11C-methionine PET improves the target volume delineation of meningiomas treated with stereotactic fractionated radiotherapy.
OBJECTIVE
To evaluate the role of 11C-methionine positron emission tomography (MET-PET) in target volume delineation for meningiomas and to determine the interobserver variability.


METHODS
Two independent observers performed treatment planning in 10 patients according to a prospective written protocol. In the first step, they used coregistered computed tomography (CT) and magnetic resonance imaging (MRI). In the second step, MET-PET was added to CT/MRI (image fusion based on mutual information).


RESULTS
The correlation between gross tumor volume (GTVs) delineated by the two observers based on CT/MRI was r=0.855 (Spearman's correlation coefficient, p=0.002) and r=0.988 (p=0.000) when MET-PET/CT/MRI were used. The number of patients with agreement in more then 80% of the outlined volume increased with the availability of MET-PET from 1 in 10 to 5 in 10. The median volume of intersection between the regions delineated by two observers increased significantly from 69% (from the composite volume) to 79%, by the addition of MET-PET (p=0.005). The information of MET-PET was useful to delineate GTV in the area of cavernous sinus, orbit, and base of the skull.


CONCLUSIONS
The hypothesis-generating findings of potential normal tissue sparing and reduced interobserver variability provide arguments for invasive studies of the correlation between MET-PET images and histologic tumor extension and for prospective trials of target volume delineation with CT/MRI/MET-PET image fusion.
Grosu
Anca-Ligia
AL
Department of Radiation Oncology, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany. anca-ligia.grosu@lrz.tum.de
Weber
Wolfgang A
WA
Astner
Sabrina T
ST
Adam
Markus
M
Krause
Bernd J
BJ
Schwaiger
Markus
M
Molls
Michael
M
Nieder
Carsten
C
D000368:Aged; D000369:Aged, 80 and over; D002250:Carbon Radioisotopes; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008577:Meningeal Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008579:Meningioma / Q000000981:diagnostic imaging* / Q000532:radiotherapy; D008715:Methionine; D008875:Middle Aged; D015588:Observer Variation; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D016634:Radiosurgery / Q000379:methods*; D014057:Tomography, X-Ray Computed
D002250:Carbon Radioisotopes; D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18; D008715:Methionine