Comparison of kilovoltage cone-beam computed tomography with megavoltage projection pairs for paraspinal radiosurgery patient alignment and position verification.
OBJECTIVE
Implanted gold markers and megavoltage (MV) portal imaging are commonly used for setup verification of paraspinal tumors treated with high-dose, single-fraction radiotherapy. We investigated whether the use of kilovoltage cone-beam computed tomography (CBCT) imaging eliminates the need for marker implantation.


METHODS
Patients with paraspinal disease who were eligible for single-fraction stereotactic body radiotherapy were accrued to an institutional review board-approved protocol. Each of 16 patients underwent implantation of fiducial markers near the target. The markers were visible on the MV images. Three MV image pairs were acquired for each patient (initial, verification, and final) and were registered to the reference images. Every MV pair was complemented by a CBCT scan. CBCT image registration was performed automatically by maximizing the mutual information using a region of interest that excluded the markers. The corrections, as determined from the MV images, were compared with these from CBCT and were used for actual patient setup.


RESULTS
The mean and standard deviation of the absolute values of the differences between the CBCT and MV corrections were 1.0 +/- 0.7, 1.0 +/- 0.6, and 1.0 +/- 0.8 mm for the left-right, anteroposterior, and superoinferior directions, respectively. The absolute differences between the corresponding pre- and post-treatment kilovoltage CBCT image registration were 0.6 +/- 0.5, 0.6 +/- 0.5, and 1.0 +/- 0.8 mm.


CONCLUSIONS
The setup corrections found using CBCT without the use of implanted markers were consistent with the marker registration on MV projections. CBCT has additional advantages, including better positioning precision and robust automatic three-dimensional registration, as well as eliminating the need for invasive marker implantation. We have adopted CBCT for the setup of all single-fraction paraspinal patients. Our data have also demonstrated that target displacements during treatment are insignificant.
Kriminski
Sergey A
SA
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, 1275 York Avenue, New York, NY 10021, USA. Sergey.Kriminski@gmail.com
Lovelock
D Michael
DM
Seshan
Venkatraman E
VE
Ali
Imad
I
Munro
Peter
P
Amols
Howard I
HI
Fuks
Zvi
Z
Bilsky
Mark
M
Yamada
Yoshiya
Y
D000465:Algorithms; D054893:Cone-Beam Computed Tomography / Q000379:methods* / Q000592:standards; D003951:Diagnostic Errors; D006046:Gold; D006801:Humans; D009068:Movement; D019736:Prostheses and Implants; D016634:Radiosurgery / Q000379:methods*; D013125:Spinal Neoplasms / Q000000981:diagnostic imaging* / Q000556:secondary / Q000601:surgery
D006046:Gold