**Core Concept**
Computed Tomography (CT) angiography has become the imaging modality of choice for diagnosing subarachnoid hemorrhage (SAH) due to its high sensitivity and specificity in detecting aneurysms and vascular malformations. The CT scan can quickly identify fresh blood in the subarachnoid space and guide further management.

**Why the Correct Answer is Right**
CT angiography is the preferred imaging technique for SAH because it provides detailed images of the cerebral vasculature, allowing for the detection of aneurysms and other vascular abnormalities. This is particularly useful in the emergency setting, as it enables prompt identification and treatment of the underlying cause of SAH. The CT scan can also be quickly performed and does not require the use of iodinated contrast media, making it a safe and effective option for patients with renal impairment.

**Why Each Wrong Option is Incorrect**
**Option A:** While non-contrast CT (NCCT) is a useful initial imaging modality for SAH, it may not provide detailed information about the cerebral vasculature, making it less suitable for detecting aneurysms.
**Option B:** Magnetic Resonance Imaging (MRI) can be useful in the evaluation of SAH, particularly in the subacute or chronic phase, but it is not typically used as the initial imaging modality due to its longer scanning time and lower availability compared to CT.
**Option C:** Digital Subtraction Angiography (DSA) is a gold standard for diagnosing and treating cerebral aneurysms, but it is an invasive procedure that requires the insertion of catheters into the cerebral vasculature, making it less suitable as an initial imaging modality for SAH.

**Clinical Pearl / High-Yield Fact**
It is essential to remember that a negative CT scan does not rule out SAH, and a repeat scan may be necessary if clinical suspicion remains high. Additionally, patients with SAH are at increased risk of developing vasospasm and rebleeding, making prompt and accurate diagnosis critical for optimal management.

**Correct Answer: C. Digital Subtraction Angiography (DSA) is a gold standard for diagnosing and treating cerebral aneurysms, but it is an invasive procedure that requires the insertion of catheters into the cerebral vasculature, making it less suitable as an initial imaging modality for SAH.