This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Radiology
Investigation of choice for retinoblastoma is 
Select and explain. 
A. X ray, B. USG, C. CECT, D. MRI
D: MRI
Answer: D: MRI 
Explanation: Retinoblastoma is malignant congenital intraocular tumour arising from primitive photoreceptor cells of the retina (included in primitive neuroectodermal tumour group)Two types -Heritable and non-heritableTrilateral retinoblastoma (rare variant)= bilateral retinoblastomas + neuroectodermal pineal tumor (pineoblastoma)Quadrilateral retinoblastoma= trilateral retinoblastoma + 4th focus in suprasellar cisternMRI is the modality of choice for pre-treatment staging on retinoblastomaPrognosis: Spontaneous regression in 1%Calcification is a ourable prognostic signContrast enhancement is a poor prognostic sign(Ref: Radiology Review ManualBy Wolfgang Dahne 6thEtd, 351)