A cavity generation method in testing onboard imaging system Investigating the clinical sensitivity of an onboard imaging system of linear accelerator of radiotherapy
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Abstract
Background: Radiotherapy is a successful therapeutic strategy to limit cancer metastases and control tumor grow locally. However, the cancer lesion could be displaced due to the intrinsic movement of an alive patient. Modern LINAC with onboard imaging system could possibly provide real-time information for observation of these variations during treatment process.
Purpose: To analyze the sensitivity of an on-board imaging system with cavity generation method.
Methods: An Arc Check system from Sun Nuclear company was used as pseudo patient, the Arc CHECK system has two inserts which are the inner plug, and the larger water equivalent outer plug. Three scenarios were generated with all plugs inserted, inner plug being out, and no plugs insert to the Arc CHECK system, And the megavoltage panel at onboarding imaging system was extended for receiving radiation dose passing through the Arc Check patient. Then a Volumetric Modulated Arc Therapy (VMAT) plan was delivered to the ARC CHECK System, and the onboarding was used to record the delivery dose, and the plan recorded dose were analyzed with portal dosimetry software from Varian Medical System. The permutational evaluation variables included distance to agreement, dose difference, and resolution.
Results: In the permutational combination orders, which were comparison of recorded images with both plugs in to inner plug out, both plugs in to both plugs out, and inner plug out versus both plug out, and the gamma value for portal dosimetry system were 95.35%, 71.10%, and 72.4% at 2% dose difference and 2.0mm distance to agreement setting.
Conclusions: An offline experimental strategy was developed with a quality assurance equipment in radiotherapy with cavity generation method; and this initial study provided operational experience in using onboard imaging system in real time tracking the therapeutical procedure in radiation oncology department. Moreover, the easy usage of the onboard imaging system in this study suggests that the clinical application plausibility of cancer radiotherapy for therapeutical outcome improvement; Furthermore, the imaging clinical resolution improvement could be a future radiotherapy direction when multiple onboard imaging modalities system are available.
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