Abstract
PurposeTo verify the practicality and safety of a treatment chair with six degrees of freedom (6DTC) through demonstrating the efficacy of the workflow in clinical settings and analyzing the obtained technical data, including intra-fraction patient movement during the use of the 6DTC.Materials and MethodsA clinical study was designed and conducted to test the clinical treatment workflow and the safety of the 6DTC. Based on the demonstrated dosimetric advantages, fifteen patients with head and neck tumors were selected and treated with the 6DTC. The positional error at the first beam position (PE-B1) and the second beam position (PE-B2) were analyzed and compared with the results from daily quality assurance (QA) procedures of the 6DTC and imaging system performed each day before clinical treatment. The intra-fraction patient movement was derived from the total patient alignment positional error and the QA data based on a Gaussian distribution formulism.ResultsThe QA results showed sub-millimeter mechanical accuracy of the 6DTC over the course of the clinical study. For 150 patient treatment fractions, the mean deviations between PE-B1 and PE-B2 were 0.13mm (SD 0.88mm), 0.25mm (SD 1.17mm), -0.57mm (SD 0.85mm), 0.02° (SD 0.35°), 0.00° (SD 0.37°), and -0.02° (SD 0.37°) in the x, y, z (translational), and u, v, w (rotational) directions, respectively. The calculated intra-fraction patient movement was -0.08mm (SD 0.56mm), 0.71mm (SD 1.12mm), -0.52mm (SD 0.84mm), 0.10° (SD 0.32°), 0.09° (SD 0.36°), and -0.04° (SD 0.36°) in the x, y, z, u, v, w directions, respectively.ConclusionsThe performance stability of the 6DTC was satisfactory. The position accuracy and intra-fraction patient movement in an upright posture with the 6DTC were verified and found adequate for clinical implementation.
Highlights
Radiation therapy with proton or carbon-ion beams offers physical and biological advantages over x ray beams for many clinical indications [1, 2]
Before the clinical study with patients commenced, a series of measurements to test the performance of the 6DTC showed that it had met the requirements for clinical applications [5]
The results presented demonstrate the efficacy of the workflow for the clinical implementation of the 6DTC
Summary
Radiation therapy with proton or carbon-ion beams offers physical and biological advantages over x ray beams for many clinical indications [1, 2]. An optimal ion beam plan can often be achieved with only two to four beam entry angles; either by rotating the beam delivery gantry, rotating the patient positioning table, or both. Due to the high cost of carbon-ion beam gantries, carbon ion centers typically only have fixed direction beam lines [3]. The flexibility of beam orientation for achieving optimal plans and treatments is naturally compromised when using fixed beam lines compared to rotating gantries. To overcome this disadvantage, a treatment chair with six degrees-of-freedom (6DTC) was designed, manufactured, and installed in Shanghai Proton and Heavy Ion Center (SPHIC) for use with a fixed beam line. Before the clinical study with patients commenced, a series of measurements to test the performance of the 6DTC showed that it had met the requirements for clinical applications [5]
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