Assessment of Tumor Volumes in Skull Base Glomus Tumors Using Gluc-Lys[{sup 18}F]-TOCA Positron Emission Tomography
- Klinik fuer Strahlentherapie und Radiologische Onkologie, Klinikum rechts der Isar der Technischen Universitaet Muenchen, Munich (Germany)
- Klinik und Poliklinik fuer Nuklearmedizin, Klinikum rechts der Isar der Technischen Universitaet Muenchen, Munich (Germany)
- Klinik fuer Strahlenheilkunde, Universitaet Freiburg, Freiburg (Germany)
Purpose: To assess a threshold for Gluc-Lys[{sup 18}F]-TOCA positron emission tomography (PET) in target volume delineation of glomus tumors in the skull base and to compare with MRI-based target volume delineation. Methods and Materials: The threshold for volume segmentation in the PET images was determined by a phantom study. Nine patients with a total of 11 glomus tumors underwent PET either with Gluc-Lys[{sup 18}F]-TOCA or with {sup 68}Ga-DOTATOC (in 1 case). All patients were additionally scanned by MRI. Positron emission tomography and MR images were transferred to a treatment-planning system; MR images were analyzed for lesion volume by two observers, and PET images were analyzed by a semiautomated thresholding algorithm. Results: Our phantom study revealed that 32% of the maximum standardized uptake value is an appropriate threshold for tumor segmentation in PET-based target volume delineation of gross tumors. Target volume delineation by MRI was characterized by high interobserver variability. In contrast, interobserver variability was minimal if fused PET/MRI images were used. The gross tumor volumes (GTVs) determined by PET (GTV-PET) showed a statistically significant correlation with the GTVs determined by MRI (GTV-MRI) in primary tumors; in recurrent tumors higher differences were found. The mean GTV-MRI was significantly higher than mean GTV-PET. The increase added by MRI to the common volume was due to scar tissue with strong signal enhancement on MRI. Conclusions: In patients with glomus tumors, Gluc-Lys[{sup 18}F]-TOCA PET helps to reduce interobserver variability if an appropriate threshold for tumor segmentation has been determined for institutional conditions. Especially in patients with recurrent tumors after surgery, Gluc-Lys[{sup 18}F]-TOCA PET improves the accuracy of GTV delineation.
- OSTI ID:
- 21172676
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 73, Issue 4; Other Information: DOI: 10.1016/j.ijrobp.2008.05.037; PII: S0360-3016(08)00925-5; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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