Reliability of the bony anatomy in image-guided stereotactic radiotherapy of brain metastases.
OBJECTIVE
To evaluate whether the position of brain metastases remains stable between planning and treatment in cranial stereotactic radiotherapy (SRT).


METHODS
Eighteen patients with 20 brain metastases were treated with single-fraction (17 lesions) or hypofractionated (3 lesions) image-guided SRT. Median time interval between planning and treatment was 8 days. Before treatment a cone-beam CT (CBCT) and a conventional CT after application of i.v. contrast were acquired. Setup errors using automatic bone registration (CBCT) and manual soft-tissue registration of the brain metastases (conventional CT) were compared.


RESULTS
Tumor size was not significantly different between planning and treatment. The three-dimensional setup error (mean +/- SD) was 4.0 +/- 2.1 mm and 3.5 +/- 2.2 mm according to the bony anatomy and the lesion itself, respectively. A highly significant correlation between automatic bone match and soft-tissue registration was seen in all three directions (r >/= 0.88). The three-dimensional distance between the isocenter according to bone match and soft-tissue registration was 1.7 +/- 0.7 mm, maximum 2.8 mm. Treatment of intracranial pressure with steroids did not influence the position of the lesion relative to the bony anatomy.


CONCLUSIONS
With a time interval of approximately 1 week between planning and treatment, the bony anatomy of the skull proved to be an excellent surrogate for the target position in image-guided SRT.
Guckenberger
Matthias
M
Department of Radiation Oncology, Julius-Maximilians University, Wuerzburg, Germany. guckenberg_m@klinik.uni-wuerzburg.de
Baier
Kurt
K
Guenther
Iris
I
Richter
Anne
A
Wilbert
Juergen
J
Sauer
Otto
O
Vordermark
Dirk
D
Flentje
Michael
M
D001932:Brain Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D006801:Humans; D009068:Movement; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D011881:Radiotherapy, Computer-Assisted; D015203:Reproducibility of Results; D012886:Skull / Q000000981:diagnostic imaging*; D013997:Time Factors; D014057:Tomography, X-Ray Computed