[Coats' disease. Important differential diagnosis for retinoblastoma]

Diffusion-weighted imaging of malignant ocular masses: initial results and directions for further study

BACKGROUND AND PURPOSE

Ocular masses represent a spectrum of malignant tumors and benign lesions that are sometimes difficult to detect and differentiate by conventional imaging techniques. The aim of this study was to characterize a group of malignant ocular masses with DWI, with the goals of establishing reference data and identifying potential clinical applications for improved noninvasive characterization.

MATERIALS AND METHODS

With institutional review board approval, 26 malignant ocular masses in 22 patients were retrospectively analyzed. Five masses were excluded from further analysis due to nonvisualization. Fifteen retinoblastomas, 5 melanomas, and 1 highly undifferentiated carcinoma were studied. Region-of-interest analysis was performed, and the ADC of each mass was measured and also compared with a normal-appearing thalamus. Lesion thickness was measured, the amount of susceptibility artifact was qualitatively assessed and graded, and the correlation between these factors and retinoblastoma ADC was determined.

RESULTS

Retinoblastomas had an ADC of 0.93 ± 0.3 × 10(-3) mm(2)/s (mean). Melanoma had an ADC of 1.18 ± 0.16 × 10(-3) mm(2)/s. The ADC of retinoblastoma was strongly inversely correlated with lesion thickness, likely representing the effect of partial volume averaging. ADC was not correlated with the amount of subjectively determined susceptibility artifact.

CONCLUSIONS

Malignant ocular tumors were consistently characterized with DWI, though with limitations due to artifact and partial volume averaging. Additional description of DWI of ocular masses and further technical improvements may lead to a clinical role for DWI.

MRI of retinoblastoma

We review the role of MRI in retinoblastoma and simulating lesions. Retinoblastoma is the most common paediatric intra-ocular tumour. It may be endophytic, exophytic or a diffuse infiltrating tumour. MRI can detect intra-ocular, extra-ocular and intracranial extension of the tumour. MRI is essential for monitoring patients after treatment and detection of associated second malignancies. It helps to differentiating the tumour from simulating lesions with leukocoria.