Investigation of choice for SAH is
**Core Concept**
The investigation of choice for Subarachnoid Hemorrhage (SAH) involves imaging techniques that can accurately detect blood in the subarachnoid space. **Non-contrast Computed Tomography (CT)** is highly sensitive for acute hemorrhage.
**Why the Correct Answer is Right**
Non-contrast CT scan is the initial imaging modality of choice for SAH due to its high sensitivity for detecting acute blood, rapid acquisition time, and widespread availability. It can quickly identify blood in the subarachnoid space, allowing for prompt management.
**Why Each Wrong Option is Incorrect**
**Option A:** Not specified, but typically other options like MRI or angiography are not the first line due to longer scan times or lower availability.
**Option B:** Similarly, not specified but usually less relevant for initial diagnosis.
**Option D:** Also not specified, but often not the primary choice for initial assessment.
**Clinical Pearl / High-Yield Fact**
Remember, in cases of suspected SAH, a non-contrast CT scan should be performed immediately due to its high sensitivity for detecting fresh blood, which is crucial for early diagnosis and treatment.
**Correct Answer:** D. Non-contrast CT.