High resolution magnetic resonance imaging of retinoblastoma

Abstract

Background/aims: Diagnosis of retinoblastoma is mainly based on indirect ophthalmoscopy, but additional imaging techniques are indispensable for the staging of the disease. A new high resolution magnetic resonance imaging (MRI) technique for the examination of the eye was evaluated. A new surface coil with a diameter of 5 cm allows a field of view of 60 mm with an in-plane resolution of 0.8 mm. We compared preoperative MRI scans with the histology after enucleation in 21 cases of retinoblastoma. Parameters studied were appearance of retinoblastoma, choroidal and scleral infiltration, extraocular extension, optic nerve infiltration, and vitreous seeding. Results: All retinoblastomas could be visualised as hypointense to vitreous on T2 weighted images and slightly hyperintense to vitreous on plain T1 weighted images with a moderate enhancement after contrast application. Histology revealed seven cases with infiltration of the optic disc or optic nerve. Preoperative MRI scans depict juxtapapillary tumour masses, but it was impossible to differentiate between a juxtapapillary retinoblastoma, a prelaminar infiltration of the optic disc, or a just postlaminar optic nerve infiltration. In five of 14 cases with a proved tumour infiltration of the choroid, MRI scans showed an inhomogeneous contrast enhancement of the choroid in enhanced T1 weighted sequences beneath the retinoblastoma. Whether this sign is specific for a choroidal infiltration or is just an artefact remains unclear. High resolution MRI scans did not allow the exclusion of this form of intraocular tumour extension. All nine cases with proved vitreous seeding were not detected by MRI scans. None of these cases showed scleral infiltration or orbital tumour extension. Therefore, it is not possible to judge the rank of this technique in detecting orbital tumour growth. Conclusion:The new MRI technique is of limited value in visualisation of prelaminar or postlaminar infiltration of the optic nerve. Advanced choroidal infiltration might be visualised by contrast enhanced T1 weighted MRI scans, but the available spatial resolution did not allow the exclusion this critical form of tumour growth by MRI scans. Nevertheless, high resolution MRI with the new surface coil has superior contrast and spatial resolution compared to computed tomograph (CT) or other available imaging techniques. MRI cannot replace CT in detecting tumour calcification but with increasing experience with this new technique it should be possible to renounce CT scans in the majority of cases of retinoblastoma.

Is CT Still Useful in the Study Protocol of Retinoblastoma?

“…MR imaging is the method of choice in depicting ocular lesions; 8,11,[25][26][27] however, CT is still the method of choice for detecting intraocular calcium and investigating orbital pathologies. 28,29 The disadvantages of CT are reduced soft-tissue contrast and spatial resolution compared with MR imaging; the presence of the potential risk of iodinated contrast administration; and radiation exposure, especially in those patients with the hereditary form of the disease, who have elevated radiosensitivity.…”

“…The development of a smaller diameter dedicated surface coil may allow the detection of very small intraocular lesions, even with a thickness of Ͻ1 mm. 27 Our study has clearly shown the possibility of detecting calcifications in retinoblastoma, when MR imaging, ultrasonographic, and ophthalmoscopic data are used jointly.…”

Contrast-Enhancement of the Anterior Eye Segment in Patients with Retinoblastoma: Correlation between Clinical, MR Imaging, and Histopathologic Findings

“…Currently, the use of orbital surface coils is recommended for retinoblastoma imaging to increase spatial resolution and signal-to-noise ratio. 5,7 Future research on retinoblastoma-associated BOB impairment and quantification of leakage across the endothelium should be performed with dynamic contrast-enhanced MR imaging, which is widely used for tumor imaging. 33 Contrast-enhanced MR imaging seems to be a useful tool for noninvasive detection of retinoblastoma-related angiogenesis and could define a subgroup of patients who would potentially profit from vascular targeting drugs in the future.…”

“…[2][3][4] MR imaging provides the opportunity for a noninvasive evaluation of these risk factors with reasonable diagnostic accuracy. [5][6][7][8] Tumor angiogenesis is also a histopathologic risk factor for local tumor invasion and systemic dissemination in retinoblastoma 9,10 ; initial reports on vascular targeting therapy in mouse models of retinoblastoma show promising results. 11 However, evaluation of angiogenic activity has been performed only in vitro on the histopathology of enucleated eyes.…”

Retinoblastoma: Value of Dynamic Contrast-Enhanced MR Imaging and Correlation with Tumor Angiogenesis

“…These characteristics can be well-detected on histopathology, but detection by conventional MR imaging is not optimal so far. [5][6][7][8][9][10][11][12][13] Therefore, it is important to assess the prospects of other MR imaging methods that could further optimize the tumor tissue characterization in vivo.…”