대한방사선치료학회지 (The Journal of Korean Society for Radiation Therapy)
- 제10권1호
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- Pages.69-77
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- 1998
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- 1598-8449(pISSN)
X선치료 조사야 내 공동의 존재에 따른 선량분포의 측정
The Influence of Air Cavity on Interface Doses for Photon Beams
- Chung Se Young (Dept. of Radiation Oncology, Korea University Hospital) ;
- Kim Young Bum (Dept. of Radiation Oncology, Korea University Hospital) ;
- Kwon Young Ho (Dept. of Radiologic Technology, Junior college of Allied Health Sciences, Korea University) ;
- Kim You Hyun (Dept. of Radiologic Technology, Junior college of Allied Health Sciences, Korea University)
- 발행 : 1998.12.01
초록
When a high energy photon beam is used to treat lesions located in the upper respiratory air passages or in maxillary sinus, the beams often must traverse an air cavity before it reaches the lesion. Because of this traversal of air, it is not clear that the surface layers of the lesion forming the air-tumor tissue interface will be in a state of near electronic equilibrium; if they are not, underdosing of these layers could result. Although dose corrections at large distances beyond an air cavity are accountable by attenuation differences, perturbations at air-tissue interfaces are complex to measure or calculate. This problem has been investigated for 4MV and 10MV X-ray beams which are becoming widely available for radiotherapy with linear accelerator. Markus chamber was used for measurement with variouse air cavity geometries in X-ray beams. Underdosing effects occur at both the distal and proximal air cavity interface. The magnitude depended on geometry, energy, field sizes and distance from the air-tissue interfaces. As the cavity thickness increased, the central axis dose at the distal interface decreased. Increasing field size remedied the underdosing, as did the introduction of lateral walls. Fellowing a