Retinoblastoma: CT and MRI

Abstract

To evaluate the effectiveness of CT and MRI at 0.5 T in the diagnosis and staging of retinoblastoma, we studied 11 patients in whom retinoblastoma was clinically suspected. Nine of the eleven had surgically proven retinoblastoma; in the other two a diagnosis of Coats' disease was made. MRI was not as specific as CT for diagnosing retinoblastoma, due to its lack of sensitivity in detecting calcification; it did, however, have superior contrast resolution. On MRI, Coats' disease was reliably diagnosed and easily differentiated from retinoblastoma. Moreover, the greater ability of MRI to differentiate subretinal fluid from tumour also confers high accuracy in measuring tumour size. CT is still the study of choice in the diagnosis of retinoblastoma, but when MRI is available, it should be performed for better differentiation from lesions such as Coats' disease.

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.…”

“…3,4 The detection of intraocular calcium deposition is a key element to differentiate retinoblastoma from simulating lesions. Histology reports show that retinoblastomas calcify in Յ95% of cases 5 ; CT has a designated sensitivity in detecting calcifications in retinoblastoma of 81%-96%, [6][7][8][9][10] whereas the sensitivity of sonography has been reported to be Յ92.5% of cases. 4 In children younger than 3 years of age, an intrabulbar calcified mass is most likely a retinoblastoma.…”

Detection of Calcifications in Retinoblastoma Using Gradient-Echo MR Imaging Sequences: Comparative Study between In Vivo MR Imaging and Ex Vivo High-Resolution CT

“…However, the accuracy of CT in depicting calcifications in soft tissues is well-accepted, and this technique was used as a reference in several studies in the past. 5,11,21 Second, the lesions studied were all retinoblastomas, without a number of simulating lesions for comparison. It is thus impossible to determine whether the absence or theoretic absence of SIVs on T2*WI or SWI in simulating diseases can be a reliable parameter to narrow the differential diagnosis.…”

“…In these complicated eyes, CT is generally the method of choice for studying intraocular calcifications, with reported sensitivities of 81%-96%. 5 Its diagnostic performance in staging retinoblastoma disease extent is limited, however, and the theoretic increased risk of radiation-induced cataracts and fatal cancers in children who are exposed to ionizing radiation should be considered. 6 Patients with hereditary retinoblastoma in particular are at an even higher risk of developing radiation-induced tumors compared with healthy children.…”

Detection of optic nerve involvement in retinoblastoma with enhanced computed tomography

“…The most serious shortcoming of MRI in retinoblastoma cases is its relative insensitivity towards calcification.4,2O On the other hand, calcification can be detected by CT with a high degree of accuracy in approximately 90% of cases. 15 Further advantages of CT are its easy enhancement capability and its potential for detecting the presence of calcified midline brain lesions. Significant improvements in CT technology have increased its spatial and density resolution as well as its ability to obtain direct volumetric acquisitions (spiral CT).…”