Prog Med Phys.  2015 Jun;26(2):106-111. 10.14316/pmp.2015.26.2.106.

Analysis of Couch Sag Using Image Processing of MVCT Images in Tomotherapy

• Park HR
• Kim YH
• Park D
• Kim W
• Ki Y
• Kim D
• Bae JS

• KMID: 1889943
• DOI: http://doi.org/10.14316/pmp.2015.26.2.106

Abstract

In Tomotherapy the couch sags during the treatment due to the weight of the patient. In this study, we developed a simple method to obtain the amount of the sag and the pitch angle of the couch using the image processing technique of MVCT images in Tomotherapy. Using the method we evaluated the sag and pitch of couch for 22 head and neck patients and one craniospinal irradiation (CSI) patient. The sag and the average pitch angle of couch were 0.40~1.54 mm and 0.7degrees for head and neck patients, respectively. For head and neck patients, the sag increased as the longitudinal length of the irradiation volume increased and the pitch angle showed no relationship with the longitudinal length. For the CSI patient the sag was 4.97 mm. Using the method the amount of the couch sag could be measured easily and the measured data could be useful in determination of margins considering the table sag error.

Keyword

Tomotherapy; MVCT; Couch sag

MeSH Terms

Craniospinal Irradiation
Head
Humans
Neck

Figure

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  Fig. 1. 토모테라피 MVCT에서 환 자 테이블 처짐으로 발생하는 영상 에서의 전단현상.

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  Fig. 2. 방사선 단층영상의 영상 이진화 결과. (a) 단층영상의 첫 번째 슬라이스에서의 영상 이진화 결과와 영상 중앙에서 종축으로의 프로파일. (b) 단층영상의 마지막 슬라이스에서의 영상 이진화 결과와 영상 중앙에서 종축으로의 프로파일.

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  Fig. 3. MVCT의 환자 테이블 처짐 분석 결과. (a) 치료범위에 따른 환자테이블 처짐. (b) 처짐 각도의 측정 결과. (c) 환자 체중에 따른 환자테이블의 처짐 각도.

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  Fig. 4. 측정한 데이터를 바탕으로 두경부 MVCT 영상에서 환자테이블의 처짐을 보정 한 결과. (a) MCVT의 첫 번째 슬라이스에서 spine을 기준으로 contour와 영상을 정합한 후 (b) 마지막 슬라이스에서 측정한 오차만큼 (c) 보정한 결과.

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  Fig. 5. 측정한 데이터를 바탕으로 두개척수조사 환자의 MVCT 영상에서 환자테이블의 처짐을 보정 한 결과. (a) MCVT의 첫 번째 슬라 이스에서 spine을 기준으로 contour와 영상을 정합한 후 (b) 마지막 슬라이스에서 측정한 오차만큼 (c) 보정한 결과.

Reference

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