Purpose: The purposes of this study were to estimate
accumulated kV X-ray imaging dose throughout dynamic tumor tracking (DTT)
irradiationby Vero4DRT system and to address an analytical skin dose
formula for well-balanced kV X-ray imaging
conditions between skin dose and image noise.Method:First, skin dose was measured using kV X-ray tube,
chamber, and water-equivalent phantoms.
Next, imaging dose for six patients in DTT treatment was computed using
log files. Subsequently, scattered dose ratiowas calculated by amount of ionization in front of flat panel
detector (FPD) for fields with size of maximum and the chamber
for 0-200 mm-thickness phantoms and
tube voltage of 60, 80, 100, 120 kV, respectively. Furthermore, image noise was computed from
FPD images. Results: The skin dose was greater by a factor of 1.4-1.6 than those in Synergy XVI system.The image noise in FPD, ？was expressed asN
= 0.045×(1/QFPDen)0.479, where QFPDen denotes amount of ionization
in front
of FPD. Then, skin dose,D (N, t, v) was formulated as (0.045/N)(1/0.479)/QFPDen/mAs
(t, v) ×D/mAs (v),whereQFPDen/mAs
(t, v) andD/mAs
(v) denote amount of ionization in front of FPDand skin dose per mAs, respectively. Using the formulae, it
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