Acceptance testing and clinical assessment of the in-vivo dose measurement EPIgray system / 中国医学装备

ABSTRACT

Objective:To assess the accuracy of dose reconstruction of the in-vivo dose verification EPIgray system in intensity-modulated radiation therapy(IMRT)and volumetric-modulated arc therapy(VMAT)through acceptance testing,and to explore the preliminarily clinical application of that.Methods:A total of 37 patients with cancer at various parts were selected for clinical testing.Referring to the suggestions of the acceptance manual of manufacturer and the American Association of Physicists in Medicine(AAPM)TG-119 report,the square field,strip field and intensity-modulated plan were adopted to test the precision of dose reconstruction of EPIgray system on phantom.The recognition ability of the system for error was researched through changed the thickness of homogeneous phantom and the skin distance of exposure source.A total of 37 patients with cancer at different parts who underwent VMAT were selected to conduct clinical test,and then,the consistence between the dose reconstruction of EPIgray system and the counted dose of treatment plan system were further analyzed.Results:In the tests of square field,EPIgray dose reconstruction demonstrated excellent linearity and higher accuracy.On the phantoms with different thicknesses of fields with different sizes,the highest precision of dose reconstruction of central axis of field was(0.10±0.39)%.The all precisions of dose reconstruction were within 3.0%besides the built region of dose and field edges.In the tests of IMRT and VMAT plan,the deviation of dose reconstruction was<5.0%.With the increasing of the complexity of plan and the heterogeneity of phantom,there was a slight decrease in the reconstruction precision,but all deviations of dose reconstruction were within the range of allowable deviations.In clinical testing of 37 patients,the average reconstruction deviation of the prescription dose point was(-0.6±4.8)%,and the average deviation of sampling points within the range of target area was(-2.1±2.7)%.The reconstruction deviations outside of field and that with large dose gradient were larger.Conclusion:The dose reconstructions of in-vivo dose verification system EPIgray has better consistency with treatment planning system in calculating dose,and the precision of dose reconstruction can meet the requirement of clinical application.