In most effective bits evaluation of waveform recorders, the prerequisite is that there is no signal source distortion, or the distortion can be neglected. But when the distortion can be neglected or how it affects th...In most effective bits evaluation of waveform recorders, the prerequisite is that there is no signal source distortion, or the distortion can be neglected. But when the distortion can be neglected or how it affects the evaluation when it can't be neglected it is not determined yet. In this paper, the influence of signal source distortion to the evaluation of the effective bits of waveform recorders is discussed, then, the correction method of the effective bits error caused by the distortion influence is given. Finally , the error limit of the effective bits is given and how to selecte the calibrator is introduced. In the end , some simulation results of the new method in test are described.展开更多
Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retro...Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI), as well as organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.展开更多
文摘In most effective bits evaluation of waveform recorders, the prerequisite is that there is no signal source distortion, or the distortion can be neglected. But when the distortion can be neglected or how it affects the evaluation when it can't be neglected it is not determined yet. In this paper, the influence of signal source distortion to the evaluation of the effective bits of waveform recorders is discussed, then, the correction method of the effective bits error caused by the distortion influence is given. Finally , the error limit of the effective bits is given and how to selecte the calibrator is introduced. In the end , some simulation results of the new method in test are described.
基金Supported by a grant of the Military Medical Metrology Project(No.2011-JL2-005)
文摘Objective The aim of the study was to compare flattening filter-free(FFF) beams and conventional flattening filter(FF) beams in volumetric modulated arc therapy(VMAT) for cervical cancer after surgery, through a retrospective planning study.Methods VMAT plans of FFF beams and normal FF beams were designed for a cohort of 15 patients. The prescribed dose was 45 Gy to 1.8 Gy per fraction, and at least 95% of the planning target volume received this dose. Doses were computed with a commercially available treatment planning system using a Monte Carlo(MC) algorithm. Plans were compared according to dose-volume histogram analysis in terms of planning target volume homogeneity and conformity indices(HI and CI), as well as organs at risk(OAR) dose and volume parameters. Results FFF-VMAT was similar to FF-VMAT in terms of CI, but inferior to FF-VMAT considering HI. No statistically differences were observed between FFF-VMAT and FF-VMAT in following organ at risks including pelvic bone marrow, small bowel, bladder, rectum, and normal tissue(NT)..Conclusion For patients with cervical cancer after hysterectomy, the FFF beam achieved target and OAR dose distribution similar to that of the FF beam. Reduction of beam-on time in cervical cancer is beneficial.
