient set-up errors. We aim to develop and implement a quality assurance (QA) programme for megavoltage (MV) based image guidance system and assess its long term performance for a period of 3 years.Materials and methodsPeriodic QA tests were performed for the MV planar and cone beam computed tomography (CBCT) imaging system to assess the system safety, mechanical and geometrical accuracy, image quality and dose. The tests were performed using the equipment supplied by the manufacturer along with the image guidance system and using simple methods developed in-house. The test results were compared with expected or baseline values established during commissioning.ResultsThe safety system was found to be functional. The results of mechanical and geometrical tests were in good agreement with the expected results. The system mechanical positioning was stable and reproducible within ±2[[ce:hsp sp="0.25"/]]mm accuracy. The image quality and the imaging dose of the planar and CBCT imaging were found to agree with the baseline values and the manufacturer specifications.DiscussionThroughout the three-year period, all the QA tests were within the specification. The mechanical and geometrical tests are most crucial as they directly affect the patient positioning accuracy.ConclusionWe conclude that the MV image guidance system is efficient to perform IGRT and insist to perform periodic QA tests and calibration for the system

    Evaluation of mechanical and geometric accuracy of two different image guidance systems in radiotherapy

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    AimTo assess the mechanical and the geometric accuracy of two different clinically used image guidance systems in radiotherapy for a period of 6 months.BackgroundWith the image guidance procedures being routine in the clinical radiotherapy department, the quality assurance tests for these systems become essential. The mechanical and geometric accuracy of these systems are crucial since it directly affects patient treatment set-up and delivery.Materials and methodsWe have assessed the mechanical and the geometric accuracy of two different image guidance systems (MV and kV based), being used clinically for a period of 6 months. The quality assurance tests such as imager positioning/repositioning, imaging and treatment beam isocentre coincidence, imager mechanical alignment, image scaling, geometric accuracy of cone beam computed tomography system, automatic image registration and offset calculation accuracy were assessed in this period.ResultsIt was found that both systems were mechanically and geometrically accurate within ±2[[ce:hsp sp="0.25"/]]mm in this period.ConclusionThe quality assurance tests for MV based image guidance system were simple compared to kV based systems. We recommend performing periodic quality assurance tests to verify the integrity of both image guidance systems

    Additional file 2: Figure S1. of Class solutions for SABR-VMAT for high-risk prostate cancer with and without elective nodal irradiation

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    Population mean dose-volume histograms (DVHs) and standard deviation (shaded areas) for selected structures for full arc (FA) plans using different energies. Left panel: prostate only (PO) single FA plans. Right panel: prostate and pelvic nodes (PPLN) dual full arc (2FA) plans. (PDF 350 kb
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