Verification of Gated Radiation Therapy: Dosimetric Impact of Residual Motion

서지정보

· 발행기관 : 한국의학물리학회
· 수록지 정보 : 의학물리 / 25권 / 3호 / 128 ~ 138페이지
· 저자명 : Inhwan Yeo, Jae Won Jung

초록

In gated radiation therapy (gRT), due to residual motion, beam delivery is intended to irradiate not only the trueextent of disease, but also neighboring normal tissues. It is desired that the delivery covers the true extent (i.e.
clinical target volume or CTV) as a minimum, although target moves under dose delivery. The objectives of ourstudy are to validate if the intended dose is surely delivered to the true target in gRT and to quantitativelyunderstand the trend of dose delivery on it and neighboring normal tissues when gating window (GW), motionamplitude (MA), and CTV size changes. To fulfill the objectives, experimental and computational studies havebeen designed and performed. A custom-made phantom with rectangle- and pyramid-shaped targets (CTVs)on a moving platform was scanned for four-dimensional imaging. Various GWs were selected and imageintegration was performed to generate targets (internal target volume or ITV) for planning that included the CTVsand internal margins (IM). The planning was done conventionally for the rectangle target and IMRT optimizationwas done for the pyramid target. Dose evaluation was then performed on a diode array aligned perpendicularlyto the gated beams through measurements and computational modeling of dose delivery under motion. Thisstudy has quantitatively demonstrated and analytically interpreted the impact of residual motion includingpenumbral broadening for both targets, perturbed but secured dose coverage on the CTV, and significant dosesdelivered in the neighboring normal tissues. Dose volume histogram analyses also demonstrated and interpretedthe trend of dose coverage: for ITV, it increased as GW or MA decreased or CTV size increased; for IM, itincreased as GW or MA decreased; for the neighboring normal tissue, opposite trend to that of IM was observed.
This study has provided a clear understanding on the impact of the residual motion and proved that if breathingis reproducible gRT is secure despite discontinuous delivery and target motion. The procedures and computationalmodel can be used for commissioning, routine quality assurance, and patient-specific validation of gRT. Morework needs to be done for patient-specific dose reconstruction on CT images.

참고자료

· 없음