Uncertainty in treatment of head-and-neck tumors by use of intraoral mouthpiece and embedded fiducials.
OBJECTIVE
To reduce setup error and intrafractional movement in head-and-neck treatment, a real-time tumor tracking radiotherapy (RTRT) system was used with the aid of gold markers implanted in a mouthpiece.


METHODS
Three 2-mm gold markers were implanted into a mouthpiece that had been custom made for each patient before the treatment planning process. Setup errors in the conventional immobilization system using the shell (manual setup) and in the RTRT system (RTRT setup) were compared. Eight patients with pharyngeal tumors were enrolled.


RESULTS
The systematic setup errors were 1.8, 1.6, and 1.1 mm in the manual setup and 0.2, 0.3, and 0.3 mm in the RTRT setup in right-left, craniocaudal, and AP directions, respectively. Statistically significant differences were observed with respect to the variances in setup error (p <0.001). The systematic and random intrafractional errors were maintained within the ranges of 0.2-0.6 mm and 1.0-2.0 mm, respectively. The rotational systematic and random intrafractional errors were estimated to be 2.2-3.2 degrees and 1.5-1.6 degrees , respectively.


CONCLUSIONS
The setup error and planning target volume margin can be significantly reduced using an RTRT system with a mouthpiece and three gold markers.
Oita
Masataka
M
Department of Radiology, Hokkaido University School of Medicine, Sapporo, Japan. oita@medsci.tokushima-u.ac.jp
Ohmori
Keiichi
K
Obinata
Kenichi
K
Kinoshita
Rumiko
R
Onimaru
Rikiya
R
Tsuchiya
Kazuhiko
K
Suzuki
Keishirou
K
Nishioka
Takeshi
T
Ohsaka
Hiroyasu
H
Fujita
Katsuhisa
K
Shimamura
Teppei
T
Shirato
Hiroki
H
Miyasaka
Kazuo
K
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D005260:Female; D006046:Gold; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy; D006801:Humans; D007103:Immobilization / Q000379:methods; D008297:Male; D008875:Middle Aged; D009064:Mouth Protectors; D009068:Movement; D019047:Phantoms, Imaging; D010610:Pharyngeal Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011859:Radiography; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated; D035501:Uncertainty
D006046:Gold