White matter: A good reference for the signal intensity evaluation in magnetic resonance imaging for the diagnosis of uveal melanoma

Abstract

Background Comparing the signal intensity (SI) of an ocular mass to that of the vitreous body has been suggested. Most ocular lesions show a hyper-intense signal compared to the vitreous body on T1-weighted (T1w) images, and malignant melanomas have been almost always determined as ‘cannot be excluded’ in reports. Purpose This study aimed to determine the accuracy of magnetic resonance imaging (MRI) in the diagnosis of uveal melanoma by using normal white matter as reference tissue for SI evaluation on T1w images and vitreous body on T2w compared to the conventional method using the vitreous body as a reference on both T1w and T2w images. Methods The MRIs of 43 patients (between August 2006 and July 2018) sent to rule out uveal melanoma were blindly reviewed by two radiologists. By using white matter as a reference for SI evaluation on T1w images and vitreous body as a reference on T2w images, uveal melanomas were suggested by hyper-intense signal on T1w and hypo-intense signal on T2w with homogeneous enhancement. The accuracy of diagnosis of uveal melanoma using white matter as a reference on T1w was compared to the conventional method using the vitreous body as a reference on both T1w and T2w images. Results The diagnosis of uveal melanoma using white matter as a reference gave a sensitivity of 92.31% (95% confidence interval (CI) 63.97–99.81) and specificity of 100.0% (95% CI 88.43–100.0). By using the vitreous body as a reference, sensitivity as high as 100.0% (95% CI 100.0–100.0) was obtained, but specificity was low at 53.33% (95% CI 34.33–71.66). Conclusions White matter is a good reference for the diagnosis of uveal melanoma, with high sensitivity and much higher specificity than conventional methods using the vitreous body as a reference.

New Perspectives in Imaging of Uveal Melanoma

“…Because of the neoplasm extension, a common concomitant condition is a retinal detachment, which could be confirmed by no contrast enhancement reaction (unlike the tumor). Still, without the use of a contrast agent, these lesions look very similar [117].…”

“…Good soft tissue contrast creates a favorable condition to visualize intra-and extraorbital compounds, tumor localization to assess tumor dimension, and the involvement of adjacent tissues [115,116]. Nowadays, the acquired images influence therapeutic decisions, evaluating tumor advancement, prognosis, and response to treatment [117]. The irrefutable advantage of MR is that patient is not exposed to ionizing radiation and avoids its potential complications.GrechFonk et al estimated the average cost of MRI at €200-€1000 (the price is lower in Asia, Australia, Europe, and higher in the USA; Table 1, Figure 1).…”

“…The presence of orbital adipose tissue enables relatively good tissue contrast [110]. The characteristic features of uveal melanoma obtained in MR (Figure 10) compared to the vitreous (because of the high-water content in the vitreous body, it is hypointense in T1w and hyperintense in T2w) include hyper-intensity on T1-weighted images, hypo-intensity on T2-weighted images, hyper-intense on PD images, and homogenous enhancement with gadolinium contrast [117][118][119]. Tissue contrast results from T1-and T2 -times shortening by unpaired electrons of melanin, and this property correlates with the quantity of melanin [110,[120][121][122].…”

“…In certain situations, the recognition of uveal melanoma may be problematic due to conditions that look similar. For example, the choroidal metastases could mimic a uveal melanoma [117]. Furthermore, the differentiation between uveal melanoma and other pathologies as vitreous hemorrhage also is challenging basing on T1w or T2w imaging [117].…”

“…For example, the choroidal metastases could mimic a uveal melanoma [117]. Furthermore, the differentiation between uveal melanoma and other pathologies as vitreous hemorrhage also is challenging basing on T1w or T2w imaging [117]. Fresh blood could be isointense or hypo-intense on the T1w or T2w image, and the hyperintensity will occur after a few weeks [123].…”