Investigation of choice for retinoblastoma is
**Core Concept**
The investigation of choice for retinoblastoma involves imaging techniques that can accurately diagnose and stage the disease. **Magnetic Resonance Imaging (MRI)** and **Computed Tomography (CT)** scans are commonly used, but one is preferred due to its superior soft tissue resolution and lack of radiation.
**Why the Correct Answer is Right**
The correct answer is MRI, as it provides detailed images of the eye and orbit without using ionizing radiation, which is particularly important in children. **MRI** can accurately detect the size and extent of the tumor, as well as any extraocular spread. It is also useful for assessing the optic nerve and detecting any **central nervous system** involvement.
**Why Each Wrong Option is Incorrect**
**Option A:** CT scans involve radiation and are less sensitive for soft tissue detail, making them less ideal for diagnosing retinoblastoma.
**Option B:** Ultrasound is useful for some ocular conditions but lacks the detail needed for staging retinoblastoma.
**Option D:** Other investigations may be used as adjuncts but are not the primary choice.
**Clinical Pearl / High-Yield Fact**
Remember, in pediatric patients, especially those with retinoblastoma, it's crucial to minimize radiation exposure due to the increased risk of secondary malignancies. **MRI** is preferred for its diagnostic accuracy and safety profile.
**Correct Answer:** D. MRI