Confirmation, refinement, and extension of a study in intrafraction motion interplay with sliding jaw motion.
The interplay between a constant scan speed and intrafraction oscillatory motion produces interesting fluence intensity modulations along the axis of motion that are sensitive to the motion function, as originally shown in a classic paper by Yu et al. [Phys. Med. Biol. 43, 91-104 (1998)]. The fluence intensity profiles are explored in this note for an intuitive understanding, then compared with Yu et al., and finally further explored for the effects of low scan speed and random components of both intrafraction and interfraction motion. At slow scan speeds typical of helical tomotherapy, these fluence intensity modulations are only a few percent. With the addition of only a small amount of cycle-to-cycle randomness in frequency and amplitude, the fluence intensity profiles change dramatically. It is further shown that after a typical 30-fraction treatment, the sensitivities displayed in the single fraction fluence intensity profiles greatly diminish.
Kissick
Michael W
MW
Department of Medical Physics, University of Wisconsin Medical School, Madison, Wisconsin 53706-1532, USA. mwkissick@wisc.edu
Boswell
Sarah A
SA
Jeraj
Robert
R
Mackie
T Rockwell
TR
D001822:Body Burden; D019583:Dose Fractionation, Radiation; D006801:Humans; D008175:Lung Neoplasms / Q000503:physiopathology* / Q000532:radiotherapy*; D008954:Models, Biological; D009038:Motion; D009068:Movement; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal / Q000295:instrumentation / Q000379:methods*; D012062:Relative Biological Effectiveness; D015656:Respiratory Mechanics