Accurate setup of paraspinal patients using a noninvasive patient immobilization cradle and portal imaging.
Because of the proximity of the spinal cord, effective radiotherapy of paraspinal tumors to high doses requires highly conformal dose distributions, accurate patient setup, setup verification, and patient immobilization. An immobilization cradle has been designed to facilitate the rapid setup and radiation treatment of patients with paraspinal disease. For all treatments, patients were set up to within 2.5 mm of the design using an amorphous silicon portal imager. Setup reproducibility of the target using the cradle and associated clinical procedures was assessed by measuring the setup error prior to any correction. From 350 anterior/posterior images, and 303 lateral images, the standard deviations, as determined by the imaging procedure, were 1.3 m, 1.6 m, and 2.1 in the ant/post, right/left, and superior/inferior directions. Immobilization was assessed by measuring patient shifts between localization images taken before and after treatment. From 67 ant/post image pairs and 49 lateral image pairs, the standard deviations were found to be less than 1 mm in all directions. Careful patient positioning and immobilization has enabled us to develop a successful clinical program of high dose, conformal radiotherapy of paraspinal disease using a conventional Linac equipped with dynamic multileaf collimation and an amorphous silicon portal imager.
Lovelock
D Michael
DM
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, New York 10021, USA. lovelocm@mskcc.org
Hua
Chiaho
C
Wang
Ping
P
Hunt
Margie
M
Fournier-Bidoz
Nathalie
N
Yenice
Kamil
K
Toner
Sean
S
Lutz
Wendell
W
Amols
Howard
H
Bilsky
Mark
M
Fuks
Zvi
Z
Yamada
Yoshiya
Y
D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007103:Immobilization / Q000295:instrumentation* / Q000379:methods*; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000295:instrumentation / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013125:Spinal Neoplasms / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*