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.
Department of Radiology, Hokkaido University School of Medicine, Sapporo, Japan. oita@medsci.tokushima-u.ac.jp
Masataka
M
Oita
Keiichi
K
Ohmori
Kenichi
K
Obinata
Rumiko
R
Kinoshita
Rikiya
R
Onimaru
Kazuhiko
K
Tsuchiya
Keishirou
K
Suzuki
Takeshi
T
Nishioka
Hiroyasu
H
Ohsaka
Katsuhisa
K
Fujita
Teppei
T
Shimamura
Hiroki
H
Shirato
Kazuo
K
Miyasaka
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