Diffusion-weighted magnetic resonance imaging and ultrasound evaluation of choroidal melanomas after proton-beam therapy.

Abstract

This study was undertaken to compare the ultrasound and magnetic resonance imaging parameters of ocular melanoma and to assess their variation after proton-beam therapy. Fifteen choroidal melanoma patients treated with proton-beam therapy were enroled in the study. All patients underwent ophthalmologic evaluations, ultrasound, conventional magnetic resonance (MR) imaging and diffusion-weighted MR imaging before the start of therapy and 3 and 6months after therapy. Basal diameters, thickness, internal reflectivity, tumour volumes and apparent diffusion coefficient (ADC) values of ocular melanomas were measured at each examination. Correlations between internal reflectivity and ADC were investigated. No significant changes were seen in tumour diameters and tumour height as assessed by B-scan and A-scan, respectively. Significant increase in mean tumour internal reflectivity was detected at 6months (baseline 35%±11; 6months 48%±8, Tukey-Kramer p=0.005). On MRI, compared to baseline (mean 547±262mm(3)), a significant reduction in volume was seen at 6months (Tukey-Kramer p=0.045) (mean volume 339±170mm(3), mean reduction 38%). A significant increase in ADC (baseline 1,002±109mm(2)/s) was detected both at 3 and 6months after proton therapy (respectively, 1,454±90 and 1,833±261mm(2)/s, both p<0.001). By MRI, in particular by ADC assessment, it is possible to detect early variations in melanoma treated by proton-beam therapy. This examination could be used together with ultrasound in the follow-up of this treatment.