Functional magnetic resonance imaging and radiosurgical dose planning.
OBJECTIVE
To assess the effect of functional magnetic resonance imaging (fMRI) on stereotactic radiosurgical (SRS) dose planning.


METHODS
Patients included those undergoing SRS whose lesions were in or near areas that could be identified with fMRI. After processing, an fMR scan was registered to the anatomic scan, and this dataset was registered to a stereotactic CT scan. The imaged functional areas were contoured along with standard anatomical targets. Dose planning was done at first with the functional volumes rendered invisible; the plans were then adjusted as needed using the functional targets. Doses were measured using a dose-volume histogram tool.


RESULTS
SRS was performed in 12 patients, 1 of whom also underwent SRT. Functional volumes studied included motor cortex in 8 patients, visual in 6 and language in 3; a total of 33 functional targets were imaged. Prescription doses ranged from 12 to 22.5 Gy (mean 19.5 Gy), and the maximum dose to functional volumes from 8 cGy to 18.5 Gy (mean 2.9 Gy). In 6 patients, arc adjustment using functional targets yielded a >50% reduction in dose to at least one functional volume; in all patients, the dose reduction to 50 and 75% of functional volumes averaged 4% (12 cGy) and 13% (30 cGy), respectively, while the reduction of maximal dose averaged 24% (50 cGy).


CONCLUSIONS
fMRI can be used in SRS to reduce irradiation of eloquent brain using standard prescription doses. Appropriate arc adjustment may allow for escalation of the dose to the targeted lesion.
Schulder
M
M
Departments of Neurosurgery and Radiology, New Jersey Medical School, Newark 07103, USA. schulder@umdnj.edu
Vega
J
J
Narra
V
V
Jacobs
A
A
Kalnin
A
A
Lange
G
G
Liu
W C
WC
D000328:Adult; D001921:Brain / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D010347:Patient Care Planning; D011832:Radiation Injuries / Q000401:mortality; D011874:Radiometry; D016634:Radiosurgery; D011881:Radiotherapy, Computer-Assisted; D013238:Stereotaxic Techniques; D016896:Treatment Outcome