Integration of functional MRI and white matter tractography in stereotactic radiosurgery clinical practice.
OBJECTIVE
To study the efficacy of the integration of functional magnetic resonance imaging (fMRI) and diffusion tensor imaging tractography data into stereotactic radiosurgery clinical practice.


METHODS
fMRI and tractography data sets were acquired and fused with corresponding anatomical MR and computed tomography images of patients with arteriovenous malformation (AVM), astrocytoma, brain metastasis, or hemangioma and referred for stereotactic radiosurgery. The acquired data sets were imported into a CyberKnife stereotactic radiosurgery system and used to delineate the target, organs at risk, and nearby functional structures and fiber tracts. Treatment plans with and without the incorporation of the functional structures and the fiber tracts into the optimization process were developed and compared.


RESULTS
The nearby functional structures and fiber tracts could receive doses of >50% of the maximum dose if they were excluded from the planning process. In the AVM case, the doses received by the Broadmann-17 structure and the optic tract were reduced to 700 cGy from 1,400 cGy and to 1,200 cGy from 2,000 cGy, respectively, upon inclusion into the optimization process. In the metastasis case, the motor cortex received 850 cGy instead of 1,400 cGy; and in the hemangioma case, the pyramidal tracts received 780 cGy instead of 990 cGy. In the astrocytoma case, the dose to the motor cortex bordering the lesion was reduced to 1,900 cGy from 2,100 cGy, and therefore, the biologically equivalent dose in three fractions was delivered instead.


CONCLUSIONS
Functional structures and fiber tracts could receive high doses if they were not considered during treatment planning. With the aid of fMRI and tractography images, they can be delineated and spared.
Pantelis
Evaggelos
E
CyberKnife Center, Iatropolis-Magnitiki Tomografia, Athens, Greece. vpantelis@phys.uoa.gr
Papadakis
Nikolaos
N
Verigos
Kosmas
K
Stathochristopoulou
Irene
I
Antypas
Christos
C
Lekas
Leonidas
L
Tzouras
Argyrios
A
Georgiou
Evangelos
E
Salvaras
Nikolaos
N
D000328:Adult; D001254:Astrocytoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000556:secondary / Q000601:surgery; D020295:Brain Stem Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000556:secondary / Q000601:surgery; D056324:Diffusion Tensor Imaging / Q000379:methods; D005260:Female; D020786:Hemangioma, Cavernous, Central Nervous System / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D006801:Humans; D002538:Intracranial Arteriovenous Malformations / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery; D008175:Lung Neoplasms / Q000473:pathology; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000528:radiation effects; D011712:Pyramidal Tracts / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000528:radiation effects; D011832:Radiation Injuries / Q000517:prevention & control*; D011859:Radiography; D016634:Radiosurgery / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D014795:Visual Pathways / Q000033:anatomy & histology / Q000000981:diagnostic imaging / Q000528:radiation effects