Multi-modality imaging of uveal melanomas using combined PET/CT, high-resolution PET and MR imaging.
We investigated the efficacy of combined FDG-PET/CT imaging for the diagnosis of small-size uveal melanomas and the feasibility of combining separate, high-resolution (HR) FDG-PET with MRI for its improved localization and detection.


METHODS
3 patients with small-size uveal melanomas (0.2-1.5 ml) were imaged on a combined whole-body PET/CT, a HR brain-PET, and a 1.5 T MRI. Static, contrast-enhanced FDG-PET/CT imaging was performed of head and torso with CT contrast enhancement. HR PET imaging was performed in dynamic mode 0-180 min post-injection of FDG. MRI imaging was performed using a high-resolution small-loop-coil placed over the eye in question with T2-3D-TSE and T1-3D-SE with 18 ml Gd-contrast. Patients had their eyes shaded during the scans. Lesion visibility on high-resolution FDG-PET images was graded for confidence: 1: none, 2: suggestive, 3: clear. Mean tumour activity was calculated for summed image frames that resulted in confidence grades 2 and 3. Whole-body FDG-PET/CT images were reviewed for lesions. PET-MRI and PET/CT-MRI images of the head were co-registered for potentially improved lesion delineation.


RESULTS
Whole-body FDG-PET/CT images of 3/3 patients were positive for uveal melanomas and negative for disseminated disease. HR FDG-PET was positive already in the early time frames. One patient exhibited rising tumour activity with increasing uptake time on FDG-PET. MRI images of the eye were co-registered successfully to FDG-PET/CT using a manual alignment approach.


CONCLUSIONS
Small-size uveal melanomas can be detected with whole-body FDG-PET/CT. This feasibility study suggests the exploration of HR FDG-PET in order to provide additional diagnostic information on patients with uveal melanomas. First results support extended uptake times and high-sensitivity PET for improved tumour visibility. MRI/PET co-registration is feasible and provides correlated functional and anatomical information that may support alternative therapy regimens.
Beyer
T
T
Department of Nuclear Medicine, University Hospital, Essen, Germany. thomas.beyer@uni-essen.de
Pietrzyk
U
U
Knoess
C
C
Vollmar
S
S
Wienhard
K
K
Kracht
L
L
Bockisch
A
A
Maderwald
S
S
Kühl
H
H
Fitzek
M
M
D019788:Fluorodeoxyglucose F18; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D008545:Melanoma / Q000000981:diagnostic imaging; D049268:Positron-Emission Tomography; D011859:Radiography; D011868:Radioisotopes; D012680:Sensitivity and Specificity; D014604:Uveal Neoplasms / Q000175:diagnosis / Q000000981:diagnostic imaging*; D014916:Whole-Body Irradiation
D011868:Radioisotopes; D019788:Fluorodeoxyglucose F18