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Validation
of a method for automatic image fusion (BrainLAB System) of CT data and
11C-methionine-PET data for stereotactic radiotherapy using a LINAC: first
clinical experience
Grosu AL, Lachner R,
Wiedenmann N, Stark S, Thamm R, Kneschaurek P, Schwaiger M, Molls M, Weber WA
Department
of Radiation Oncology, Technical University Munich, Munich, Germany.
anca-ligia@lrz.tum.de
Purpose. (a) To implement a fully automatic method to integrate
(11)C-methionine positron emission tomography (MET-PET) data into stereotactic
radiation treatment planning using the commercially available BrainLAB System,
by means of CT/MET-PET image fusion.
(b) To validate the fully automatic CT/MET-PET image fusion technique with
respect to accuracy and robustness.
(c) To give a short glance at the clinical consequences for patients with brain
tumors.
Methods
and Materials. In 12 patients with brain tumors (9 meningeomas, 3 gliomas),
CT, MRI, and MET-PET were performed for stereotactic fractionated radiation
treatment planning.
The CT and MET-PET investigations were performed using a relocatable mask for
head fixation.
Fifteen external reference markers (5 on each lateral and 5 on the frontal
localizer plate) that could be identified in CT and MET-PET were applied on the
stereotactic localizer frame; the marker positions were exactly defined for both
investigations.
The MRI/CT fusion was done completely automatically.
The CT/MET-PET fusion was performed using two different methods: The gold
standard was the CT/PET fusion based on the reference markers, and the test
method was the automatic, intensity-based CT/PET fusion, independent of the
external markers.
The markers visible on CT and transmission PET were matched using a
point-to-line matching algorithm.
To quantify the amount of misregistration, the two fusion methods were compared
by calculating the mean value of deviation between corresponding points inside a
cubic volume of interest of > or =512 cm(3) defined within the cranial
cavity.
The gross tumor volume (CT/MRI) outlined on CT and T1-MRI with contrast medium
was compared with the gross tumor volume (PET) defined in the reoriented MET-PET
data sets.
The clinical impact of MET-PET in tumor volume definition for stereotactic
radiotherapy will be discussed.
Results.
The fully automatic integration of MET-PET into stereotactic radiation treatment
planning was successfully realized in all patients investigated.
Mean deviation of the intensity-based automatic CT/PET fusion compared with the
external marker-based gold standard was 2.4 mm; the standard deviation was
0.5.
The algorithm's robustness was evaluated, and the discrepancy of fusion results
due to different initial image alignments was determined to be below 1 mm inside
the test volume of interest.
In patients with meningiomas and gliomas, MET-PET was shown to deliver
additional information concerning tumor extension.
Conclusion.
The precision of the automatic CT/PET image fusion was high.
A mean deviation of 2.4 mm is acceptable, considering that it is approximately
equal to the pixel size of the PET data sets.
MET-PET improves target volume definition for stereotactic fractionated
radiotherapy of meningiomas and gliomas.
PMID: 12873691 [PubMed - indexed for MEDLINE]
Source: http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12873691&dopt=Abstract
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