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Imaging dose of megavoltage computed tomography (MVCT) for treatment verification in the tomotherapy of breast cancer

Published online by Cambridge University Press:  02 November 2017

K. W. Cheung*
Affiliation:
Tung Wah College, Homantin, Kowloon, Hong Kong St. Teresa Hospital, Kowloon, Hong Kong
K. K. Sang
Affiliation:
Tung Wah College, Homantin, Kowloon, Hong Kong Queen Elizabeth Hospital, Kowloon, Hong Kong
H. I. Lam
Affiliation:
Tung Wah College, Homantin, Kowloon, Hong Kong
W. M. Chan
Affiliation:
Tung Wah College, Homantin, Kowloon, Hong Kong St. Teresa Hospital, Kowloon, Hong Kong
P. M. Wu
Affiliation:
Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong
H. F. Choi
Affiliation:
Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong
Y. W. Ho
Affiliation:
Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong
M. Y. Y. Law
Affiliation:
Tung Wah College, Homantin, Kowloon, Hong Kong Hong Kong Sanatorium & Hospital, Happy Valley, Hong Kong
*Corresponding
Correspondence to: K. W. Cheung, Tung Wah College (TWC), Wylie Road, Kowloon, Hong Kong. Tel: +852 60543663 31. E-mail: ckw620@gmail.com

Abstract

Aim

The purpose of this study was to investigate whether significant difference exists on radiation dose delivered to organs at risks in megavoltage computed tomography (MVCT) verification using three predefined scanning modes, namely fine (2 mm), normal (4 mm) and coarse (6 mm). This will provide information for the imaging protocol of tomotherapy for the left breast.

Materials and methods

Organ doses were measured using thermoluminescent dosimeters (TLD-100) placed within a female Rando phantom for MVCT imaging. Kruskal–Wallis test was conducted with p<0·05 to evaluate the significant difference between the three MVCT scanning modes.

Results

Statistically significant difference existed in organ absorbed dose between different scan mode selections (p<0·001). Relative to the normal scan selection (4 mm), the absorbed dose to the organs of interests can be scaled down by 0·7 and scaled up by 2·1 for coarse (6 mm) and fine scans (2 mm) respectively.

Conclusions

Optimisation of imaging protocols is of paramount importance to keep the radiation exposure ‘as low as reasonably achievable’. The recommendation of undergoing daily coarse mode for MVCT verification in breast tomotherapy not only mitigates the radiation exposure to normal tissues, but also trims the scan-acquisition time.

Type
Technical Note
Copyright
© Cambridge University Press 2017 

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