[Repositioning accuracy of cerebral fractionated stereotactic radiotherapy using CT scanning].
OBJECTIVE
To evaluate the accuracy of patient repositioning in fractionated cerebral stereotactic radiotherapy using a Brain Lab stereotactic cranial mask in conjunction with standard dental fixation.


METHODS
Fifty planning and checking CT scans were performed in 25 patients. The check CT scan was performed before or after one of the three sessions of treatment. Coregistration to the planning CT scan was used to assess alignment of the isocentre to the reference markers. The relative position of the PTV with regard to isocentre allowed us to determine its total displacement (3D vector).


RESULTS
Mean isocentre translations (+/-SD) taking into account direction were -0.01+/-0.7, -0.2+/-1.3 and 0.07+/-0.5mm in mediolateral, craniocaudal and anteroposterior directions respectively. Mean rotations (+/- SD) were -0.02+/-0.6, -0.08+/-0.3 and -0.1+/-0.3 degree in mediolateral, craniocaudal and anteroposterior axes respectively. Mean overall PTV displacement was 1.8+/-1.5mm. PTV displacement was smaller than 2 and 3mm in 19/25 and 23/25 patients respectively.


CONCLUSIONS
The accuracy of patient positioning using a stereotactic cranial mask system is similar to those reported in the literature and shows a satisfactory reproducibility with a standard dental fixation.
Pasquier
D
D
Département universitaire de radiothérapie, centre O.-Lambret, Combemale, 59020 Lille, France. davidpasquier@free.fr
Dubus
F
F
Castelain
B
B
Delplanque
M
M
Bernier
V
V
Buchheit
I
I
Kerr
C
C
Santoro
I
I
Huchet
A
A
Causse
N
N
Lartigau
E
E
D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000556:secondary / Q000601:surgery*; D006801:Humans; D007103:Immobilization / Q000295:instrumentation* / Q000379:methods; D008397:Masks; D055805:Moving and Lifting Patients; D016634:Radiosurgery / Q000295:instrumentation* / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods