Abstract
Purpose: :
18F-Fluorodeoxyglucose Positron Emission Tomography integrated with Computed Tomography (18F-FDG PET-CT) has been used for the diagnosis and follow-up evaluations of intraocular tumours, using Standardised Uptake Value (SUV). The aim of our study is to assess the feasibility of quantitative analysis to obtain the metabolic rate of glucose (MRglu, ml/min/100gr) of intraocular tumours and evaluate whether MRglu or SUV parameters can differentiate low (spindle cell type) from high risk (mixed and epithelioid cell type) uveal melanoma.
Methods: :
Twelve patients (mean age 58.5+12.8years) with intraocular tumours candidate for enucleation or transcleral resection were enrolled. In all patients, a complete ophthalmologic examination, ocular ultrasonography (US), metastatic work-up, and pre-operative 18F-FDG PET-CT images were carried out and evaluated drawing regions of interest (ROIs) over the lesion using a 70% threshold level for SUV max. and SUV mean. For statistical analysis two sample T-test was used.
Results: :
All intraocular lesions were visualised at 18F-FDG PET-CT. The mean volume measured by ultrasonography was 48+0.96cc3 and since the volume values were similar in all intraocular tumours (n=12), the partial volume effect correction has not been performed. The mean value of SUV max and SUV mean were 3.96+1.94 and 3.24 +1.51, respectively; and high correlation was found between SUVmax and SUVmean: r2=0.99, p=0.000. A good correlation was also found between SUV values and volume (r2=0.74, p=0.006). SUVmax and SUVmean values of low risk intraocular lesions were significantly (p=0.02) lower than those observed in high risk lesions.
Conclusions: :
High risk melanomas showed higher values either SUV or MRglu when compared with low risk melanomas. More aggressive type cells have higher metabolism and higher 18F-FDG uptake. Differences in glucose consumption among tumours with same histology can be found.
Keywords: melanoma • uvea • imaging/image analysis: clinical